AND PERSONALITY 



In young males castration prevents the development of 

 the typically male characteristics, namely, the larger brain, 

 more powerful muscles, larger blood volume, and the mental 

 characteristics of pugnacity. 



Therefore, we may presume that, just as the thyroid 

 hormone reaches the brain cells through the blood stream 

 and continues to influence the brain cells as long as the 

 thyroid gland functions normally, so the testicular hormone 

 reaches the brain cells through the blood stream and con- 

 tinues to influence the brain cells as long as the testes 

 function normally. 



If the billions of brain cells take up the sex hormones, 

 then every brain cell in the gray matter of a great bull is a 

 bull brain cell, and, correspondingly, in the white matter 

 there are bull action patterns. Thus may we account for 

 the characteristic behavior of bulls, boars, rams, and 

 stallions. When the male is castrated, no matter at what 

 age, a change occurs at once; the masculine characteristics, 

 physical, mental, and emotional, are lost. 



In the female there is an analogy between the mobiliza- 

 tion of the thyroid hormone in summer and winter and 

 the mobilization of the thyroid hormone in the cycles of mat- 

 ing, fertilization, pregnancy, and lactation. In the female 

 the neuroglandular mechanism governing reproduction is 

 stepped up by the thyroid hormone, which, in turn, in- 

 creases the metabolism of the body. 



As in the act of fight or flight, the organism is so inte- 

 grated that it is directed to the one purpose only, and 

 energy is withdrawn from such diverse mechanisms as 

 eating and digestion, until the fight or flight is concluded. 

 If, however, during the integration for reproduction the 

 more powerful integration of fear involving flight is started, 

 the integration of fear supersedes the integration for 

 reproduction. 



Thus, through selective breeding, on the one hand, and 

 desexing, on the other hand, man has "invented" domestic 



