Blood within the living vessel is a fluid; but when shed, or after the death of the vessels, becomes solid by the process known as coagulation. The average specific gravity of human blood is 1056, varying from 1045 to 1075 within the limits of health. It has an alkaline reaction, which in shed blood rapidly diminishes up to the onset of coagulation.
Blood may, in general terms, be considered as consisting by weight of more than one-third and less than one-half of corpuscles, the rest being plasma, the corpuscles being supposed to retain the amount of water proper to them. Human blood: corpuscles 513, plasma 487. The average quantity of fibrine in the human blood is said to be two per cent.
Composition of serum: In 100 parts there are in round numbers:
Water, 90 parts. Proteid substance, 8 to 9 ,, Fat extractives and saline matter, 2 to 1 ,,
Of the proteid substances the great mass consists of the so-called serum-albumen.
Composition of red corpuscles: The red corpuscles contain less water than the serum. In 100 parts of red corpuscle there are:
The solids are almost entirely organic matter, the inorganic salts in the corpuscles amounting to less than 4 per cent. In 100 parts of dried organic matter of the corpuscles of human blood there are:
Hæmoglobin, 90.54 Proteid substance, 8.67 Lecithin, .54 Cholestrin, .25
The blood is distributed as follows in round numbers:
In the heart, lungs, large arteries and veins, About one-fourth. In the liver, ,, ,, In the skeletal muscles, ,, ,, In the other organs, ,, ,,
The average proportion of the principal constituents of the blood in 1,000 parts is:
Water, 784 Red corpuscles (solid residue), 130 Albumen serum, 70 Saline matter, 6.03 Extractive fatty matter, 7.77 Fibrine, 2.20
The chemical composition of hæmoglobin is:
54.2 7.2 0.42 16.0 21.5 6.7 Mucine, 52.2 7.0 12.6 28.2 Proteids, 51.5 6.9 15.2 20.9 0. to 54.5 to 7.3 to 17.0 to 23.5 to 2.0
The principal organs of respiration consist of larynx, trachea, bronchi, lungs.
The larynx is affixed to the upper end of the windpipe, and is not only the entrance for air into the respiratory organs from the pharynx, but also the organ of voice.
The trachea measures from four inches to four inches and a half in length, and from three-quarters of an inch to one inch in width; but its length and width are liable to continual variations, according to the position of the larynx and the direction of the neck.