294 BRAIN MECHANISMS AND LEARNING 



influence of oestronc but also elicited it in animals in which it had not 

 been present previously. The phenomenon is based on the antagonistic 

 action of two endocrine factors influencing the central nervous system. 

 The point of attack has not been quite clarified as yet, although we have 

 findings which suggest that certain subcortical systems play an important 

 role in this mechanism. Thus electrolytic lesions of amygdale or of the 

 area pyriformis and destruction of the septal region, will also abolish 

 maternal aggrcssivity in the lactating rat. Another noteworthy observa- 

 tion of ours is that after removal of the amygdale and the hippocampal 

 formation, the mouse-catching reaction of the cat is abolished for a 

 longer period, although the animal feeds well and the somato-motor 

 activities are satisfactory (Endroczi and Martin and Bata, 1958). These 

 investigations show that the above-mentioned archicortical structures not 

 onlv play a role in the organization of emotional behaviour but can also be 

 influenced by endocrine factors. 



CpdB 

 Xll XIII XIV XV k XVII 



I 



3 6 9 12 15 18 2f 24 27 30 33 36 39 42 A5 48 



\ I 1 1 i I 1 1 \ ■ ' ■ ■ ■ \ ' ■ 



Fig. I 



Papcrchroinatogram showing the difference of corticoid composition in the blood of the 

 adrenal vein in wild and domesticated rats. 



XII (Reichstein, S) : the main component in the wild rat. 



XIII and XIV : trace-components in wild and domesticated rats. 



Cpd B (Corticosterone) : the main components in the domesticated rat. 

 XVII: occasionally in the domesticated rat. 



As is generally known, the hypophysial-adrenocortical system is 

 important in keeping the endocrine system in a state of balance, to 

 changes in which — as has been pointed out in previous detailed studies — 

 the adrenal cortex will respond specifically by a change in the composition 

 of its secretion. Not many investigators pay attention to the variations in 

 the composition of the adrenocortical secretory products, which, accord- 

 ing to our findings, are not only important m the control of vegetative 

 and metabolic processes but also affect complex behavioural processes. 

 Analysis of adrenocortical function is complicated by the fact that not 

 only are there wide differences between species but that even within the 

 same species, wide individual qualitative and quantitative variations may 



