334 THE PHYSIOLOGY OF REPRODUCTION 



injections were discontinued, the combs and wattles underwent 

 shrinkage and eventually became reduced almost to their original 

 condition. Geoffrey Smith, 1 however, on repeating the experiments, 

 obtained negative results, and is of opinion that the effects obtained 

 by Walker were really those of normal periodic growth. 



The effects of castration in the cock are thus summed up by 

 Morgan 2 who bases his description mainly upon the results obtained 

 by Goodale 3 : "The feathers are little changed; some of them, the 

 hackles especially, become longer. The lowermost tier of wing 

 coverts are elongated as compared with those of the cock. The 

 spurs are practically the same in the capon and cock. The capon is 

 disinclined to give voice, but at times he crows. The moulting is 

 not affected. The size of the capon is larger. He pays little 

 attention to the hens. He is not pugnacious, and if attacked will 

 not often fight. As a rule, he does not pursue the hens, but if a hen 

 squats down as the capon approaches he will mount and go through 

 the characteristic mating reaction. The comb is extremely small, 

 much smaller than that of the female of the same race ; it is infantile 

 rather than feminine." 



Pezard's results 4 are similar. He found castration inhibited the 

 growth of the erectile organs (comb, wattles, etc.), the capacity to 

 crow, and the fighting instincts, etc. The spurs and general plumage 

 were not affected. Castration in pheasants led to practically identical 

 results. In a general way castration in the male and ovariotomy in 

 the female produced a neutral type identical in each case. Injection 

 of interstitial testicular extract prepared by aqueous maceration of 

 gland of pig caused the comb, etc., to grow completely, but with 

 the cessation of the injections regression took place. By grafting 

 testicular tissue on to a castrated hen rapid growth of the comb could 

 be induced. Injections into castrated males caused similar results, 

 the lighting instinct being regained. 



The question as to the precise elements responsible for the 

 production of the internal testicular secretion is discussed by Morgan 

 and by Pezard. The former investigator was the first to show that in 

 Sebrights and some other varieties of poultry in which the cocks are 

 often " hen-feathered " castration resulted in the development of male 



1 Smith, " Studies on the Experimental Analysis of Sex," Part 5, Quar. Jour. 

 Micr. Science, vol. Ivi., 1911. 



2 Morgan, The Genetic and Operative Evidence relating to Secondary Se.vual 

 Characters, Carnegie Inst. (Washington) Pub. No. 285, 1919. 



3 Goodale, Gonadectomi/, Carnegie Inst. (Washington) Pub. No. 243, 1916. 



4 P6zard, "Le Conditionnement Physiologique des Caracteres Sexuels 

 Secondaires chez les Oiseaux," Thesis, University of Paris, 1918. See also 

 Comptes Rend, de I'Acad. Sci., 1911, 1917, 1918, 1919, and 1920. Pezard states 

 (1919) that an exclusively meat diet with cocks leads to genital atrophy and 

 castration results. For the "Numerical Law of Regression of Certain Secondary 

 Sex Characters," see Jour. Gen. Phys., vol. iii., 1921. 



