INTERNAL SECRETION OF TESTICLE 125 



We have not personally investigated the question whether 

 well developed interstitial cells are temporarily present in the 

 guinea pig and the rabbit during intrauterine life. 



The development of the interstitial tissue has also been 

 studied in man. We shall record here the results of Kasai 

 (1908), in whose paper the older literature on this question is 

 to be found. Kasai examined testicles of different ages, the 

 youngest being in the fourth month of intrauterine life, the 

 oldest being 84 years of age. In accordance with other authors 

 Kasai stated that in the testicle of a human embryo of four 

 months (Fig. 54a) the interstitial cells are present in a relatively 

 great quantity; they occupy the greater part of the testicle; the 

 cellular masses are w^ell vascularized. In the seventh and in the 

 following months of intrauterine life the relative quantity of 

 the interstitial tissue diminishes, whereas the space occupied 

 by the seminiferous tubules increases. In the new-born indi- 

 vidual one finds fewer interstitial cells than in the embryo. 

 According to Kasai this does not change till the age of 14. 

 In most cases examined by Kasai there was a remarkable 

 increase of interstitial cells at the time of puberty. After 

 puberty Kasai records a decrease of interstitial cells. They 

 are, however, always present in the testicle of the adult man, 

 but sometimes they are not very numerous. It seems that the 

 decrease after puberty is a relative one only, caused by the 

 enlargement of the seminiferous tubules and distribution of 

 the interstitial cells in a large space. It must be mentioned, 

 that the statements of the different authors do not agree 

 with one another in regard to the quantity of interstitial cells 

 in the testicle of the adult man. But there can be no doubt 

 that the interstitial cells are always present in the normal 

 testicle of the adult man. In old age the interstitial tissue 

 increases relatively, as the space occupied by the seminiferous 

 tubules undergoing degeneration is diminished. It may be that 

 even the absolute quantity of the interstitial cells is increased 

 in old age [Goddard, 1920; a man of 78). 



The condition of the interstitial cells at different ages is of a 

 still greater interest for us. In the foetus of four months they 

 generally contained protoplasm which stained well; the 

 nucleus was big and spherical. In the following months the 

 size of the cells and of the nucleus was diminished and the proto- 

 plasm less well stained. At the time of puberty when, as 



