06 On the Sterilitji of the Tortoiseshell Tom Cat 



females all had kittens, before or afterwards, to other sires, so that it 

 seemed evident that the tortoiseshell tom was sterile. 



The external genitalia of the cat are perfectly normal: there is 

 a normal well developed penis, and both testes are descended into the 

 scrotal sac ; this latter point is important, for as will be shown later 

 failure of descent of the testes is almost invariably associated with 

 sterility. • 



In order therefore to endeavour to discover the reason of this 

 sterility, in March 1915 we decided to examine one of the testes 

 microscopically in the hope of finding whether at some stage of 

 spermatogenesis an abnormal division took place which prevented the 

 further development of the sperms, as is the case with some hybrids. 



Dr F. H. A. Marshall, to whose help we are greatly indebted, 

 undertook the removal of one testis. This seemed perfectly normal, 

 the only difterence being that when the testis was cut up preparatory 

 to placing it in preservative, no seminal fluid was exuded, as is usually 

 the case with the normal animal. Different portions of the organ were 

 preserved in strong Flemming, acetic sublimate, and Bouin's fluid, the 

 last giving by far the best results. . Sections of 5/x thickness were cut, 

 and then stained with iron haematoxylin. Upon examination it was 

 found that there was no trace of spermatogenesis, but there was a con- 

 siderable excess of interstitial tissue between the tubules. 



Before describing this in detail, perhaps it would be advisable to 

 give an account of the testis of a normal cat for the sake of comparison. 



The tubules are large and placed in fairly close proximity, the 

 spaces between them being filled with interstitial tissue. The individual 

 cells of this tissue are not easy to distinguish one from another, but the 

 nuclei are very distinct and numerous : also it is easy to distinguish what 

 appear to be two types of nuclei, one, which under a low power appears 

 almost black (PI. XX, Fig. 1, d.n.) when stained with iron haematoxylin; 

 the other much lighter showing a distinct nucleolus (Fig. 1, c.ii.). 

 Examination under a high power reveals the fact that the two kinds of 

 nuclei differ only in that one is more granular than the other; both 

 have the same kind of nucleolus. 



Scattered among the cytoplasm there are numerous black granules, 

 which Bouin and Ancel in a paper published in the Archives de Zoologie 

 experiiiientale et geiierale for 1903, 4 Serie, Tome 1, p. 437, entitled 

 " Recherches sur les cellules interstitielles du testicule de Mammiferes," 

 assert to be of secretory origin, and of a fatty nature (Fig. 1, d.g.). 

 Vacuolation can also be noted to a small extent. The tubules are 



