122 MEMOIE OF MAGENDIE. 



the nervous current, these discoveries of new nerves and new ganglions will not 

 only be useless, but prejudicial; they will serve only to increase the confusion." 



A single philosophical, but just and precise idea sufficed M. Bell for the re- 

 moval of this confusion. He sees two distinct nerves distribute their branches 

 to all parts of the face ; three nerves of different origin proceeding to the tongue, 

 four to the throat; the nerves of the neck presenting a most complicated ar- 

 rangement; and he inquires why is this ? Why this multiplication of nerves — 

 why different nerves for the same part ? Why, for example, two nerves for 

 the face ? " Here," says M. Bell, " we naturally ask, whether these nerves fulfil 

 the same function — whether they contribute a double contingent of the same 

 property or faculty, or whether they do not fulfil different functions % After 

 having called to our aid," he continues, " all the information furnished by the 

 structure of the human body and by comparative anatomy, we proceed to de- 

 cide the question by experiments." Thus we see, it is always anatomy which 

 proposes the question, which suggests the idea ; but, as we further see, it is al- 

 ways experiment, and experiment inevitably, which gives the answer.* 



M. Bell therefore divides, in an animal, the seventh pair, that is to say one 

 of the two pairs between which a decision is to be pronounced, and the animal 

 loses only the respiratory movement of the face, simply the dilatation of the 

 nostrils. He divides the fifth pair in another animal ; this loses the movement 

 of the lips which serves for manducation, a voluntary movement ; but it preserves 

 the movement of the nostrils, a respiratory movement. The former no longer 

 respires by its nostrils, yet uses its lips to collect its food ; the latter respires by 

 its nostrils as usual, but can no longer use its lips to collect its food and eat. 

 Nor is this all : when the seventh pair is cut, the animal does not suffer ; and 

 when the fifth pair is cut, it experiences acute pain. Again, the seventh pair 

 being cut, the face preserves all its sensibility, while, the fifth pair being cut, 

 all the sensibility of the face is lost. A difference of properties, then, of the 

 most express nature separates the seventh pair from the fifth. The former is 

 insensible, is pvuely motive, and serves only for the resjnratory movement of the 

 face; the latter is at once sensible and motive, and serves at the same time for 

 the sensibility of the face and its voluntary movement. 



There are nerves, therefore, which are only motors, like the seventh pair ; 

 others which are at once motors and sensitive, like the fifth ; and others still 

 which are only sensitive, like all the nerves, for example, of the special senses. 

 And, as regards each nerve, its property, its function depends on its origin. 

 The nerve of the fifth pair springs from two roots, the one anterior, the other 

 posterior ; it derives from the former its motive faculty, and from the latter its 

 sensitive faculty ; it is a double nerve, a nerve composed of two nerves, one 

 anterior, the other posterior — one for movement, the other for sensation. Though 

 springing from the encephalon, it is, from its two-fold origin and its two-fold 

 function, a true nerve of the spine.f The nerve of the seventh pair, on the 

 contrary, is a single nerve; it has but one origin, and that is anterior; it is 

 purely motive. Lastly, the nerves of the senses have also but one origin, but 

 this is posterior, and they are purely sensitive. 



Upon this principle cf their radication, then, (and the great result of the re- 

 searches of M. Bell is to have taught us that it is by their radicles that we must 



* "Experiments," says M. Bell, " have never led to discoveries." {Natural System, &c., p. 

 251.) This is not wisely said; it is to make experimental art bear the whole bm-den of tho 

 ill-humor entertained towards the experiments of M. Magendie. " Let the physiologists of 

 France," M. Bell further says, "borrow from us and follow up our opinions with experiments," 

 (p. 257.) This troublesome M. Magendie has cost us many a sarcasm. 



t Add to this that, hke the nerves of the spine, the posterior root, that namely of sensation, 

 is provided with a ganglion. It was supposed, previous to M. Bell, that the office of the 

 ganglions was to arrest sensibility. It has been found, by experiment, that the posterior, 

 that is the sensitive nerves are precisely those which have a ganglion, and they are the only 

 ones which have it. 



