MEMOIR OF MAGENDIE. 117 



to the immediate, the direct destruction of the tactile sensibility. It destroys 

 vision, smell, hearing, only by the consecutive disorder. M. Magendie himself 

 verified this as regards vision, or the sensibility of the retina. " I cut the optic 

 nerve at its entrance into the eye ; if the nerve of the fifth pair or any other could 

 perceive light, the section thus made could not prevent it. But it is quite other- 

 wise; the sight is completely abolished, as well as all sensibility, to the strongest 

 light, even that of the sun concentrated by a lens. Wishing to submit to this 

 last proof an animal whose fifth pair alone was divided, I easily recognized that 

 on causing the eye to pass suddenly from shade to the direct light of the sun, 

 there was an impression, for the eyelids closed. All sensibility, therefore, is not 

 lost in the retina by the section of the fifth pair, though there is but a feeble 

 •portion which remains." (Precis Elc?ncntaire de Physiologie, t. i, p 100,) 

 M. Magendie had thus formed a just idea as regards vision ; and the same would 

 have been the result as regards audition and olfaction if he had made on the 

 acoustic and olfactory nerves the experiment which he performed on the optic 

 nerve. 



2. It was known from the admirable experiments of M. Bell that the sensibility 

 of the face proceeds from the fifth pair, and the respiratory movement from the' 

 seventh. A very fine experiment of M. Eschricht, of Copenhagen, suggested 

 to M. Magendie an inquiry in order to determine the action of the fifth pair on 

 the seventh. (See Journal de Physiologie, t. viii, p. 228 and 339.) In his 

 Lectxires we follow, step by step, the progression by which he passes from the 

 idea of a recurrent sensibility by nervous anastomosis to the idea of a simple 

 association of the fibres of one pair with those of another. 



" The sensibility of the facial nerve," he says, (Legons sur le Systeme Ner- 

 veux, t. ii, p. 166,) "is communicated to it by its anastomosis with the fifth 

 pair. This expression of anastomosis will cease to represent a just idea if, by 

 anastomosis, we understand the fusion of two nerves into a single one; there 

 is no true fusion in the case. I had heretofore thought the contrary, but my 

 last experiments force me to modify my views. The branches of the fifth 

 pair, and of the seventh, which we find united, have their fibres associated 

 in such a manner that each fibre preserves the respective properties of the 

 nerve from which it emanates. Thus the fibres of the fifth pair remain sensitive 

 fibres; the fibres of the seventh pair remain motive fibres. The trunk which 

 they constitute by their association is thus a trunk composed of motive and of 

 sensitive fibres, and not of a single order of fibres sensitive and motive at the 

 same time. Cut the nerve of the fifth pair ; there remain only motive fibres, 

 and all sensibility disappears. If then I avail myself indiscriminately of the 

 words association, anastoiyiosis, you will know what signification I give them. 

 (Lecons, Sfc, t. ii, p. 185.) We know now what is to be understood by anasto- 

 mosis between a nerve of sensibility and a nerve of movement. The sensitive 

 fibres associate themselves with the motive fibres, and wherever the former exist 

 you meet with sensibility. The association of two nerves is attended with no 

 confusion of their properties ; they arc exercised conjointly in the same nervous 

 trunk, but they remain independent, since we can isolate them. (Ibid, p. 191.) 

 The seventh pair receives from the fifth, not sensibility, but sensitive fibres. Its 

 own fibres form a nerve exclusively motive. {Ibid, p. 209.) 



Cerebrospinal liquid. — As early as 1825 M. Magendie had read to the acad- 

 emy a memoir on this subject; he read a second in 1826, a third in 1828, 

 Long before, however, in 1769, the celebrated Italian physician Cotugno had 

 recognized and described this liquid; but what Cotugno had said was altogether 

 forgotten when M. Magendie in turn occupied himself with this important sub- 

 ject.* 



* Circa meduUam, per sphtutn descendentem, &c. — "Around the medulla, as it descends 

 through the spine, there is a considerable space ; but this extra space is not wholly free. 

 Along it descends the dura mater, which, formed into a tube at its exit from the great ocinp- 



