FUNCTIONS OP THE CEREBELLUM 



869 



the trunk and tail region are located in the remainder of the cerebellum. 

 These conclusions are the basis of the accompanying map of the cerebellum. 

 Basing his work on these anatomic conclusions, Van Eijnberk has studied 

 the effect of circumscribed extirpation of certain lobules of the cerebellum 

 on the muscular control of the different parts of the body, with the following 

 results. Total or partial extirpation of the lobulus simplex produces side to 

 side oscillations of the head, indicating the removal of the influences of the 

 cerebellum that control the movements of the muscles of the neck. Complete 

 extirpation of the crus primum of the lobuli ansiformes causes as an imme- 

 diate irritative effect dynamic disturbances of the fore limb of the same 

 side, replaced later by a condition of atonia, which makes the limb hang 

 limp, and of asthenia, which makes it feeble in its movement when it 

 is excited to contract. Extirpation of the crus secundum has a similar 



Fig. 224. Schema of the parts of the mammalian cerebellum spread out in one plane. (After Bolk 

 by Van Rijnberk from Luiciani. Op. cit.) On the right side of the figure the relation of the 

 different lobules to the functional development of the musculature is indicated according to the 

 theory of Bolk noted in the text. (From Davidson Black.) 



influence on the muscles of the hind limb of the corresponding side. Extir- 

 pation of both crura of the lobulus ansiformis causes marked asthenia and 

 atonia in both fore and hind limb on the same side as the lesion. A char- 

 acteristic disturbance in walking develops as a late effect of this extirpation. 

 It has been termed the ''hen's gait." Extirpation of the lobulus para- 

 medianus causes rotation on the longitudinal axis of the body, with pleuro- 

 thotonus to the operated side. (Fig. 224.) 



Just as in the case of cerebral localization, so in cerebellar we find that 

 within each of the largest centers a more particular localization can be made 

 out; thus, in each of the centers for the upper and lower extremities, 

 there is a definite arrangement of subsidiary centers for the direction of 

 the activities of antagonistic muscle groups concerned in the movements of 

 particular joints. It must be remembered, however, that in all these cases 

 no real paralysis is produced by extirpation, but only a want of coordina- 



