Hæmoglobin differs from albumin, to which it is allied in chemical composition in its power of crystallising, and in the affinity it has for oxygen and some other gases. The crystals of hæmoglobin, with the exception of those of the squirrel, which are hexagonal, are formed upon the rhombic system, the forms varying in different animals. In man the crystals consist of four-sided prisms, with dihedral summits; in the guinea-pig the crystals are tetrahedral; and in the cat and dog they are needle-shaped, terminated by one plane surface. The crystals of hæmoglobin are soluble in water and in alkaline solutions, but insoluble in alcohol, chloroform, ether, fatty oils, benzole, turpentine, and carbon disulphide. When heated, hæmoglobin solutions coagulate, and the hæmoglobin itself breaks up into hæmatin and globulin, yielding about 4 per cent of the former to 96 of the latter. The ash of blood shows a great excess of sodium over potassium salts, and of the chlorides over the phosphates, this being the opposite of what is found in muscle ash. FUNCTIONS OF THE BLOOD. The blood is an all-pervading tissue, per I meating every organ and texture of the body. From it the tissues withdraw the materials required for their nutrition, which exist ready formed in the blood, or are capable of production by a process of chemical transformation. Into it also the tissues pass their effete materials, and it forms the medium by which they are conveyed to the organs which are set apart for their elimination. It conveys, through the agency of its coloured corpuscles, the oxygen taken up at the lungs to the tissues of the organism, and in like manner returns to the capillaries of the lungs and skin, there to be expelled, the carbonic acid, which is the outcome of the action of the oxygen on the tissues of the body. The consideration of its physiological uses must be further studied in the physiological text-books. Canaliculi, 31 Classification of, 21 Vascular supply of, 25 Of external ear, 28 Of Eustachian tube, 28 Cell genesis, 4 Cell vegetable, 2 Animal, 3 Cellular sheath of a nerve, 59 |