evidently a feature not dependent upon the effusion of fibrine. It is, however, doubtful whether the desquamation of the epithelium in tubular masses does take place without the effusion of fibrine into its central canal. I have never seen casts consisting of the epithelium only; and in deposits where such casts, very similar to the tubular pieces of epithelium obtained by scraping from the cut surface of a healthy kidney, were present in abundance, I always discovered a large number of casts, consisting clearly of fibrine, with only a few epithelial cells imbedded. By this observation I will by no means deny that casts consisting of the epithelium only may occur, as has been asserted by other observers. (Figs. 3, 4, Pl. III.)

Dr. Beale has met with casts of medium diameter, containing well formed dumb-bell crystals of oxalate of lime. These casts were found in the urine of a patient suffering from cholera. In the same specimen, also, several octahedra of oxalate of lime were present, but these latter were not entangled in the casts.'

Granular casts.-When the epithelium of the urinary tubule has been destroyed by chronic disease, it assumes the form of granular matter, and as such is entangled with the matter deposited in the tubes. (Fig. 3, Pl. IV.)

This deposit is always accompanied by granular matter not in the form of casts; so that there also the question arises, whether the degenerated epithelium is desquamated without the aid of cylinders. This can only be decided by long and careful observation. It cannot, however, be doubted that the effused matter materially assists in quickly removing desquamated epithelium, by the contraction which it undergoes soon after coagulation; a process by which the epithelium, when entangled, is completely separated from the basement membrane, and the cast is enabled to pass the tubule, pressed onwards by the continued secretion and exudation from the Malpighian bodies, and perhaps by some contractile action of the matrix of the kidney.

Casts containing fatty matter.-These casts are of different diameters, but more generally of the medium diameter. They are formed in tubules, the epithelium of which is in a state of fatty degeneration. The casts may be hyaloid, with only a few oil-globules imbedded in their substance; or they may entangle some epithelial cells, filled with oil, showing that the fat is formed in the interior of the epithelial cells: or the fat may be present in large quantities. Free fatty cells are always present. (Fig. 4, Pl. IV.)

The Microscope,' p. 207.

Casts of considerable diameter. 3th of an inch.

The diameter of these casts is nearly equal to that of the urinary tubules in which they have been formed. They are mostly perfectly transparent, hyaloid, of a glistening aspect, resembling in appearance the surface of wax as it cools after having been melted, which similarity caused Dr. Johnson to term them "waxy." They rarely include much granular matter in their substance, owing to the very cause of their large size being the total absence of epithelium from the basement membrane in which they are moulded. When granular, however, in one part, and hyaloid in the other, they are, perhaps, not always of the largest size. Sometimes they may contain a few epithelial cells. Dr. Beale has observed and figured casts of considerable diameter, which were composed of a material in the interior differing from that which formed the circumference of the casts. With these large casts the sediment mostly contains granular casts of medium diameter, and granular débris of degenerated epithelium of the tubules. (Fig. 6, Pl. IV.)

Pathological indications of Casts of Uriniferous Tubules.

The presence in the urine of intratubular hyaloid casts indicates a chronic disease of the kidneys, termed non-desquamative nephritis, which is caused by a vitiated condition of the blood. As the expulsion from the organism of poisons causing this and similar diseases of the kidneys is mostly effected by a process, in which desquamation of the epithelium of the urinary tubules plays an important part, the fact of the epithelium not being cast off is an unfavorable symptom, indicating the retention of the poison in the blood. These casts, therefore, where they form the entire bulk or greater part of a urinary deposit, must excite serious apprehension for the ultimate welfare of the patient.

The presence in the urine of epithelial casts is a symptom of a disease of the kidneys, caused by the entrance into the blood of a morbid substance-a poison-the elimination of which is effected by these organs. The poisons of cantharides, turpentine, scarlatina, and cholera are illustrations of this. In all the diseases caused by these poisons, their elimination through the kidneys is accompanied by a process, of which the desquamation of the epithelium of the urinary tubules is an essential part. The presence of epithelial casts in urine for a limited period of time is therefore a favorable symptom of

the affection of the kidneys, as exhibited by other symptoms, and indicates that the poison is being actively eliminated. But when the epithelial casts become mixed with much blood or pus, or when the desquamation has a tendency to become of a chronic nature, from the causes continuing to influence it, then it becomes an unfavorable symptom in proportion to its duration.

