The fourth nerve (patheticus) has already come under our notice, taking its origin on the valve of Vieussens, and curiously winding a long course, though but a delicate thread, to attain the involuntary superior oblique muscle of the eye. In many animals the two nerves join together and do not appear attached at all to the encephalon. The fourth nerve in fishes certainly sometimes originates from beneath and behind the optic lobes, as in man; a fact, denied by the generally accurate Desmoulins.

The fifth pair of nerves (trigemini) are very large; enormous in such animals as have the face or its appendages much developed. Bell considered it to arise by a double root, one being a smaller motor portion, generally allowed to arise from the pons and the anterior crura of the cerebellum, the other, the large sensory root, as plainly traceable to the posterior columns of the medulla oblongata, but no doubt in part from the middle involuntary tract; and this circumstance throws light on various phenomena, for instance, why irritating the nasal fossæ should produce the convulsive respiratory action of sneezing, the consent of the buccal, palatal, and other muscles in yawning and breathing, the loss of taste in catarrhs, &c. We have already mentioned the Casserian ganglion, combining the three nerves, going through the orbit and upper and lower jaws. The motor portion of the nerve does not enter the ganglion, but is distributed, in conjunction with the sensitive part of the third branch of the nerve, to the muscles and parts of mastication. Another important function, a modification, however, of common sensation, taste, is said by some to be the endowment of the lingual branch of this inferior maxillary nerve, but to form which, under the name of gustatory nerve, the lingual first receives a small but remarkable nerve, the Vidian.* When the fifth nerve is diseased it gives the

* According to Valentin, the glosso-pharyngeal is the sensuous, the fifth the sensitive nerve of the tongue. When irritated experimentally, the glosso-pharyngeal appears in some instances to have produced pain, in others muscular contractions of the parts to which it is distributed, as

exquisite pain of tic douloureux, when it is paralysed loss of sensation in the face takes place, also the power of feeling or moving the food in the affected side of the mouth; in some cases, perhaps, the motor portion may be unaffected, and then the patient would still have the power of using the temporal and masseter muscles, and of biting. In these cases of paralysis smell and sight remain, but the sensibility of the ocular envelopes, its great safeguard being gone, in chronic cases the cornea becomes opaque from attacks of inflammation. Motion of the face remains perfect, at least the involuntary or respiratory motions derived from the seventh nerve.

The sixth nerve (abducens oculi) arises from the corpora pyramidalia, immediately behind the pons from which it receives some fibres; it has been already mentioned as a motor nerve of the eye.

The seventh nerve consists of two others, very different in function. The auditory or nerve of hearing (portio mollis), originates from the posterior part of the medulla oblongata at the bottom of the fourth ventricle, and the facial (portio dura) is placed in apposition with it in its course, conveying motion to the superficial muscles of the face, and no doubt originating from the middle respiratory tract, in some animals perhaps rather from the motor tract, and in them it may be an ordinary motor nerve. Paralysis of this nerve on one side is very common, being popularly known as a blight, and is often more curious than serious, yet even now not understood by some. Its cause is seldom dependent on cerebral lesion, but on cold, enlarged glands, earache, &c. The symptoms are interesting; the face on the affected side is perfectly inanimate in talking, smiling, or sneezing, whilst the corresponding muscles of the other side, having lost the resistance of their antagonists, draw up the features and well as increased flow of saliva, these last probably by reflex action. We believe Valentin's view to be correct; the back of the palate certainly has taste, as may be proved by touching it with a stick of sugar-it has nerves from the glosso-pharyngeal, but not from the gustatory.

mouth in a remarkable manner; the orbicularis of the eyelids cannot close the eye, and some inflammation of this organ may thus arise in this case, as in paralysis of the fifth. A common case is now before the author, in a young woman, who twelve months back had the affection on the opposite side earache preceded the attack for about a fortnight, pain in the face and neck extending to the shoulder, curious distortion when she attempts to whistle or smile, slight numbness or stiffness on the affected side, and of that side of the tongue, which is protruded straight, smell and taste affected a little on the same side. Bernard attributes the last symptom to the chorda tympani branch being affected.

The auditory nerve accompanying the facial part way through the temporal bone, enters the internal ear, that beautiful organ which in all animals seems to have its nerves in relation to the respiratory, constituting a provision for the animal's safety in case of surprise or attack, as well as a relation between the voice and hearing. The auditory no doubt also has other connexions with the greater nervous centres, the cerebrum and cerebellum.

