We have measured the spatial density of cones and rods in eight whole-mounted human retinas, obtained from seven individuals between 27 and 44 years of age, and constructed maps of photoreceptor density and between-individual variability. The average human retina contains 4.6 million cones (4.08-5.29 million). Peak foveal cone density averages 199,000 cones/mm2 and is highly variable between individuals (100,000-324,000 cones/mm2). The point of highest density may be found in an area as large as 0.032 deg2. Cone density falls steeply with increasing eccentricity and is an order of magnitude lower 1 mm away from the foveal center. Superimposed on this gradient is a streak of high cone density along the horizontal meridian. At equivalent eccentricities, cone density is 40-45% higher in nasal compared to temporal retina and slightly higher in midperipheral inferior compared to superior retina. Cone density also increases slightly in far nasal retina. The average human retina contains 92 million rods (77.9-107.3 million). In the fovea, the average horizontal diameter of the rod-free zone is 0.350 mm (1.25 degrees). Foveal rod density increases most rapidly superiorly and least rapidly nasally. The highest rod densities are located along an elliptical ring at the eccentricity of the optic disk and extending into nasal retina with the point of highest density typically in superior retina (5/6 eyes). Rod densities decrease by 15-25% where the ring crosses the horizontal meridian. Rod density declines slowly from the rod ring to the far periphery and is highest in nasal and superior retina. Individual variability in photoreceptor density differs with retinal region and is similar for both cones and rods. Variability is highest near the fovea, reaches a minimum in the midperiphery, and then increases with eccentricity to the ora serrata. The total number of foveal cones is similar for eyes with widely varying peak cone density, consistent with the idea that the variability reflects differences in the lateral migration of photoreceptors during development. Two fellow eyes had cone and rod numbers within 8% and similar but not identical photoreceptor topography.

Human photoreceptor topography

Allometry and size in ontogeny and phylogeny.

T _ HE work reviewed in this paper is aimed at establishing connections between two fundamental aspects of living organisms, their metabolism and growth. What we call growth of even a simple organism is a tremendously complex phenomenon from the biochemical, physiological, cytological, and morphological viewpoints. There are, however, certain aspects that are amenable to quantitative analysis, and such an approach appears to lead to some insight into the connections between metabolism and growth, and to some answer to the seemingly trivial, but in fact hardly explored question, \"Why does an organism grow at all, and why, after a certain time, does its growth come to a stop?\

Quantitative Laws in Metabolism and Growth

We quantified the spatial distribution of presumed ganglion cells and displaced amacrine cells in unstained whole mounts of six young normal human retinas whose photoreceptor distributions had previously been characterized. Cells with large somata compared to their nuclei were considered ganglion cells; cells with small somata relative to their nuclei were considered displaced amacrine cells. Within the central area, ganglion cell densities reach 32,000-38,000 cells/mm2 in a horizontally oriented elliptical ring 0.4-2.0 mm from the foveal center. In peripheral retina, densities in nasal retina exceed those at corresponding eccentricities in temporal retina by more than 300%; superior exceeds inferior by 60%. Displaced amacrine cells represented 3% of the total cells in central retina and nearly 80% in the far periphery. A twofold range in the total number of ganglion cells (0.7 to 1.5 million) was largely explained by a similar range in ganglion cell density in different eyes. Cone and ganglion cell number were not correlated, and the overall cone:ganglion cell ratio ranged from 2.9 to 7.5 in different eyes. Peripheral cones and ganglion cells have different topographies, thus suggesting meridianal differences in convergence onto individual ganglion cells. Low convergence of foveal cones onto individual ganglion cells is an important mechanism for preserving high resolution at later stages of neural processing. Our improved estimates for the density of central ganglion cells allowed us to ask whether there are enough ganglion cells for each cone at the foveal center to have a direct line to the brain. Our calculations indicate that 1) there are so many ganglion cells relative to cones that a ratio of only one ganglion cell per foveal cone would require fibers of Henle radiating toward rather than away from the foveal center; and 2) like the macaque, the human retina may have enough ganglion cells to transmit the information afforded by closely spaced foveal cones to both ON- and OFF-channels. Comparison of ganglion cell topography with the visual field representation in V1 reveals similarities consistent with the idea that cortical magnification is proportional to ganglion cell density throughout the visual field.

Topography of ganglion cells in human retina.

