Showing papers in "Biological Reviews in 1936"

The retention and physiological role of urea in the elasmobranchii

Abstract: Summary. The high urea content (2·0 and 2·5 per cent.) that characterises the blood, body fluids and tissues of the Elasmobranchii owes its origin to the relative impermeability of the gills and integument to this substance, and to the circumstance that the urea is actively conserved by the elasmobranch kidney. In consequence of this physiological uraemia, the elasmobranch is osmotically superior to its environment, even in sea water, and is able to absorb at least a minimum quantity of water for the formation of a urine that is isotonic or hypotonic to the blood, in accordance with the osmotic limitations of the fish kidney. We may suppose that the uraemic state tends to develop and to be regulated more or less automatically; urea is constantly being formed by the ordinary metabolic combustion of protein; water shortage leads to oliguria and urea retention, and the accumulated urea in the blood raises the osmotic pressure of the latter to a point where water is again available by direct absorption. Water plethora (as in fresh water) leads to diuresis and increased urea excretion, which in turn lowers the osmotic pressure of the blood and in some measure, at least, reduces the rate of water absorption. Trimethylamine oxide, which imparts about one-quarter as much osmotic pressure to the blood as does urea, is also conserved by the elasmobranch; the fact that this substance is present in the urine in lower concentration than in the blood suggests that, like urea, it is actively reabsorbed from the glomerular filtrate. This physiological uraemia is apparently an archaic biochemical habit acquired early in elasmobranch evolution, since it is shared by the divergent orders of the subclass. Presumably it is a secondary mode of osmotic regulation superimposed upon the more primitive one of branchial regulation, as observed in the teleostomes. The cleidoic egg, unique (among the fishes) in the Elasmobranchii, and the viviparous mode of reproduction, are viewed as adaptations to urea retention, protecting the embryo against the loss of urea during its early development. Urea retention enables the Elasmobranchii to maintain a considerably greater rate of urine formation (water excretion) than is observed in the marine teleosts, a fact that perhaps explains why the former do not show the glomerular degeneration or the aglomerular development observed in the latter. Whereas urine formation in the marine teleosts appears to be carried on normally at a reduced level considerably below the maximum possible rate, the elasmobranchs appear to maintain a maximal (though small) degree of glomerular activity at all times. Unlike the teleosts, they appear to possess no mechanisms for reducing glomerular activity; it may be that because of their superior osmotic position, due in turn to their physiological uraemia, they have never been faced with the necessity for conserving water to an excessive degree in the kidneys, and have therefore never evolved the means for doing so.

Selectivity controlling the central-peripheral relations in the nervous system

Abstract: Summary 1. In 1922 it was discovered that a supernumerary transplanted limb in amphibia invariably duplicates the movements of the normal limb in whose nerve plexus it shares. This phenomenon, called “homologous response”, has been demonstrated to be an expression of the more fundamental fact that, in every reflex and spontaneous action, multiple muscles of the same name (synonymous muscles), innervated from the same functional district and the same side of the spinal cord, contract simultaneously and with approximately equal intensities, regardless of their anatomical position, the details of origin and distribution of their nerve supply, and the functional effects of their contractions with regard to the body as a whole. Homologous response of synonymous muscles, observed under such a variety of different conditions as enumerated in Section II (1), has led to the realization that the linkage between the nervous centers and the non-nervous periphery is based upon mutual relations discriminative for each peripheral organ and much more specific than had previously been suspected. Further experimental analysis of this relationship has led to the following conclusions. 2. The specific relations between muscles and centers are not secondarily established by adjustments of the “conditioning” or “learning” type; for, the principal features of the latter, modifiability and adaptive functional value, are absent in the phenomenon of homologous response. In fact, the phenomenon is not even dependent upon the presence of sensory control at all, since it is likewise obtained from limbs with purely motor innervation (III (I)). 3. Nor is the specific relation between muscles and centers the result of morphological selectivity in the formation of peripheral nerve connections. Abundant evidence is on hand showing not only that in general no affinity whatever exists between a given nerve fiber and a particular muscle, but more specifically, that such an assumption can be decisively ruled out for the experimental cases exhibiting homologous response. Many new facts have been added in substantiation of this point and are discussed in Section III (2). 4. Other explanations being excluded, the specific relation between centers and muscles must be regarded as due to a primary physiological relationship, resembling in principle the specific linkage found in resonance-like mechanisms. Every muscle is constitutionally (presumably biochemically) different from every other non-homologous muscle, and to deal with this diversity the centers are endowed with a capacity to produce a corresponding variety of forms or modes of motor impulses, each one exclusively appropriate to a single muscle. Thus, the activation of a muscle becomes a matter of dual activities: release of discriminative emissions from the centers, and the selective reception of these by the periphery. 5. Experiments involving the transplantation of single supernumerary muscles in adult toads (IV (1) a) have indicated that the peripheral muscle-specific selection does not actually occur in the muscle fiber itself but in some part of the peripheral nervous system acquiring its muscle-specific selectivity through a specifying (“modulating”) effect extending from the muscle. It is assumed that motor neurones subjected to these peripheral influences are gradually rendered specific to such an extent that they will no longer admit from the centers motor impulses other than those appropriate for the particular muscle at their peripheral ends. A study of the reappearance of motility in denervated and re-innervated limbs in the toad has revealed that the specification of a nerve by its muscle is a slow process. Specification is, at least up to a certain age, reversible, the connection of a nerve with a new muscle resulting in corresponding respecification. Thus, the specific diversity of the muscles is projected into the motor nerves, and E. Hering's postulate of the diversity (“Ungleichartigkeit”) of nerves becomes, after all, a fact. 6. Concerning the spinal centers, the conclusion has been reached that their functioning cannot be satisfactorily envisaged in terms of switch-board or other geometrical schemes (IV (2)). We have been forced to concede to the limb center, for instance, the property to produce, release, and circularize within certain intracentral limits, a variety of specific effects matching the existing variety of individual limb muscles. To judge from experimental evidence, the release of impulses specific for limb muscles is confined to the limb level of the spinal cord. 7. It has not yet been possible to offer any suggestion as to the presumable nature of the described selective affinity between central impulse and peripheral nerve fiber. But reasons have been advanced which, it would seem, allow us to reject the idea that specific frequencies or specific chronaxie relations (isochronism) are involved.

