THE WEIGHT OF THE BRAIN AND SPINAL CORD. 9! 



the hemisphere is separated into two portions, a smaller 

 basal portion composed of the basal ganglia (optic thala- 

 mus and corpora striata, together with the portion pf cor- 

 tical substance covering the striata and forming the island) 

 and the more massive enveloping portion, the mantle. 



FIG. 16. Showing the principal divisions of the encephalon made 

 for the study of its weight : i. Hemisphere, seen from the 

 side, fissuration according to Eberstaller; 2. Mid-brain, region 

 of the corpora quadrigemina ; 3. Pons ; 4. Cerebellum, or 

 hind-brain ; 5. Bulb, or after-brain. Parts 2, 3, and 5, taken 

 together, form what is designated the " stem " in the tables 

 of Boyd. (Modified from Ouain's Anatomy.} 



The mantle consists of a central mass of white matter 

 completely covered over with grey cortex. Sometimes 

 the mantle is still further divided into lobes, but the 

 value of these subdivisions and the extent to which they 

 have been employed can be best discussed when the 



