Chap. XXIIL] INTERNAL STRUCTURE OF BRA [N. 429 



differences in regard to the absolute or relative size of 

 divisions of the Brain, with which the reader is already- 

 familiar from their occurrence in lower animals. The 

 possession of a basis of comparison of this kind can 

 scarcely fail to infuse great additional interest into the 

 study of the brain of Man, and it will often obviate the 

 necessity for anything like lengthy descriptions. 



What is to be said in this chapter as to the internal structure of 

 the Human Brain may be most conveniently grouped under the 

 following headings: — (1) Internal Topography ot the Human 

 Brain ; (2) Distribution of the Fibres composing the Cerebral 

 Peduncles, with an account {a) ot their relation to the Thalami 

 and Corpora Striata, and (b) their relations (as well as that of 

 Fibres which simply issue from, or go to, these 'great Ganglia) 

 with different parts of the cortex of the Cerebral Hemispheres; 

 (3) The microscopic anatomy of the Cerebral Convolutions ; (4) The 

 relations of the Commissures of the Brain, including (a) those 

 connecting similar regions in the two Hemispheres, (6) those con- 

 necting different regions in the same Hemisphere, and (c) those 

 bringing the Cerebellum into relation with the Cerebral Hemi- 

 spheres; (5) The general structure of the Cerebellum and its 

 relations with other parts; (6) The microscopic anatomy of the 

 Cortex of the Cerebellum ; (7) The central connections of the 

 various Cranial ISTerves; (8) The relations of the Visceral System 

 of JSTerves with the Brain. 



1.— Internal Topography of the Human Brain. 



The nature of the ' lateral ' and other Ventricles, and 

 the relations of all of them, except the fifth, to the origin- 

 ally wide canal of the primitive Cerebro- Spinal Nerve 

 Tube, has already been indicated (pp. 267, 333, 338). 



The Lateral Ventricles in the healthy and well- 

 developed Human Brain are comparatively narrow 

 cavities, represented in the main by three spurs or 

 * cornua.' (Fig. 151.) The arrangement of parts in and 

 about these Lateral Ventricles is essentially similar to 



