44 INTERNAL SECRETIONS 



entirely infantile. As regards sexual instincts Goodale and 

 Pezard agree that they are absent in the castrated hen. 



After partial resection of the ovary no castration results 

 occur if the remaining particle is not too small. It seems that 

 small particles of ovarian tissue left in the abdominal cavity 

 can hypertrophy and counteract the results of castration. 



Similar observations to those on domestic fowls were made 

 on other birds with very marked sexual differences. Pezard 

 (1911, 1918, ch. V.) castrated golden and silver pheasants at an 

 age at which male sexual characters were not yet developed. 



Fig. 31. — Normal Rouen duck. — From a coloured plate 

 of Goodale's. 



The growth of the spurs was not inhibited by castration; after 

 moulting the animals acquired a male plumage. The erectile 

 head apparel did not develop in the silver pheasant, and 

 sexual instincts were absent. Fitzsimons (1912) has described 

 an ostrich hen with male plumage after castration. 



Somewhat more complicated is the case of the duck, on which 

 Goodale (1910, 1916) made very extensive experiments. Female 

 Rouen ducks castrated when a few weeks old acquired a male 

 plumage (Figs. .31-33), and after moulting invariably assumed 

 a fresh male plumage. In one experiment the female duck 

 acquired even a voice that was more or less like that of a male. 

 On the other hand the drake keeps his male plumage after 