Über den gehörsinn der fische

Abstract: Zusammenfassung I. Reaktionen auf Schallreize wurden bisher an 32 Fischarten (aus 14 Familien) zuverlassig nachgewiesen. 2. Spontane Reaktionen auf Tone sind nicht zu erwarten, da die von uns angewendeten Tonsignale fur die Fische keine biologische Bedeutung haben. Zuverlassige Reaktionen erhalt man daher nur nach Dressur auf Tone. Diese Methode ermoglicht auch eine weitgehende Analyse des Horvermogens bei Fischen. 3. Die obere und untere Horgrenze ist bei Fischen mit gut entwickeltem Gehorsinn angenahert dieselbe wie beim Menschen. 4. Die Fahigkeit der Tonunterscheidung ist fur Elritzen (Phoxinus laevis) und Zwergwelse (Amiurus nebulosus) sicher nachgewiesen. Bei einem Intervall von etwa einer Oktave wurden zwei verschieden hohe Tone im Gedachtnis behalten und wiedererkannt. Der beste Fisch lernte sogar die Unterscheidung einer kleinen Terz. Auch mehr als zwei (bis zu funf) Tone konnen gleichzeitig im Gedachtnis behalten werden. 5. Die Horscharfe ist bei den gepruften Cypriniden, Siluriden und Characiniden angenahert dieselbe wie die des menschlichen Ohres. 6. Bei der Elritze (Phoxinus laevis) ist die pars inferior des Labyrinths, also Sacculus und Lagena, der Sitz des Gehorsinnes. Die pars inferior hat keine statische Funktion. Die pars superior (Utriculus und Bogengange) ist der Sitz des Gleichgewichtssinnes; dieser Teil des Labyrinths hat keine Horfunktion. 7. Tiefe Tone (unter 100–150 v.d.) werden, wenn sie sehr intensiv sind, von der Elritze auch durch den Tastsinn der Haut, sehr tiefe Tone (16 v.d.) nur durch den Tastsinn wahrgenommen. 8. Bei den Ostariophysen (Cypriniden, Siluriden, Characiniden und Gymnotiden) steht die Schwimmblase durch die Weberschen Knochelchen mit dem Sacculus in Verbindung. Der Sacculus-Otolith ist zum Auffangen der auf diesem Wege zugeleiteten Schallwellen besonders umgestaltet. Hierdurch erklart sich die abweichende Form der pars inferior bei den Ostariophysen. Diese Einrichtung dient der Steigerung der Horscharfe. 9. Die Nicht-Ostariophysen sind daher im allgemeinen fur Schallreize weniger empfindlich. Dass auch sie durch die pars inferior des Labyrinths horen, ist noch nicht uberzeugend nachgewiesen, aber ausserordentlich wahrscheinlich. 10. Auch bei manchen Nicht-Ostariophysen finden sich Einrichtungen, die der Steigerung der Horscharfe dienen durften. Sie sind aber physiologisch noch nicht untersucht. 11. Das Labyrinth der Fische vermittelt eine Tonwahrnehmung und Tonunterscheidung ohne Basilarmembran. Die Basilarmembran im Ohr der Landwirbeltiere ist wahrscheinlich ein Apparatzur Verfeinerung des Tonunterscheidungsvermogens. 12. Die Fahigkeit der Tonerzeugung durfte bei Fischen sehr weit verbreitet sein. Daher ist auch die biologische Bedeutung ihres Horvermogens nicht so ratselhaft, wie sie fruher erschien. Summary 1. Reactions to sound stimuli have so far been reliably demonstrated in 32 species of fishes (14 families). 2. Spontaneous reactions to musical tones are not to be expected, since the sound signals used by us have no biological significance for fishes. Reliable reactions can therefore only be obtained by conditioning to tones. This method also allows of a thorough analysis of the capacity of hearing in fishes. 3. The upper and lower limit of hearing in fishes that have a well-developed capacity of hearing is approximately the same as in man. 4. The capacity of discrimination of frequencies has been shown certainly to exist in minnows (Phoxinus laevis) and in a cat-fish (Amiurus nebulosus). Two different frequencies about an octave apart could be remembered and recognised. The best fish learned even to discriminate a minor third. And more than two (up to five) tones can be remembered at the same time. 5. In the Cyprinidae, Siluridae and Characinidae tested, the sensitiveness of hearing is approximately the same as that of the human ear. 6. In the minnow (Phoxinus laevis) the pars inferior, that is the sacculus and the lagena, is the seat of the sense of hearing. The pars inferior has no static function. The pars superior (utriculus and semicircular canals) is the seat of the sense of equilibrium; this part of the labyrinth has no auditory function. 7. In the case of the minnow, low frequencies (below 100–150) are perceived also by the touch sensitivity of the skin if they are of high intensity, while very low frequencies (16) are perceived by the touch sense only. 8. In Ostariophysi (Cyprinidae, Siluridae, Characinidae and Gymnotidae) the swim bladder is linked up with the sacculus by the Weberian ossicles. The saccular otolith is specially modified for the reception of the sound waves directed towards it by the above mechanism. That explains the special shape of the pars inferior in the Ostariophysi. These dispositions are responsible for the increase iii sensitiveness of hearing. 9. Fishes other than the Ostariophysi are therefore generally less sensitive to sound stimuli. It has not yet been convincingly proved that these fishes also hear by means of the pars inferior of the labyrinth, but this is very probably the case. 10. In some of the non-Ostariophysi there are, nevertheless, structures which may serve in increasing the sensitiveness of hearing. These have hot vet been investigated physiologically. 11. The labyrinth of fishes has the capacity of the reception of sound and the discrimination of tones, though it has no membrana basilaris. The membrana basilaris in the ear of land vertebrates is probably an organ for the refinement of tone discrimination. 12. The capacity of sound production appears to be very common in fishes. The biological significance of their ability to hear is therefore not so puzzling as it previously appeared.

