Ist. Ingredients characteristic of the se-) cretion, produced by the destructive assimilation of tissues, and separated, from the blood by the kidneys.

Urea, uric acid, coloring and odorous principles.

2d. Ingredients developed principally) Hippuric acid, lactic from the food during the process of acid? accidental con

assimilation.

stituents.

II. SALINE PRODUCTS.

3d. Saline combinations separated from)

the blood, and chiefly derived from Phosphates, Chloride,

the food.

4th. Saline combinations chiefly gene

of sodium.

rated during the process of destruc- Sulphates. tive assimilation.

III.

INGREDIENTS DERIVED FROM THE URINARY PASSAGE.

5th. Mucus of the bladder.

6th. Debris of epithelium.

"Of these, the first class of ingredients can alone be considered as really essential to the urine, and characteristic of it as a secretion, the kidneys being the only organs which normally secrete these elements from the blood. The saline ingredients of the second class are met with in most secretions of the body, with the exception of the sulphates, which are rarely found except in the urine. The third class of elements is met with in all fluids passing over mucous surfaces."

The urea, which is the characteristic ingredient of urine, bears a striking proportion to the quantity of azote taken in the food, as appears from the following table, copied by our author from Dr. Lehmann, of Leipsic:

Among the other constituents of urine is sulphuric acid, which Dr. Bird maintains is found in too large a quantity to

be explained by its presence in the food, and which, therefore, he refers to the oxydation of sulphur, one of the elements of the protein compounds.

The urine, which in health, and while its constituents maintain their proper relation to each other, is clear and of a pale amber color, becomes turbid when any of its ingredients exist in a comparative or real excess. All the deposits found in it may be divided according to our author into the four following classes:

"Class 1.-Deposits composed essentially of ingredients formed directly or indirectly from the metamorphosis of tissues, or from the organic elements of food.

Uric acid and urates.

Uric oxide.

Oxalate of lime.
Cystine.

"Class 2.-Deposits composed of ingredients of inorganic origin; including

Phosphate of lime.

Ammonio-phosphate of magnesia.
Carbonate of lime.

Silicic Acid.

"Class 3.-Highly colored deposits (black or blue) of doubt

ful origin,

Cyanourine.

Melanourine.
Indigo.

Prussian blue.

"Class 4.-Deposits consisting of non-crystalline organic products; including

A. Organized.

Blood.
Pus.

Mucus.

Organic globules.
Epithelium.

B. Non-organized.

Milk.

Fatty matter.

The first deposit described is the uric acid, the diagnosis of which is thus given:

"When heated in the urine, the uric acid deposit does not dissolve; the crystals merely become opaque. It generally becomes more distinct from the solution of urate of ammonia, which is frequently mixed with it, and sometimes completely conceals it from view. Hence the best mode of discovering this deposit, is to warm urine, turbid from excess of urate of ammonia, in a watch glass; the acid becomes visible in the centre of the glass, as soon as the urate dissolves. Heated with liquor potassa, the uric acid deposit dissolves, from the formation of an urate of potass of sparing solubility. Hydrochloric and acetic acids are without any action, but the nitric readily dissolves it, and by careful evaporation a residue of a beautiful pink color becoming of a rich purple, on being laid over the vapor of ammonia, is left. This colored residue is the murexid of Liebig, the purpurate of ammonia of Dr. Prout. Exposed to heat in a platinum spoon, the uric acid deposits burn, evolving an odor of bitter almonds; and finally leave a small quantity of a white ash, which generally contains phosphate of soda or lime.

"Characters of urine depositing uric acid-When urine contains an excess of this acid, it generally lets fall crystals on cooling, uric acid being very seldom deposited before emission. It usually possesses a deeper amber tint than natural, sometimes being of a reddish brown color. Very high colored urine, however, seldom deposits uric acid until after the addition of a stronger acid. Urine never lets fall spontaneously all its uric acid as a deposit, for after being filtered from a sediment of this substance, the addition of a drop of nitric acid generally causes the deposition of an abundance of crystals of uric acid in a few hours.