We

The eighth or proper respiratory nerves may be divided into three others on each side, the glosso-pharyngeal, the pneumo-gastric or vagus, and the spinal accessory. All of these may be said to arise in a line, by many roots or funiculi, from the lateral columns, the last as low down as the sixth cervical nerve, rising up into the skull, and again making its exit with the glosso-pharyngeal and vagus. shall refer to these again. The eighth nerve in fishes gives branches to the side of the body, and is one of the electromotor nerves of the torpedo; in the carp it forms, according to Desmoulins, the nerve of taste. The vagus has been supposed to be sensitive as well as respiratory, the spinal accessory purely motor, but the anatomy does not quite agree with this last view. That the latter is motor and efferent indeed has been proved, because when it is cut across, and the distal end irritated, muscular movement has taken place; when the cut end next the brain is irritated no motion is

produced in the vagus or any other respiratory nerve, proving the spinal accessory not to be a nerve of sensation or afferent. Hence Bernard, Reid, and Valentin, consider its functions to be motor and not respiratory, but its peculiar and curious origin and connexions appear to connect it with the latter system. When both the vagus and spinal accessory are cut across experimentally the movements of swallowing are spoiled, the food remaining in the passage to the stomach. The upper laryngeal branch of the vagus is probably sensitive as far as the larynx is concerned, the lower motor. When the trunk of the vagus is irritated, the movements of the stomach, heart, and bowels, are affected. Dr. Reid found on cutting that nerve, that the movements of the heart slackened-on removing the brain they fell still more.

The ninth nerve (lingual or hypoglossal) supplies the muscles of the tongue, and arises from the same line as the motor roots of the spinal nerves. The tongue has, however, two other principal nerves, and the ninth in man is perhaps the nerve of speech in conjunction, it may be, with the inferior maxillary branch of the fifth, but much more with his higher intellectual faculties. It gives off a curious branch descending in the neck, which connects it with the phrenic and diaphragm (sometimes given off by the vagus), the meaning of which appears obvious. The respiratory movements of the tongue and pharynx, some will say, depend upon the glosso-pharyngeal; the sympathy of these two latter parts is required in the act of breathing, and particularly breathing in combination with swallowing.

The tenth nerve (suboccipital) is analogous to the other spinal nerves. It is sometimes, however, destitute of a posterior root.

The brain itself has no nerves, but there are some fine twigs, especially from the sympathetic, which go to the meninges, and also send up branches along the great vessels, and form some small ganglia upon them; in fact this nerve may be said to communicate with all the cerebral nerves, and particularly with several ganglia situated upon them—

the ciliary or lenticular, for instance, in the orbit, mentioned already. Meckel's ganglion is situated in the spheno-palatine fissure, uniting the nerves of the maxillary division of the fifth before they go to, or rather leave the middle parts of the face, the nose, palate, antrum, orbit, and pharynx, in the same way that the Casserian ganglion unites the primary division of the same nerve, also communicating with the general ganglionic system by means of the Vidian nerve, and some of its filaments, it may be, conferring that gustatory power to the back of the palate which it evidently possesses; the Vidian also appearing to be a curious connexion between the palate, the gustatory nerve, and the salivary ganglia.

There are some very curious nervous connexions in the internal ear and temporal bone by means of minute branches of nerves of the fifth and the Vidian, the sympathetic, the facial, the glosso-pharyngeal, and the vagus-in this minute cavity, or just around it, anastomose nerves of sense, common sensation, motion, respiration, and organic life. The keen eyes of modern anatomists have traced these apparently constant and regular filaments, and discovered other minute ganglia which cannot be described here, the media probably of different sympathies about the head and face. The submaxillary ganglion supplies the gland of that name, curiously connected with the gustatory nerve as already observed.

The union of the branches of the fifth nerve in the ganglia of Casserius and Meckel, explains how, in irritation of one branch of the nerve (from a carious tooth, for instance), the sensation may be reflected and attributed to the extremity of some other.

The spinal cord is double and symmetrical like the brain. The principal prominences above have no doubt tracts continued from them downwards, being marked more or less by grooves, the anterior tracts (motor), the two lateral (respiratory), and the two posterior (sensitive). The anterior and posterior roots of the nerves also, arising from the slight