72 APPENDIX. 



the fibres of the anterior roots are much smaller than those of the posteriorya ch*- 

 cumstance which, when viewed in connexion with what has been advanced on the sub* 

 ject by Mr. Charles Bell* and M. Magendie shows that each set of fibres (posterior and 

 anterior) is more immediately allotted to the performance of a distinct function, that 

 the posterior roots are devoted to the sensibility 'of the parts which these nerves sup- 

 ply, and the anterior to the muscular contractions. But it appears, from the experi- 

 ments of M. Magendie, .that one of these functions does not exclusively belong 1 to one 

 order of these roots ; for, when the posterior roots, or those which more particularly 

 belong 1 to sensibility", are irritated, contractions are occasioned in the muscles to which 

 their nerves are distributed, although the contractions are much more strong and much 

 more complete when the irritation is directly applied to the anterior roots of the nerves. 

 Slight appearances of sensibility are also occasioned when irritation is made on the an- 

 terior roots. It must therefore be concluded, that sensibility, although chiefly, is not 

 exclusively, in the posterior roots, nor motion in the anterior. 



This defect of complete isolation of these two functions may arise, as M. Ollivier 

 supposes, from the gray matter of each lateral half of the marrow, which seems to be 

 concerned in their production, being entirely confounded at their central points of 

 contact ; and from the intimate union which takes place between both the roots, be- 

 low the spinal enlargement (intervertebral ganglions) and which must contribute still 

 farther to combine these functions so as to prevent their perfect separation. 



It should be recollected that the functions ought not to be attributed to the roots of 

 the nerves themselves. M. Magendie found, that when these nerves were divided close 

 to the marrow, and irritation then made on their roots, no sensible effect followed : 

 whereas, while their connexion with the marrow was preserved, the slightest irritation 

 was productive of effect ; and the nearer that it was made to the spinal cord, the more 

 intense was the influence occasioned by it. Hence it follows that the gray substance 

 of the cord, whence arise the roots of the spinal nerves, is much more intimately con- 

 cerned in the production of the operations in question than the roots of the nerves 

 themselves ; but this substance itself seems to depend more upon the differts parts 

 composing the encephalic mass, for whatever influence it may exert in the production 

 of the phenomena under consideration, than M. Ollivier appears to allow. He attri- 

 butes them both almost exclusively to the gray substance of the centre of the cord, 

 which he considers to be voluminous in proportion as these faculties are developed. 

 This part of the cord, although altogether necessary to, and instrumental in, their pro- 

 duction, can only be viewed as one of three distinct classes of structure, each of which, 

 as M. Flourens has stated, performs distinct actions, which by their combination, con- 

 stitute but an individual function, that could not result from any one or two only of the 

 actions composing 1 it, but is the consequence of a more or less perfect co-operation of 

 the whole*. 



* Mr. Bell's attention was attracted by " the difference in the distribution of the 

 nerves of the head from those of the body, and the fact that all the spinal nerves arise 

 by double roots. Observing that this form of origin was the same in all animals pos- 

 sessing a spinal cord, and considering that the anterior column of the spinal marrow 

 was continuous with the crura of the cerebrum, and the posterior with the crura of 

 the cerebellum, he conceived that by experiments on the roots of these nerves, 

 he might discover the functions of the the two columns, and, perhaps, through 

 them, arrive at a more accurate knowledg of the relations and individual uses of 

 the cerebrum and cerebellum." Previously, however, to these experiments, Mr. 

 Bell entertained the opinion that the anterior column of the spinal cord was dif- 

 ferent in function from the posterior; and that, through the former, the simple 

 voluntary power of moving particular parts was conveyed. He deduced this from 

 observing, that the two nerves, which are generally supposed to be purely motors, 

 arise from the anterior fasciculus. The experiments which these opinions suggested, 

 although they were not conclusive, yet encouraged the view he had taken, and gave 

 results in some degree similar to those which Magendie subsequently obtained from 

 his experiments. To Mr. Bell, therefore, the honour of having originated these views 

 clearly belongs. 



* Of the distinct functions of the cerebellum, numerous opinions have been lately en- 

 tertained. Dr. Gall considers it to be the seat of physical love. Mr. Rolando, who 

 adopts the opinion of a nervous fluid, which he regards as analogous to the galvanic 

 fluid, places the source and seat of the principle of muscular contraction in the cere- 

 bellum, which, owing to the disposition of its laminated convolutions, he considers to 



