Abstract
It occurred to us that the epidermis may be a tissue in which cell proliferation can be readily determined in a quantitative manner and that in this way a method might be worked out which would allow us to determine the effect of various conditions and substances on cell growth in general. We have therefore determined quantitatively the number of mitoses occurring in the epidermis of several species of animals and also the number of cells in the lower and upper layers of the squamous epithelium.
In this report we shall limit ourselves to a statement concerning the differences which we found in the mitotic proliferation of the epidermis of the guinea-pig in normal adult males on the one hand, and in females in various stages of sexual activity, on the other hand. We found that in adult female guinea pigs during the sexual cycle the mitotic cell proliferation is distinctly less active than in adult males otherwise living under the same conditions. It seems to be weakest at the time of oestrous and then rises very slowly towards the end of the cycle, without, however, reaching the average of the mitotic activity in the male even as late as 15 to 16 days following heat. In castrated female guinea pigs cell proliferation is low; we must assume that castration as such lowers the proliferative activity of the epidermis. On the other hand in pregnant guinea pigs it is definitely higher than in animals during the ordinary cycle, although it does not reach the average of adult male guinea pigs. This rise which takes place during pregnancy, to some extent is maintained during the period of nursing, although it is then not quite so high as during the former period.
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