INTERNAL SECRETION OF TESTICLE 191 



castration may be observed. As Lauche points out, the 

 hypertrophy of the testicular fragment in the frog is caused 

 especially by a proHferation of the generative cells within the 

 seminiferous tubules. He concludes from his experiments 

 that this hypertrophy of the generative elements is to be con- 

 sidered as compensatory in regard to the endocrine function of 

 the testicle. But I think that the great difference in the be- 

 haviour of the remaining testicle, or of the testicular fragment 

 in mammals and in the frog, is sufficient to show that the factor 

 here involved is not simply the need of hormones, but something 

 else which is not yet known to us ; it seems very hkely that a 

 variety of factors come into play. 



Patzelt (1923) has observed a frog with testicular atrophy and 

 far-going degenerative changes in the seminiferous tubules. 

 The interstitial cells were well developed and likewise the sex 

 characters such as the pads and the vasa deferentia with their 

 enlargements. The fatty bodies were abnormally voluminous. 



4. Birds. 



For the purpose of a comparative physiological study of 

 the problem before us, investigations on birds should be of 

 special interest, since in this class the dependence of the sexual 

 characters upon the sexual glands is particularly striking. 

 There is, moreover, in many species of birds a cyclic change in 

 the appearance of the external sexual characters. Those 

 who have described the histology of the testicle in birds do 

 not agree upon the question as to the quantity in which 

 interstitial cells are present, or indeed as to whether they occur 

 at all. They disagree also in regard to the data concerning 

 time relations. Detailed investigations on all these questions 

 have been made in the last few years by Boring and Pearl, by 

 Pezard, Morgan, Nonidez, Massagha, Punnett and Pease, 

 and still more recently by Courrier and Benoit in Bouin's 

 laboratory. 



One of the first studies on the interstitial cells in the testicle 

 of the cock was made by des Cilleuls (1912). He found the 

 interstitial tissue in the first weeks to be not very well de- 

 veloped; this is the time when the sexual characters which 

 depend upon the sexual glands have not yet manifested them- 

 selves. Des Cilleuls reports that at about the forty-fifth day 

 the connective tissue cells begin en juasse to transform 



