The chemical history of fibrine and albumen having been already given, it remains only to describe the peculiar coloring matter, for the most accurate knowledge we possess concerning which, we are indebted to Lecanu’s elaborate researches on the blood. Pure hematosine or coloring matter, when it is coagulated, is a dark brown mass, tasteless and inodorous; when heated it does not smell, but swells up and evolves ammoniacal products; it is insoluble in water, alcohol and ether; _it forms, with the mineral acids, compounds which are insoluble in water but soluble in alcohol_. By caustic alkalies it is dissolved with a red-blood color, and these combinations are soluble in water, alcohol and ether. Hematosine contains neither phosphorus nor sulphur, but iron in large quantities. The state in which iron exists in hematosine has been, up to the present day, an object of much discussion among chemists; but with the knowledge we now possess of hematosine in its pure form, we must consider the iron to be an integral part of its organic constitution, as sulphur in albumen, or arsenic in alkarsine, and the opinion of its being oxydized and combined with the true organic element as a kind of salt can no longer be supported. If a solution of hematosine be acted on by chlorine gas, a white, flocculent precipitate is produced, and the solution contains chloride of iron. Although hematosine is the coloring principle of the globules of the blood, it is present but in very small quantity; one hundred parts of dried globules containing but four to five parts of hematosine; in the blood globule the hematosine exists in its uncoagulated state, and possesses properties somewhat different from those of its coagulated form. A solution of the colored blood globules in water, when exposed to the air, becomes of a brighter red color, being thus partially arterialized; it is _coagulated also by alcohol and by acids_; the hematosine then passes into the condition of insolubility, already described. The colorless ingredient in the blood globules has already been spoken of as being albumen, with which, indeed it is identical in properties, but differ in some points. It has been termed globuline. In its uncoagulated condition it can not be separated from hematosine, and is there distinguishable from albumen, principally by being insoluble in even a very dilute saline solution, which dissolves albumen readily. It is, hence, that the globules of the blood swim unaltered in the serum, but are readily dissolved by pure water.