The genetical conception of the species

Abstract: Summary. 1. Previous work on the behaviour of genes in interspecific crosses is discussed, and it is concluded that allelomorphic relationships exist between the genes of crossable species whether these are in the same genus or in reputedly different genera 2. Genetical experiments on interspecific hybrids in six species of the genus Gossypium enable the following main conclusions to be drawn: (a) Although allelomorphic relationships exist throughout the six species in respect of all genes examined, cases of identity (apparent or real) are practically confined to recessive genes only. Geographical isolation over a long period of time has resulted in the production of new alleles at most loci. These may be termed “species alleles”. Species endemic in the Galapagos and Hawaiian Islands are characterised by species alleles not found in mainland species. (b) The introduction of genes from one species into another indicates that species differ not only in the mode of distribution of alleles functioning as main genes, but also in the modifier complexes accompanying such alleles. The degree to which modifier complexes differ in species is of primary importance from a taxonomic point of view. (c) The bearing of experiments with the “Crinkled” mutant on the Fisher theory of dominance is discussed. It is shown that a number of normal alleles of crinkled exist, which are distinguishable only by their dominance potency, that the dominance relation is due to the interaction of a normal allele of specific potency with a modifier complex to which it is precisely adjusted, and that the genes constituting the dominance modifier complex have been preserved not because of their function as modifiers of initially disadvantageous heterozygotes, but because of their selective value on their own account. It is believed, however, that on the appearance of the crinkled mutant, selection probably ensued in favour of alleles with greater dominance potency, i.e. that the “Haldane effect” has been operative. (d) Examples are given of three different ways in which homologous characters can be genetically constructed in the genus Gossypium. It is pointed out that the conception of continuous change with time in the genetical architecture of an organ is probably of profound evolutionary significance. 3. The Darwinian process of evolution by natural selection, involving mere gene substitution, has probably been the main mechanism involved in the profound changes induced in the genus Gossypium through geographical isolation.

The physiological effects of pressure

Abstract: Summary Our knowledge of physiological effects of pressure is as yet too incomplete to permit of generalizations, and we are still very much in the dark regarding the mechanism of pressure action. Any influence of hydrostatic pressure must be secondary to a decrease in volume. In non-living systems this results in important changes in physical and chemical properties and gives a basis for the explanation of the changes produced in living material. Such factors as the velocity of chemical reaction and the viscosity of fluids are, in general, increased quite out of proportion to the volume change. High pressures bring about an irreversible polymerization of many substances, including proteins. The same order of pressure inactivates most enzyme solutions, bacterial toxins, antibodies, viruses, and other biological agents. The simpler forms of life, such as bacteria and yeast cells, are only slightly less resistant, but all are killed by sufficiently high pressure. On higher forms relatively low pressures cause death, especially when long continued. There are many known instances where small pressures cause a stimulation of physiological processes, and this may prove to be a general phenomenon occurring at pressures below those resulting in depression. In the case of muscle contracting under pressure there is a marked augmentation in the response, and the application of pressure may, independently of any other form of stimulus, result in the prolonged liberation of energy. Provided that the pressure increase is not too extreme, all the changes observed are reversed with decompression. The action of pressure on physiological mechanisms has a special interest because it is a fundamental one on molecular relationships extending throughout the cell structure. Furthermore, it is an agent which can be supplied and removed with great rapidity and as such provides a unique tool for the study of physiological problems.

The equilibrium function of the vertebrate labyrinth

Abstract: Summary. 1. The vertebrate labyrinth can be divided into a pars superior, consisting of the utriculus and the semicircular canals, and a pars inferior, consisting of the sacculus and its various appendages. 2. Only the pars superior is concerned with the maintenance of muscle tone and with reflex reactions to gravity and to linear and angular accelerations. This has been demonstrated for fishes, amphibia and mammals, and, although the evidence is not completely satisfactory, it probably holds for reptiles and birds as well. The pars inferior takes no part in any of these functions (again with the above reservation as to reptiles and birds), but, even in those vertebrates which lack the organ of Corti, is concerned with sound reception. Breuer's theory of the localisation of the non-acoustic function of the labyrinth has thus been shown to be erroneous. 3. Attempts have been made to discover which of the receptor endings of the pars superior are involved in each of its functions, by eliminating separately the various endings. The results obtained are not entirely consistent. Production of the static reflexes and of the reflexes to centrifugal force and fast linear acceleration is in all probability the main function of the otolith organ (utriculus). It appears, however, that the assumption that the otolith organ is purely static in function is incorrect, for it has been shown that the utriculus can be involved in dynamic responses to rotations. The main function of the semicircular canals is the release of the dynamic reflexes. It has, however, been claimed that the vertical canals take part in the production of static reflexes as well. Both the utriculi and the semicircular canals are involved in the maintenance of muscle tone. 4. In the discussion of the general conclusions as to the function of the utriculi and of the semicircular canals it is shown that one of the important functional differences between the two receptors consists in their different reaction time, which may be due to the difference in their auxiliary structures and to a different pattern of their nervous connection with the effector organs.

