MAMMALIAN TESTIS 



31i 



tility iiotential of cryptorchid human testis, 

 regardless of the cause, is seriously dam- 

 aged. Sterility is not an inevitable conse- 

 quence of bilateral cryptorchism in man as 

 indicated by the report of sperm in the ejac- 

 ulate of bilaterally cryptorchid men (Soh- 

 val, 1954). The work of Gross and Jewett 

 (1956) also indicates that cryptorchism does 

 not always produce irreversible damage be- 

 cause some patients do become fertile when 

 orchidopexy is carried out at puberty. 



The studies of Engberg (1949) and Ra- 

 boch and Zahof (1956) indicate that the 

 function of the Leydig cells of cryptorchid 

 testes also may be impaired. The former 

 found that bilaterally cryptorchid men ex- 

 creted reduced amounts of urinary androgen 

 and estrogen and had a lessened concentra- 

 tion of acid phosphatase (a secondary sex 

 characteristic) in the semen. The latter 

 two authors, contrary to previous reports, 

 noted a high incidence of regressive Leydig 

 cells. Also, severe androgenic insufficiency 

 occurs in bilateral cryptorchid men in mid- 

 dle and old age. The affect of cryptorchism 

 on hormonal function is best ascertained in 

 experimental animals and will be considered 

 shortly. 



Spontaneous cryptorchism is found in 

 many animals. Schultz < 1938 1 found that 5 

 per cent of the wild gibbons shot during the 

 Asiatic Primate Expedition of 1937 were 

 cryptorchid. Many veterinary reports show 

 cryptorchism in various farm animals and 

 pets. Cryptorchism also results from a de- 

 ficiency of biotin in the laboratory rat 

 (Manning, 1950). None of these reports 

 deals with functional aspects of retention. 



Experimental cryptorchism maintained 

 for 28 days in the rat is followed by re- 

 covery of spermatogenesis in 40 to 100 days 

 after restoration of the testes to the scro- 

 tum. With a proportionally longer sojourn 

 in the abdomen, fewer and fewer of the 

 tubules recover until finally tubular damage 

 is irreparable. Androgenic function is grad- 

 ually lost. Castration cells appear in the 

 pituitary in 75 days, the seminal vesicles 

 are reduced in size after 240 days, and the 

 prostate becomes atrophic in 400 days. This 

 sequence parallels the requirement for an- 

 drogen; the seminal vesicles need more an- 

 drogen (2.5 times) than does the prostate 

 for maintenance, and the prevention of cas- 



tration changes in the anterior pituitary re- 

 quires twice as much androgen as does 

 maintenance of the seminal vesicles (Nel- 

 son, 1937). These results were confirmed 

 by Moore (1942), who added that the 

 effects of cryptorchism on androgen produc- 

 tion are dependent on the age at which it is 

 induced. Old rats are less affected than 

 young animals. 



In the guinea pig, old experiments showed 

 that tubular degeneration occurs rapidly but 

 that secretion of androgen continues for 

 more than a year. Using the condition of the 

 accessory sex organs and sex behavior as 

 end points for the activity of male hormone, 

 Antliff and Young (1957) found no evidence 

 of diminished production of androgen in 

 animals made cryptorchid two days after 

 birth. 



In the boar, bull, and stallion secondary 

 sex characteristics can be maintained by 

 bilateral retained testes or by the testis 

 made unilaterally cryptorchid after re- 

 moval of the scrotal mate (Moore, 1944). 

 Schlotthauer and Bollman (1942) removed 

 one scrotal testis from an adult dog and 

 placed the other in the abdomen; the pros- 

 tate was maintained for two years. Hanes 

 and Hooker (1937) found that cryptorchid 

 testes in swine contained only half the nor- 

 mal amount of androgen. Kimeldorf (1948) 

 reported that cryptorchism in rabbits results 

 in a decrease of some 40 per cent in the total 

 urinary 17-ketosteroids, a change similar to 

 that after castration. He suggested that al- 

 tered metabolism of testicular hormone 

 caused by high temperatures may be re- 

 sponsible for this decrease. In general, then, 

 the cryptorchid testis is capable of produc- 

 ing androgen but, depending on species, 

 probably m amounts less than normal. The 

 longer the state of cryptorchism exists, 

 the more deficient is the capacity to secrete 

 androgens. 



IV. Breeding Patterns 



The breeding pattern of adult male mam- 

 mals may be divided into two major types 

 (Moore, 1937). The first type is that of the 

 seasonal breeder, including such animals as 

 the ground squirrel, weasel, stoat, ferret, 

 mole, hedgehog, and shrew (Asdell, 1946). 

 In these animals, there is a short period of 

 time, the duration of which varies in differ- 



