386 MUSCULAR MOTION. 



axis. This conclusion, of course, applies only to the higher classes of 

 animals; for we have seen, that the polypus is capable of division into 

 several portions, so as to constitute as many distinct beings; and it is 

 probable, that the principal seat of volition may extend much lower 

 down in the inferior tribes of created beings. 



Successful attempts have been made to discover, whether the whole 

 brain is concerned in volition, or only a part. Portions have been dis- 

 organized by disease, and yet the person has not been deprived of 

 motion; at other times, as in paralysis, the faculty has been impaired; 

 and again, considerable quantities of brain have been lost, owing to 

 accidents (in one case the author knew nineteen tea-spoonfuls), with 

 equal immunity as regards the function in question. Experiments, 

 executed on this subject, go still farther to confirm the idea, that voli- 

 tion is not seated exclusively in the encephalon. MM. Rolando and 

 Flourens 1 performed several, with the view of detecting the seat of the 

 locomotive will, or of that which presides over the general movements 

 of station and progression ; and they were led to fix upon the cerebral 

 lobes. Animals, from which these were removed, were thrown into a 

 sleepy, lethargic condition; were devoid of sensation and spontaneous 

 motion, and moved only when provoked. On the other hand, M. Magen- 

 die 2 affirms, that the cerebral hemispheres may be cut deeply in different 

 parts of their upper surface, without any evident alteration in the 

 movements. Even their total removal, if it did not implicate the cor- 

 pora striata, he found to produce no greater effect ; or, at least, none 

 but what might be easily referred to the suffering induced by such an 

 experiment. The results, however, were not alike in all classes of ver- 

 tebrated animals. Those mentioned were observed on quadrupeds, and 

 particularly dogs, cats, rabbits, Guinea-pigs, hedgehogs, and squirrels. 

 In birds, the removal or destruction of the hemispheres the optic tu- 

 bercles remaining untouched was often followed by the state of stupor 

 and immobility described by MM. Rolando and Flourens; but, in 

 numerous cases, the birds ran, leaped, and swam, after the hemispheres 

 had been removed, the sight alone appearing to be destroyed. In rep- 

 tiles and fish, the removal of the hemispheres seemed to exert little 

 effect upon their motions. Carps swam with agility; frogs leaped and 

 swam as if uninjured ; and their sight did not appear to be affected. 

 Magendie 3 properly concludes, from these experiments, that the spon- 

 taneity of the movements does not belong exclusively to the hemi- 

 spheres ; that in certain birds, as the pigeon, adult rook, &c., this seems 

 to be the case; but not so in other birds. To mammalia, reptiles, and 

 fish, at least such of them as were the subjects of experiment, his 

 conclusion is, however, applicable. 



Of the nature of the action of the brain in producing volition we 

 know nothing. It is only in the prosecution of direct experiments on 

 the encephalon that we can have an opportunity of seeing it during the 

 execution of the function ; but the process is too minute to admit of 

 observation. Our knowledge is confined to the fact, that the encephalon 

 acts, and that some influence is projected from it along the muscles, 



1 Op. citat. * Precis Elementaire. 3 Ibid., i. 336. 



