430 THE BRAIN. 



cerebrum, it contains, in proportion to its size, a much larger quan- 

 tity of gray matter. 



In examining the comparative development of the brain, also, in 

 different classes and species of animals, we find that the cerebellum 

 nearly always keeps pace, in this respect, with the cerebrum. These 

 facts would lead us to regard it as a ganglion hardly secondary in 

 importance to the cerebrum itself. 



Physiologists, however, have thus far failed to demonstrate the 

 nature of its function with the same degree of precision as that of 

 many other parts of the brain. The opinion of Gall, which located 

 in the cerebellum the sexual impulse and instincts, is at the present 

 day generally abandoned ; for the reason that it has not been found 

 to be sufficiently supported by anatomical and experimental facts, 

 many of which are indeed directly opposed to it. The opinion 

 which has of late years been received with the most favor is that 

 first advocated by Flourens, which attributes to the cerebellum the 

 power of associating or "co-ordinating" the different voluntary 

 movements. 



It is evident, indeed, that such a power does actually reside in 

 some part of the nervous system. No movements are effected by 

 the independent contraction of single muscles; but always by 

 several muscles acting in harmony with each other. The number 

 and complication of these associated movements vary in different 

 classes of animals. In fish, for example, progression is accom- 

 plished in the simplest possible manner, viz., by the lateral flexion 

 and extension of the vertebral column. In serpents it is much the 

 same. In frogs, lizards, and turtles, on the other hand, the four 

 jointed extremities come into play, and the movements are some- 

 what complicated. They are still more so in birds and quadrupeds; 

 and finally, in the human subject they become both varied and 

 complicated in the highest degree. Even in maintaining the ordi- 

 nary postures of standing and sitting, there are many different mus- 

 cles acting together, in each of which the degree of contraction, in 

 order to preserve the balance of the body, must be accurately pro- 

 portioned to that of the others. In the motions of walking and 

 running, or in the still more delicate movements of the hands and 

 fingers, this harmony of muscular action becomes still more evident, 

 and is seen also to be absolutely indispensable to the efficiency of 

 the muscular apparatus. 



The opinion which locates the above harmonizing or associating 

 power in the cerebellum was first suggested by the effects observed 



