scribed and delineated ganglions in the iris of the whale, and had even found in the iris of man a few "small nodules" connected with the nerves. The fibrils from the oculo-motor, the fifth, and the sympathetic in the iris, Budge has not found to present such difference of microscopical characters as to enable him to distinguish one from the other. 1st. Sympathetic. It is the cervical portion of the sympathetic which contains the fibrils destined for the iris. Budge calls these fibrils the iridal sympathetic; they cannot indeed be isolated from the other fibrils in the same nervous trunk; but by Budge's experiments, their origin and course appear to have been as exactly determined as the origin and course of any other nerves of the body.

The fibrils of the iridal sympathetic reach the trunk of the cervical portion of the sympathetic, from the spinal marrow, and medulla oblongata, through the communicating branches of the second and first dorsal, the eighth and seventh cervical, and the hypoglossal.

2nd. Oculo-motor Nerve.-In the rabbit's brain, Budge finds that the oculo-motor nerve arises in five or six fasciculi, of which the strongest disappears in the crus cerebri of the same side, whilst the others turn inwards in order to pass into the crus of the opposite side. Lastly, anteriorly and externally the nerve is joined by more fibres, which run from before backwards, and appears to have a connexion with the anterior pair of the corpora quadrigemina.

3rd. Fifth Nerve.-At the origin of the portio major of this nerve, which alone comes under consideration here, there are an inner and an outer fasciculus, of which the former runs towards the fossa Sylvi, the latter towards the corpus restiforme.

Determination of the Nerves of the Iris.-On cutting the optic nerve, experimenters have not observed any symptom of pain; but at the moment of section of the ciliary nerves, the animal struggles. The seat of this sensibility are the fibrils from the fifth nerve.

Irritation of the optic nerve or retina directly excites the sensation of light and colour only. The pain extending to the head when the eyes are exposed to very strong light, or when mechanical impressions are made on the retina, is indirectly excited; being the result of irradiation from the optic to the fifth nerve.

When nervous irradiation is prevented by section of the optic nerve on the one hand, or of the fifth nerve on the other, exposure of the eye to intense light appears to cause little or no pain. On section of the oculo-motor nerve, neither Budge nor Longet have ever observed any indication of sensibility.

The cervical sympathetic also Budge has found to be insensible, but not so the superior cervical ganglion, which evinces sensibility when irritated.

As a result of Budge's experiments, it appears probable that the sensibility of the iris is dependent solely on the fifth pair.

Influence of the Oculo-motor and cervical Sympathetic on the Iridal Muscles.-Irritation of the trunk of a mixed motor and sensitive nerve causes muscular action directly through the centrifugal fibres, and by reflexion through the centripetal fibres. The reflex muscular action may be more extensive than the direct. If the nerve be cut, and the

distal segment alone be irritated, direct muscular excitement will be the only result. When therefore a nerve has the same sphere of action after division as it has before, it is to be inferred that it is composed of centrifugal or motor fibres only.

Now Budge finds that the contraction of the pupil is as great when he irritates the oculo-motor nerve after section, as when it is still in connexion with the brain. From this it is evident that that nerve is composed exclusively of centrifugal or motor fibres.

When the oculo-motor nerve in mammals and birds is irritated, the pupil contracts; and when the cervical sympathetic in mammals (not in birds) is irritated, the pupil dilates. The experiment on the oculomotor nerve Budge recommends to be performed immediately after death, but that on the sympathetic on the living animal.

A mistake has prevailed, that galvanization of the oculo-motor nerve causes contraction of the pupil at first, but dilatation afterwards. This Budge shows to be owing to care not having been taken to prevent the communication of the galvanism to the adjacent fifth nerve, which contains the sympathetic fibres, on the excitement of which the dilatation of the pupil depends, and that, too, at a period after death when the oculo-motor has already lost its irritability. In birds, in which the sympathetic has nothing to do with the motions of the pupil, the same mistake cannot occur. In short, the only effect on the pupil from excitement of the still irritable oculo-motor is contraction, never dilatation.

Galvanic irritation of the eyeball itself excites contraction of the pupil, the oculo-motor being more irritable than the sympathetic. Again, in birds, in which the iris receives no branches from the sympathetic, galvanic irritation causes contraction; and when the galvanization is suspended, the pupil dilates by elasticity.

