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sibility is complete after division of the nerve behind the Gasserian ganglion, these results may not follow. Nor are they explained by deficiency in the lachrymal secretion, for they are not observed when both lachrymal glands have been extirpated. They are not due to exposure of the eyeball, for they do not follow upon section of the facial. Nor are they due simply to an enfeebled general condition, for, in the experiment we have detailed, the animal died of inanition after section of the nerve, without any evidences of inflammation. In view of the fact that section of sympathetic filaments is well known to modify the nutrition of parts to which they are distributed, producing congestion, increase in temperature, and other phenomena, it is rational to infer that the modifications in nutrition which follow section of the fifth after it receives filaments from the sympathetic system, not occurring when these sympathetic filaments escape division, are to be attributed to lesion of the sympathetic, and not the division of the sensory nerve itself.

A farther explanation is demanded for the inflammatory results which follow division of the sympathetic filaments joining the fifth, inasmuch as division of the sympathetic alone in the neck produces simply exaggeration of the nutritive processes, as evidenced chiefly by local increase in the animal temperature, and not the well-known phenomena of inflammation.

It has been remarked by Bernard, that the "alterations in nutrition appear more promptly in animals that are enfecbled." Section of the small root of the fifth, which is unavoidable when the nerve is divided in the cranial cavity, generally interferes so much with mastication as to influence seriously the general nutrition; and this might modify the

1 BERNARD, Leçons sur la physiologie et la pathologie du système nerveux, Paris, 1858, tome ii., p. 62. Bernard (op. cit., p. 518), in discussing the effects upon calorification and nutrition of the face of division of the sympathetic in the neck, states that "the effects of calorification of the great sympathetic may be transformed into inflammatory phenomena when the animal becomes enfeebled." He divided the sympathetic with the pneumogastric in the neck of a dog, on the

nutritive processes in delicate organs, like the eye, so as to induce those changes which are called inflammatory. The following observation, communicated by Dr. W. H. Mason, Professor of Physiology in the Medical Department of the University of Buffalo, is very striking in this connection:

The fifth pair of nerves was divided in a cat in the ordinary way. By feeding the animal carefully with milk and finely-chopped meat, the nutrition was maintained at a high standard, and no inflammation of the eye occurred for about four weeks. The supply of food was then diminished to about the quantity it would be able to take without any special care, when the eye became inflamed, and perforation of the cornea and destruction of the organ followed. The animal was kept for about five months; at the end of which time, sensation on the affected side, which had been gradually improving, was completely restored.'

The explanation we have to offer of the consecutive inflammatory effects of section of the fifth with its communicating sympathetic filaments is the following: By dividing the sympathetic, the eye and the mucous membranes of the nose, mouth, and ear are rendered hyperemic, the temperature is probably raised, and the processes of nutrition are exaggerated. This condition of the parts would seem to require a full supply of nutritive material from the blood, in order to maintain the condition of exaggerated nutrition; but when the blood is impoverished, probably as the result of deficiency in the introduction of nutritive matter, from paralyleft side. A few days after, he made experiments on the salivary secretion, and finally took away a portion of the cephalo-rachidian fluid. "This last operation made the animal sick and produced an inflammation of the nervous centres: death occurred five days after. What was remarkable was that the mucous membranes on the side of the face corresponding to the section of the sympathetic became the seat of violent inflammation, from the moment that the animal began to become enfeebled from the disease. There was abundant suppuration from the nostril, the buccal mucous membrane, and the conjunctiva of the left side, while on the opposite side the corresponding mucous membranes were in the normal condition."

1 Written communication from Prof. Mason.

sis of the muscles of mastication upon one side, the nutritive processes in these delicate parts are seriously modified, so as to constitute inflammation. The observation just detailed is an argument in favor of this view; for here the inflammatory action seemed to be arrested when the action of the paralyzed muscles was supplied by careful feeding. With this view, the disorders of nutrition observed after division of the fifth may properly be referred to the sympathetic system.

Pathological facts in confirmation of experiments upon the fifth pair in the lower animals are not wanting; but it · must be remembered that, in cases of paralysis of the nerve in the human subject, it is not always possible to locate exactly the seat of the lesion and to appreciate fully its extent, as can be done when the nerve is divided by an operation. In studying these cases, it sometimes occurs that the phenomena, particularly those of modified nutrition, are more or less contradictory.

