714 



THE CEREBELLUM 



cerebellar nuclei (Deiters'). Very similar results have been obtained 

 by destroying circumscribed areas of the cerebellar cortex. Thus, 

 it has been observed by Ryerberk^ that the excision of the lobulus 

 simplex produces forced movements of the head (head-nystagmus), a 

 condition which is caused by a faulty control of the muscles of the 

 neck. Quite similarly, the destruction of the ansiform lobule next to 

 the crus primum, gives rise to a disordered action of the muscles of the 

 foot of the same side, while lesions of the crus secundum cause a dis- 

 turbance in the movements of the foot. In accordance with the older 



schema of Bolk, the present state of cere- 

 bellar localization may be represented as 

 in Fig. 358, A and B. Stress should, how- 

 ever, be laid upon the general fact that 

 different areas of the cerebellum control 

 different groups of muscles, rather than 

 upon the kind of muscle actually domi- 

 nated by any particular area of this organ. 

 The observations of Holmes^ upon 

 soldiers suffering from lacerations and gun- 

 shot wounds of different portions of the 

 cerebellum, have failed to yield positive 

 results. In many of these cases, however, 

 the exact location of the lesion could not 

 be made out. It is true that injuries to 

 the vermis most generally produced affec- 

 tions of the n uscles of the head, neck and 

 trunk, including those of phonation and 

 articulation. Small superficial lesions pro- 

 duced only slight and transient symptoms 

 which involved whole limbs rather than 

 particular muscles, but the defects were 

 invariably hmited to the side of the lesions. 

 But, though these clinical observations do 

 not lend support to the physiological con- 

 tention that the localization in the cere- 

 bellum is perfectly definite, they cannot 

 be considered as proof that such a minute localization does not exist. 

 The Function of the Cerebellum. — The foregoing data pertaining to 

 the ablation and excitation of the cortex and intrinsic nuclei of the 

 cerebellum, have been employed repeatedly as a possible basis for 

 a more precise doctrine regarding the function of this organ. But 

 while the general activity of this organ is clearly discernible, physi- 

 ologists have not succeeded as yet in detecting the precise nature of the 

 mechanism by means of which it is able to consummate its action. 

 It has been stated above that Flourens regarded this organ as a center 



lErgebn. der Physiologie, vii, 1908, 643, and xii, 1912, 533. 

 2 Brain, xl, 1918,461. 



Fig. 358. — Diagram Illustrat- 

 ing Cerebellar Localization. 

 A, Upper surface and B, 

 lower surface of human cere- 

 bellum; PrF, primary fissure; 

 PcF, postcleval fissure; GLF, 

 great longitudinal fissure; GHF, 

 great horizontal fissure; PF, 

 pyramidal fissure; ACL, anterior 

 crescentic lobe; SSL, superior 

 semilunar lobe; JSL, anterior 

 semilunar lobe; BL, biocentral 

 lobe. 



