This substance is not a constituent of healthy urine, although it is sometimes found as a temporary contamination. When existing as a permanent condition it is a matter of serious importance, inasmuch as it indicates the existence of organic disease of some part of the urinary apparatus, most frequently the kidneys.

Albumen is recognized by adding to a small quantity of the suspected urine, in a test-tube, a few drops of nitric acid, when the albumen, being coagulated, falls to the bottom of the glass as a grayish flocculent deposit. Boiling also produces the same effect.