MAMMALIAN TESTIS 



349 



u}) to 10 days of age. The lumenlcss tubules 

 contain two types of cells; one is a small 

 cell with one nucleolus; the other is a large 

 round cell containing two or three nucleoli. 

 Oval cells resembling Leydig cells are pres- 

 ent in the interstitium. At 19 to 24 days of 

 age, both testes are ecjual in weight. The 

 diameter of the tubules increases, a lumen is 

 present, and the tubular wall becomes dif- 

 ferentiated. Sertoli cells, spermatogonia, and 

 spermatocytes are evident, and the Leydig 

 cells are maturing. At 30 to 38 days of age, 

 the testis on the abnormal side is noticeably 

 smaller. The Leydig cells remain normal, 

 but the tubules are decreased in size. Be- 

 tween 45 and 47 days of age, spermatogene- 

 sis ceases and the tubules become atrophic. 

 Thick collagenous and elastic fibers are 

 found in the tubular wall. This disorder 

 seems to be an inherited defect with delayed 

 somatic manifestations. In some aspects, the 

 pathogenesis of this testicular disorder in 

 rats resembles that in Klinefelter's syn- 

 drome. 



Congenital spermatogenic hypoplasia oc- 

 curs in guinea pigs (Jakway and Young, 

 1958) . It ranges from germinal aplasia in 

 most of the seminiferous tubules to a condi- 

 tion in which the appearance of the tubules 

 is almost normal and the percentage of fer- 

 tile matings is only slightly reduced. When 

 sterility is present, the testes are smaller 

 than those of normal males. The hormonal 

 production, as reflected by the size of the 

 penis and seminal vesicles and by sexual 

 behavior, is normal. 



The mule has a J-shaped chromosome 

 which is contributed by the ass (Makino, 

 1955). Spermatogenesis in the mule does 

 not proceed beyond meiotic prophase, de- 

 generation occurring without formation of 

 the metaphase of the first division. Hence, 

 sperm cells will not form. The testes become 

 atroi^hic, and only a few^ spermatogonia re- 

 main. The Leydig cells are normal. 



Different types of hypogonadism, some of 

 which are inherited, are encountered in 

 bulls. Hypoplasia associated wuth urate 

 crystals in the semen probably results from 

 disintegration of the seminiferous epithelium 

 (Barron and Haq, 1948) . Idiopathic necrosis 

 of the tubule also may cause massive tes- 

 ticular calcification (Barker, 1956). Seven 

 cases of hypogonadism in Belgian bulls were 



reported as a form of congenital sterility 

 (Derivaux, Bienfait and Peers, 1955) ; pho- 

 tomicrographs of the testes in these cases 

 are similar to those of germinal aplasia in 

 the human. Testicular hypoplasia occurs 

 also in goats (Rollinson, 1950). 



Captive wild animals become sterile. 

 Bushman, the famous gorilla at the Chicago 

 Zoo, died at the age of approximately 22 

 years. Necropsy revealed neuropathy, car- 

 diopathy, hemosiderosis, and testicular scle- 

 rosis (Steiner, Rasmussen and Fisher, 1955). 

 No cells of the germinal epithelium were 

 present except occasional Sertoli cells. The 

 Leydig cells were normal. The testicular 

 atrophy of Bushman was similar to that of 

 Bobby, at the Berlin Zoo. Whether this de- 

 generative testicular lesion is caused by nu- 

 tritional deficiency or by the "stress" of 

 captivity is not known. 



XVI. Tumors of the Testis 



Testicular tumors are more common 

 among lower animals than in man (Innes, 

 1942). Spontaneously occurring Sertoli-cell 

 and Leydig-cell tumors of animals have 

 been studied more than seminomas pre- 

 sumably because of the greater endocrino- 

 logic interest attached to them. Huggins and 

 Pazos (1945) found 64 testicular tumors in 

 41 dogs; of these, 33 were Leydig-cell tu- 

 mors, 19 were seminomas, 9 were tubular 

 adenomas, and 3 were undifferentiated tu- 

 mors. Zuckerman and McKeown (1938) 

 found tumors in 35 of 243 dogs. A few of 

 these were Sertoli-cell tumors which were 

 associated with metaplasia of the prostate. 

 The life span of dogs varies from 8 to 15 

 years, and testicular tumors occur most fre- 

 quently at 7 years of age or older; in fact, 

 more than half of old dogs are found to have 

 such tumors (Scully and Coffin, 1952). The 

 most common tumor of the dog testis is a 

 Leydig-cell tumor. Five per cent of testicu- 

 lar tumors in dogs occur in undescended 

 testes. The neoplasms in cryptorchid testes 

 are usually Sertoli-cell tumors (Greulich 

 and Burford, 1936; Coffin, Munson and 

 Scully, 1952; Mulligan, 1944). 



The veterinary diagnosis (Blum, 1954) of 

 Sertoli-cell tumors is easily made, because 

 the dogs become feminized. For this reason, 

 the chief comjilaint of the owners is tlutt 

 normal male dogs, after a brief olfaciMi} 



