UBRARt 



NUMERICAL LAW OF REGRESSION OF CERTAIN 

 SECONDARY SEX CHARACTERS. 



By a. PEZARD. 



(From the Laboratory of General Biology of the College of France, Paris.) 



(Received for publication, October 22, 1920.) 



Postpuberal Castration. 



When a young cock is deprived of its genital glands (prepuberal 

 castration), it is found that the fleshy appendices which the head bears 

 (Fig. 1), i.e. the comb, barbules, and "oreillons," do not develop, or 

 that at least they follow the general law of growth of the body; more- 

 over, instead of acquiring the brilliant color which they have in the 

 normal adult cock, they remain pale and are covered with a fine, white 

 film due to epithelial desquamation (farinaceous appearance). ^ Since 

 these organs attain complete development when minute fragments of 

 testicle are inserted into the peritoneum of castrated fowl, or when 

 frequent injections of fresh testicular extract are given, we conclude 

 that they are related to an internal secretion produced by the male 

 genital glands. The question arises whether, once the comb and sim- 

 ilar organs have developed, the testicle is still necessary to assure their 

 maintenance. 4 



To determine this point we have castrated not only cockerels but 

 also adult cocks in full possession of their secondary sex characters. 

 Regression of the comb begins during the first days following operation 

 (Fig. 2). It is at first rapid but gradually diminishes until at the end 

 of a few weeks (5 to 12) the comb and similar organs reach a stable 

 condition in which they present the reduced size and farinaceous 

 aspect which characterize those of the castrated fowl of our first series. 

 This result demonstrates conclusively that the internal secretion of 



^ Pezard, A., Le conditionnement physiologique des caracteres sexuels secon- 

 daires chez les Oiseaux, Bull. biol. France et Belg., 1918, Hi, 1. 



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