360 INNERVATIOX. [cHAP.Xl. 



dividing either eras cerebelli, the animal was seen to roll over 

 on its long axis towards the side on which the injury was 

 inflicted. 



The effects of injuries to the cerebellum, according to the reports 

 of the experimenters above referred to, contrast in a very striking 

 manner with those of the much more severe operation of removing 

 the cerebral hemispheres. " Take two pigeons/' says M. Longet, 

 " from one remove completely the cerebral lobes, and from the other 

 only half the cerebellum ; the next day, the first will be firm upon 

 his feet, the second will exhibit the unsteady and uncertain gait of 

 drunkenness." 



Experiment, then, appears strikingly to favour the conclusion 

 which Flourens has drawn, namely, that the cerebellum possesses 

 the power of co-ordinating the voluntary movements which originate 

 in other parts of the cerebro-spinal centre, whether these move- 

 ments have reference to locomotion or to other objects. 



That this power is mental, i.e., dependent on a mental operation 

 for its excitation and exercise, is rendered probable from the expe- 

 rience of our own sensations, and from the fact that the perfection 

 of it requires practice. The voluntary movements of a new-born 

 infant, although perfectly controllable by the will, are far from 

 being co-ordinate : they are, on the contrary, remarkable for their 

 vagueness and want of definition. Yet all the parts of the cerebro- 

 spinal centre are well developed, except the cerebellum and the con- 

 volutions of the cerebrum. Now, the power of co-ordination im- 

 proves earlier and more rapidly than the intellectual faculties; and 

 we find, in accordance with Flourens' theory, that the cerebellum 

 reaches its perfect development of form and structure at a much 

 earlier period than the hemispheres of the cerebrum. 



It may be stated, as favourable to this view of the mental nature 

 of the power by which voluntary movements are co-ordinated, that, 

 in the first moments of life, provision is made for the perfect per- 

 formance of all those acts which are of the physical kind. Thus, 

 respiration and deglutition are as perfect in the new-born infant as 

 in the full-grown man ; and the excitability of the nervous centres 

 to physical impressions is much greater at the early age, partly per- 

 haps in consequence of the little interference which is received at 

 that period from the will. 



That the cerebellum is an organ favourably disposed for regulating 

 and co-ordinating all the voluntary movements of the frame, is very 

 apparent from anatomical facts. No other part of the encephalon 

 has such extensive connexions with the cerebro-spinal axis. It is 





