veins in the orbit, without cutting the ciliary and optic nerves, dimness of the cornea still ensued. Of two rabbits, Budge cut, in one the optic with the ciliary nerves; in the other, he made all the preparations to do so, but did not. In both experiments the bleeding was considerable. In both cases the cornea became opaque, though in the one in which the nerves were cut the opacity was much greater than in the other.

Budge conjectures, therefore, that the opacity of the cornea after section of the Gasserian ganglion depends partly on the nerves, and partly on the loss of blood. It might with greater probability be said that the opacity partly depends on the interruption to the free return of blood from the eye, occasioned by the section of the ophthalmic veins. Still there can be little doubt that the principal cause is the section of the sympathetic fibrils.

CENTRE OF THE IRIDAL NERVES.

Determination of the Centre of the Iridal Sympathetic, by artificial Excitement of Power.-That the pupil contracts when the sympathetic in the neck is cut, and that the pupil dilates when the end of the upper segment of the divided nerve is irritated, had been already established as physiological facts; it had moreover been rendered probable by Valentin's experiment of dividing the connecting branches between the spinal nerves and sympathetic in the neck, that the iridal sympathetic springs from the cervical portion of the spinal marrow, when, by a series of experiments performed partly in conjunction with Dr. Waller, and partly by himself alone, Budge claims to have succeeded in establishing that the iridal sympathetic does spring from the spinal marrow.

By irritating one part of the sympathetic after another, down to the lowest cervical ganglion, dilatation of the pupil was always called forth. From the place where the thoracic sympathetic lies behind the second thoracic ganglion, there was never the slightest action in the dilator pupilla to be observed in numerous experiments. Here, therefore, were the limits to the centre of the iridal sympathetic.

It was accordingly to be inferred, that the iridal sympathetic comes either from the ganglionic chain or from the spinal marrow. But as section of the nerve behind the ganglions was followed by contraction of the pupil, it became evident that the spinal marrow must be the centre whence the iridal sympathetic springs.

The following is Budge's experimentum crucis:-Having cut through the spinal marrow immediately behind the fifth cervical vertebra, he applied the galvanic wires in such a way that the galvanic stream might pass through both halves of the exposed part of the spinal marrow. The result was that both pupils immediately dilated exactly as if the sympathetic nerves in the neck had been irritated. Having next isolated the two halves of the spinal marrow, by division, from each other, and galvanized one of them only, the pupil of the corresponding side was alone observed to dilate. If the sympathetic on one side was previously divided, and the galvanic stream sent through

both halves of the spinal marrow, the pupil on the side on which the sympathetic had been cut did not dilate; the pupil on the sound side alone did.

In addition to the section immediately behind the fifth cervical vertebra, Budge now cut through the spinal marrow close in front of the fourth dorsal vertebra, and galvanized the piece of spinal marrow thus separated from all connexion with the rest. The effects on the iris were the same as those above described. By irritation of the other parts of the spinal marrow-above as well as below-no such effects were transmitted to the iris.

It thus appears that the centrum cilio-spinale inferius, as Budge calls it, is comprised in the portion of the spinal marrow between the sixth cervical and fourth dorsal vertebra. Having determined this, Budge considered it further necessary to experiment on the roots of the nerves coming from the iridal centre of the spinal marrow-the posterior roots by themselves, and the anterior roots by themselves. The following were the results which he found to be constant:

1st. Dilatation of the pupil when the two roots of the seventh or eighth cervical, or of the first and second dorsal nerves were galvanized separately.

2nd. The same result, when the posterior root was first divided, and only the anterior root irritated, and that even when this root (the anterior) was detached from the spinal marrow.

3rd. From irritation of the posterior root also, dilatation of the pupil took place, but it was neither so great nor so permanent as that excited by irritation of the anterior root. It is, however, to be observed, that never the slightest effect on the pupil was noticed if the posterior root had been first detached from the spinal marrow, and then galvanized; showing that the irritation of the posterior roots acts most probably by reflexion to the anterior root through the spinal

marrow.

Determination of the Centre of the Iridal Sympathetic by Artificial Suspension of Power.-By extirpation of the centrum cilio-spinale inferius, its limits admit of being more exactly determined than by the above-described method. After this operation the pupil contracts.

