symptom of paralysis of these muscles is inability to corrugate the brow upon one side, as in frowning.

Paralysis of the muscles that dilate the nostrils has been shown to have an important influence upon respiration through the nose. It was the synchronism between the acts of dilatation of the nostrils and the movements of inspiration which first led Sir Charles Bell to regard the facial as a respiratory nerve. In instances of complete paralysis of the nostril of one side, there is frequently some difficulty in inspiration. Sir Charles Bell refers to a case in which, when "the patient lay with the sound side against the pillow, he was under the necessity of holding the paralytic nostril open with the fingers, in order to breathe freely." In the horse, the movements of the nostrils are essential to respiration, the animal being unable to breathe through the mouth. When both facial nerves are divided in this animal, the nostrils collapse and are occluded with each effort at inspiration, and death takes place from suffocation.*

Sir Charles Bell' and others have also noted the interference with olfaction, due to the inability to inhale with one nostril, in cases of facial paralysis. The influence of the nerve in the act of conveying odorous emanations to the olfactory membrane is sufficiently evident after what we have remarked concerning the action of the facial in respiration.

The effects of paralysis of the other superficial muscles of the face are manifested in the distortion of the features, from the unopposed action of the muscles upon the sound side; a phenomenon which is sufficiently familiar to the prac

1 BELL, The Nervous System of the Human Body, London, 1844, p. 54. The case referred to is No. VI., in the Appendix; but this seems to be an error, as no such circumstance is mentioned in this case. Still the fact illustrated is not to be doubted.

2 BERNARD, Leçons sur la physiologie et la pathologie du système nerveux, Paris, 1858, tome ii., p. 38.

3 BELL, Of Smelling as influenced by the Portio Dura of the Seventh Nerve,The Nervous System, London, 1844, p. 134.

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tical physician. When facial palsy affects one side and is complete, the angle of the mouth is drawn to the opposite side, the eye upon the affected side is widely and permanently opened, even during sleep, and the face has upon that side a peculiarly expressionless appearance. When a patient affected in this way smiles or attempts to grimace, the distortion is much increased. The lips are paralyzed upon one side, which sometimes causes a flow of saliva from the corner of the mouth. In the lower animals that use the lips in prehension, paralysis of these parts interferes considerably with the taking of food. The flaccidity of the paralyzed lips and check in the human subject sometimes causes a puffing movement with each act of expiration, as if the patient were smoking a pipe.

We have already seen that the buccinator is not supplied by filaments from the nerve of mastication, but is animated solely by the facial. Paralysis of this muscle interferes materially with mastication, from a tendency to accumulation of the food between the teeth and the cheek. Patients complain of this difficulty, and sometimes keep the food between the teeth by pressure with the hand. In the rare instances in which both facial nerves are paralyzed, there is very great difficulty in mastication from the cause just mentioned.

The functions of the external branches of the facial are thus sufficiently simple; and it is only as its deep branches affect the taste, the movements of deglutition, etc., that it is difficult to ascertain their exact office. As this is the nerve of expression of the face, it is in the human subject that the phenomena attending its paralysis are most prominent. When both sides are affected, the appearance is most remarkable, the face being absolutely expressionless and looking as if it had been covered with a mask.

CHAPTER VI.

SPINAL ACCESSORY AND SUBLINGUAL NERVES.

Spinal accessory nerve (third division of the eighth)-Physiological anatomyProperties and functions of the spinal accessory-Functions of the internal branch from the spinal accessory to the pneumogastric-Influence of the spinal accessory over the vocal movements of the larynx-Influence of the internal branch of the spinal accessory upon deglutition-Influence of the spinal accessory upon the heart-Functions of the external, or muscular branch of the spinal accessory-Sublingual, or hypoglossal nerve (ninth)— Physiological anatomy-Properties and functions of the sublingual-Glosso-labial paralysis.

A DESCRIPTION of the properties and functions of the spinal accessory and the sublingual completes the physiological history of the motor nerves emerging from the cranial cavity. The functions of these nerves are important, and, in the case of the spinal accessory, possess considerable interest, from the fact that physiological investigations have, only within a few years, determined the significance of certain of its anatomical relations. As we have done in studying the other motor nerves, we will treat successively of their anatomical relations, general properties and functions.

Spinal Accessory Nerve. (Third Division of the Eighth.) -The spinal accessory nerve, from the remarkable extent of its origin, its important anastomoses with other nerves, and its curious course and distribution, has long engaged the attention of anatomists and physiologists, who have advanced many theories with regard to its office. We will content ourselves, however, with a simple description of its

anatomy as it appears from late researches, and will begin its physiological history with the comparatively recent experiments which have advanced our positive knowledge of its properties.

Physiological Anatomy.-The origin of this nerve is very extensive. A certain portion arises from the lower half of the medulla oblongata, and the rest takes its origin below, from the upper two-thirds of the cervical portion of the spinal cord. That portion of the root which arises from the medulla oblongata is called, by the French, the bulbar portion, the roots from the cord constituting the spinal portion. Inasmuch as there is a marked difference between the functions of these two portions, the anatomical distinction just mentioned is important.

The superior roots arise by four or five filaments from the lower half of the medulla oblongata below the origin of the pneumogastrics. These filaments of origin, in preparations hardened by prolonged immersion in alcohol, are shown to be connected with the lateral portion of the medulla, and not with the posterior columns. Their origin scems, therefore, to be from the motor tract.'

The spinal portion of the nerve arises from the upper part of the cervical division of the spinal cord, between the anterior and posterior roots of the upper four or five cervical nerves. The filaments of origin are from six to eight in number. The most inferior of these is generally single, the other filaments being frequently arranged in pairs. These take their origin from the lateral portion of the cord, rather nearer the posterior median line than the roots from the medulla oblongata.

Following the nerve from its most inferior filament of origin upward, it gradually increases in size by union with its other roots, enters the cranial cavity by the foramen magnum, and passes to the jugular foramen, by which it

1 SAPPEY, Traité d'anatomie descriptive, Paris, 1852, tome ii., p. 298.

emerges, in connection with the glosso-pharyngeal, the pneumogastric, and the internal jugular vein.

In its course, the spinal accessory anastomoses with several nerves. Just as it enters the cranial cavity, it receives filaments of communication from the posterior roots of the upper two cervical nerves. These filaments, however, are not constant. It frequently, though not constantly, sends a few filaments to the superior ganglion, or ganglion of the root of the pneumogastric. After it has emerged by the jugular foramen, it sends a branch of considerable size to the pneumogastric, from which nerve it also receives a few filaments of communication. This branch will be again referred to in connection with the distribution of the nerve. In its course, it also receives filaments of communication from the anterior branches of the second, third, and fourth cervical nerves.

In its distribution, the spinal accessory presents two branches. The first, or anastomotic branch, passes to the pneumogastric just below the plexiform enlargement which is sometimes called the ganglion of the trunk of the pneumogastric.

The internal, or anastomotic branch, is composed principally, if not entirely, of the filaments that take their origin from the medulla oblongata. As it joins the pneumogastric, it subdivides into two smaller branches. The first of these forms a portion of the pharyngeal branch of the pneumogastric. The second becomes intimately united with the pneumogastric, lying at its posterior portion, and furnishes filaments to the inferior, or recurrent laryngeal branch, which is distributed to all of the muscles of the larynx except the crico-thyroid. The passage of the filaments from the spinal accessory to the pharyngeal branch of the pneumogastric is easily observed; but the fact that filaments from this nerve pass to the larynx by the recurrent laryngeal has been ascertained only by physiological experiments. The external, or large branch of the spinal accessory,