The passive iron wire model of proto-plasmic and nervous transmission and its physiological analogues

Abstract: Summary The phenomena of activation and transmission in the passive iron wire model are described, and the various parallels with the irritable living system, especially nerve, are discussed. In general, the similarity of behaviour is to be referred to a single structural feature common to both systems, namely the presence of a thin, polarisable and chemically alterable interfacial layer or surface film (oxide film; plasma membrane) situated at the boundary between the metal, or the protoplasm, and the surrounding medium. This film undergoes characteristic changes of chemical composition and physical properties, e.g. of permeability and electrical polarisation, when traversed by an electric current of an intensity and duration sufficient to produce a certain critical degree of chemical decomposition. The activity of the system as a whole is controlled by the electrochemical oxidations and reductions occurring in the film under these conditions. Hence both the model and the living system are electrically sensitive and transmit local states of activity, local changes on the film being associated with local electric circuits which have electrochemical effect at regions beyond. Hence, also, the essential conditions under which electrical activation occurs are the same in both systems (polar activation, intensity-duration relationship, etc.). Activation and transmission are similarly affected in both by changes of temperature, by variations in the composition of the medium, by electrical polarisation (analogy to electrotonus), and by surface-active compounds (analogy to narcosis). Closely analogous processes of progressive recovery occur in both systems after the passage of an activation wave (refractory phase). Other resemblances are seen in the phenomena of automatic rhythm, the mutual interference of activation waves, the transmission of inhibitory influence, irreciprocal transmission, and distance influence, excitatory and inhibitory. Biological analogies of a more general kind, relating to mutual interdependence between processes occurring in spatially separated regions traversed by the same electric current—a possible factor in certain types of integration—are briefly discussed.

Cephalic sutures and their bearing on current classifications of trilobites

Abstract: Summary 1. The cephalic sutures are defined; their distribution and interrelationships discussed. Few facts are available concerning the evolutionary movements of these, but various theoretical deductions have been made. 2. Opinion on the supposed function of these sutures is summarised and it is concluded that the sutures probably did not exist solely for the purpose of ecdysis. 3. Consideration is given to the historical aspect of trilobite classification into three orders where the ordinal character is the course taken by some of the cephalic sutures. This classification has been adversely criticised; attention is called to the fallacy of assuming that the chosen cephalic sutures were: (a) relics of primary segmentation, (b) homologous in all groups, (c) in themselves alone of phylogenetic significance. 4. Three orders have been erected in turn to accommodate, according to their founders, the most primitive trilobites; none contains a single family in common with another of the orders. Pompeckj's and Swinnerton's objections to Beecher's order Hypoparia are upheld, as are Warburg's and Rud. Richter's objections to Swinnerton's order Protoparia. 5. The order Mesonacida (as defined by Poulsen) has a unique position; Poulsen regarded it as the most primitive group of known trilobites; Raw, as the most specialised group at least as far as the cephalic “segmental” spines and sutural evolution is concerned. Disagreement is expressed with this opinion of Raw's, essentially because of a more probable interpretation of the particular segmental origin of one series of spines homologised by Raw, and because there are doubts whether the remaining two spine pairs are necessarily of metameric (segmental) origin. 6. Though absolute proof is as yet lacking, Swinnerton and Poulsen are thought to have justifiably stated that the absence of true facial sutures in Mesonacidae is primary; some of the supposed primitive features of the family (or order using Poulsen's restricted sense) are discussed. 7. The bearing of recent ontogenetic work on the relationship of Proparia and Opisthoparia suggests that the proparian condition may be regarded as arrested development, and therefore previous failure to recognise this has resulted in the establishment of a group here held to be polyphyletic. 8. A satisfactory classification of the group might be evolved, as sufficient reliable knowledge accumulates, by combining allied families into superfamilies. Two attempts at this form of classification are discussed and summarised; these however are based on the primary ordinal value of the supposed (adult) static condition of part of one of the cephalic sutures, and can only be regarded as provisional.

