ENCEPHALIC SEAT OF MUSCULAR MOTION. 



are as ignorant of the character of this influx, as we are of that of the 

 nervous phenomena in general. 



The parts of the encephalon and spinal marrow, concerned in mus- 

 cular motion, are very distinct from those that receive the impressions 

 of external bodies. The function of sensibility is comprised in the 

 medulla oblongata and in the posterior column of the spine, whilst the 

 encephalic organs of muscular motion appear to be the corpora striata, 

 the thalami nervorum opticorum, at their lower part; the crura cerebri; 

 the pons Varolii; the peduncles of the cerebellum; the lateral parts of 

 the medulla oblongata, and the anterior column of the medulla spi- 

 nalis. This is proved by direct experiment, as will be shown presently; 

 and, in addition to this, pathology furnishes us with numerous examples 

 of their distinctness. In various cases of hemiplegia or palsy of one 

 side of the body, which is of encephalic origin, we find motion 

 almost lost ; yet sensibility may be slightly or not at all affected ; and, 

 on the other hand, instances of loss of sensation have been met with, 

 in which the power of voluntary motion has continued. Modern dis- 

 coveries in the system of vertebral nerves exhibit how this may hap- 

 pen. A considerable space may exist between the roots of a nerve, 

 one of which shall be destined for sensation, the other for motion ; yet 

 both may pass out enveloped in one sheath ; the same nervous cord 

 thus conveying the two irradiations, if they may be so termed. Ac- 

 cording to Sir Charles Bell's system the spinal column is divided into 

 three tracts; the anterior for motion; the posterior for sensibility; 

 and the two are kept separate and united by the third the column for 

 respiration. The existence of the last column is now admitted by few. 1 



The experiments performed by the French physiologists especially, 

 for the purpose of discovering the precise parts of the encephalon con- 

 cerned in muscular motion, have attracted great and absorbing interest. 

 We wish it could be said, that the results have been such as to afford 

 determinate notions on the subject. According to those of M. Flou- 

 rens, the cerebral lobes preside over volition, and the medulla oblon- 

 gata over the locomotive influx : to the latter organ he assigns, also, 

 sensibility. We have seen, that the results of his experiments have 

 been contested; and with them, of course, his deductions. The facts 

 and arguments, already stated, throw doubts on all except the last pro- 

 position, which refers sensibility to the medulla oblongata; and even it 

 is not restricted to that organ, or group of organs, whichsoever it may 

 be considered. 



MM. Foville and Pinel Grand- Champ 2 have affirmed that the cere- 

 bellum is the seat of sensibility. To this conclusion they were led by 

 the remarks they had made, in the course of their practice, that the 

 cases of paralysis of sensibility, which fell under their notice, suc- 

 ceeded more especially to morbid conditions of the encephalon. In 

 this view they conceive themselves supported by the discovery of 

 columns in the spinal marrow destined for particular functions ; and, 

 as the posterior column is found to be the column of sensibility, and 

 the cerebellum seems to be formed from this column, they think it 

 ought to be possessed of the same functions. M. Adelon 3 remarks, that 



1 See page 89. 3 Sur le Systeme Nerveux, Paris, 1820. 3 Op. citat., ii. 38. 



