HORMONES AND REPRODUCTION 53 



by van Oordt and his associates in Utrecht. A re- 

 examination of conditions in the cock^^o has shown that 

 the interstitial cells are of two types; the lipoid cells 

 which store large quantities of fatty material and the 

 secretory cells which do not. It is concluded that the 

 lipoid cells can take no part in secretion, unless perhaps 

 they store the chemical reserves from which the hormone 

 is manufactured. 



The evidence regarding the secretory cells is circum- 

 stantial and may be stated as follows. When male 

 hormone is being secreted the comb and wattles on the 

 cock's head enlarge considerably so that their size can 

 be used as a quantitative indication of the amount of 

 hormone circulating in the body. An increase in size 

 occurs when normal animals reach maturity and when 

 birds are treated with a mixture of the pituitary hor- 

 mones, and it is always accompanied by an increase in 

 the number of the secretory cells. Thus the number 

 of these cells present at any time, like the size of the 

 comb and wattles, can be used as a quantitative estimate 

 of the amount of hormone present. 



However, even if the main site of male hormone 

 secretion is in the interstitial cells of the testis, the 

 production of this substance is also carried on elsewhere. 

 Even after the removal of the testes some hormone 

 continues to be formed, probably mainly in the adrenal 

 cortex. 63 



5. THE TESTIS HORMONES 



The most obvious function of the male, or androgenic, 

 hormones is their stimulation of the accessory sexual 

 organs and secondary sexual characters, and it is by 

 means of these reactions that they are commonly 

 assayed. The main methods used are the rat test and the 

 capon test. Castrated rats or castrated cocks are injected 

 with the test substance which can then be standardized 

 according to the degree of growth of the accessory sexual 