The specific dynamic action of protein and amino acids in animals

Abstract: Summary When food is ingested by an animal in an environmental temperature above 25°C. his energy metabolism increases. This is known as the specific dynamic action of foodstuffs. The largest specific dynamic action is exerted by protein and amino acids. The specific dynamic action of injected amino acids, other things being equal, is approximately the same as protein taken by mouth. This and other evidence exclude the work of digestion and absorption as the source of this increase in metabolism. The other of the older hypotheses proposed in explanation of this phenomenon referred the increased heat production and respiration to an increased metabolism of the cells, apart from digestion, absorption and excretion. That of Voit was that the increased metabolism was a plethora effect, the result of an increased concentration of metabolites in the cell; of Rubner that the increased heat production represented reactions in which part of the protein was converted to glucose, the remainder not convertible to glucose is burned with the nitrogen-carrying moiety. The heat produced in these reactions, according to Rubner, is not utilisable by the organism and hence appears only as heat. Lusk restated these hypotheses in terms of specific chemical reactions and subjected them to experimental test. He first took the position that though the increased metabolism following the ingestion of carbohydrate and fat were plethora effects, the calorigenic effect of amino acids was of different origin and represented a specific stimulation of the cells without the amino acids themselves necessarily undergoing oxidation. Later he modified this view and held that the specific dynamic action of amino acids represented the heat loss in converting the deaminised residues to glucose, and this specific dynamic effect was an absolute and characteristic constant for each amino acid, in spite of the fact that his observations, as a rule, terminated long before the metabolism of the amino acid administered was complete. Lusk held also that the metabolism of the nitrogen—deamination, urea formation, and excretion—was not responsible for any of the increase in metabolism observed. This contention was based mainly on the observation that glutamic acid exerts no specific dynamic effect, an observation which all other observers have shown to be erroneous. Lusk's explanation fails to account for the large specific dynamic effects of amino acids, such as tyrosine and phenylalanine, which are not converted to glucose. Although it was emphasised by Lusk (at first at any rate) that the increase in energy metabolism is proportional to the amount of protein or amino acid metabolised, the practice arose, particularly among clinical workers, of considering the increase in energy metabolism observed in the first few hours as an absolute quantity to be referred to the quantity of protein or amino acid administered, rather than to the quantity metabolised in the interval through which the energy metabolism was observed. This is chiefly responsible for the conflicting reports regarding variations in the specific dynamic action of protein in endocrine and nutritional disorders. The specific dynamic action of protein is not constant. It is usefully expressed as a ratio of calories in excess of the basal to urinary nitrogen in excess of the basal. Nearly all the data on record which can be expressed in this form are collected. A theory of the specific dynamic action of protein is presented which accounts for the variations, and the minimum and maximum values observed for the ratio of excess calories to excess urinary nitrogen. According to this theory the specific dynamic action is a composite of two factors, one nearly constant, representing the increased energy production attending the metabolism and excretion of the nitrogen, and amounts to 7–10 calories per gram of nitrogen; the other—more variable, and at times larger fraction—arises from the metabolism of the carbon. Since the amino acids do not act as primary stimulants to cellular metabolism (the evidence for this is discussed in detail) the increase in metabolism follows their deamination—hence the parallel between the increase in energy metabolism and the increased concentration of amino acids in the blood, the increased urinary excretion of uric acid in man, and of glucose in the phlorhizinised dog. For the same reason when the organs in which deamination occurs are removed—the liver, and to a lesser extent the kidneys and small intestine—injected amino acids exert no specific dynamic action; and in the normal animal the specific dynamic action is confined to the viscera. In the metabolism of the nitrogen, the heat produced in oxidative deamination is not available to the organism for work because the stoichiometrical requirements when oxygen combines directly with a metabolite must be satisfied. For the same reason in the coupled reactions whereby urea and other products (glycogen) are synthesised, the excess energy is not available for physiological work. The metabolism of the carbon is responsible for the observed variations in the specific dynamic action of protein. In general it may be compared to the recovery phase of muscular exercise. An oxygen debt is incurred, and the cost of its repayment varies with the nutritional state and the nature and fate of the deaminised residue. Accordingly the specific dynamic action of protein is not available for muscular or other work in the organism. It will vary according to the extent that the deaminised residues spare tissue carbon, whether they are converted to glucose or fat, and according to the nature of the fuel mixture supporting these syntheses and conversions. This theory accounts for most of the hitherto anomalous phenomena in the specific dynamic action of protein. Reference of the increase in metabolism to the quantity of nitrogen metabolised shows that there is no “neutralisation” of the specific dynamic effects of amino acids when these are given with protein; and the specific dynamic action of protein is not particularly low or absent in endocrine or nutritional disorders. Analysis of the physiology of coupled reactions, taking into account the mode of deamination of individual amino acids (whether oxidative or hydrolytic), and the nature of the deaminised residue indicates the reasons for the high specific dynamic effects of ketogenic amino acids such as tyrosine and phenylalanine, and of glutamic acid, and also for certain possible low figures, as in the cases of arginine and histidine.

On the evolution of bony fishes during the triassic period

Abstract: Summary The Palaeoniscidae was the dominant group of bony fishes during Carboniferous and Permian times. This large and varied group of fishes has usually been called the “family Palaeoniscidae”, but it appears to consist of several independent lines. The Holostei were evolved from the Palaeoniscidae before the beginning of the Triassic, Acentrophorns, the earliest member, appearing in the upper Permian. About the close of the Palaeozoic era the Palaeoniscidae gave rise to several independent families which become modified to a greater or less extent toward the holostean grade of structure. These groups are referred to as the sub-holostean families. The parallel modifications they display include the reduction of the scaly lobe of the tail, reduction of the fin rays, loss of the cosmine layer of the scales, and the swinging forward of the suspensorium. The modifications proceeded much further in some groups than in others. It is shown that although these Triassic families did not give rise to the Holostei, they provide a perfect Sci of intermediate forms between the palaeoniscid and the holostean condition. One of the sub-holostean families, the Catopteridae, is analysed and its evolving characters separated into those which are parallel (also undergone by other groups) and those which are characteristic of the family. Reasons are Sci out for supposing the Catopteridae to have been derived from the Dicellopygae group of the Palaeoniscidae.

The transformation of organic designs: a review of the origin and deployment of the earlier vertebrates

