To the causes already enumerated must be added the loss of the nervous influence, for it is not intended, in what has preceded, to assert that the section of the fifth has no share in the production of the changes in the eye, but only that it is not the primary or essential cause of them. Indirectly it must contribute powerfully to produce and a;gravate, or it may even excite them ; for by destroying the sensation of the organ, it must leave it exposed to the unin terrupted influence of many irritating agents, which naturally would excite inflammation, were it not that we are warned through the sensibility of the organ to avoid or to remove them, but in every such case they are the im mediate, and the insensibility only the mediate cause of the effects produced, and such, it ap pears to the author, is the part played by the section of the fifth in giving rise to inflamma tion in the eye. It is further to be observed that the occurrence of inflammation in the eye in cases in which the influence of the fifth nerve upon it had been lost, had been noticed and given to the public by Bell prior to the publication of it by Magendie. In the Philo sophical Transactions for 1823, (Magendie's memoir dates 1824,) Sir C. Bell reports the case of a patient under the care of his colleague Dr. Macmichael, in which the surface of the eye was totally insensible, and the eye re mained fixed and directed straightforward, while the vision was entire. " The outward apparatus being without sensibility and mo tion, and the surface not cleared of irritating particles, inflammation has taken place, and the cornea is becoming opaque; thus proving the necessity of the motions of the eye to the preservation of the organ." And in the same volume he reports also a case from the expe rience of Mr. Crampton of Dublin, bearing strongly upon the question, because it shews satisfactorily that the sensation of the organ, and consequently the influence of the nerve, may be obliterated, and inflammation not ensue until a stimulus have been applied, though the conjunctiva manifestly retained its susceptibility to the impression of that sti mulus. Mr. Crampton's account of the case is as follows: " When she told me her eye was dead, as she expressed it, to be certain I drew my finger over its surface, and so far was this from giving her pain, that she assured me she could not feel that I was touching it at all. The eyelids made no effort to close, while I was doing this; but the conjunctiva appeared sen sible to the stimulus, as a number of vessels on the surface of the eye became immediately in jected with blood." Another circumstance may be advanced in fa vour of the opinion that the nerve influences the nutrition of the parts, to which it is necessary to allude, viz. the wasting of the muscles of masti cation in cases of the loss of the nerve's influence. This fact may be otherwise explained; the de velopment of muscles is always influenced by their exercise, which being lost they waste, and it is neutralized by the counter-fact that, though these masticatory muscles waste, the muscles of the face and its other structures do not. In fine there appears to the writer to be no good reason for attributing to the fifth nerve a direct influence upon the nutrition of the structures to which it is distributed; the existence of such an influence would be incompatible with the simplicity of natural laws, for in such case there must be two such influences in existence, one in the nerve directing the nutrition of the parts with which it is connected, and another elsewhere to direct that of the nerve.
Magendie confirms his view of the influence exerted by the fifth nerve upon the functions and nutrition of the eye, by reference to a case published by Serres in the fifth volume of the Journal of Physiology, which " presented all the phenomena attending section of the fifth pair,' and in which there existed complete alteration of the trunk of the nerve in its sen sible portion; " followed by loss of sight, of smell, of hearing, and of taste on the same side." Before detailing this case, the writer cannot refra.n from observing that in such cases none but unquestionable evidence can be admitted if we would arrive at a certain and unquestionable conclusion. Whether the case of Serres be such, it rests with the reader to decide; and first, what was the condition of the patient in other respects? Serres replies : " Ills air was dull; his physiognomy gave, at first sight, the idea of imbecility; he seemed to conceive slowly and to comprehend with difficulty, the questions which were put to him. When he wished to reply, it was evi
dent that he experienced difficulty in express ing himself; he pronounced with difficulty, and the little that he said seemed to require, on his part, a considerable effort : his cranium was voluminous compared to the rest of his body ; some pupils suspecting a commencing hydrocephalus, thought that they observed a separation between the parietal and temporal bones, but the prominence of the eyes made me reject that conjecture ; the maxillary and malar bones were a little separated, which had produced a flattening of the nose; the pa tient had some difficulty in moving the tongue; the motions and sensibility of the limbs were not affected, only he moved the lower extre mities less freely than the upper; he had been for some time subject to epilepsy; he had a sister deaf and dumb." A case so complicated as this, in which there manifestly existed ex tended disease of the encephalon, must be rejected as altogether inconclusive. But to proceed, the patient was admitted into hospital in September 1823: at his admission he had a chronic ophthalmia of his right eye, which was considered scrofulous. In the course of De cember he was attacked by an acute ophthalmia of the same eye, attended by adema of the lids, and commencing opacity of the cornea; the ophthalmia was dispersed after ten or twelve days; but the cornea was rendered altogether opaque throughout its whole extent; of course the loss of vision on that side was the neces sary result. In the course of January 1824 it was observed that the right eye was insensible, and soon after that the eyelid and nostril of the same side were also insensible, and likewise the tongue on that side, while all was natural on the other ; soon after the gums inflamed upon the right; they were red, some white places existed here and there, they were swollen at the circumference of the sockets; the tongue moved always with difficulty; the hearing was not then affected ; in July the affection of the gums extended to the left side, but the right was always more affected than the left. During August the gums became separated on the right from the necks of the teeth ; there existed between the latter and the gums spaces into which tartar and portions of food had pene trated ; the patient suffered from the epileptic paroxysms with variable degrees of severity : he next fell into a general cachexy, with extreme debility, impeded respiration, small frequent pulse, great alteration of countenance, and un usual taciturnity: It is stated that in August he acknowledged deafness on the right, which diminished and again increased; the sensibility was perfectly preserved in all the extent of the right side of the face ; the patient died on the 12th of August. Both the brain and the fifth nerve were found after death much diseased, the brain on the left and the nerve on the right side.
The details of the case have been given more at length than may perhaps seem necessary, but the question is interesting, and as the bearing of the case upon it could not be determined otherwise, the writer has endeavoured to give them faithfully. The difficulty of obtain ing precise knowledge from so complicated a case has been already adverted to. We come next to inquire how far it substantiates the writer's views, or how far it can be considered to establish the opinion of Magendie. Serres, as has been already stated, announces it as an instance of disease of the fifth nerve followed by loss of smell, sight, &c. Surely the loss of these several functions, thus an nounced, should have been satisfactorily esta blished, before asserted ; but such does not appear to have been the case. For the first, notwithstanding the announcement, we find Serres himself, after the patient's death, ac knowledging, " toutefois l'odorat n'avait pas completement disparu, puisque,"* &c. The sense of smell then plainly was not lost. In the next place there was loss of vision, but from what cause? from opacity of the cornea, and, so far as we have data for forming a judgment, from it alone. We have no reason to think that any alteration had been pro duced in the power of the eye to receive sensations of light, any disturbance in the function of the retina, or any other change than the occurrence of a physical impediment to the exercise of a function, which the organ may have retained in full vigour, had it only been allowed to exert it: the evidence, there fore, afforded by the case, is too imperfect to be of value.