Showing papers in "Philosophical Transactions of the Royal Society B in 1953"
TL;DR: In spite of variations in different species of animal a basic pattern can be discerned in the major arteries supplying the head, and it is suggested that this basic pattern is related to a primitive stapedial artery, and that the variations seen are due to modifications of the branches of this earlier vessel.
Abstract: This work records an investigation of the anatomy of the cranial blood supply in various species of mammal. The findings were based on a study of radiographs of specimens injected with a radioopaque mass and of casts of the vessels made by injection of neoprenc latex, and on dissections of injected preparations. A well-developed carotid rete was found to be present in the cat, sheep, goat, ox and pig, and a rudimentary form of this structure was found in the dog. In the cat the rete is situated extracranially, but in the other species it lies within the cranium in the cavernous sinus. There is no carotid rete in the rabbit or the rat. The carotid rete consists of a compact network of intertwined, freely anastomosing arteries, and is related to the branches of the trigeminal nerve. When the rete is situated intracranially there is a variable degree of communication across the mid-line with the rete of the opposite side. Whether situated intracranially or extracranially the rete lies within a venous lake. The presence of a well-developed carotid rete was associated with the non-persistence of, or a degenerating internal carotid artery. A thin fibrous cord was the only remnant of this artery found in the cat. In the goat, sheep and pig the internal carotid artery was absent proximal to the rete, but the large trunk which connected the rete with the circle of Willis was identified as representing the still persisting distal segment of this artery. In the ox (a young animal) a similar trunk connecting the rete with the circle of Willis formed the continuation of a still persisting but relatively narrow proximal segment of the internal carotid artery. The main vessels which may supply the carotid rete are the internal maxillary artery (usually via the ramus anastomoticus and the arteria anastomotica), the ascending pharyngeal artery, and the occipital artery. In the cat, sheep, goat and ox the chief vessel of supply is the internal maxillary artery, but in the pig it is the ascending pharyngeal artery. In the ox a substantial contribution is provided by the occipital artery. Both the ramus anastomoticus and the arteria anastomotica form connexions between the external and internal carotid systems and they join one another within the cavernous sinus. It is at his site that the intracranial carotid rete is developed, but the extracranial carotid rete, seen in the cat, is situated around the internal maxillary artery at the site of origin of the arteria anastomotica of the artiodactyls. The variations in the situation of the carotid rete in different species is along the line of the arteria anastomotica. It is suggested that the arteria anastomotica and the ramus anastomoticus respectively are homologous with the recurrent meningeal and the middle meningeal arteries of the rabbit and man. The arteries which supply the orbital and the ethmoidal regions are described and the homologies of the external ophthalmic artery are discussed. The great variability in the supply of these territories which was seen in the cat is thought to be associated with the presence of an extracranial carotid rete. In spite of variations in different species of animal a basic pattern can be discerned in the major arteries supplying the head. It is suggested that this basic pattern is related to a primitive stapedial artery, and that the variations seen are due to modifications of the branches of this earlier vessel. The circle of Willis was found to derive its blood supply from one or more of five sources: the internal carotid artery, the external carotid arterial system, the ascending pharyngeal artery, the vertebral artery (via the basilar artery) and the occipital artery. In the absence of an internal carotid artery the greatest contribution of blood passes to the circle of Willis through the carotid rete. An occipito-vertebral anastomosis seems to be of some importance in supplying the circle of Willis in the cat, pig, dog and rabbit. In the sheep, goat and ox the direction of the flow of blood in the basilar artery would appear to be away from and not towards the circle of Willis. In the pig the two anterior cerebral arteries anastomose in the mid-line and continue forward as a single vessel. The peculiar structure of the vessels which compose the carotid rete suggests that this compact network has a haemodynamic significance, and since the rete lies in the pathway of the major artery or arteries which supply the brain, its existence and possible influence should be borne in mind when problems of the cerebral circulation are considered in species in which this structure is present.
279 citations
TL;DR: It is argued that the branched cells of superficial strata represent effete melanocytes which, having discharged or otherwise lost their pigment, participate in the general outward movement of epidermal cells to be cast off at the skin surface.
Abstract: The branched cells of the superficial epidermis of mammals are divisible into two classes: those that occupy a position in the basal layer, and those that occur in more superficial layers. The first class comprises melanocytes visible in the living epidermis after its enzymatic fission from the corium; cells that blacken upon exposure to dihydroxyphenylalanine; cells that maintain quinoneimine dyes in the oxidized state in living skin; and clear cells. It is shown that these are merely different preparation images of the same cell, the melanocyte. The second class comprises cells that may be more or less specifically impregnated by metallic gold (Langerhans’ cells); cells stainable in living skin by quinone-imine dyes; and the ‘clear cells’ of superficial strata. It is shown that these, too, are so many preparation images of the same cell. It is argued that the branched cells of superficial strata, which have never been seen to divide, represent effete melanocytes which, having discharged or otherwise lost their pigment, participate in the general outward movement of epidermal cells to be cast off at the skin surface. This argument is supported by evidence of their similarity of structure, mode of branching, and relationship to neighbouring Malpighian cells; by their position in the epidermis; by their one-to-one correspondence of number; and by their coincidence of distribution.
