FIFTH PAIR OF NERVES. 



311 



no such influence exists; and indeed the 

 <l:ilu ii|i(ni which it has been assumed, instead 

 of proving the position, leave it precisely as it 

 wav ; lor insomuch as the occurrence of the 

 phenomena upon the section prove the exist- 

 emc of the inHnence of the nerve, in the same 

 degree does the absence of the phenomena 

 upon the section of the nerve disprove it. 



Hut was the inflammation caused by the 

 section of the nerve ? This question, which cer- 

 tainly ought to have been determined satisfac- 

 torily before a theory had been founded upon 

 the assumption, appears to the writer to have 

 been decided too hastily in the affirmative. If 

 the section were the cause, no sufficient re nson 

 can be assigned why it should occasion inflam- 

 mation in one part, to which the nerve is distri- 

 buted, and not in another, yet such is the case; 

 the eye is the only part in which inflammation 

 supervenes, either so uniformly or so quickly 

 as to afford any ground for attributing the pro- 

 cess to the section. In the second place, were 

 the section the real and essential cause, it can- 

 not be supposed either on the one hand that 

 non-essential circumstances could influence, or 

 at all events prevent the effect, or on the other, 

 that they could produce it. Now it will pre- 

 sently appear that both the one and the other 

 may take place ; and a comparison of Magen- 

 die's experiments and their results would alone 

 suffice to shew that the real cause is to be 

 sought elsewhere than in the section of the 

 nerve. Magendie divided the nerve in three 

 different situations ; first, through the temporal 

 fossa ; secondly, within the cranium, between 

 the Gasserian ganglion and the pons Varolii ; 

 and thirdly, at the margin of the fourth ventri- 

 cle ; and his own general account of the results, 

 which has been already cited, is as follows : 

 " those alterations in the nutrition of the eye are 

 the less complete, the less rapid, as we recede 

 more from the point of branching ol the nerves 

 of the fifth pair, and as we cut, within the cra- 

 nium, its fasciculus of origin the nearer to its 

 insertion ; finally, the section on the margin of 

 the fourth ventricle no longer produces any 

 alteration." It is plain, then, that the nerve 

 may be cut, and the changes in the eye ensue 

 or not, according to circumstances to be yet 

 explained. On the other hand, that effects 

 similar in kind, if not equal in degree, may be 

 produced by circumstances not essential to their 

 production, according to the doctrine main- 

 tained, but incidentally associated with the 

 supposed cause, that such effects may be pro- 



buccal membrane." In neither of those extracts is 

 >hrre mention of inflammation or sloughing ; and 

 the utccration which is mentioned, is attributed to 

 . nun IHT cause than the section of the nerve. On 

 t!ie other band, the writer b as frequently divided 

 the lingual branches of the fifth nerve and |>re- 

 served the animals for months afterward, and he 

 has been unable to delect any change in the condi- 

 tion of the tongue, except this, that in some the tip 

 of the organ, from being allowed to remain between 

 the teeth, and thus lo be exposed to injury, ulce- 

 r.iled, and this continued until the tip was re- 

 moved, when (he extremity of the organ healed . 

 and it appeared to be in all other respects as 

 before. 



dmed liy such circumstances, when dissociated 

 from the other and operating separately, the 

 author feels justified in asserting, from the re- 

 sult of some experiment:! lately made by him- 

 self, which lead to the conclusion that similar 

 effects may be produced without the section of 

 the nerve at all, and that an injury in the vici- 

 nity of the orbit may excite them though nei- 

 ther the trunk of the fifth itself, nor its ophthal- 

 mic division have been divided. In an endea- 

 vour to determine the nerves of taste, he under- 

 took the removal of the ganglion of Meckel 

 from the dog ; in order to accomplish this it was 

 necessary to displace the zygoma and the coro- 

 noid process of the jaw ; he attempted it seve- 

 ral times before he succeeded, and failed at 

 different stages of the operation ; but in almost 

 every instance tlie eye of the same side became 

 bleared within the next two days. The animal 

 kept it nearly closed : a whitish puriform mat- 

 ter was discharged from it, in quantity propor- 

 tioned to the case, which concreted between 

 the lids ; and the animal made no attempt to 

 remove the matter or cleanse the eye : the affec- 

 tion of the eye was always proportioned to the 

 violence done, and abated with the inflamma- 

 tion of the wound ; and in one of the instances 

 in which the ganglion was removed, it actually 

 produced opacity of the cornea, and ulceration 

 in that structure, which continued utter the 

 lapse of more than a month from the operation ; 

 yet most assuredly neither infra-orbital nor 

 ophthalmic nerves had been divided. Thus, 

 if, on the one hand, the nerve may be cut and 

 the changes not ensue, on the other it may be 

 left uncut, and the changes may occur. 



It may be objected that the effects here de- 

 scribed fall very far short of those which took 

 place in the experiments of Magendie. That 

 they fall short of those which occurred on the 

 division of the nerve in the temporal fossa is 

 quite true, but it is equally so that they far ex- 

 ceed those consequent upon the section at the 

 margin of the fourth ventricle. The objection, 

 therefore, would be devoid of weight, and if 

 we suppose superadded to the violence already 

 done when the nerves are not divided, the ad- 

 ditional violence necessarily inflicted in the 

 division of them, we shall have a ready expla- 

 nation furnished of the higher degree to which 

 the effects produced amount in one case than 

 in the other. 



From the preceding considerations it appears 

 to the author necessary to infer, that the changes 

 which supervene in the eye after the section of 

 the fifth nerve in certain cases, take place inde- 

 pendently of the section, as the primary, imme- 

 diate, or proper cause ; for were it otherwise, 

 it cannot be supposed either that the difference 

 of half an inch to one side or the other, as re- 

 gards the point of section, could so influence the 

 cause as to preventer allow these chan 

 that they could occur, even in degree, without it. 



How, then, are the phenomena to be ex- 

 plained ? It has been suid by Magendie that 

 they are less marked the more we recede from 

 the point of branching of the nerve; but it is 

 to be further observed, that, as we recede from 

 the point of branching of the near, u. 



