202 HUMAN PHYSIOLOGY. 



the movements become more irregular, and the pigeon becomes rest- 

 less ; when the last portions are removed, all power of Hying, walking, 

 standing, etc., is entirely gone, and the equilibrium can not be main- 

 tained, the power of coordinating muscular movements being wholly 

 lost. The same results have been obtained by operating on all classes 

 of animals. 



The following symptoms were noticed by Wagner, after removing 

 the whole or a large part of the cerebellum : 



1. A tendency on the part of the animal to throw itself on one side, 

 and to extend the legs as far as possible. 



2. Torsion of the head on the neck. 



3. Trembling of the muscles of the body, which was general. 



4. Vomiting and occasional liquid evacuations. 



Forced Movements. Division of one crus cerebelli causes the 

 animal to fall on one side and roll rapidly on its longitudinal axis. 

 According to Schiff, if the peduncle be divided from behind, the ani- 

 mal falls on the same side as the injury ; if the section be made in 

 front, the animal turns to the opposite side. 



Disease of the cerebellum partially corroborates the result of 

 experiments ; in many cases symptoms of unsteadiness of gait, 

 from a want of coordination, have been noticed. 



Comparative anatomy reveals a remarkable correspondence between 

 the development of the cerebellum and the increase in complexity of 

 muscular actions. It attains a much greater development, relatively 

 to the rest of the brain, in those animals whose movements are very 

 complex and varied in character, such as the kangaroo, shark, and 

 swallow. 



The cerebellum may possibly exert some influence over the sexual 

 functions, but physiologic and pathologic facts are opposed to the 

 idea of its being the seat of the sexual instinct. It appears to be 

 simply a center for the coordination and equilibration of muscular 

 movements. 



THE CEREBRUM. 



The cerebrum is the largest portion of the encephalic mass, con- 

 stituting about four fifths of its weight; the average weight of 

 the adult male brain is from forty-eight to fifty ounces, or about 

 three pounds while that of the adult female is about five ounces less. 



