MALE OBGANS OF REPRODUCTION 489 



cells laden with lipoid debris are abundant. Their presence, however, is 

 transient, and their abundance reciprocal to the abundance of degenerat- 

 ing follicles. This observation, reasoning by analogy, would explain their 

 abundance in the testes of cryptorchid horses, mules, and in the third 

 abdominal testicle ; for here also degenerative processes are going on among 

 the sex cells. Testicles of cryptorchid horses and mules are characterized 

 by an unusual abundance of interstitial cells, and degeneration of sex cells. 

 These animals experience heat, but are infertile; this was true also of the 

 stallion from whom two testicles had been removed and in whom subse- 

 quently the third abdominal testicle was discovered. These observations 



ABC D 



FIG. 434. INTERSTITIAL CELLS FROM THE HUMAN TESTIS. 



A, B, and C, from a twenty-five year old man; A shows the idiosome, bacillary 

 centrosomes, lipoid granules and crystalloids; B, with two nuclei; C, with four 

 nuclei (probably the result of amitotic division) and eight centrosomes. D, from 

 a 41-year-old man, showing large and small crystalloids. Highly magnified. (Wini- 

 warter, Anat. Anz., 41, 11, 1912.) 



would seem to indicate that the sexual instinct depends upon an internal 

 secretion on the part of the interstitial cells. The two results can be har- 

 monized on this basis: The internal secretion may actually be formed by 

 the cells of the seminiferous tubules; when these degenerate the products 

 are removed by the interstitial cells; since even in healthy testes there is 

 some degeneration of sex cells, all testes contain a few interstitial cells; 

 these are more abundant at puberty ; the secretory products of degenerating 

 sex cells are included among the debris removed by the interstitial cells 

 from which they may be passed into the capillaries of the testicular stroma. 

 The suggestion that t\ie interstitial cells are in some way connected 

 with secondary sex characters seems disproved by various castration experi- 

 ments. For example, the spayed hen takes on male secondary sexual charac- 

 ters; if these were dependent exclusively upon the interstitial cells of the 

 testis, they could not appear in the absence of both ovaries and testes. 