"Urine depositing uric acid always reddens litmus paper, and often contains an excess of urea, so as to crystalize slowly when mixed with nitric acid in a watch-glass. Its specific gravity is generally rather above 1.020. An exception to the above character is presented by the pale urine of infants at the breast, among whom deposits of uric acid are

common. These often appear as a yellow crystalline sand, whilst the supernatant urine is frequently of low specific gravity, often 1.006, as pale as water, and nearly destitute of urea."

Urate of ammonia, another of the urinary deposits, is recognized by the following characters:

"These deposits vary in color from absolute whiteness to a pale fawn color, which is the most frequent tint, brick-red, pink, or purple. All these various colored deposits present certain characters in common; they never appear in the urine until after it has cooled, and disappear with the greatest readiness on the application of heat. The purple deposits require rather a higher temperature for solution than the other. The addition of liquor ammoniæ, or liquor potassæ, immediately dissolves deposits of urate of ammonia. Their chemical constitution is shown in a very interesting manner by examining a drop of the turbid urine with the microscope between two plates of glass; an amorphous powder will be alone visible, unless uric acid be present; then add a drop of hydrochloric acid, the turbidity will disappear, and in a short time crystals of uric acid will be seen growing in the fluid, the ammonia having deserted this substance to unite with the acid which had been added.

"Characters of urine depositing urate of ammonia.-The following modifications are most important.

1st. A pale urine of low specific gravity (1.012), becoming opaque on cooling from the deposition of nearly white urate of ammonia, which, instead of readily falling, forms rope-like masses in the fluid, and presents on a superficial view so much the appearance of muco-pus, as to be mistaken for it. Its disappearance on the application of heat at once will discover the error.

2d. A pale amber colored urine of moderate density (1.018), which on cooling lets fall a copious fawn colored deposit, resembling bath-brick grated into the urine, disappearing with the utmost readiness on applying a gentle heat. This deposit is of frequent occurrence, is often very transient, and is so constantly an attendant on the slightest interferrence with the cutaneous transpiration, that a 'cold' is popularly diagnosticated whenever this state of things exists.

3d. Whenever febrile excitement prevails, the urine becomes concentrated, rises in density (1.025,) and deposits on

cooling a reddish brown sediment, constituting the wellknown lateritious, or brick dust sediment. This variety of urine generally becomes turbid on the addition of a drop of nitric acid, not from the coagulation of albumen, as has been frequently erroneously supposed, but from the precipitation of uric acid. This is always in minute microscopic crystals, notwithstanding the amorphous appearance it presents to the naked eye.

"4th. In well-marked affections of the portal circulation, especially when connected with organic disease of the liver or spleen, or when suppuration, particularly of a strumous character, is going on in the body, the urine is generally found to possess in many instances a deep purple or copper color, often verging on crimson, so as to have led to the idea of blood being present. These deep tints appear to me to depend upon the presence of an excess of purpurine.Whenever a deposit of urate of ammonia occurs in such urine, either spontaneously or by immersing it in a freezing mixture, it combines with the pink pigment forming a kind of lake, and which is often so abundant as not to entirely disappear by heat, until the urine is diluted by the addition of water. These deposits do not exhibit their delicate tints until af ter being collected in a filter; they readily give up their coloring matter to alcohol, which leaves their urate of ammonia nearly unchanged."

[TO BE CONTINUED.]

ART. V.-Elements of Pathological Anatomy; Illustrated by colored engravings and Two Hundred and Fifty Woodcuts. By SAMUEL D. GROSS, M.D., Professor of Surgery in the Medical Institute of Louisville; Late Professor of Pathological Anatomy in the Medical Department of the Cincinnati College; Surgeon to the Louisville Marine Hospital, etc., etc. Second Edition, thoroughly Revised and greatly Enlarged. Philadelphia: Ed. Barrington & Geo. D. Haswell. Louisville: James Maxwell, jr. 1845. Super-royal 8vo. pp. 822.

The words, "thoroughly revised, and greatly enlarged," however loosely applied in other instances, mean something on the present occasion. On comparing the former edition. of this work with the present, it will be found not only that