IIG MEMOIE OF MAGENDIE. 



first experienced from the blood lost, and that the wound which has become cold 

 may have regained a certain degree of heat and reaction. 



These experiments prove : First, that the posterior root is exclusively and 

 essentially sensitive ; I say essentially, because if we divide the anterior root 

 the posterior remains not the less sensitive. Secondly, that the anterior root is 

 essentially motive ; essentially, because if we divide the posterior root the an- 

 terior does not the less remain motive. And, on the contrary, the latter (the 

 anterior) is essentially sensitive ; for if we cut the posterior root it immediately 

 ceases to be so. It is not so, then, in itself — it is only so through the other ; 

 and so exclusively through the other that if, leaving this other (that is, the pos- 

 terior root) intact, it be itself cut, it is that one only of its two ends which is 

 attached to the other (to the posterior root) that remains sensitive. 



There remained a final experiment, and this M. Magendie proceeded to make. 

 The sensibility of the anterior root flows to it, is derived from the posterior root, 

 but how and by what means ? What route does it pursue ? Js this derivation 

 accomplished immediately on the junction or union of the two roots, or aftei'wards ? 

 " This extinction," says M. Magendie, "of the sensibility of the anterior root 

 by the section of the posterior root is a constant fact, and suggests the experi- 

 ment of cutting the nerve beyond the junction of the roots, leaving these latter 

 intact. I isolate the trunk of a rachidian pair at nearly six lines from the gang- 

 lion. You see plainly that the roots of this nerve are sensitive ; I irritate them 

 one after the other, and the animal appears to feel almost as acutely when I 

 touch the anterior as when I touch the posterior root. I now cut the trunk of 

 the nerve at about four lines from the junction of the roots. Let us try whether 

 these roots remain sensitive : I pinch the posterior root and the sensibility is 

 the same — it has neither diminished nor augmented. I pinch the anterior root 

 and find that this is no longer sensible. I conclude, then, that the sensibility 

 furnished by the posterior root to the anterior is transmitted at a point still more 

 remote than that on which 1 have operated. New researches must be made be- 

 fore the place of the nerve can be determined at which this transmission occurs. 

 Can we suppose that it is at the very extremity of the nervous divisions, and 

 that the fibres of termination inosculate with one another?" (Lectures on the 

 Nervous System, S^c, t. ii, p. 344.) 



I have also repeated this experiment many times and with a uniform result ; 

 the section of the two roots, immediately after their junction, abolishes the sensi- 

 bility of the anterior root just as it is abolished by the section of the posterior 

 root itself. 



EXPERIMENTS ON THE FIFTH AND SEVENTH PAIRS. 



1. One of the finest experiments of M. Magendie was that which he per- 

 formed on the Jifth pair. M. Bell had already made this experiment, but by 

 another procedure. He had contented himself with cutting the sub-orbital and 

 frontal nerves, and the nerves of the chin at their exit from the canals of which 

 they bear the name. M. Magendie was the first who cut the fifth pair within 

 the cranium. 



" The nerve which presides over the sensibility of the whole face," he says, 

 "is the fifth pair. You will see that, by cutting it in the cranium, we abolish 

 not only the tactile sensibility of the skin and soft parts, but even the special 

 sensibility of the senses in the whole side of the face corresponding to the sec- 

 tion. Thus the vision, the smell, the hearing, the taste, will be lost from the 

 fact alone that the fifth pair has been cut ; and yet the nerves that it is agreed 

 to regard as presiding over the exercise of each of these senses shall have si;f- 

 fered no injury." (Lectures on the Nervous Syste??i, II, p. 27.) This is what 

 he first said ; he afterwards stated more exactly : " The section of the fifth pair 

 acts on the nutrition of the organ of smell as on that of the eye ; the disorders 

 are secondary." {Ibid., p. 43.) The section of the JiftJi pair is limited, in effect, 



