712 THE CEREBELLUM 



make it move results in excessive and asymmetrical muscular contrac- 

 tions which make it tumble in all directions. It is to be noted, however, 

 that this loss of the power of coordinated movement is not caused by 

 a paralytic condition of the different muscles but by an inability to 

 correlate their actions for the attainment of a particular purpose. 

 This swaying, staggering behavior constitutes the condition of ataxia. 

 It is true, however, that these symptoms are not permanent, but grad- 

 ually disappear in the course of time until merely a certain unsteadiness 

 in the gait is left behind. In reptilia and amphibia the cerebellum 

 is rudimentary. It cannot surprise us, therefore, to find that its 

 ablation produces no noticeable defects in these animals. 



Luciani^ has extended these experiments to the mammals. He 

 states that a dog, after unilateral removal of the cerebellum, shows a 

 rigidity of the extremities, a curvature of the spine toward the operated 

 side (opisthotonos), a deviation of the head toward the normal side, 

 a slight nystagmus, and strabismus. The latter condition presents 

 itself as a deviation of the eyes downward and inward on the operated 

 side, and upward and outward on the normal side. Among the 

 dynamic symptoms are mentioned atonia, or loss of the tonus of the 

 musculature, asthenia, or loss of force, astasia, or loss of steadiness, 

 and ataxia, or loss of the purposeful action of the musculature. These 

 defects are chiefly unilateral and produce forced movements toward 

 the abnormal side.^ The latter consist in rolling motions toward the 

 injured side as well as in movements in a circle toward the same side. 

 Most generally, however, the more intense symptoms disappear in 

 the course of from eight to ten days and are superseded by tremors. 

 The general character of these defects as well as their rather short 

 duration, led Luciani to assume that the cerebellum is an organ which 

 by processes that remain below the threshold of consciousness, produces 

 a reinforcement of the activity of the musculomotor centers. In 

 this beUef, however, he merely followed the views of du Petit (1710), 

 Laf argue (1838), and others. 



A number of cases are on record of inherited defects of the cere- 

 bellum in man, as well as of tumors which in the course of time de- 

 stroyed large segments of this organ. ^ The symptoms noted in these 

 persons, show a decided similarity to those observed in the lower 

 mammals. Briefly stated, cerebellar disease produces a condition 

 of asynergia, ^.e., an inability properly to associate movements of 

 greater or less complexity into functionally definite acts. If we adhere 

 to this view, that the cerebellum is the seat of synergia, this organ 

 assumes a position very similar to that of an association center of the 

 cerebrum. It then becomes the center for the coordination of all 

 muscular activity by reason of its power of associating those sensory 

 impulses upon which movements depend. 



1 Arch. ital. de Physiol., xxi, 1894; Fisiol. et Pathol, del Cervelletto, Padova, 

 1897, and Ergebn. der Physiol., iii, 1904, 259. 



2 Eckhard, Herrmann's Handb. der Physiol., ii, 1883, 102. 



3 Mills and Weisenburg, Jour. Am. Med. Assoc, Nov. 21, 1914. 



