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 will be more 

 correctly defined in the de- 

 scription of the human brain. 



Internal Differences. Fia 68. Brain and Spinal Cord of Kan- 



n , e , garoo (Macropus). (Owen.) 1. Section of 



Uniy a lew OI the mOSt im- Spinal Cord in situation from which Nerves 

 nnvtflnt and nhvimmnf thpP to anterior extremities are given off ; 2. Sec- 



i tnese tion through lower dorgal region . 3 Section 



Can be here referred tO. through lumbar swelling of Cord. Each of 



a\ T^Vi 4- f\ 4-* * nese sections shows the double area of 



.; me tWO UptlC ' grey ' ganglionic matter within the Spinal 



Lobes become relatively Cord ' 



smaller in higher Quadrupeds, though in all of them they 



