CHAPTER XXXI. 



THE BRAIN OF MAMMALS. 

 BY THEODOR MEYNERT, 



OF VIENNA. 



GENERAL ACCOUNT OF THE STRUCTURE OF THE BRAIN. 



IN the structure of the brain are united two principal features : 

 on the one hand there is everywhere considerable uniformity 

 in the elementary parts ; on the other hand there is the utmost 

 variety in their arrangement. It is because the significance of 

 the elements is determined only by the particular locality in 

 which they occur, that a purely histological description would 

 but slightly aid the comprehension of the subject, and it is 

 indispensable to take into account at the same time the proxi- 

 mate divisions of structure. Indeed, we must steadily keep in 

 view the position of all minute details with respect to the 

 larger masses. While we have in these considerations a justifi- 

 cation for wandering in the following pages beyond the bounds 

 of strictly histological fact, the compass of a manual permits 

 in this respect of nothing more than a suggestive brevity : the 

 more deeply inquiring student must be referred to the original 

 sources of information. While this more discursive treatment 

 of the morphological side allows of a more satisfactory arrange- 

 ment of the subject, the reader will himself be able to aid most 

 efficiently in making it clear, if he take with him as his guide 

 in these difficult matters three firm and unshaken physiological 

 principles- which appear to lie at the foundation of the archi- 

 tecture of the brain. 



1. The nerve cells possess a functional attribute; (viz., suscep- 

 tibility to impressions). This must be regarded as a general 



