SECONDARY SEXUAL CHARACTERS. 39 



as usual surrounded by denser fibrous tissue. At one pole of the 

 gland a system of ducts and acini lined by higher and larger 

 epithelium extended into the surrounding fat tissue. The lumen 

 of these ducts and acini was wider. Mitoses could not be seen 

 in the mammary gland. The mammary gland of the other side, 

 which was also surrounded by fat, was smaller, at least the 

 amount of gland tissue found on sections, which had been through 

 different parts of the piece, was less; but it still surpassed con- 

 siderably that found in normal animals. Furthermore, the acini 

 were composed of high cylindrical cells, surrounding a rather 

 large lumen. There were a few desquamated cells in the gland 

 lumina, the acini being arranged around the larger ducts. Here 

 and there mitoses were seen in the acini. The stroma between 

 the acini was loose in texture and contained a number of fibro- 

 blasts. 



Discussion.- The following are the chief points of interest in 

 these observations: 



i. We have in this case apparently to deal with an undescended 

 testicle in an adult guinea pig. Such testicles have been observed 

 in man and several species of animal, especially in the horse and 

 pig. This case is an example of the same condition in the rodentia. 

 Common to all cases which have been so far described is an imper- 

 fect development of the seminiferous tubules and a hypertrophy 

 or a hyperplasia of the interstitial cells of the testicle. As to the 

 literature concerning such cases we may refer especially to Bouin 

 and Ancel (i) Tandler and Grosz (2), and Whitehead (3). Both 

 of the features we mentioned are present in a marked degree in 

 our case. Spermatogonia are completely absent; the tubules 

 consist entirely of Sertoli cells. The retention of the testicle 

 acted in a way comparable to the ligation of the vas deferens 

 which brings about similar results which are, however, usually 

 not quite so far going. In addition, it is very probable that the 

 condition which prevented the normal descent of the testicle was 

 directly responsible for the lack of development of spermato- 

 gonia. As to the overdevelopment of the interstitial gland, in 

 those cases, we may conclude that it stands in some causal rela- 

 tion and is subsequent to the underdevelopment of the seminif- 

 erous tubules. In various other conditions in which atrophy 