Abstract: Summary Paley argued that because natural mechanisms often work like human mechanismsthey must have been made by a great designer; but this was an anthropomorphicfallacy which left the time element out of account. Darwin was able to show thatin many cases intergrades are known that connect even the most complex naturalmechanism with simpler antecedents; also his principle of the natural selectionof heritable variations seemed to provide a mechanism for the production ofmechanisms. However, the discovery of great numbers of what have been calledorthogenetic series has obscured the principle that the natural selection of smallheritable variations (mutations of the geneticists) I ˜nservesa nd integrates originallyindependent variables and tends to eliminate aberrant or “fortuitous” variationsand lethals that lie too far to one side of the curve. That there is indeed a subsidiarymechanism for the elimination of the vast majority of merely random variations issuggested by the discovery of “orbhers”, which preside over the course ofdevelopment and tend to keep it within prescribed limits (Spemann, 1927). It is not, however, the purpose of the present article to discuss the causes ofevolution but merely to formulate in general terms the ways in which organicdesigns of known history have originated and evolved, especially during theemergence and deployment of the vertebrates. An organic design is defined as acollocation of parts of an organic whole, varying in magnitude, emphasis or distancein space or time from the chosen point of origin or reference. As thus defined thechanges in many typical organic designs of known history may all be expressed asthe resultant of two co-operative principles of individual development and phylogeneticevolution: the first may most briefly be called repetilion, the second emphasis. The principle of repetition has long been recognised in part under such names as “repetitive acceleration” (Cope), “metamerism” (Gegenbaur), “merism” (Bateson), “aristogenesis” (Osborn), while the principle of uneven development or emphasishas been called “differentiation” (Spencer), “alloiometry” (Osborn), “heterogony” (Pezard, J. S. Huqley), and so forth. For some years past the writer has beencalling the products of organic repetition polyisomnes and the general method ofrepetition, budding or reproduction polyisomerish; while for parts or regions that become unevenly developed, increased, decreased or fused with their neighboursthe term anisomeres is employed and the process itself is called anisornetism. Now one and now the other of these processes may predominate, but both are constantlyaltering organic designs to a greater or less degree. The term secondary polyisomerism is used to denote the important fact that when one polyisomere acquires a certaindetailed character its neighbours all along the line usually change in the samedirection. This, as it were, throws a screen of small details over the surface andimparts an often false appearance of simplicity, homogeneity and primitiveness towhat is in reality a very advanced stage of specialisation. When anisomeres areaffected by secondary polyisomerism the pattern tends toward dedifferentiation. After long periods of divergent evolution each of the diversified descendantgenera of a common stock will be found to be in possession of: (a) a mask of changedorganic designs relating especially to its particular mode of life, which is collectivelycalled its habitus, and (b) a smaller fund of unchanged organic designs or charactRtisticsinherited from the remote common stock, the totality of such charactersbeing called its anatomic heritage. Part of the habitus of a remote common ancestorafter a change of function becomes part of the heritage of its descendants, and thetwo correlative terms may be qualified so as to indicate such conditions as therelative phyletic ages of any particular habitus and heritage, or the relativesystematic values. Thus the swordfish-like ordinal habitus of ichthyosaurs datesfrom Triassic times, but their reptilian clms heritage is of Permian age; the family habitus of the Macropodidae is kangaroo-like, but their superfamiZy heritage isphalangeroid, By extension of the same principle we may speak of the habitusand heritage features of some particular division of an organic design, such as thejaws and dentition, the feet, the reproductive system and the like. Changes in habitus and heritage, if proceeding at slow rates or for relativelyshort periods, often convey the impression of orthogenesis, or undeviating evolution, but by combining the best established results of comparative anatomy and embryologywith the records of palaeontology over long periods of geologic time we discoverthe reality and frequence of the phenomenon of transfomtion. In reviewing the transformation of organic designs as seen in the deploymentof the vertebrates, the writer holds that his method has on the whole not been a priori, since the foregoing principles were established objectively after the actualhistory of the vertebrates had been illuminated by the largely independent laboursof a great number of geologists, palaeontologists and comparative anatomists, whofor the most part were always interested in solving concrete historical problemsrather than in considering the general principles of evolution. The principles ofrepetition and emphasis, of habitus and heritage, of undeviating evolution, transformationand the like, enable us to conceive the discrete facts of evolution ingeneral terms, but these concepts to be effectively applied must naturally besupplementary to discovery of the historical facts. With these provisos the writer has given a very brief review of the historicproblem of the origin of the vertebrates, rejecting the claims of various phyla, suchas the annelids, nemerteans, arthropods, etc., on different grounds and showingthat astonishing changes among certain echinoderms from an essentially quinqueradiateto a functionally bilateral symmetry warn us not to overlook thepossibility that the invertebrate ancestors of the vertebrates may not have beenbilaterally symmetrical, fusiform, free-swimming types but possibly sessile bottomlivingforms with a strong dorso-ventral asymmetry. The conclusions reached may be summarised as follows: Amphioxus is secondarily polyisomerous in many respects and anisomerous inothers, and may well be a degraded and highly specialised derivative of the oldestknown chordates, the ostracoderms. The contrasts are great between these earliest known chordates and any knowninvertebrates, with the posaible exception of the carpioid echinoderms. The most primitive of the ostracoderms appear to be among the Heterostraci, especially the poraspids. These are fusiform fishes with an armour of five platescovering the head and front part of the thorax. In the thelodonts and coelolepidsthe shield is represented by a great number of small tubercles or scales which havearisen by secondary polyisomerism from a once continuous head shield (Kiaer). The Heterostraci have paired nasal sacs, and according to Kiaer are related tothe ancestors of the jaw-bearing fishes and higher vertebrates. From presentevidence this relationship may well be much closer than would be possible underthe older view that the heterostracous ostracoderms were a highly specialized side branch. The gnathostomous or jaw-bearing vertebrates probably arose by transformationfrom agnathous creatures that bore no special resemblance to them except in thepossession of certain “basic patents”, especially the serial gill pouches. With regard to the origin of the modem Agnatha (lampreys and hagfishes), the superb material and intensive investigations of Stensio leave no doubt that thelampreys are derived from the cephalaspid ostracoderms, a result of great importancein the morphology of the central nervous system, since it confirms the conclusionsof neurologists that the arrangements of the cranial nerves and general brain patternsof the larval lamprey are on the whole much more primitive than those of theelasmobranchs. The investigations of Patten and Stensio on BothriOZepis and of Stensio on theArthrodira have proved that these long extinct placoderms represented earlyoffshoots from the base of the jaw-bearing series of classes. They seem to thepresent writer also to be derived eventually from some agnathous but branchiateancestors who could not be very far from the most primitive of the heterostracousostracoderms. Heintz's admirable work an the evolution of the Arthrodira fromthe acanthaspids has also provided a clear example of the interaction of polyisomerisrnand anisomerism. The same principles are everywhere apparent in the recorded deployment ofthe higher vertebrates, as illustrated by the changes in the body form in the teleosts, or by the strange transformation of the mandible in the ancestry of the mammals. Thus one may gain a new perspective on the origin of that peculiarly variablesystem of organic designs that has called itself Homo sapiens, who after a prodigiousexpansion of his neopallium began to make organic designs for himself; then, withgrowing pride and egotism and with all the prejudices of his race, nationality andprofession, easily persuaded himself that he was a respectable even if much reducedcopy of a “Great Designer”.