Budge extirpated successively on one side only different parts of the spinal marrow, and noted which of them no longer showed any influence on the pupil.

The parts of the spinal narrow in rabbits covered by the third, fourth, and fifth cervical vertebræ were thus operated on, without any effect on the pupil being observed. But when one half of the portion of the spinal marrow corresponding to the sixth cervical vertebra was extirpated, the pupil on the corresponding side was observed to

contract.

In one case, having removed a small piece close behind the anterior end of the exposed portion of spinal marrow, Budge observed no change in the pupil; but, on the contrary, when he cut away a piece posteriorly in the same animal, the contraction of the pupil was quite evident; so that the portion of spinal marrow intermediate between the sixth

and seventh cervical vertebræ may be considered as the place which corresponds to the anterior (in man the upper) limits of the ciliary centre.

From similar experiments, the posterior boundary of the ciliary centre appeared to be between the third and fourth dorsal vertebræ. The arch of the third dorsal vertebra having been removed, and the half of the exposed part of the spinal marrow cut out, a very distinct contraction of the pupil on the corresponding side took place. On the contrary, not the slightest effect was perceived when, in another animal, the spinal marrow under the fourth dorsal vertebra was treated in a similar manner. It may hence be concluded that the nervous centre which governs the dilatation of the pupil (centrum cilio-spinale inferius) begins behind (in man under) the giving off of the sixth cervical nerve and ends before (above) the giving off of the third dorsal nerve. At this place, therefore, a force is generated, which, through the medium of the cervical sympathetic, extends to the dilator pupille, and of which we observe the suspension after destruction of the part mentioned.

Which of the two columns of the spinal marrow-the anterior or the posterior-must be destroyed in order to abolish the action of the iridal sympathetic? and which of the two roots of the spinal nerves must be cut in order to isolate the centre from its periphery (in the iris)?

For the solution of these questions by experiment, Budge found frogs better adapted than mammals. In reference to the experiments on the frog, however, it is well to remind the reader that movements of the pupil in that animal, in obedience to variations in the degree of light, still take place after section of all the nerves of the eye, and even after extirpation of the eye. The difference between the pupil on the side operated on and that on the side not operated on, may, however, be admitted as the real effect of the experiments.

The limits of the ciliary centre in the spinal marrow are in frogs the same as in mammals. When from this portion of the spinal marrow, the upper half (the posterior columns) only was removed, a contraction of the pupil did take place, but it was only transitory, and not very well marked. When, on the contrary, the whole half was extirpated, the contraction of the pupil began as soon as the etherization passed off. The difference between the two pupils was then very evident.

In order to demonstrate more fully the action of the anterior and posterior columns, Budge extirpated in a frog the right half of the centre wholly, but of the left half only the posterior column. The result was, that the pupil of the right eye became contracted, while that of the left remained unaltered. A corresponding result was obtained when the anterior or posterior roots alone were cut.

Budge has made the remarkable observation, that as soon as the posterior root only was cut, the pupil began to contract in half a minute, or even earlier; but that, on the contrary, a longer time elapsed before the same effect was produced when the anterior root

only was cut. The contraction after the first operation, however, was only transitory, whereas that after the second was permanent. From this it would appear that the fibrils which the anterior roots give to the iridal sympathetic spring from the spinal marrow, and not from the spinal or any other ganglion. As these fibrils show the most enduring action, it is to be inferred that the anterior column of the spinal marrow at the place indicated is the most essential part of the inferior ciliary centre.

Everything, it may be concluded, speaks for the proposition that the iridal sympathetic consists of centripetal and centrifugal, or excitor and motor fibrils; that the former go in the direction from the iris to the spinal marrow, and the latter from the spinal marrow to the iris; and that as yet no relation has been proved to exist between the ganglions through which the iridal sympathetic passes, and the nerve fibrils which govern the dilatation of the pupil.

