I02 INTERNAL SECRETIONS 



irritability of the nervous centres involved in this mechanism 

 seems to be regulated by the hormones of the testicle. 



How much more complicated must be the physiological 

 mechanism underlying the psycho-sexual behaviour of the 

 mammal or man! One realises how manifold must be the 

 variations in psycho- sexual behaviour which have arisen on so 

 complex a physiological basis, especially when one takes into 

 consideration that the inter-play of irritation and inhibition 

 may be changed by variation in the activity of the hormone- 

 producing sexual gland. 



3. The Psycho-sexual Behaviour of Man. 



The observations which have been made on castrated men 

 leave no doubt that the internal secretion of the sex gland is 

 one of the physiological conditions of the characteristic psycho- 

 sexual behaviour in the human species. After seeing how 

 complicated the mechanism of the clasp reflex is, we come to 

 understand how hopeless it is at present to attempt to build 

 up a comprehensive account of human sexual behaviour on 

 purely physiological lines. What we know about these 

 physiological conditions is very little, and theories in this field 

 are usually elaborated rather on analogies than on real 

 knowledge of facts. 



It must not be forgotten also that the influence of external 

 factors on the sexual behaviour attains in man the highest 

 degree observed in the animal kingdom. There is in the 

 psycho-sexual behaviour of man almost unlimited variation. 

 Every epoch, every social class, every profession, and even 

 every individual has a characteristic sexuality very different 

 from that of others. The conditions determining the psycho- 

 sexual behaviour of man relate not only to a certain type of 

 structure of the nervous system and to the hormones of the sex 

 gland, but at the same time to the whole complex designated 

 under the terms "culture" or "civilisation." We must 

 admit that the psycho-sexual behaviour may be very 

 different even when the physiological basis is the same 

 (Lipschutz, 1922). It is absolutely necessary to emphasize 

 this, because it would be dangerous for human society 

 to overlook the external conditions on which sexuality in 

 man depends. This is true not only within the limits of 

 normal sexuality, but also for all the numerous pathological 



