CHAPTEK XXIII. 



THE INTERNAL STRUCTURE OF THE HUMAN BRAIN. 



THE internal structure of the Human Brain is so complex, 

 and at the same time so very imperfectly known, as to make 

 it difficult to give any account of it which shall be intel- 

 ligible to the majority of readers. The adequate com- 

 prehension even of its general plan or groundwork will 

 require a full amount of attention. In the present chap- 

 ter multitudes of technical details, whose significance is 

 either unknown or incapable of being appreciated by any 

 one who has not previously made a close study of the 

 subject, will be excluded. The discussion of such details 

 may be found in more technical and purely anatomical 

 works. 



By tracing upwards some of the more elementary forms 

 of the Nervous System met with among Invertebrates, 

 and afterwards describing the principal external or grosser 

 variations of the Brain as they present themselves in the 

 Vertebrate Series, the best preparation has perhaps been 

 made for such a study of the structure of the Brain of 

 Man, as is compatible with the plan of this work. The 

 reader will thus have been gradually introduced to the 

 representatives of the several parts of the Human Brain, 

 and the description of this organ ought thereby to have 

 been rendered both simpler and more interesting than it 

 would otherwise have been. No parts absolutely new will 

 be met with, though it will not be difficult to note mary 



