CEREBELLAR LOCALIZATION 713 



The asynergia developed in the course of cerebellar disorders, pre- 

 sents itself in various forms, namely, as: 



(a) Hypermetry, or dismetry, i.e., a faulty measurement of the movements. 

 In this particular instance, the patient is unable to associate the motor constituents 

 of such acts as putting the index finger to the tip of the nose when the eyes are 

 closed. Invariably, the finger misses its mark by a distance which increases with 

 the degree of the hypermetry. 



(6) Adiadochokinesis, or an inability to produce fine motor associations of an 

 antagonistic character. This is shown by the fact that the patient is quite unable 

 to pronate and supinate the hand when the forearm is flexed upon the arm. 



(c) Tremors, shown in grasping for objects or in walking. The gait is trunkal, 

 i.e., the trunk constantly leaves its accustomed position, but is immediately sup- 

 ported in its new place by the legs in a stilt-like, sprawling manner. The cere- 

 bellar patient, however, knows his difficulty and makes compensatory movements 

 to counteract these forced movements. In this regard he differs very decidedly 

 from a person who is under the influence of alcohol. The latter reels in any direc- 

 tion without, at least in the final stage, being able to antagonize his movements. 

 This loss of compensation is due, of course, to the fact that the alcohol has rendered 

 the cerebral centers inactive. Cerebellar defects, on the other hand, need not be 

 accompanied by cerebral depression. The cerebellar patient also exhibits an asyn- 

 ergia of the tongue and laryngeal muscles which gives rise to a jerky and crackling 

 speech. The head is generally carried in the plane of the trunk. The eyes are 

 seldom at rest. 



(d) Atonia, or loss of tonus and relaxation of the muscles. This condition is 

 dependent upon the fact that the tonic impulses from the cerebral cortex cannot 

 become effective when the movements are asynergic. 



(e) Asthenia, or loss of force. This condition is due to the exhaustion which 

 results whenever the efforts to perform purposeful movements can no longer be 

 properly controlled, 



(/) Astasia, or loss of steadiness. 



(g) Ataxia, or loss of the purposeful action of the muscles. This is a complex 

 symptom resulting in consequence of the other defects. 



Cerebellar Localization. — It has been shown by Ferrier that the 

 stimulation of the surface of the hemispheres of the cerebellum or of 

 its superior vermis, gives rise to movements on the same side of the 

 body. In order to evoke these motor results, it becomes necessary to 

 use much stronger stimuli than are ordinarily required for the excitation 

 of the cortex of the cerebrum. This observation is in keeping with 

 the histological arrangement of the cerebellar neurons, because the 

 cortex is really the end station of the afferent paths, while the efferent 

 paths as such begin in the more deeply seated nuclei. 



Naturally, when we speak of localization of function in the cere- 

 bellum, we realize that this organ, contrary to the cerebrum, mediates 

 only one kind of activity, namely, that of coordinating the movements 

 of skeletal muscle. Thus, the only question before us is, whether 

 different muscles or groups of muscles are controlled by different regions 

 of this organ. That such a division of labor actually exists, has been 

 shown very clearly by the experiments of Horsley and Clarke^ which 

 yielded movements of the eyes and head on excitation of the roof nuclei, 

 and movements of the trunk and limbs on stimulation of the para- 



1 Brain, xxviii, 1905, 13. 



