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shape, and holds about one pint. It is composed of four coats, serous, muscular, the fibers of which are arranged longitudinally and circularly, areolar, and mucous. The orifice of the bladder is controlled by the sphincter vesicæ, a muscular band about half an inch in width.

As soon as the Urine is Formed it passes through the tubuli uriniferi into the pelvis, and from thence through the ureters into the bladder, which it enters at an irregular rate. Shortly after a meal, after the ingestion of large quantities of fluid, and after exercise, the urine flows into the bladder quite rapidly, while it is reduced to a few drops during the intervals of digestion. It is prevented from regurgitating into the ureters on account of the oblique direction they take between the mucous and muscular coats.

Nervous Mechanism of Urination.—When the urine has passed into the bladder, it is there retained by the sphincter vesicæ muscle, kept in a state of tonic contraction by the action of a nerve center in the lumbar region of the spinal cord. This center can be inhibited and the sphincter relaxed, either reflexly, by impressions coming through sensory nerves from the mucous membrane of the bladder, or directly, by a voluntary impulse descending the spinal cord. When the desire to urinate is experienced, impressions made upon the vesical sensory nerves are carried to the centers governing the sphincter and detrusor urinæ muscles and to the brain. If now the act of urination is to take place, a voluntary impulse originating in the brain passes down the spinal cord, and still further inhibits the sphincter vesicæ center, with the effect of relaxing the muscle, and of stimulating the center governing the detrusor muscle, with the effect of contracting the muscle and expelling the urine. If the act is to be suppressed, voluntary impulses inhibit the detrusor center and possibly stimulate the sphincter center.

The genito-spinal center controlling these movements is situated in that portion of the spinal cord corresponding to the origin of the 3d, 4th and 5th sacral nerves.

URINE. Normal urine is of a pale yellow or amber color, perfectly transparent, with an aromatic odor, an acid reaction, a specific gravity of 1.020, and a temperature when first discharged of 100° Fahr.

The color varies considerably in health, from a pale yellow to a brown hue due to the presence of the coloring matter, urobilin or urochrome.

the day.

The transparency is diminished by the presence of mucus, the calcium and magnesium phosphates, and the mixed urates.

The reaction of the urine is acid, owing to the presence of acid phosphate of sodium. The degree of acidity, however, varies at different periods of

Urine passed in the morning is strongly acid, while that passed during and after digestion, especially if the food is largely vegetable in character, is either neutral or alkaline.

The specific gravity varies from 1.015 to 1.025.

The quantity of urine excreted in 24 hours is between 40 and 50 fluid ounces, but ranges above and below this standard.

The odor is characteristic, and caused by the presence of taurylic and phenylic acids, but is influenced by vegetable foods and other substances eliminated by the kidneys.


967. 14.230


Other nitrogenized crystalline bodies, uric acid, prin-

cipally in the form of alkaline urates,
Creatin, creatinin, xanthin, hypoxanthin,
Hippuric acid, leucin, tyrosin, taurin, cystin, all in

small amounts, and not constant,
Mucus and pigment,
Salts :-

Inorganic: principally sodium and potassium sul-
phates, phosphates, and chlorids, with magnesium
and calcium phosphates, traces of silicates and

Organic: lactates, hippurates, acetates, formates,

which appear only occasionally,
Gases (nitrogen and carbonic acid principally).


a trace.


The Average Quantity of the principal constituents excreted in 24 hours is as follows:Water,

52 fluid oz. Urea,

512.4 grains. Uric acid,

8.5 Phosphoric acid,

45.0 Sulphuric acid,

31.II Inorganic salts,

323.25 Lime and magnesia,



To Determine the Amount of solid matters in any given amount of urine, multiply the last two figures of the specific gravity by the coefficient of Hæser, 2.33; e. 8., in 1000 grains of urine having a specific gravity 1.022, there are contained 22 X 2.33 = 51.26 grains of solid matter.

Organic Constituents of Urine.-Urea is one of the most important of the organic constituents of the urine, and is present to the extent of from 2.5 to 3.2 per cent. Urea is a colorless, neutral substance, crystallizing to four-sided prisms terminated by oblique surfaces. When crystallization is caused to take place rapidly, the crystals take the form of long, silky needles. Urea is soluble in water and alcohol ; when subjected to prolonged boiling it is decomposed, giving rise to carbonate of ammonia. In the alkaline fermentation of urine, urea takes up two molecules of water with the production of carbonate of ammonia.

The average amount of urea excreted daily has been estimated at about 500 grains. As urea is one of the principal products of the breaking up of the albuminous compounds within the body, it is quite evident that the quantity produced and eliminated in 24 hours will be increased by any increase in the amount of albuminous food consumed, by a rapid destruction of albuminous tissues, as is witnessed in various pathological states, inanition, febrile conditions, severs, etc. A farinaceous or vegetable diet will diminish the urea production nearly one-half.

Muscular exercise when the nutrition of the body is in a state of equilibrium does not seem to increase the quantity of urea.

Seat of Urea Formation.—As to the seat of urea formation, little is positively known. It is quite certain that it preëxists in the blood and is merely excreted by the kidneys. It is not produced in muscles, as even after prolonged exercise hardly a trace of urea is to be found in them. Experimental and pathological facts point to the liver as the probable organ engaged in urea formation. Acute yellow atrophy of the liver, suppurative diseases of the liver, diminish almost entirely the production of


to urea.


Uric acid is also a constant ingredient of the urine and is closely allied

It is a nitrogenized substance, carrying out of the body a large quantity of nitrogen. The amount eliminated daily varies from 5 to 10 grains. Uric acid is a colorless crystal belonging to the rhombic system. It is insoluble in water, and if eliminated in excessive amounts it is deposited as a “ brick red” sediment in the urine. It is doubtful if uric acid exists in a free state, being combined for the most part with sodium and potassium bases forming urates. It is to be regarded as one of the termi

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