SEX BIOLOGY AND PSYCHOLOGY 145 



would appear in such cases that the similarity of male 

 and female internal secretion is so great that quite 

 slight changes in nervous or metabolic activity can 

 cause the nervous centres for the opposite sex's mode 

 of behaviour to become activated. 



In human beings we are confronted with various 

 grades of sexual organization and behaviour besides 

 the typically feminine and the typically masculine. 

 In the first place, it is matter of common knowledge 

 that many women, who so far as their physical re- 

 productive capacity goes are perfectly normal, show 

 various mental traits which are more characteristic 

 of men, and vice versa. What is more, the ' mas- 

 culinoid ' woman (to use the current jargon) tends 

 physically also to be less feminine, to have the feminine 

 secondary sexual characteristics in stature, form of 

 skeleton, distribution of fat, breasts, etc., less strongly 

 developed than normal, while the ' feminoid ' man 

 shows the reverse tendency (Blair Bell, '16). 



In trying to analyse these facts further, we are 

 brought up against new depths of complication. It 

 is becoming ever clearer that the gonads do not operate 

 as independent organs, but in conjunction with the 

 whole of the rest of the endocrine system — thyroid, 

 pituitary, adrenal, and the rest. In the first place, 

 it seems to be established that the reproductive organs 

 must be in some way activated by other ductless glands 

 before they become normal, just as they in their turn 

 must activate the sexual centres in the brain. This 