The granular casts are indicative of chronic desquamative nephritis, and of degenerated condition of the epithelium of the urinary tubules. These casts and the casts containing fatty matter are frequently found in gouty subjects, and then give rise to an unfavorable prognosis. The prognosis is better in cases where the chronic desquamative nephritis is the sequel of the acute process.

The casts containing fat or fatty epithelium are most frequently the sequel of non-desquamative disease of the kidneys, and indicate the presence of fatty degeneration of the kidneys in the so-called granular form.

The casts of considerable diameter may occur in all diseases of the kidneys, and may therefore accompany all different descriptions of casts described. The presence of these casts is under all circumstances evidence that there are Bellinian tubules totally deprived of their epithelium. Their importance as a pathological indication is therefore in a great measure dependent upon the nature of the affection, in the course of which they have been deposited.

CHAPTER XXI.

ALBUMEN.

THE composition of albumen, as it occurs in the blood, is very similar to that of white of eggs.

White of eggs. Albumen from blood.

We possess no chemical formula or symbol for albumen, as its rational composition is unknown. According to the quantity of sulphur, white of eggs must contain more than 90, and albumen of blood more than 110 equivalents of carbon.í Notwithstanding this, the chemical characters of both descriptions of albumen are so much alike, that it is difficult to distinguish them by chemical tests.

Albumen is formed in plants, and introduced into the animal economy as food; it there undergoes certain modifications, serves the purposes of the economy, and becomes disintegrated, leaving the body mostly in the form of urea. But when albumen, as such, is discharged in the urine, this is a sign of severe disease of the blood or of the kidneys.

General characters of Albumen.

Albumen occurs in a soluble and an insoluble modification. The former is present in all the fluids of animal and vegetable bodies, and may be transformed into the latter by Strecker, Dr. A., Kurzes Lehrbuch der organischen Chemie,' 2te Aufl. Braunschweig, 1857, p. 485.

boiling with water, or by contact with absolute alcohol, acids, or alkalies. The soluble modification may be obtained in a solid state by evaporating the solution at a temperature not exceeding 50° C. (122° F.), or by drying in vacuo over sulphuric acid. It is a yellowish transparent mass, of 1.314 specific gravity, which swells up with water, and, after a time dissolves. It has an alkaline reaction, and contains about 5 per cent. of free alkali and salts, which may be partly removed by washing with water, as they dissolve quicker than the albumen itself. The albumen, thus freed from alkalies, is insoluble in pure water.

The insoluble modification of albumen is a flaky or lumpy mass, without taste or smell, insoluble in water, alcohol, and ether, soluble in dilute caustic alkali by the aid of a gentle heat, from which solution it may be precipitated by the addition of an acid. The precipitate is changed in some degree, having lost part of its sulphur, which is sometimes evolved in the form of sulphuretted hydrogen. The insoluble modification is also soluble in concentrated acetic acid and common phosphoric acid; and in these solutions a precipitate is produced by ferrocyanide and ferricyanide of potassium. It is soluble in very dilute mineral acids, or at least is transformed into a jelly-like mass; the addition of a larger amount of acid to these solutions produces a precipitate. Concentrated hydrochloric acid, or sulphuric acid somewhat dilute, or a mixture of concentrated hydrochloric acid and some sulphuric acid, dissolve the insoluble modification of albumen formed by the aid of heat, and decomposes it. When this solution is boiled, and the air has free access to it, it becomes indigoblue, or of a violet colour, which soon changes into brown. Concentrated nitric acid imparts a deep-yellow colour to solid albumen, when the mixture is gently warmed. A solution of mercury in nitric acid (containing salts of the suboxyde and of the protoxyde, Strecker), which is made by dissolving one part of mercury in two parts of nitric acid, containing 4 equivalents of water, and having a specific gravity of 141 (Neubauer), imparts a saturated red colour to albumen in the solid or dissolved state, when the mixture is warmed to 140° or 212° F. The colour is not removed by the influence of the air, or by protracted boiling. This is said to be the most delicate test for albumen (Neubauer). On this I must remark that it is not applicable to the urine, as three different precipitates are formed in it by this mercurial solution; one of the suboxyde with chlorine (calomel), one of the protoxyde with urea, and one of the albumen with the free nitric acid of the mercurial solution.