140 citations
TL;DR: The findings are discussed with reference to the phylogenetic position of the genus, the probable role of the corpus luteum in pregnancy, and the significance of the results in relation to the conservation of existing wild elephant populations.
Abstract: Between December 1946 and December 1948, and January to March 1950, 150 elephants made available in the course of control work carried out by the Uganda Game Department were examined in greater or less detail according to circumstances. Eighty-one were females, of which sixty-seven were adult and thirty-one had an embryo in the uterus. All the dissections were carried out in the field, and the present account includes observations on the terrain, the food of the elephant, and other aspects of its ecology. Linear measurements of the carcasses and photographs of the molar teeth provide a guide to the age of specimens. Tusk growth is nearly similar in males and females until puberty, after which those of females generally cease to grow. The reproductive organs of the male are briefly described; those of the female are described in more detail, and discrepancies between existing accounts are considered in the light of this relatively extensive series of specimens. The mode of formation of the ovarial sac is unusual and is described from foetal, neonatal and adult specimens. There is marked hypertrophy of the interstitial tissue of the foetal gonads during the later stages of gestation. Breeding occurs at all times of year, but mating is possibly more frequent in the period December to March than at other times. Both sexes reach maturity at 8 to 12 years, and the female continues to breed until old age. Parturition is followed by a lactation anoestrus, after which the female undergoes a number of brief oestrous cycles until pregnancy ensues, lactation being continued throughout the subsequent gestation period. The interval between parturition and subsequent conception is normally of the same order of duration as the gestation period, and the normal calving interval appears to be rather less than four years. The ovarian cycle of the adult is characterized by the occurrence of multiple ovulation and the presence of many apparently active and histologically indistinguishable corpora lutea in both ovaries at all the stages of pregnancy which were encountered. It is probable that the corpus luteum of pregnancy develops from one of a number of follicles which ovulate under the same hormonal stimulus, and that it persists together with the accessory corpora lutea, some of which arise from follicles which ovulate and some from follicles which luteinize without ovulating. The corpora lutea are replaced about mid-pregnancy by a second set, which are formed by the luteinization of all the follicles with antra in both ovaries; some at least of the larger ones ovulate while many smaller ones do not. Follicular growth is suppressed in the later stages of pregnancy. The cycle of events bears some resemblance to that which occurs in the mare, and the comparison is discussed in detail. The ovarian periphery is characterized by numerous subsurface crypts and papillose projections which increase the area of the germinal epithelium. A description of the placenta and foetal membranes is in preparation, and preliminary study reveals a striking similarity to Hyrax , particularly in the quadri-lobulate allantois. The findings are discussed with reference to the phylogenetic position of the genus, the probable role of the corpus luteum in pregnancy, and the significance of the results in relation to the conservation of existing wild elephant populations.
123 citations
TL;DR: The sequence of drift deposits in an area between Leamington and Warwick has been established by mapping following an extensive program of auger drilling as mentioned in this paper, and a broad differentiation into Older Drift now capping the higher land and Newer Drift forming terraces along the upper Avon and Leam.
Abstract: The sequence of drift deposits in an area between Leamington and Warwick has been established by mapping following an extensive programme of auger drilling. There is a broad differentiation into Older Drift now capping the higher land and Newer Drift forming terraces along the upper Avon and Leam. The Older Drift includes relics of an ancient glaciation correlated with the First Welsh (Berrocian) or Mindel phase, and thick deposits belonging to the Great Eastern and Second Welsh (Catuvelaunian) or Riss episode. Details of the lithology, disposition and fauna of both the Older and Newer Drifts are given. Suggested correlations with neighbouring areas are made. The deposits of the Catuvelaunian episode are shown to be largely of clay or sand laid down in a lake whose extent is traced over a wide area of the Midlands. To it the name 'Lake Harrison' has been given. It is shown that it formed in a great pre-glacial valley of very gentle slope which ran from the region of Bredon Hill down towards Leicester, forming part of the Trent system, and which was impounded at each end by Welsh and north-eastern ice respectively. The lake was eventually overridden by the north-eastern ice which went as far south as Moreton-in-the-Marsh. Not until this ice retreated was the Avon river system developed. Associated with this great and very recent change of drainage pattern are others of less importance affecting the Tame and Soar basins.
118 citations
TL;DR: In this article, conodonts from the Llandeilo Limestone of South Wales, the Gelli-grin and Pen-y-garnedd Limestones of North Wales and the Aymestry Limstone of Staffordshire and Shropshire are described.
Abstract: Conodonts have been studied intensively for the last twenty years in the United States, but little attention has been paid to them in Britain. Digestion in acetic acid of some of the Lower Palaeozoic limestones of England and Wales has revealed the presence of at least four faunas. Conodonts from the Llandeilo Limestone of South Wales, the Gelli-grin and Pen-y-garnedd Limestones of North Wales and the Aymestry Limestone of Staffordshire and Shropshire are described. Four new genera, Balognathus, Holodontus, Icriodella and Sagittodontus, and a number of new species are described, and the conodont faunas are compared with those of a similar age from the United States. The value of the conodonts as index fossils is discussed.
108 citations