As transversely-striated muscular fibres are distinguished by the rapidity of their contraction, so in birds the sphincter pupillae, the fibrils of which are transversely striated, contracts more rapidly when irritated than the sphincter pupillæ of mammals and frogs, the fibrils of which are not striated.

The sympathetic in the neck of a rabbit being isolated and galvanized, the pupil becomes dilated in from one to three seconds. The pupil is dilated also when the galvanic wires are applied to the uppermost cervical ganglion, the carotid twigs, the Gasserian ganglion, and ophthalmic branch of the fifth. Thus is indicated the course of the iridial sympathetic to the iris. The fifth nerve itself, as will be seen below, has no such effect on the motions of the iris-only the sympathetic fibres bound up in it.

Irritation of the Sympathetic in Birds.-In pigeons, Budge has found galvanization of the sympathetic in the neck produce no effect on the motions of the iris. And equally resultless was section of the nerve.

Irritation of the Optic Nerve, and its Influence on the Movement of the Iris. From the experiments of Mayo on birds, and Longet on mammals, it is known that irritation of the optic nerve calls forth contraction of the pupil; and that when the optic nerve is divided this effect follows irritation of the end of the proximal segment, but

not of the end of the segment in connexion with the eyeball. This is thus an example of reflex nervous action from the optic, through the brain, to the oculo-motor nerve.

The experiments of Flourens have shown that it is the corpora quadrigemina through which this reflexion takes place. If the oculomotor nerve be cut, irritation of the optic nerve is not followed by contraction of the pupil.

Influence of the Fifth Nerve on the Movements of the Iris, and Nourishment of the Eye.-After Magendie's experiment of section of the fifth nerve where it lies on the petrous bone, there was loss of common sensation in and about the eye. The vapour of ammonia no longer excited lachrymation nor winking. The pupil was contracted and immovable. The eye became inflamed, with a white puriform discharge. Opacity of the cornea supervened; but before this, iritis was observed to have taken place, with exudation of lymph into the anterior chamber. On the eighth day after section of the nerve, the cornea sloughed away, the humours were evacuated, and the eyeball became collapsed.

Magendie afterwards found that these effects did not, except in a slight degree, ensue when the nerve was divided close to its escape from the pons. On the seventh day the cornea was only slightly opaque, and some exuded lymph was visible in the anterior chamber. Magendie's experiments have been repeated, and the same results observed, by Eschricht, Schöps, Baker, Longet, and Valentin.

The two effects of section of the fifth nerve which call for particular notice here, are the contraction of the pupil, and the disturbance of the nutrition of the iris.

The first of these phenomena-the contraction of the pupil-the above-named experimenters have observed in rabbits; pathological cases have shown that it occurs also in man. According to Longet, on the contrary, dilatation of the pupil is the result of section of the fifth nerve in dogs and cats.

Budge has observed contraction of the pupil in the frog after section of the fifth nerve. But as the pupil in the frog will continue to contract and dilate under the influence of light, not only after section of all the nerves of the eye, but even after the eye has been extirpated, not much weight can be laid on his experiments on the frog as regards the point which Budge had in view-viz., to ascertain whether the fifth contains motor fibrils which determine contraction of the sphincter pupillæ. Section of the fifth nerve in the frog, Budge has always found followed by contraction of the pupil. It makes a well-marked difference whether the fifth be cut behind or in front of the Gasserian ganglion. In the former case, the contraction of the pupil is not so great and, what is to be particularly noted, not permanent. This difference, Budge thinks, is probably owing to implication of the sympathetic fibres in the section in front of the ganglion.

After section of the fifth nerve in the rabbit, whether before the Gasserian ganglion or behind it, or at the medulla oblongata, the pupil

contracts, but subsequently dilates, with the difference, that when the section is behind the ganglion or at the medulla oblongata, the dilatation ensues much earlier than when the section is in front of the ganglion. In this latter case the pupil never attains the diameter of that on the sound side.

By the third day, the supervening opacity of the cornea prevents any further observation of the state of the pupil. The phenomenon is explicable by the fact that in the ganglion the sympathetic joins the fifth, and that therefore section in front of the ganglion implicates the two nerves. The two effects, however, as above mentioned, are in their nature quite different, contraction of the pupil after section of the sympathetic being permanent-that after section of the fifth, temporary.

