of support, consisting alternately of eggs, milk, wine, and porter. The medicines were repeated.

14th. Had a good night; pulse not so frequent, nor discharge so copious.

In a few days she was taken out in a gig, and required to be as much in the air as possible, by the bracing effects of which she rapidly recovered, and has since enjoyed uninterrupted good health, and been as useful as ever to her family.

In the summer of 1830, Mrs Stonehouse was again with child, and requested me to attend her. As the circumstances of her case had been so formidable before, I requested that my partner might be in readiness to attend with me in case of any unpleasant symptom. This was fortunately unnecessary. I was called to her in the night of the 17th July, and found her going on very well. I slept in the house until my assistance was required. In a few hours time I was called up, and found the child advancing regularly with a breech presentation. I of course did not interfere, as all went on well; but the contractions of the uterus were not sufficiently active between the birth of the shoulders and head to enable me to save the life of the child. It was, however, a fine boy, and had evidently died during the strangulation of the funis by the compression from the head. She very rapidly recovered, and I heard no more from her till December 6, when she had a violent hemorrhage, and parted with a substance resembling a false conception. She is again quite well.

Oct. 27, 1831. I am again desired to be in readiness to attend the same patient, who is just now at the full period of her pregnancy. The result I shall communicate to you.

A few days after, Mrs S. was delivered of a full-grown living child, which is now, February 9th 1833, alive.

ABT. IX-Notice relative to the Pigmentum Nigrum of the Eye. By THOMAS WHARTON JONES, Esq. Surgeon.

THE Pigmentum Nigrum of the eye is that dark-coloured

matter which is found on the posterior surface of the iris, on the ciliary processes, and on the inner surface of the choroid.

In these different places it does not present the same characters, having on the inner surface of the choroid the appearance of a thin and uniform layer, whilst behind the iris and on the ciliary processes, it occurs in greater quantity, particularly in the eyes of the horse, ox, &c. in which it is so loosely contained

in the cellular tissue which supports it, that when the eye is examined under water, it readily diffuses itself in that fluid.

As the posterior surface of the iris, and the anterior extremities of the ciliary processes are in contact with the aqueous humour, the pigment might be at first supposed liable to mingle itself with that fluid, but this is prevented by a very delicate membrane, which is found lying over the pigment on the posterior surface of the iris, enveloping the free extremities of the ciliary processes, and from thence reflected to the circumference of the capsule of the lens, and probably continued over its anterior surface. With the minutest dissection and microscopical examination, I have not been able to trace this membrane farther than the pupillary margin of the iris, where I am inclined to think it terminates-an opinion, I am aware, contrary to that generally received.

In 1790, Carlo Mondini of Bologna published, in the Commentationes Bononienses, microscopical observations on the pigmentum nigrum of the eye, which showed that it is not merely a mucus or varnish, as is generally believed, but a real membrane, formed, according to him, of innumerable globules, by the union of which an excessively delicate net-work is composed.

Michele Mondini, son of the preceding, published in 1818, in the Opuscoli Scientifici dell' Universita di Bologna, additional observations on the black pigment of the eye, to which I shall have occasion to allude as I proceed. But before entering on the subject matter of this memoir, I deem it necessary to make some preliminary observations, in order to correct certain false notions, which are very prevalent, with regard to the parts situate between the retina and choroid. Rudolphi (Grundriss der Physiologie, Zweiter Band,) acknowledges the confusion which exists on this subject.

In speaking of the pigment, Haller, (Elementa Physiologiæ, Vol. v. p. 383,) says, "ut magnas maculas nigras sæpe retinæ tunicæ adhærentes viderim in homine, ave, quadrupede. Ex maculæ in pisce in membranæ speciem confluunt totamque retinam tegunt."

This expression, which evidently refers to small pieces of the membrane of the pigment, has been made use of by some to detract from the originality of the discovery of Dr Jacob of Dublin, who, in a paper in the Philosophical Transactions for 1819, entitled "An Account of a Membrane of the Eye, now first described," after speaking of the vascular and nervous layers of the retina, says, "exclusively of the two layers here noticed, the retina is found to be covered on its external surface by a delicate transparent membrane, united to it by cellular substance

and vessels. If the sclerotica be removed, and the choroid membrane carefully torn and everted, small portions of the structure here alluded to can be detached, or a globule of air, or even of quicksilver, may be insinuated beneath it, by which means it is raised, and can be seen distinctly if held towards the light."

This membrane, from its extreme tenuity, is very apt to be overlooked, unless carefully examined under water, when it appears distinctly but almost like a film. Hence many, not having been able to make it out, still talk of and describe the membrane of the pigment as that discovered by Dr Jacob.

