Chap. XVI.] THE BRAIN OF QUADRUPEDS. 



255 



^® 



spheres, will be found to attain their maximum develop- 

 ment in Man. 



The third external pecu- 

 liarity is a consequence of 

 the second. It consists in 

 the gradual increase of the 

 'pons Varolii/ a part of 

 the brain which stretches 

 across the inferior surface 

 of the Medulla in a bridge- 

 like fashion. Hence its 

 name — coupled with that 

 of one of the earlier ana- 

 tomists. This structure, 

 which was formerly believed 

 to be merely a great trans- 

 verse commissure uniting 

 the lateral lobes of the Cere- 

 bellum with one another, 

 becomes well developed in 

 higher Quadrupeds and in 

 Cetacea, though it is repre- 

 sented in Birds only by a 

 few barely perceptible fibres. 

 Its true nature v/ill be more 

 correctly defined in the de- 

 scription of the human brain. 



Internal Differences. ^'*^- 68.— Brain and Spinal Cord of Kan- 



„ . garoo {3Iacrop^ls). (Owen.) 1. Section o 



Only a lew OI the most im- Splnal Coid in situation from winch Nerves 



portant and obvious of these ^^"Z!f"T'T ^'."'^^f V'?" 



r tion through lower dorsal region ; 3. Section 



can be here referred to. through lumbar swelling of Cord. Each of 



/-. v^ rpi • /^ +• t^sse sections shows the double area of 



[i..) ine two up lilC 'grey' ganglionic matter within the Spinal 



Lobes become relatively *^°^^- 



smaller in higher Quadrupeds, though in all of them they 



