240 PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



from the incomplete data of clinical neurology, very much lesg 

 evident in man. In man the motor control of the voluntary 

 muscular system through the cerebrum is more highly developed 

 than in the lower animals. 



The Psychical Functions of the Cerebellum. — In the cerebel- 

 lum, as in the other nerve centers below the cerebrum, we have to 

 consider the possibility of a psychical or conscious side to the activity 

 of the organ. It seems clear, however, that the degree of conscious- 

 ness, if any, exhibited by the cerebellum is of a much lower order 

 than that shown by the cerebrum. AU observers agree that there 

 is no apparent loss of sensations after removal of the cerebellum, 

 but Luciani, Russell, and others state their belief that in some 

 indefinable way the mentality of the animal is affected by such 

 operations. Whatever functions of this kind are present we can 

 define only by the unsatisfactory term of subconscious rather than 

 unconscious. As far as can be determined, this effect is felt mainly 

 upon the muscular sense and the sense of position and of direction. 



Localization of Function in the Cerebellum. — All observers 

 agree that so far as the influence of the cerebellum on the muscula- 

 ture of the body is concerned, it is homolateral, — that is, each 

 half of the cerebellum is connected with its own half of the 

 body. The connection with the motor areas of the brain is the 

 reverse, the right half of the cerebrum being in relation with the 

 left half of the cerebellum. These relations are, in the main, 

 borne out by the anatomical course of the motor and sensory 

 paths described above. There arises, however, the question 

 whether or not there is a localization of function in the cere- 

 bellum, that is, whether definite parts of the cerebellar cortex are 

 in specific relations with separate muscles or groups of muscles. 

 The possibility of a localization of function was suggested years 

 ago by experiments made by Ferrier, in which electrical stimula- 

 tion of the cortex gave definite movements of the head, limbs, and 

 especially of the eyes, the movements varying somewhat accord- 

 ing to the part stimulated. These indications of a localization 

 have been strengthened by the results of comparative anatomy, 

 and especially by the effects of ablation of definite parts of the 

 cortex. Earlier experimenters, using the method of ablation, 

 obtained quite negative results from the standpoint of localiza- 

 tion, but this seems to have been due to the fact that a faulty 

 anatomical schema was used; a whole hemisphere, or the entire 

 vermiform lobe, etc., was removed. Later experimenters* have 

 adopted the newer anatomical schemata, which take account of 

 the true genetic relations of the various lobes and lobules of the 



* Van Rynberk, "General Review in Ergebnisse der Physiologic," 7, 

 653, 1908, and 12, 533, 1912. Also Thomas and Durupt, "LocaUsations 

 cerebelleuses," 1914. 