Über die tiergeographischen verhältnisse der circumantarktischen süsswasserfauna

Abstract: Summary This review gives a survey of endemic organisms of the fresh-water fauna of the circumpolar regions, which have geologically, but not ecologically, separate habitats. A number of examples has been selected which indicate that various animals occur in approximately the same geographical distribution areas as Irmscher established for his plants, although the insufficiency of our knowledge of large regions (e.g. Western and Northern Australia, New Guinea, the west of the Argentine Republic) does not allow of the zoological maps being so complete as the botanical. The similarity of the animal and plant results, however, may perhaps support Wegener's theory.

Die herkunft des zellmaterials bei regenerativen vorgängen der wirbellosen tiere

Abstract: Allgemeine Zusammenfassung. 1. Die Herkunft des Regenerationsmaterials wurde bisher bei den Poriferen, Coelenteraten, Turbellarien, Nemertinen, Polychaten, Oligochaten, Sipunculoiden, Bryozoen und Tunikaten, sowie in einzelnen Fallen auch bei Arthropoden, Mollusken und Echinodermen verfolgt. 2. Die Wundheilung geschieht in den meisten Fallen durch Uberdeckung der Wunde mit der Epidermis, deren Zellen aktiv daruber hinwegwandern, manchmal unterstutzt durch von unten einwandernde mesenchymale Zellen. 3. Unter den drei Keimblattern ist das Entoderm das selbstandigste. Der Darm wird fast immer vom Stumpf aus regeneriert, wahrscheinlich unter Benutzung der Basalzellen. Wo kein Stumpf vorhanden ist, kann seine Bildung manchmal vom Mesenchym aus erfolgen. 4. Das Ektoderm ist bei der Regeneration auf die Unterstutzung durch totipotente Zellen angewiesen, unter deren Wirkung vielfach eine Embryonalisierung der Epidermis erfolgt. Das Ektoderm ist also die am weitesten differenzierte Korperschicht. 5. Das Mesoderm (s. 1.) ist das am wenigsten differenzierte Keimblatt und liefert in vielen Fallen totipotente oder dedifferenzierte Zellen, die zuweilen alle Organe wiederherstellen konnen. 6. Die totipotenten Zellen treten entweder in der Form der Neoblasten oder als Basalzellen, vielleicht auch als Peritonealzellen auf. Alle diese Formen von Regenerationszellen konnen als Blastocyten (Stolte) zusammengefasst werden. 7. Die Schwamme besitzen zahlreiche Zellformen, die, kunstlich getrennt, nach teilweiser Dedifferenzierung die Organe wieder aufbauen. Die totipotenten Zellen sind hier die Archaocyten. 8. Wo ein Mesoderm fehlt, wie bei den Coelenteraten, liegen die sog. interstitiellen Zellen im Ektoderm, konnen aber auch in das Entoderm uberwandern. 9. Fur die Tunikaten ist noch nicht entschieden, ob die Regenerate von mesenchymalen Zellen, speziell von den sog. Tropfenzellen (Spek) aufgebaut werden. 10. Bei den hoher differenzierten Tiergruppen der Arthropoden, Mollusken und Echinodermen ist uber die Herkunft des regenerativen Zellmaterials bisher nur wenig bekannt geworden. Die gute Regenerationsfahigkeit der Asteroiden, Ophiuriden und Holothurien unter den Echinodermen lasst vermuten, dass in diesen Organismen uberall Zellreserven zur Verfugung stehen. Summary. 1. The origin of regenerative material has been studied in sponges, coelenterates, turbellarians, nemerteans, polychaetes, oligochaetes, sipunculids, polyzoa and tunicates, and in a few instances also in arthropods, molluscs and echinoderms. 2. In most cases the healing of a wound is accomplished by the active migration of epidermal cells, often aided by mesenchyme cells moving up from beneath. 3. Of the three germ layers, the endoderm is the most independent. The gut is almost always regenerated from its stump, probably with the help of basal cells. When there is no stump, the formation of the gut may be sometimes accomplished by mesenchyme. 4. The ectoderm, which is the most differentiated germ layer, is assisted in regeneration by totipotent cells, which to a great extent render the epidermis embryonic. 5. The mesoderm is the least differentiated germ layer and in many cases it furnishes totipotent, or dedifferentiated, cells which in certain cases can regenerate all organs. 6. The totipotent cells take the form either of neoblasts or of basal cells, and perhaps also of peritoneal cells. All these types of regenerative cells may be called blastocyts. 7. Sponges possess many sorts of cells, which, when artificially separated from one another, can reconstitute the organs, after they have undergone partial dedifferentiation. In this case the archaeocytes are the totipotent cells. 8. When there is no mesoderm, as in the coelenterates, the so-called interstitial cells lie in the ectoderm, but can also migrate into the endoderm. 9. In tunicates it has not yet been decided whether or not regeneration is accomplished by mesenchyme cells, and particularly by the so-called “drop-cells”. 10. Little is known concerning the cellular basis of regeneration in the more highly differentiated groups of arthropods, molluscs and echinoderms.

Disease relationships in grafted plants and chimaeras

Abstract: Summary Disease relationships in grafted plants and chimaeras are shown to have both theoretical and practical significance. Grafting experiments have been employed as a means of investigating the nature of resistance and susceptibility to diseases caused by pathogenic fungi and bacteria. The effects of grafting may be direct, owing to transmission through the graft union of the substance or substances actually responsible for the reaction concerned, or indirect, due to a change in the normal response to environmental conditions. Negative results, while necessarily inconclusive, indicate that resistance and susceptibility are either genotypic properties of the protoplasm, or else are due to some factor that is not, as such, transmissible. Inoculation experiments have also been used in the interpretation of graft hybrids and chimaeras. In the case of the artificially induced Solanum chimaeras, experiments with Septoria lycopersici have shown that the two components retain their characteristic reaction to infection unaltered. Unless this assumption can be made in other forms, whose mode of origin is unknown, it becomes impossible to distinguish the two components, as such, from the modified tissues of a true graft hybrid. Results with the Crataegomespili and Pirocydoniae are not altogether consistent with the periclinal chimaera theory. Examples are given of the practical importance of grafting in the prevention and control of disease and mechanical injury in fruit trees and other ornamental trees and shrubs. Choice of suitable stocks may entirely prevent leaf scorch and other physiological disorders, and a large body of information has accumulated concerning the influence of root-stock on quality and storage life of the fruit. The importance of incompatibility between stock and scion is discussed, and examples are quoted in which grafting has led to the transmission of an unsuspected virus disease. Improper fitting and tying of the graft union is liable to result in the production of wound overgrowths, and also increases the danger of external infection.