On the basis of his extensive and elegant anatomical investigations on the visual cortex, Poliak (1932) suggested that a mathematical projection of the retina on the cerebral cortex must exist. Talbot & Marshall (1941) used physiological methods to map the central part of the visual field on to the posterolateral surface ofthe cortex in the monkey. They devised an index of cortical representation expressed as the increment of the angle, measured radially from the centre of gaze, which is represented on each millimetre of cortex. We have confirmed their observations and have extended the mapping to the buried visual cortex in the horizontal and vertical calcarine fissures. We have preferred to use the reciprocal of their index and to call it the cortical magnification, M. When this is measured along radii and at right angles to them, it provides the empirical quantitative relation which Polyak wanted. It also defines the shape and size of the visual receptive field. We have made such a surface, folded it and compared it with the calcarine cortex of the monkey. A preliminary account of this work has been published (Daniel & Whitteridge, 1959).

https://physoc.onlinelibrary.wiley.com/doi/pdf/10.1113/jphysiol.1961.sp006803

The representation of the visual field on the cerebral cortex in monkeys.

Visual Sensory Units and the Minimal Angle of Resolution

Visual Acuity within the Area Centralis and its Relation to Eye Movements and Fixation

FAINSCHMIDT, O. I. 1936. Ammonia formation in the brains of hibernating animals. Biochimiya, 1:450. Cited from Chem. Abst., 31:3116. FELIN, F. 1940. The seasonal fluctuation of benthic macrofauna and limnetic plankton in Searsville Lake; a contribution to the biology of fluctuating reservoirs. Thesis, Stanford University. FIELD, J., II; BELDING, H. S.; and MARTIN, A. W. 1939. An analysis of the relation between basal metabolism and summated tissue respiration in the rat. I. The post-pubertal albino rat. Jour. Cell. and Comp. Physiol., 14:143. FISKE, C. H., and SUBBAROW, Y. 1929. Phosphocreatine. Jour. Biol. Chem., 81: 629. Fox, H. M., and WINGFIELD, C. A. 1937. The activity and metabolism of poikilothermal animals in different latitudes. Proc. Zo6l. Soc. (London), Ser. A, Part III, p. 275. GRAY, J. 1928. Ciliary movement. Cambridge, England: Cambridge University Press. HEILBRUNN, L. V. 1937. An outline of general physiology. Philadelphia: Saunders. HOAGLAND, H. 1936. Some pacemaker aspects of rhythmic activity in the nervous system. Cold Spring Harbor Symp. Quant. Biol., 4:267. HUBBS, C. L., and BAILEY, B. M. 1940. A revision of the black basses (Micropterus and Huro). Misc. Pub. Mus. Zo6l. Univ. Mich., No. 48. KAHN, I. L., and CHEKOUN, L. 1935. Degagement d'ammoniaque par le cerveau suivant l'6tat d'excitation naturelle. Compt. rend. Acad. sci. Paris, 201:505. KERR, S. W. 1935. Studies on the phosphorous compounds of brain. I. Phosphocreatine. Jour. Biol. Chem., 11o:625. KREBS, H. A. 1935. Metabolism of amino acids. IV. The synthesis of glutamine from glutamic acid and ammonia and the enzymic hydrolysis of glutamine in animal tissues. Biochem. Jour., 29:1951. PAGE, I. H. 1937. Chemistry of the brain. Springfield: Thomas. PALLADIN, A. W., and RASHBA, E. I. Creatine contents of various parts of the brains of vertebrates. Ukrain. Biochem. Zhur., 7:85. Cited from Chem. Abst., 30:5276, 1936. PEMBREY, M. S. 1898. Chapter on \"Animal heat,\" in SCHXFER, E. A., Textbook of physiology, 1:785. Edinburgh.

Total and Tissue Respiration in Relation to Body Weight a Comparison of the Kelp Crab with Other Crustaceans and with Mammals

Visual perception and the retinal mosaic

1. The present paper is a study of the growth of a clam ( Siliqua patula ) under natural conditions and over a wide range of latitude.

2. Various constants derived from the growth data are compared for the different localities. For this species, over the range considered, growth in the southern localities as compared with the northern is initially more rapid but less sustained, leads to a smaller total length and is associated with a shorter life span.

3. Reasons are presented for considering the relative growth-rate as a particularly significant constant leading to more sound biological conclusions than the use of the absolute growth-rate.

4. On the basis of the relative growth-rate, current mathematical expressions for the course of growth are discussed and a formula used which emphasises Minot's conception of a growth-rate constantly declining with age.

This expression

L = Be - ce - ce - kt ,

in which L = length at time t , e = base of natural logarithms, and B , c and k are constants, is found to graduate the extensive data in clam growth with significant accuracy.

Published with the permission of the United States Commissioner of Fisheries.

Frank W. Weymouth

Papers

Visual Sensory Units and the Minimal Angle of Resolution

Visual Acuity within the Area Centralis and its Relation to Eye Movements and Fixation

Total and Tissue Respiration in Relation to Body Weight a Comparison of the Kelp Crab with Other Crustaceans and with Mammals

Visual perception and the retinal mosaic

Latitude and Relative Growth in the Razor Clam, Siliqua Patula