THE CEREBELLUM 275 



the muscles remains, the animal cannot contract them in a regu- 

 lar or coordinate manner. When it is remembered that well- 

 nigh every voluntary act requires concerted or consecutive mus- 

 cular movements some idea is gotten of the helpless condition 

 sequent upon such a lesion. If it be granted that there is a cen- 

 ter presiding over the coordination of the voluntary muscles, 

 that center is in the cerebellum, and an animal deprived of this 

 organ is as powerless, so far as this function is concerned, as a 

 person is to see when the optic centers are destroyed. Its action 

 is crossed. 



It has been noted already that lesions of the posterior white 

 columns of the cord are followed by disturbances of coordination, 

 and that the cerebellum is connected with these columns through 

 the inferior peduncles and restiform bodies. Fibers in these 

 columns serve only as anatomical connections by which the co- 

 ordinating center communicates with the muscles whose move- 

 ments it is to regulate, and of necessity any lesion of these fibers 

 destroying that connection is followed by the loss of control of the 

 center over the muscles. However, in degeneration of the pos- 

 terior columns (locomotor ataxia) an effort at coordination can 

 be made, so that progression is possible by the aid of fixed atten- 

 tion. It is possible also that the coordinating messages are 

 carried in such cases by the motor fibers, though in an unsatis- 

 factory manner. 



It has been supposed that the cerebellum is in some way con- 

 nected with the generative function, and this much is probably 

 true, though the evidence submitted is not sufficient to warrant 

 the assumption that the cerebellum is the seat of the sexual 

 instinct. 



THE CRANIAL NERVES. 



The cranial nerves, twelve in number on each side, take their 

 origin from some part of the encephalon, pierce the dura mater 

 and leave the skull by various openings. They have been num- 



