BLOOD. The fluid which circulates in the heart and blood-vessels. When viewed under the microscope it appears to consist of very minute red globules, or spheroids, floating in a colourless fluid. The average quantity in an adult man is estimated at about 28 lbs. ; it is of two distinct colours in the arterial and venous systems, florid red approaching to scar let in the former, and dark crimson in the latter. Its specific gravity is between P050 and 1.070. When drawn from its vessels it gelatinizes or coagulates in the course of a few minutes of common tem perature, and soon separates spontane ously into serene and coagulum. The serum is a yellowish soapy-feeling fluid, of the specific gravity of about P080. It exhibits a slight alkaline reaction upon test papers ; when heated it becomes opaque, and at 156° it coagmates. It is also coagulated by alcohol. .nd by most of the acids ; acetic acid ar...d ether do not coagulate it ; solutions of corrosive sub limate, of subacetate of lead, and of chlo ride platinum, occasion precipitates in it, even when considerably diluted with wa ter. These properties of serum are de pendent upon the presence of a peculiar proximate animal principle called albu men • the same substance, and with very nearly the same properties, constitutes the white of egg, the coagulability of which by heat is well known. Besides the above there is another most delicate test of albumen in solution, which con sists in adding to the liquid suspected to contain it a little strong acetic acid, and afterwards a few drops of ferrocyaitate of potash. If albumen be present, a white cloud is produced. This is even a more accurate test than corrosive sublimate.
White of egg is coagulated by ether, while serum is not. According to Mar cet, 1000 parts of serum of human blood are composed of water 900, albumen, 86.8, muriates of potassa and soda 6.6, muco extractive 4, carbonate of soda P65, sul phate of potassa 0•35, earth phosphates 0'60.
The coagulum of the blood is or a more or less firm texture, and has a greater specific gravity than the serum. It con tains the coloring particles of the blood ; and when carefully washed, these are carried out of it, and a tenacious whitish matter remains, which has been termed fibrin, but which, in all essential points, has the properties of coagulated albumen.
The coloring matter of the blood, luema tosine, may be obtained by evaporating its aqueous solution at a temperature be low 100°; it then appears almost black, hut resumes its red color when dissolved in water. It is soluble in acids and in alkalies. These solutions are dark-color ed; but when mixed, so as to become neutral, the hwmatosine falls of a bright red color. Accordingly, when the clot of blood is put into acids it becomes brown or blackish, and is very similarly disco lored by alkalies ; but most neutral salts render it florid.
The chief use of blood is as a manure made into a compost of 50 gallons of blood with a quarter of peat-ashes and charcoal powder ; on light soils, 48 bush els have been laid on each acre, or half a hundred weight with twelve tons of farm dung. It is now rarely used in sugar re fining. It is used to make animal char coal in Prussian blue works, and also in some Turkey-red dye works.