476 GENERAL ANATOMY. 



phenomena, if it is attached to a particular nervous part, has 

 probably its seat in the superior part of the spinal marrow. 



It has often been attempted to determine, by observation 

 and experiment, the organic seat of sensation and volition. 



Rolando regards the hemispheres of the brain as the seat of 

 these two actions, and the cerebellum as the organ which sends 

 to the muscles the motive principle under the direction of the 

 brain. 



According to Flourens, the spinal marrow, at the place 

 where it is surmounted by the tubercula quadrigemina, is the 

 common point of the arrival of the sensations, and of the de- 

 parture of the nervous influence of muscular motion. The 

 cerebellum, according to this physiologist, balances the mo- 

 tions or arranges and regulates them; according to him the ab- 

 straction of the cerebellum renders the animal incapable of 

 acting in a regular and proper manner, with respect to station 

 and locomotion. 



Magendie, supporting his position by the experiments of 

 Lorry, Legallois, and his own, thinks that sensibility is inhe- 

 rent in the spinal marrow. This able physiologist is of opinion 

 that the will or the faculty of determining muscular motions, 

 resides in the most elevated part of the cranial portion of the 

 spinal marrow, even in the optic thalami and the crura cere- 

 bri; that the optic thalami are necessary to lateral motions; 

 that the hemispheres of the brain are necessary for the pro- 

 duction of anterior motions, and the cerebellum for motions 

 in the opposite direction. The removal of one or the other 

 of these organs suppresses its action, and determines the irre- 

 sistible action of the other; the removal of an optic thalamus 

 determines a rotatory motion. 



Foville and Pinel Grandchamps have been led by observa- 

 tions in morbid anatomy, to which they have joined experi- 

 ments on animals, to establish the seat of sensibility in the 

 cerebellum, and that of voluntary motion in the medullary 

 substance of the hemispheres; the anterior part and the cor- 

 pora striata for the abdominal members, the optic thalami and 

 the posterior part of the hemispheres for their superior mem- 

 bers. 



