The serum of the blood, when coagulation has been perfect, is of a yellowish, sometimes greenish, color; its taste is dull and salty; it is thick fluid, like olive oil; when heated to 140° it coagulates.
If we examine under the microscope the appearance presented by blood, we find that it consists of a great number of red particles swimming in a nearly colorless liquor. These red particles are flattened disks; in man they are round. Their size is variable, being in man from one four-thousandth to one eight-thousandth of an inch in diameter, but larger in other animals.
The blood contains a large quantity of albumen, partly dissolved and remaining in the serum after coagulation, partly in a solid state, forming the great mass of the globules.
In the living body the blood also contains fibrine in solution, but this separates soon after extraction from the body; it assumes a solid form, and investing, as a sponge, the red globules, forms with them the coagulum.
The fibrine is thus the element active in the coagulation of the blood, the globules being but passively engaged in it. In addition to this essential organic element, the blood contains a variety of salts, as common salt, phosphate of magnesia, ammonia and lime, lactates of soda and magnesia. The best analyses of the blood are those of Lecanu, and the results for blood and serum are that they contain, in the human subject of each sex:
| Water, | 75.00 |
| Albumen, | 5.00 |
| Globules, | 7.14 |
| Fibrine, | .20 |
The fatty substance of the blood is a mixture of cholesterine with stearic and oleic acid and a peculiar fatty substance termed seroline, the history of which is yet incomplete. None of the fats of the brain, however, seem to exist in the blood.
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.