THE BRA IX. 437 



The inference from these phenomena is that the power of coordi- 

 nation for voluntary movements resides in the cerebellum, and is im- 

 paired by injury of its substance. We have already seen (page 407) that, 

 for the body and limbs, in the acts of standing and locomotion, a 

 power of coordination exists in the spinal cord ; and that it apparently 

 depends on the integrity of the posterior columns, which serve as con- 

 necting longitudinal tracts between its different parts. But to produce 

 an appreciable disturbance of this power in the spinal cord, the poste- 

 rior columns must be divided at several successive points ; thus disas- 

 sociating its parts from each other for a considerable extent. The 

 cerebellum is the only nervous centre in which a single injury produces 

 a want of coordination for all voluntary movements whatever. Accord- 

 ing to this view, it is a nervous centre of highly developed structure, 

 superadded to the cerebro-spinal tracts, for the complicated association 

 of their motor impulses. This association cannot be properly carried 

 out in any particular part, unless the corresponding peripheral tracts be 

 also in a state of integrity ; but it is in the gray substance of the cere- 

 bellum that the nervous coordination is originally effected. 



Restoration of the Coordinating Power in Operated Animals. It is 

 a remarkable fact that after the coordinating power has been seriously 

 impaired by partial destruction of the cerebellum, it may in some in- 

 stances be recovered, without regeneration of the nervous substance. 

 This recovery was observed by Flourens both in the fowl and in the 

 pigeon, and has been seen by Flint* in the pigeon after removal of 

 about two-thirds of the cerebellum. We have also met with four in- 

 stances of the same kind. In the first, about two-thirds of the cere- 

 bellum were taken away by an opening in the posterior part of the 



FIG. 117. FIG. 118. 



BRAIN OP HEALTHY PIGEON Profile BRAIN OF OPERATED PIGEON Profile 



view. 1. Cerebral Hemisphere. 2. Optic view showing the mutilation of the 



Tubercle. 3. Cerebellum. 4. Optic Nerve. Cerebellum. 

 5. Medulla Oblongata. 



cranium. Immediately afterward, the pigeon showed all the usual 

 effects of the operation, being incapable of flying, walking, or even of 

 standing still, but only reeled and sprawled in a perfectly helpless man- 

 ner. In five or six days he had regained a considerable control over 

 the voluntary movements, and at the end of sixteen days his power 

 of muscular coordination was so nearly perfect that its deficiency, if 



* The Physiology of Man ; Xervous System. New York, 1872, p. 367. 