But whichever be the place where the fifth nerve is cut, the consequent contraction of the pupil takes place very slowly-often not until a minute after, or even longer. When it is established, however, the contraction is very considerable, and when the operation is performed behind the Gasserian ganglion or at the medulla oblongata, twentyfour to forty minutes not unfrequently elapse before the pupil recovers its former diameter.

Contraction after irritation of the oculo-motor is quite otherwise. When the oculo-motor is cut, Budge has observed that the pupil contracts at the moment, and when the section is completed, the diameter of the pupil becomes as before.

Budge concludes that we cannot explain the action on the sphincter which takes place after section of the fifth by supposing it to be through the medium of the oculo-motor. He has in rabbits repeatedly detached the oculo-motor at its origin, and then cut the fifth, but nevertheless observed contraction of the pupil take place as usual. He cannot therefore admit a connexion between the fifth and oculomotor through the central organ to explain the influence of the fifth on the sphincter pupillæ. If in the section of the fifth the sympathetic fibrils were involved, the dilator pupille would be paralysed. The sphincter having been already paralysed by the detachment of the oculo-motor at its origin, the result on the pupil would be neither contraction nor dilatation.

It might be said that the ciliary ganglion is a reflecting centre between the fifth and oculo-motor. But to this Budge objects, that in rabbits in which the pupil contracts on section of the fifth, this nerve has no connexion with the ciliary ganglion at all. Budge therefore concludes that the temporary contraction of the pupil which supervenes on division of the fifth nerve is not owing in any manner to the oculo-motor.

By these experiments it is, indeed, not fully established that the fifth contains motor fibres exciting the contractility of the sphincter. A remarkable circumstance is, that immediately after general death, no reaction of the iris is to be observed on irritating the fifth. It is also remarkable that the contraction takes place so slowly, and when once established, does not so readily cease. A third remarkable phe

nomenon is, that even long after death this contraction of the pupil does not again cease. Lastly, it is worthy of remark, that in some In cases of anaesthesia of the fifth, the pupil was found contracted. the cases related by Serres and Meyer, the ganglion was much diseased.

If, now, on the one hand, these phenomena are not of a kind which we are in the habit of recognising as actions of motor nerves, so, on the other hand, we cannot, says Budge, set aside those marks which argue in favour of such an admission. Other nerves are known, after irritation of which, the action only slowly ensues and continues that long. And it is a character proper to irritation of motor nerves, the action again ceases.

In the pathological cases in which, with anæsthesia of the fifth, contraction of the pupil is also mentioned, the Gasserian ganglion was found morbidly softened and changed in composition. We may therefore presume the existence of some co-affection of the sympathetic nerve, and thence explain the contraction of the pupil. To this head, lastly, belong the cases in which, after irritation of other branches of the fifth in man, contraction of the pupil takes place. If, according to the above recorded observations, there be no reflexion from the fifth to the oculo-motor, no other way remains through which this contraction of the sphincter (e.g., after the application of irritants to the conjunctiva) can take place, but through the fifth nerve itself. It is consequently, Budge thinks, quite probable that the first branch of the fifth contains motor fibres for the sphincter iridis, though further researches are required to warrant a decision on the point.

We would remark that in inflammation of the iris the pupil contracts. Now, after section of the fifth, inflammation of the eye comes on, in which the iris is involved. It is therefore very likely that one cause of the contraction, of the pupil under consideration, is the inflammation, especially as, according to Budge, the contraction does not

cease after death.

The cause of the contraction of the pupil which supervenes on irritation of the conjunctiva remains to be explained. The phenomenon has very much the appearance of being the result of reflexion from the fifth to the oculo-motor. But if there be, as Budge's experiments seem to indicate, no connexion between the fifth and oculomotor, whereby reflex action may take place, it might be conjectured that irritation of the fifth reacts on the optic nerve (as no doubt the optic nerve can re-act on the fifth), and that from the optic, reflexion takes place to the oculo-motor.

More striking even than the contraction of the pupil after section of the fifth nerve, are the inflammation and exudation of which the conjunctiva, cornea, and iris are the seat. These effects, Budge observes, might be attributed to the influence of the Gasserian ganglion, though he thinks this is far from being proved. It appears to him that the bleeding which takes place in the experiment has an important share; having observed that when he wounded the ophthalmic