638 Growth of Deer Antlers 



lature of the blood vessels of the antlers inducing a nutritional disturbance, 

 so that the antlers die and are eventually cast off. In a second article Olt"* 

 concludes further that there is a seasonal inhibition of antler growth by the 

 testes, expressed by the withering of the velvet and subsetjuent death of the 

 antlers. The present observations on the annual cycle of gonads and seminal 

 vesicles indicate that the basic assumption of Olt is false; contrary to his belief, 

 the present evidence supports the conclusion that the internal secretion of 

 the testes, which is responsible for the changes in the male accessories, in- 

 creases and declines annually in a time sequence coinciding with the rise and 

 fall of spermatogenic activity. 



The present writer would interpret the annual sequence of events in the 

 normal antler-gonad cycle, viewed in the light of the results obtained by cas- 

 tration, as demonstrating that nongonadal factors are responsible for the ini- 

 tiation of antler growth in adult deer, but that full maturation of the antlers 

 in all species of deer depends to some degree on the presence of intact gonads. 

 This conditioning by the testes is greater in the Virginia deer and roebuck, 

 however, than in the reindeer. Nevertheless, in the latter, contrary to the 

 conclusion reached by Tandler and Grosz, an appreciable testicular effect is 

 actually present, judged by observations made following castration (increased 

 size, failure to harden completely, longer retention of velvet). In female deer, 

 on the contrary, judging from the fragmentary observations of Tandler and 

 Grosz, whether the female possesses antlers (reindeer) or not, gonadectomy 

 produces no apparent change in regard to antler formation, and hence in the 

 female the antlers or their rudiments are possibly unconditioned. 



From what has been observed in normal as well as castrate deer, it ap- 

 pears that the antler cycle must be regulated by both nongonadal and gonadal 

 factors. In the normal cycle of the white-tailed deer the nongonadal factor 

 obviously initiates antler growth before the testes have revived from their 

 involution of the previous winter, while in castrate deer this factor must be 

 responsible for the continued formation of antler tissue. The gonadal factor, 

 on the contrary, apparently does not begin to come into play vmtil six to eight 

 weeks after antler growth has been initiated. This factor evidently exercises 

 normally a role in the internal reconstruction and hardening of the July and 

 August antlers by the laying down of the compact or cortical bone which re- 

 places much of the initial spongy bone. Contrariwise, upon removal of the 

 gonadal influence by castration, the capacity to form compact bone is abolished 

 and shedding of the velvet never occurs. 



Whether the shedding of the velvet in the normal animal is directly con- 

 trolled by testicular hormone is more difficult to answer. Olt"' regards the 

 testicles as being directly responsible, basing his judgment upon the retention 

 of the velvet after castration, as well as on the occurrence, during the normal 

 shedding of the velvet, of a local "eosinophilia," the nature of which he does 

 not further elucidate. Caton'" and Macewen,""' on the contrary, regard local 



