diminished in quantity. In six weeks the urine, when voided, was transparent; but a considerable deposition of the phosphates took place, when it had remained for some hours at rest. In this state he left London, and has since informed me, that the sediment gradually diminished under the use of the carbonic acid, that his urine is never turbid, and that the irritation in the bladder has entirely subsided.

It did not appear necessary to detail the minutiae of the above cases; they have been selected with a view to elucidate the treatment of the disease, as far as it depends upon chemical principles, and to furnish the data upon which the following conclusions are founded.

1. That where alkalies fail to relieve the increased secretion of uric acid, and to prevent its forming calculi in the kidneys, or where they disagree with the stomach, magnesia is generally effectual, and that it may be persevered in for a considerable time without inconvenience, where the tendency to form excess of uric acid remains.

2. When the alkalies, or magnesia, are improperly continued, after having relieved the symptoms connected with the formation of the red sand, or uric acid, the urine acquires a tendency to deposit the white sand, consisting of the ammoniaco-magnesian phosphate and phosphate of lime.

3. The mineral acids, (muriatic, sulphuric, and nitric) diminish, or entirely prevent the deposition of the phosphates; but are apt to induce a return of the red gravel.

4. That vegetable acids, especially the citric and tartaric, are less liable to produce the last mentioned effects, even when taken in large doses for a long time; and that carbonic acid is particularly useful in cases, where the irritable state of the bladder prevents the exhibition of other remedies.

XXVII. Additions to an Account of the Anatomy of the Squalus Maximus, contained in a former Paper; with Observations on the Structure of the Branchial Artery. By Sir Everard Home, Bart. F.R. S.

Read June 24, 1813.

My former account was taken from a Squalus Maximus caught at Hastings, in November, 1808, and the parts which I examined were brought to London by Mr. CLIFT, who went down, at my desire, to dissect them; but the weather being stormy and cold, the fish was brought no further than the beach, so that the examination was conducted under great disadvantages, and the parts brought away were in a mutilated state. The sketch of the fish made upon the spot by Mr. CLIFT is now found to be generally correct, except the omission of a small fin between the anus and tail, which had been buried by the weight of the fish in the sand.*

Two fishes of the same species have since been caught at Brighton, and one of them was brought to London in December, 1812, which I had an opportunity of examining, assisted by Mr. CLIFT. It is not my intention, on the present occasion,

* The omission of this small fin in the drawing is an error of considerable importance, as it deprived the fish of one of its characteristic marks, and has led naturalists, who have since had the opportunity of examining other specimens with more accuracy, to conclude that this fish was a distinct species from those which they described; I am therefore particularly desirous to correct the mistake.

to enter into minutiæ, but to render my former account more complete, and apply the dissection of this large fish to its proper use in comparative anatomy, which is, by means of it, to illustrate the functions of the organs of fishes of an ordinary size.

In addition to my former description of the fins, I have now annexed a drawing (Pl. XVI.) which shews the structure of the pectoral fin, a beautiful example of the mechanism of the fins of cartilaginous fishes in general.

The stomach was examined in its entire state, and the annexed drawing (Pl. XVII.) is an accurate representation of the appearance of its internal surface, which is exposed in one view, shewing that the pyloric portion is longer and narrower than I had before represented it.

The situation of the pancreas is correctly noticed in my former paper; the gland is oblong, thick and round where it is attached to the duodenum, and becoming thin, flat, and bifid towards its loose extremity.

The ducts of the liver are six in number, and inclosed in a broad flat band, which passes obliquely down before the stomach, till it is connected to the duodenum; each of the ducts opens, by a separate oblique orifice, into a common cavity of an oval form, from which there is a direct opening into the duodenum. This swell or enlargement might be considered as a substitute for the gall-bladder, which is wanting, were it not that a similar enlargement is also met with in fishes which have one. In the cod there is the same dilatation, and the hepatic ducts open into it in the same oblique manner; but there is also a gall-bladder, and the cystic duct, as well as the others, terminates in this dilatation.

The oblique openings of the hepatic ducts in the Squalus

Maximus, being so different from those of quadrupeds, explain the general principle on which the hepatic ducts in fishes, whose livers are loaded with oil, are formed. The substance of their liver is so exceedingly tender, that this contrivance is employed to prevent the bile from being forced back into the liver, which is not found necessary in the solid livers of land animals.

The heart was particularly examined, and the annexed drawing (Pl. XVIII.) shews its internal cavities, and the valves of the branchial artery; more particularly a muscular structure met with in the coats of that vessel, extending for some way after it leaves the ventricle.

The situation of the kidneys is mentioned in my former account; the ureters open into the cavity, common to the urine and semen, by two orifices, three quarters of an inch in diameter.

The structure of the body of the testicles had been destroyed; the epididymis consisted of innumerable convolutions of a tube three-eighths of an inch in diameter, at the upper part coiled up into two or three lobes or masses, which could not be unravelled, from which the vas deferens went off, making irregular convolutions down towards the anus. The lower part for three feet in length is straight, and the canal seven inches in diameter, having broad valvulæ conniventes; the widest are near the termination, and are two inches and a half broad. The contents of this portion, as I have remarked in my former paper, are different from those of the epididymis, and upper portion of the vas deferens, being a substance like starch broken down into rounded portions in a thinner fluid. This circumstance leads to the idea, that the straight portion