Albumen is secreted in the kidneys chiefly in the Malpighian capsules, where, if at all abundant, it may be easily demonstrated after death by hardening the kidneys by boiling. This coagulates the albumen in situ, where it may be shown by sections prepared in the usual method. It has been supposed that albumen is normally secreted in the capsules of the healthy kidney, and afterward absorbed by the epithelium lower down; but this view can easily be shown to be erroneous by subjecting a kidney which has not secreted albuminous urine to the process just described, which shows no coagulated albumen in the place where it ought to be most abundant. The albumen found in the urine is chiefly that which forms the most important portion of the blood-serum, although other albuminoid bodies have from time to time made their appearance and have some diagnostic importance. Semmola[13] states that the albumen appearing in the urine in true Bright's disease differs from that found with the cardiac or amyloid kidney. The distinction can, according to him, be shown in {35} the appearance of the precipitate to a practised observer, and also by a more rapid diffusibility through animal membranes. He admits, however, that he has in vain sought for any distinct and clear chemical test by which the difference can be recognized. [Footnote 13: _Archives de Physiologie_, 2d Serie, tome ix., and 3d Serie, tome iv.] Fibrin may occur in inflammatory conditions in the form of coagulated masses, and hence cannot affect the question of the presence of albumen. Casein has not been detected with certainty. Various albuminoid bodies, called albuminose, paralbumen, metalbumen, and serum-globulin, are occasionally met with in renal disease, and may give rise to some confusion during an analysis. They are at present, however, more suitable for chemical than for clinical study. A variety of albumen is said to occur in osteomalacia which is not coagulated by heat alone nor by heat and nitric acid. This has been called Bence Jones's albumen, but has been seen by others. Peptone has been found in urine, but usually in such specimens as have been or which afterward become albuminous. Its exact signification when alone cannot be more exactly stated, as it has appeared in a variety of diseases, though not in perfect health. Finally, a protein body, a ferment called nephrozymase, may be thrown down from every urine by an excess of alcohol. Hæmoglobin gives a dark-red color to the urine, which on boiling forms a brown coagulum floating on the surface. Hæmoglobinuria may be produced in animals by the intravenous injection of large quantities of water, causing a dissolution of the corpuscles, but the degree of hydræmia necessary to produce this condition is much in excess of any met with in diseases of the human being.