Histological Differentiation of the Retina and Electro-Retinographic Critical-Fusion-Frequency

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Abstract
In previous publications, the conclusion was formed with some reservations, that the state of the canine on the 20th day post patum is comparable with the state of the human retina during the 8th month of pregnancy. From these anatomical findings and the fact that in human neonates the CFF curve is completely comparable with the adult curve it is evident that for the study of the electro-physiological development of the growing retina, human neonates are not suitable. The same is true for the monkey (Cercopithecus Aethiops Sabaeus). Dogs are ideal for this purpose as the Retina is undifferentiated at birth and develops rapidly afterwards. We recorded CFF curves in dogs from immediately after birth till the 57th day of life. The chief results of these studies was that only CFF values (below 25-30/sec) in very young animals can be obtained if high light intensities are used. Subsequently, by the 19th-20th day, higher CFF values are seen in response to high light intensities. Later, higher values (70/sec) occur even at lower light intensities. A study of the histological structure of the retina in these stages taught us that the stages differ in terms of sensory cell differentiation, in the stage of low CFF values we found short rods and cones, often sparse in number; with higher CFF values we saw elongation of the rods cones and an increase in the number of sensory cells. After 57 days, when high CFF values occur even at low light intensities, the retinal histology is virtually identical with that in fully developed animals.