180 George B. Wislocki 



The following results were obtained : 



(1) Administration of testosterone to bucks which had never 

 had antlers, as a result of castration as fawns, induced antler 

 growth. 



(2) Administration of testosterone to bucks, which had been 

 castrated as yearlings or later and which bore permanent 

 antlers in the velvet, induced prompt shedding of the velvet 

 and subsequent shedding of the antlers (tendency to restore 

 the antler cycle). 



(3a) Administration of testosterone to normal bucks during 

 the period of antler growth induced shedding of the velvet. 



(3b) Its administration to normal bucks, subsequent to the 

 shedding of the velvet, inhibited the normal casting off of the 

 antlers and led to their retention for many months. 



(4) Administration of testosterone to ovariectomized 

 female deer caused the growth of well-developed antlers 

 (masculinization). 



The information gained about the seasonal changes in the 

 antlers and gonads of Virginia deer, combined with the 

 observed effects of castration and administration of testo- 

 sterone upon antler growth, led to the conclusion that the 

 phases of the seasonal antler cycle in Virginia deer are con- 

 trolled, on the one hand, by testosterone and, on the other 

 hand, by an "antler-growth stimulus", the latter probably of 

 anterior pituitary origin (Wislocki, Aub and Waldo, 1947; 

 Waldo and Wislocki, 1951). The effects of castration of adult 

 deer indicate the existence of a non-gonadal (hypophyseal) 

 factor responsible for antler growth and of a testicular factor 

 mainly responsible for the secondary hardening (internal 

 reorganization) of the antlers and loss of the velvet. Mating 

 takes place in the autumn, during a time when the testosterone 

 level is high and the antlers consist of bare, dead bone. 

 Afterwards the testosterone level declines, whereas the antler- 

 growth stimulus reappears. In the opinion of these investi- 

 gators (Waldo and Wislocki, 1951 ; Wislocki and Waldo, 1953), 

 based upon histological studies and observations on living 

 deer, shedding of the antlers is due to the reappearance of 



