George B. Wislocki 645 



the skeletal tissues which give rise to the antlers, while the second consists of 

 gonaclotrophic hormone activating the testes. 



The hypophysial and gonadal influences, here described as initiating and 

 regulating antler growth, may not differ fundamentally from the hormonal 

 control of growth of ordinary skeletal parts, for recent investigations demon- 

 strate that androgens and estrogens, as the case may be, supplement hypo- 

 physial factors in the normal process of ossification and matiuation of the 

 growing skeleton (Silberberg and Silberberg^"-*'*^). 



Summary and Conclusions 



1. The Virginia deer exhibits seasonal changes in the size and histological 

 picture of the testes and seminal vesicles. Examination of the testes reveals 

 the presence of spermatozoa beginning in July, being maximal in October, 

 and diminishing in December and January. The seminal vesicles, inactive in 

 June and July, commence to grow in August, and reach a high degree of ac- 

 tivity by October. 



2. The antlers begin their annual renew^al at a time when the testes and 

 seminal vesicles are most inactive; they become hard and the velvet is shed 

 when the testes and seminal vesicles are rapidly enlarging, while the antlers 

 are lost when the reproductive organs have begun to decline. 



3. Following castration, as reported in the literature, the antlers of most 

 species of deer are retained permanently, continue to grow irregularly, and 

 never lose the velvet. 



4. Consideration of the normal seasonal cycle of antlers and gonads in the 

 Virginia deer, and the restdts of castration of adtdt deer, indicate that the 

 initiation of antler growth is independent of the testes. For various reasons 

 presented in the text the assumption is made that the hypophysis, activated 

 by light in the spring and early summer, is responsible for stimidating the 

 growth of the antlers (May), and for the subseqtient activation of the testes 

 (July). Subsequently the testicular hormone, either alone or more probably 

 interacting with the hypophysial antler-growth-stimulating factor, induces 

 the internal reconstruction of the antlers (August). The shedding of the velvet 

 occurs after the antlers have hardened (September), but the evidence available 

 at present is inconclusive as to whether the atrophy of the blood supply, re- 

 sponsible for this event, is directly under hormonal control. Normal with- 

 drawal of testicular hormone after the rutting season, or abnormally (following 

 castration), produces hyperemia and decalcification of the pedicles, resulting 

 in casting off of the antlers (January). The concept proposed here assumes 

 that antler giowth is primarily initiated and controlled by the hypophysis, 

 although the subsequent internal reconstruction and hardening of the antlers, 

 as well as their ultimate shedding, are regulated by the testes, either alone oi 

 in conjunction with the pituitary. 



5. The gonads and male accessories, under the influence of the pituitary, 