The significance of the chlorides in tissues and animals

Abstract: Summary 1. Chlorine is an important component of an adult animal organism as a whole, since its depletion quickly results in serious consequences. 2. Chloride occurs in large and characteristic amounts in all tissues and fluids. Although a constant net composition is maintained, this chloride is not fixed, but an extensive movement occurs daily between different systems of the body. No conclusive demonstration of large chloride reserves has as yet been made. 3. A study of teleost eggs showed that the total base concentration remained constant, that during development the chloride concentration was reduced, and that new bicarbonate, phosphate and protein anions compensated for the chloride lost. Growth proceeded through changes in anions rather than changes in cations. Chloride reduction is a characteristic of all embryonic growth. 4. That chloride reduction accompanies specialisation is shown in embryonic development. Also the chloride concentration of adult tissues and fluids is inversely proportional to their degree of specialisation. 5. The loss of chloride with growth cannot be explained by theories of membrane equilibria. The energy necessary for the excretion of chloride is derived from metabolic processes involving bicarbonate and phosphate anions. Chloride ions do not participate in oxidative reactions but behave as relatively inert complements to other anions. 6. Because chloride is so easily determined, and since its movement attends changes in the concentration of other anions, and since low chloride is a sign of high specialisation, its concentration in tissues and fluids is useful as an initial indicator of the electrolyte make-up or an electrolyte change in a system.

Physico‐mathematical methods in biological sciences

Abstract: Summary 1. The fundamental method of exact physico-mathematical sciences, that of abstraction and of a systematic study of abstract, idealised cases, is outlined and the timeliness of its application to biology indicated. 2. This method is applicable to the study of general biology. The most general property of all cells being metabolism, the mathematical study of metabolising systems in general is indicated. First it is shown that regardless of the special character of metabolic reactions in and around any metabolising system, the concentrations of the various substances involved in metabolism is not uniform, the non-uniformities being determined by the rates of reactions, size and shape of the system, etc. Making use of the general physical laws connecting the concentration of a dissolved substance with the osmotic pressure, the conclusion is reached that in and around any metabolising system the distribution of osmotic pressure is not uniform. Applying next a fundamental theorem of mechanics, we find that therefore any metabolising system is the seat of mechanical forces, the distribution of which is determined by the rate and type of reactions and other factors. A further mathematical study of the effects of non-uniformities of concentration shows also that the osmotic pressure is not the only factor that produces mechanical forces. Inter-molecular attractions and repulsions also result, in cases of non-uniform concentration, in mechanical forces acting on each element of volume of the system. A closer consideration of the system of forces thus produced by metabolism shows that, for substances produced in the cell and diffusing outwards, these forces are generally also directed outwards. One of their effects is the tendency to expand the system, and to contribute to its growth. For substances diffusing into the cell and consumed there, the forces have in general the opposite direction and inhibit the growth of the system. A detailed mathematical investigation of the other effects of those forces shows that, for the case of produced substances, those forces cause a spontaneous division of the system when the latter exceeds a critical size. Calculations of this size gives values identical with the average size of actual cells. The forces due to consumed substances inhibit spontaneous division. In a system which, like ah actual cell, produces and consumes a great number of substances, the effect will depend on which type of forces prevail. Calculations show that forces produced by reactions connected with cell respiration considerably exceed the forces due to all other reactions. In the first approximation therefore only respiratory reactions may be considered. Mathematical analysis shows that when oxydation of sugar is complete and no appreciable amount of lactic acid is formed, the forces inhibiting growth and division prevail. When glycolysis is strong, the forces which produce division and accelerate growth prevail. This is pointed out to be in agreement with O. Warburg's findings that abnormally growing and dividing tumor cells have an abnormally high glycolytic coefficient. A further study of other possible effects of the forces produced by metabolism shows that they also will in general affect the permeability of the cell. Since the forces exist only as long as the cell metabolises, the death of the cell must result in sudden change of permeability, as is actually the case. The study of still more complex cases shows that the cell may possess two configurations of equilibrium. One is characterised by relatively low permeability and low glycolysis, hence by low rate of growth and multiplication. The other is characterised by a higher permeability and high glycolysis, hence rapid growth and multiplication. The cell, in such a case, can be brought irreversibly from the first configuration into the second, by temporary asphyxiation. This again is in agreement with Warburg's experiments on production of tumor-like growth by asphyxiation. 3. The non-uniformities of concentrations, and therefore the forces, are present not only within the cell, but also outside it. This results in forces of repulsion and attraction between cells. Cells in which the dividing forces prevail usually repel each other. Cells in which the inhibiting forces prevail, attract. The mathematical theory of the configurations assumed by cellular aggregates under the influence of such forces indicates a way to a physico-mathematical theory of organic forms of metazoans. 4. A physico-mathematical theory of nerve excitation and nerve conduction accounts for a number of empirical data. The generalisation of the ionic theory of excitation to the case of two types of ions, one exciting, the other inhibiting, gives a natural explanation for the excitation at the anode on opening a constant current, for the non-excitability by slowly rising currents, and for various electrotonic phenomena. A formula is derived for the velocity of nervous conduction, which is verified by experimental data. 5. The generalisation of the above results and their application to the central nervous system opens the way to a physico-mathematical theory of brain activity.