MEMOIR OF MAGENDIE 109 



following the process in which the great canals of the spinal dura mater is 

 opened, I do not think that this method of making the experiment should be 

 pursued in preference to the former. 



" I desired afterwards to submit to a particular proof the results of which I 

 have previously spoken. Every one knows that the nux vomica causes in man and 

 animals general and very violent convulsions. It was a matter of curiosity to 

 know whether these convulsions would still take place in a member whose 

 nerves of motion had been cut, and whether they would show themselves as 

 strong as usual when the section of the nerves of sensation had been made. 

 The result has proved altogether accordant with those preceding that is to say, 

 that in an animal in which the posterior roots were cut, the tetanus was com- 

 pleted and as intense as if the spinal roots had been all intact ; on the contrary, 

 in an animal in which I had cut the nerves' of movement of one of the 

 posterior members, that member has remained supple and motionless at the 

 moment when, under the influence of the poison, all the other muscles of the 

 body underwent tetanic convulsions of the most decided kind. 



"By directly irritating the nerves of sensation or the posterior spinal roots, 

 would contractions be produced? Would direct irritation of the nerves of 

 motion excite pain % Such are the questions which I proposed to myself, and 

 which experiment alone could resolve. 



" I commenced by examining under this aspect the posterior roots or nerves 

 of sensation. What I have observed is this : on pinching, pulling, pricking 

 these roots, the animal evinces pain, but not to be compared, for intensity, with 

 that which is developed if the spinal marrow be touched, even lightly, at the 

 place whence these roots spring. Nearly every time that the posterior roots 

 are thus excited, contractions are produced in the muscles where the nervers are 

 distributed ; these contractions are, however, but sl'ghtly marked, and vastly 

 more feeble than when the medulla itself is touched; when at the same time a 

 fasciculus of the posterior roots is cut, a movement of the whole is produced in 

 the member to which the fasciculus proceeds. 



*' The same trials were made upon the anterior fosciculi, and analogous results 

 obtained, but in an inverse sense ; for the contractions excited by pinching, 

 pricking, &c., are very strong and even convulsive, while the signs of sensibility 

 are scarcely visible. Tiiese facts, then, are confirmative of those which I have 

 announced ; only, they seem to establish that sensation resides not exclusively 

 in the posterior roots, any more than movement in the anterior. Yet one diffi- 

 culty may be raised. When, in the experiments which precede, the roots have 

 been cut, they were continuous with the spinal marrow : might not the shock 

 communicated to this be the real origin both of the contractions and of the pain 

 experienced by the animals ? To resolve this doubt, I have repeated the experi- 

 ments after having separated the roots from the medulla, and would say that 

 except in two animals in which I observed contractions when I pinched or pulled 

 the anterior and posterior fasciculi, I perceived in all the other cases no sensi- 

 ble efi'ect from the irritation of the anterior or posterior roots thus separated 

 from the medulla. 



"I had still another kind of test to which to submit the spinal roots : this was 

 galvanism. I have, consequently, excited those parts by this means; first 

 while leaving them in their ordinary state, and then by cutting them at their 

 spinal extremity, so as to place them on an isolating body. In these difilerent 

 cases I have obtained contractions with the two kinds of roots, but the con- 

 tractions which followed the excitation of the anterior roots were, in general, 

 much stronger and more complete than those produced when the electric current 

 was established by the posterior ones. The same phenomena took place whether 

 the zinc or copper pole were applied on the nerve. 



"It would now remain to render an account of the researches which I have 

 made in attempting to follow the isolated sensation and movement beyond the 