This error has, in no instance I am aware of, been carried to a greater extent, than in a paper published in the Transactions of the Royal Society of Edinburgh for 1826, entitled "Inquiry into the Structure and probable Functions of the Capsules forming the Canal of Petit, and of the Marsupium Nigrum, or the peculiar Vascular Tissue traversing the Vitreous Humour in the Eyes of Birds, Reptiles, and Fishes. By Robert Knox, M. D. F. R. S. E. &c.-Read March 15th 1824." In this essay, at page 249, the author, after speaking of the membrane of the pigment as the membrane of Jacob, goes on to say, " in the meantime I shall take the liberty of stating a few observations I have made relative to it which seem hitherto to have escaped notice." "The membrane of Jacob is generally of a brownish colour, and sufficiently opaque to arrest the rays of light, supposing them to have passed through the transparent retina; hence we perceive that a part of the functions heretofore assigned by physiologists to the choroid must belong to the membrane of Jacob. In those animals in whose eyes there exists a tapetum, the membrane of Jacob is not absent, as I supposed, but has the same degree of transparency as the retina. Lastly, in most animals it is of a deeper colour than in man. If to these we add the fact, that it does not possess any blood-vessels, and that the colouring matter is absent in albino animals, most comparative anatomists will agree with me in thinking, that in the membrane of Jacob we may perceive a structure, the product of orga nization, itself inorganic and quite analogous to the coloured portion of the rete mucosum of the skin."

The preceding observations, if they refer to anything, refer to the membrane of the pigment, and not to that described by Dr Jacob, which the author, when he wrote them, had evidently never seen.

Having endeavoured to show that the membrane of Jacob must not be confounded with that in which the pigment is deposited, I proceed to describe the structure of the latter, as developed by the microscope, and to explain my ideas regarding its con

tinuity with the tissue which contains the pigment of the ciliary processes and iris. But before doing this it will be proper to give the results of Mondini's investigations.*

According to him, "if a portion of the membrane composing the pigment be examined with the microscope, it appears composed of small oblong bodies, analogous to globules, which are rendered more or less opaque by the presence of a multitude of small black points, and are more transparent towards the bottom of the eye than on the sides, and still less on the ciliary processes; they are joined together by a very delicate cellular tissue. If a more powerful lens is employed, it is distinctly perceived that each globule is formed of black points, more numerous at its circumferance than at the centre. On the posterior surface of the iris they are superposed, one above the other, so as to form two layers,-hence the deeper tint of the black colour in this part.

"This membranula has the same structure in the other Mammifera, only the globules are smaller in the Carnivora and Rodentia. The globules are very white in the young of certain species, and become yellow with age, in the part called the tapetum, which produces the azure or greenish appearance of the bottom of the eye in these animals."

I now proceed to describe what I have myself observed.

When a fresh eye is laid open, and the humours, retina and membrane of Jacob removed, the inner surface of the choroid is found covered by a dark-coloured matter, which may be detached in small pieces. This matter is of a brown colour in the human eye; and in that of the horse, ox, sheep, &c. inclining to black, except over the tapetum, where it is almost transparent.

This is what is commonly called the pigmentum nigrum. But, according to my observations, it is a continuous and curiously organized membrane-the seat of the pigment, but not the pigment itself, which I shall therefore call the membrane of the pigment.

In the human eye, with the exception of its being a little lighter in tint around the entrance of the optic nerve, the membrane of the pigment is of a uniform colour, as far as the termimation of the nervous part of the retina, that is about two lines behind the roots of the ciliary processes; here it becomes of a darker tint inclining to black.

In those animals in which there is a tapetum, the membrane is not of a uniform tint, but in proportion as the colour of the

Not having been able to procure the Opuscoli Scientifichi dell' Universita di Bologna, I quote from an abstract of Mondini's paper, in the fifth volume of the Archives Generales de Medecine.

tapetum increases in intensity, the membrane becomes lighter, and almost transparent, so that the colour of the tapetum appearing through it, many have supposed that it did not extend over that structure. Haller (Elementa Physiologia, Vol. v. p. 383.) says, "In animalibus quadrupedibus ab ea parte abest, in qua tapetum illud lucidum conspicitur."

And Mondini, as is shown in the extract I have made from his memoir, appears to ascribe the production of the tapetum to an alteration in the state of the membrane of the pigment induced by age.

Having shown, that what is commonly called the pigmentum nigrum is a distinct membrane, the seat of the colouring matter, but not that matter itself, which may or may not be present, I come to the description of the peculiar structure, which I have discovered it to possess.

If a portion of this membrane be examined by the aid of the microscope, it is seen to consist of very minute plates, of an hexagonal form, accurately joined together by their edges, in which plates are deposited numerous black particles, which are to be considered as properly constituting the pigment, but not essential to the hexagonal plates composing the membrane; because these may and do exist without the black particles.

This is found to be the case with regard to the colourless part of the membrane, covering the tapetum, which is in like manner composed of an aggregation of hexagonal plates, but less developed, being smaller and separated from each other by greater intervals, and many of them having their angles rounded.

The pigment is said to be wanting in the eyes of albino animals. The colouring matter is certainly absent, but I have found, as from reasoning a priori I had expected, the membrane of the pigment to exist; the plates composing which, however, are still less developed than those of that part of the membrane which lies over the tapetum in the eyes of the horse, ox, &c. They are in fact, not hexagonal, but circular,-a structure similar to which I have found in the eye of a very young human fœtus.

Hence we may draw the following conclusions.

1. That the colouring matter is not essential to the membrane, although the plates composing it are always more developed when the former exists.

2. That the plates composing the membrane of the pigment in the fœtus exist in the same rudimentary state which is found to be proper to the membrane in albino animals,—and in the colourless part of the membrane in those animals which possess a tapetum.

As exactly analogous to the circumstance of the membrane VOL. XL. NO. 116.

F