In nearly all the works on physiology, we find references to cases of paralysis of the fifth in the human subject. One of the most interesting is the case already referred to, reported by Mayo, which was published before the experiments of Magendie.' Numerous cases of this kind have been collected by Longet. In the appendix to the work of Sir Charles Bell on the Nervous System, several cases are reported, observed by himself and collated from various sources. We have already referred to the cases cited by Schiff and by Lussana, some of which showed alteration of taste, while in others this symptom was absent. In a recent article by Dr. H. D. Noyes, Professor of Ophthalmology in the Bellevue Hospital Medical College, two interest

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page 196.

2 LONGET, Anatomie et physiologie du système nerveux, Paris, 1842, tome ii., et seq.

p. 191,

3 BELL, The Nervous System of the Human Body, London, 1844, Appendix. 4 See page 195.

It is unnecessary to cite all the cases reported of paralysis of the fifth, but they are quite numerous. In addition to those already referred to, the following

ing cases are reported, which we had an opportunity of examining during the progress of treatment. In both of these cases, there was inflammation of the eye. In one case, the tongue was entirely insensible upon on side, but there was no impairment of the sense of taste. An interesting feature in one of the cases was the fact that an operation upon the eyelid of the affected side was performed without the slightest evidence of pain on the part of the patient.'

These cases of paralysis of the fifth in the human subject in the main confirm the results of experiments upon the inferior animals. In all the cases in which the fifth nerve alone was involved in the disease, without the portio dura of the seventh, there was simply loss of sensibility upon one side, the movements of the superficial muscles of the face being unaffected. When the small root was involved, the muscles of mastication upon one side were paralyzed; but in certain cases in which this root escaped, there was no muscular paralysis. The sense of sight, hearing, and smell, except as they were affected by consecutive inflammation, were little, if at all, disturbed in uncomplicated cases. The sense of taste in the anterior portion of the tongue was perfect, except in those cases in which the seventh, the chorda tympani, or the lingual branch of the fifth after it had been joined by the chorda tympani, was involved in the disease. In some cases, there was no alteration in the nutrition of the organs of special sense; but in this respect the facts with regard to the seat of the lesion are not so satisfactory as in experiments upon the lower animals, it being difficult, in most of them, to limit the exact boundaries of the lesion.

are the most important and satisfactory in their details: The case reported by Montault (Journal de physiologie, Paris, 1829, tome ix., p. 113); a case by Dr. Beveridge (Medical Times and Gazette, London, 1868, No. 921, p. 199); a case by Althaus (Medico-Chirurgical Transactions, London, 1869, vol. lii., p. 27); and two cases by Rosenthal (Medicinische Jahrbücher, Wien, 1870, Bd. xix., Heft ii. und iii., S. 163).

1 NOYES, Paralysis of the Fifth Cerebral Nerve, and its Effects.-New York Medical Journal, 1871, vol. xiv., p. 163, et seq.

CHAPTER VIII.

PNEUMOGASTRIC, OR PAR VAGUM NERVE.

Pneumogastric nerve (second division of the eighth)-Physiological anatomyProperties and functions of the pneumogastric-General properties of the roots-Properties and functions of the auricular nerves-Properties and functions of the pharyngeal nerves-Properties and functions of the superior laryngeal nerves-Properties and functions of the inferior, or recurrent laryngeal nerves-Properties and functions of the cardiac nerves, and influence of the pneumogastrics upon the circulation-Depressor-nerve of the circulation-Properties and functions of the pulmonary branches, and influence of the pneumogastrics upon respiration-Properties and functions of the œsophageal nerves-Properties and functions of the abdominal branches -Influence of the pneumogastrics upon the liver-Influence of the pneumogastrics upon the stomach and intestines-Summary of the distribution, properties, and functions, of the pneumogastrics.

Of all the nerves emerging from the cranial cavity, the pneumogastric, the second division of the eighth pair, presents the greatest number of anastomoses, the most remarkable course, and the most varied and interesting functions. Arising from the medulla oblongata by a purely sensory root, it communicates with at least five motor nerves in its course, and is distributed largely to muscular tissue, both of the voluntary and the involuntary variety. Finally, there is no nerve that has been the subject of such extended and elaborate anatomical and physiological investigations, and none, concerning the properties and exact functions of which there has been so much difference of opinion.

We shall have to treat of the influence of the pneumogastric upon the act of deglutition, the heart and circulatory

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