In various forms of disease the appearance, quantity and smell of the urine, are important diagnostic signs of the state and progress of the disease, and should be carefully observed.

In cases of fever, as the disease approaches a crisis, the previously clear urine becomes thick, and forms a half floating cloud. If this cloud sink, a favorable crisis may be expected, while on the contrary if it remain buoyant near the top, a somewhat unfavorable issue may be anticipated.

As the crisis of the disease declares itself, when the urine has been perfectly clear before, a sediment is now perceptible, and in those cases where the urine has been thick and turbid, the same sediment is perceptible, but the urine above it is clear and transparent. If the sediment is of a smooth, light or greyish color, and is deposited shortly after emission, it is a favorable indication, but if it should be dark or black, it denotes a putrid state, if bilious or red, it indicates a rheumatic or intermittent type of the disease, and if it is disturbed, heavy, muddy or of a purple color, forming half of the whole quantity discharged, it is an unfavorable sign.

The red or high colored urine, if the pulse be accelerated, indicates the presence of fever. Urine of a saffron color marks the presence of bile in the blood, and shows derangement of the liver.

If matter is found in the urine, it shows that suppuration is going on internally.

In children, a milky appearance of the urine is looked upon as an indication of worms in the intestines. A very light or watery appearance of the urine may denote some disturbance of the nervous system.

Copious perspiration or watery diarrhoea may cause a decrease in the secretion of urine.

The appearance of the urine may indicate the presence of Diabetes, or tendency to various forms of calculi in the bladder and kidneys.

The voiding of a large quantity of straw colored urine of a disagreeable odor and of a sweetish taste, may denote the presence of Diabetes. The lithic or uric acid calculus is shown by the red brick dust sediment.

The calculi formed by the combination of phosphoric acid, magnesia and ammonia, is indicated by fetid urine and a whitish mortar-like sediment. For a description of the above, together with other forms of calculi, see that subject in the chapter on urinary affections.