OF THE CEREBELLUM, AND ITS FUNCTIONS. 



731 



Gallinaceous birds, whose powers of flight are small, or than that of the Struthious 

 tribe, in which they are altogether absent. Lastly, on comparing its proportional 

 size in the different orders of mammalia, with the number and variety of muscular 

 actions requiring combined movements, of which they are respectively capable, 



[Fig. 194*. 



This figure exhibits those fibres from the anterior columns which, ascending to the cerebellum, con- 

 nect the motor tract with that portion of the cerebral mass. E. Cerebellum, x. Pons Varolii. T. Pyra- 

 midal eminences, s. Olivary bodies, w w. Corpus restiforme, its surface having been carefully scraped, in 

 order to show the superficial cerebellar fibres of the anterior columns. They are represented rather more 

 distinct and thick than they really appear, though their course, direction, and relation to the olivary body 

 are faithfully given. ED.] 



we observe an even more remarkable correspondence. In the hoofed Quadru- 

 peds, in which the muscular apparatus of the extremities is reduced to its greatest 

 simplicity, and in which the movements of progression are simple, the Cere- 

 bellum is relatively smaller than it is found to be in some Birds ; but in pro- 

 portion as the extremities acquire the power of prehension, and together with 

 this a power of application to a great variety of purposes still more, in propor- 

 tion as the animal becomes capable of maintaining the erect posture, in which a 

 constant muscular exertion, consisting of a number of most elaborately combined 

 actions, is required do we find the size of the Cerebellum, and the complexity 

 of its structure, undergoing a rapid increase. Thus, even between the Dog and 

 the Bear there is a marked difference ; the latter being capable of remaining for 

 some time in the erect posture, and often spontaneously assuming it ; whilst to 