Relations of the Inferior Centre of the Iridal Sympathetic to other Organs.-Besides the contraction of the pupil, there takes place, according to the discovery of Bernard, as a result of section of the sympathetic in the neck, increase of heat on the side of the head corresponding to that operated on. This phenomenon of increased heat appears to be owing to an acceleration of the circulation,* and not, as Budge thinks, to a stagnation of blood in the vessels of the head. By section of the sympathetic, the contractility of the arteries, which receive their nerves from it, is suspended or impaired. The result is dilatation of the calibre of these vessels, and consequent acceleration of the flow of blood, not only through them, but also through the capillaries and corresponding veins.

When the centrum cilio-spinale inferius on one side is extirpated, Budge has found a similar result on the vessels to that arising from section of the sympathetic in the neck. In respect to its relations to the arteries, the centrum, according to Budge, is bounded by the same limits and seated in the same columns of the spinal marrow and in the same roots of the nerves, as it has above been shown to be in respect to its relations to the iris. Consequently, the apparatus of fibres which in the cervical sympathetic acts on the vessels, springs in the spinal marrow at the above-mentioned place. It may therefore be said that the cervical sympathetic, so far as it has been investigated by Budge in reference to its function, has its origin in the spinal marrow between the sixth cervical and fourth dorsal vertebræ.

According to Dr. Brown Séquard's experiments, the centre of the fibrils which go from the sympathetic nerve in the neck to the arteries of the corresponding side of the head, extends as far as the ninth or tenth dorsal vertebra.

After section of the sympathetic in the neck, the pupil on the same side is smaller than that on the other, even in the shade, and still more so in the light. The influence of light on the pupil is thus not lost,

* See a paper, by the writer of this article, On the State of the Blood and the Bloodvessels in Inflammation, in the Transactions of the Medical and Chirurgical Society of London, for 1853.

nor is it altered. In other words, what Budge means might be ex pressed as follows:-When the dilator of the pupil is paralysed by section of the sympathetic in the neck, the unrestrained action of the sphincter does not take place to its fullest extent, just as when the internal rectus is cut or paralysed, the eyeball is not much turned towards the temple by the external rectus: the sphincter pupillæ, equally with the external rectus, retaining the power of contracting more fully under the usual conditions.

Section of the Sympathetic in different parts of the Neck.-If the trunk of the sympathetic in the neck be cut, and some five or six days thereafter subjected to galvanism, no effect is produced on the pupil; but galvanization of any part of the nerve above the superior cervical ganglion-the carotid branches, the Gasserian ganglion, or the eyeball itself-still excites dilatation of the pupil. It is quite otherwise if the superior cervical ganglion be extirpated, and the animal killed a week after. Not the slightest dilatation of the pupil is observed on the operated side in answer to the galvanic irritation immediately after death, whether applied to the Gasserian ganglion or to the eyeball.

The cause of this difference, Budge thinks, can only be, that in addition to the source which the iridal sympathetic has below the superior cervical ganglion, there is another source in the situation of this ganglion, so that if even the sympathetic below the superior cervical ganglion were compressed by a tumour, or otherwise injured, dilatation of the pupil might still be possible.

The Upper Centre of the Iridal Sympathetic.-Having shown that the iridal sympathetic receives a second supply of power in the situation of the superior cervical ganglion, Budge next proceeds to ascertain by experiment the exact centre from which this is derived. From numerous experiments he has found that section or irritation of the branches of communication between the sympathetic and upper cervical nerves has no effect on the pupil; but that, on the other hand, the effect is very striking when the communicating branch between the hypoglossal nerve and sympathetic is cut. Accordingly, if this communicating branch be divided, as well as the trunk of the sympathetic below the superior cervical ganglion, both sources of the power of the dilator pupillæ are cut off, just as when the superior cervical ganglion itself is extirpated. In one case Budge succeeded, soon enough after the death of the rabbit, to isolate and galvanize the communicating branch between the hypoglossal and sympathetic, and found the result to be dilatation of the pupil.

It thus appears made out, that the communicating branch between the hypoglossal and superior cervical ganglion gives to the iridal sympathetic a second set of motor fibrils.

After having ascertained this, Budge searched for the same action at the origin of the hypoglossal itself. Immediately after death he laid bare the nerve in a rabbit, and irritated it, but could observe no effect on the pupil, owing probably, he thinks, to the speedy extinction of the nervous irritability. In the frog he cut the hypoglossal, whereupon a transitory dilatation first occurred, as when the sympathetic is cut—