THE BRAIN. 



513 



dulla may be regarded in some sense as the oldest (phylogeneti- 

 cally) part of the brain. In it are lodged those cells (centers) 

 which are required for th§ maintenance of the functions essen- 

 tial to somatic life. This may serve to explain how it is that 

 so many centers are there crowded together. It is remarkable 

 that so small a part of the brain should preside over many im- 

 portant functions ; but the principle of concentration with pro- 

 gressive development, and the law of habit making automatism 

 prominent, throw some light upon these facts, and especially 

 the one otherwise not easy to understand, that so much impor- 

 tant work should be done by relatively so few cells. Possibly, 

 however, if localization is established as fully as it may eventu- 

 ally be, this also will not be so astonishing. 



The law of habit has, in connection with our psychic life 

 and that of other mammals, some of its most striking develop- 

 ments. This has long been recognized, though that the same 

 law is of universal application to the functions of the body has 

 as yet received but the scantiest acknowledgment. 



We shall not dwell upon the subject beyond stating that in 

 our opinion the psychic life of animals can be but indifferently 

 understood unless this great factor is taken into the account ; 

 and when it is, much that is apparently quite inexplicable be- 

 comes plain. That anything that has , happened once any- 

 where in the vital economy is liable to repetition under a 



Fis. 369. 



Fig. 370. 



Fig. 369. — Brain of cat, seen from above (after Tiederaann). 

 Fig. 370.— Brain of dog, seen from above (after Tiedemann). 



slighter stimulus, is a law of the utmost importance in physiol- 

 ogy, psychology, and pathology. The practical importance of 

 this, especially to the young animal, is of the highest kind. 

 Synoptical. — There is as yet no systematized clear physiology 



33 



