114 MEMOIR OF MAGENDIE. 



sensibility. Of the two ends whicli result from tlie section of tliis posterior 

 root, that which adheres to the ganglion has become insensible, while that 

 attached to the medulla still possesses an acute sensibility. Hence this root di- 

 rectly receives its sensibility from the spinal marrow. 



" I shall dwell no further on these results, which are literally the same that I 

 announced to the academy in 1839, and which I have demonstrated in ray 

 lectures at the College of France ; I will only add that I maintain them to 

 be rigorously exact, and that I am now, as then, always ready to exhibit them 

 to those who signify a desire that I should do so. At present I proceed to 

 report certain facts which are of a nature to throw new light on the phenomenon 

 of the recurrent sensibility of the anterior roots. 



"Differing in this from the posterior roots, which are constantly sensible, it 

 sometimes happens that on interrogating the anterior root we find it deprived of 

 sensibility. This is particularly observable when, the opening of the rachis and 

 the separation of the root having been laborious, the animals are weakened by 

 pain and loss of blood. But this insensibility is only temporary; it suffices to 

 wait a few instants, and the phenomenon reappears and subsists as long as the 

 state of the wound and of the environing parts allows of its being observed. 



"This momentary disappearance of sensibility in the nerve is a very singular 

 phenomenon which pertains to the recurrent sensibility, and which distinguishes 

 it essentially from the direct sensibility of the posterior root, a sensibility which 

 I have never known completely to disappear. When, however, the experiment 

 is suitably made, we recognize immediately, on the opening of the rachis, the 

 recurrent sensibility of the anterior root, and I have realized that, to succeed, 

 the best process is that in which the spinal marrow is laid bare only on one side 

 and to the extent of one or two vertebras. I have moreover remarked that, when 

 the experiment has been as well performed as possible, if the animal has lost a 

 certain quantity of blood, the phenomenon is not manifested ; and I add that, at 

 the moment when it is most apparent, it may be made to disappear by the opera- 

 tion of blood-letting. 



" In my first experiments, before I knew the influence of the causes just pointed 

 out, it had happened that I had found the anterior roots sometimes sensible, 

 sometimes insensible. This result, which might then have appeared contra 

 dictory, is, however, but the rigorous expression of the facts, and depends on 

 that remarkable peculiarity, that a sensitive nerve may, imder certain influences, 

 temporarily lose it sensibility and afterwards recover it. 



"The sensibility which I call recurrent does not pertain exclusively to the 

 anterior roots of the rachidian nerves ; 1 have found it also in the facial nerve, 

 and it exists probably in still other nerves. I am now occupied with researches 

 in this respect, and shall probably have the honor of communicating them to 

 the academy. I shall merely add to this note the recital of some experiments 

 which I have made with my habitual collaborator, Dr. Bernard, well known to the 

 academy, and who has taken the trouble to describe them. First experiment : In 

 a living and healthy dog, three to four months old, the lumbar medulla was laid 

 bare on the right side to the extent of two vertebrae ; the nervous roots ex- 

 posed wore the fourth and fifth lumbar. Immediately after the experiment, by 

 which the animal was somewhat distressed, the anterior root of the fourth lumbar 

 pair was pinched and yielded no manifest signs of sensibility ; neither did the 

 anterior root of the fifth lumbar pair. Those two roots were then cut in such a 

 way that there might result from the section peripheric ends and ends adjoining 

 the marrow. The animal evinced no pain at the moment of the section of the an- 

 terior nervous roots, and the pressure upon these two ends of nerves, resulting 

 from the section of the root, produced no evident signs of sensibility. Afterwards 

 the facial nerve on the jaw was laid bare anditsbranches were transversely divided, 

 when again the peripheric ends, on being pricked, manifested no signs of sensibility. 

 After these first trials the animal was left for some moments at rest from the general 



