744 Comparative Animal Physiology 



iferous epithelial tissue become transformed to produce a glandular body, 

 and this transformation is temporally associated with the differentiation of 

 the characteristic seasonal secondary sexual adornments in the male. De- 

 struction of this glandular tissue is the equivalent of total castration in pre- 

 venting development of these characters. In the stickleback, Gasterosteus, 

 there is very close correlation between the annual cycle of differentiation of 

 interstitial glandular cells and the cycle of secondary sex characters and be- 

 havior such as skin-coloration, secretion of nest-building mucus, and mating 

 behavior. The latter characteristics in this species, on the other hand, show 

 no relationship to amount of spermatogenic activity. That the seminal epithe- 

 lium is not a significant source of androgen has also been demonstrated by 

 removal of the greater part of the testes of cocks and assay of these organs 

 after regeneration. The regenerated organs are principally seminal epithelial 

 tissue with a great paucity of interstitial tissue, and, correspondingly, there is 

 evidence of only little androgen production by such organs. 



These and numerous other experiments indicate that the interstitial gland 

 ular cells are the points of origin of testicular androgens. 



Androgens are also produced by organs other than the testes. Male acces- 

 sory reproductive structures have been maintained in full functional activity 

 in castrated specimens by grafted ovarian tissue. Among fowl, the combs 

 of both the cock and the hen are stimulated by androgens. The ovaries of 

 the hen normally produce enough androgen to maintain a certain degree of 

 development of the comb; after ovariectomy there is atrophy of the comb. 

 The seasonal yellowing of the bills of both male and female starlings and 

 blackening of the bills of male and female English sparrows are responses 

 to androgens, estrogens being ineffective in this respect. Black-crowned night 

 herons show, during the breeding season, certain changes in plumage colora- 

 tion common to both sexes, an effect due to androgens. Many observations 

 such as the foregoing establish decisively the ovaries as a site of androgen 

 production. 



Another source of androgens is the adrenal gland. Implantation of adrenal 

 tissue in young cocks results in precocious development of male sex char- 

 acters and behavior. Castration of young rats does not result in atrophy of 

 accessory genital structures for many days unless there is simultaneously 

 complete adrenalectomy. Androgens are still excreted in the urine of ani- 

 mals after castration. Extracts of adrenal tissue have been found to yield the 

 androgens adrenosterone and desoxycorticosterone, the latter ha\'ing an ac- 

 tivity about the equivalent of that of androsterone, and the former having 

 activity of about one fifth of this value. 



There is little evidence of any significant storage of androgens in the body. 

 They are usually rapidly destroyed and therefore must be constantly pro- 

 duced if their influence is to be maintained. Certain poeciliid fishes^ ^^ can 

 be treated with androgens for only a few hours but the activity of the andro- 

 gens continues for many days. This observation appears to indicate either an 

 actual or an effective storage within the body. The pigmented fat-body of 

 the hibernating woodchuck, the so-called hibernating gland, has a remark- 

 ably high androgen content. The androgens are inactivated principally in the 

 liver. The androgenic activity of blood leaving the liver is much less than 

 that of blood entering this organ. Products of the inactivation arc both in- 



