HEYIOGLOBINE, the principal constituent of the red blood-corpuscles. It is the coloring matter of these bodies and consequently the coloring matter of the blood. It was formerly supposed that limonite, a substance which is intimately combined with a proteid body to form hemoglobine, was the coloring matter of the blood; but although iron plays an important part in respiration and in the changes of the color of the blood which take place in the various functions of nutrition, and although the iron is specially a constituent of the hematine factor of hemoglobine, it does not perform the functions connected with oxidation and with dioxidation except when in combination with that proteid body; in other words, except as it forms a part of the body called hemo globine. The exact nature of the proteid constituent has not been precisely determined, but has been regarded as the globuline(q.v.) of the older physiologists; whence the name. hemoglobine, contracted from hematoglobuline. Hematine is therefore regarded as a derivative of hemoglobine, and not as a true proximate principle. Hemoglobine obtained from the rat, guinea-pig, squirrel, hedgehog, horse, dog, eat, and goose, crystallizes readily, in slender four-sided rhombic prisms. Those from the blood of the guinea-pig are rhombic octahedrons. Those of the squirrel are six-sided plates. Hemoglobins obtained from the blood of the ox, sheep, rabbit, pig, and man, .crystallizes with diffi culty. The causes of these differences are not known, but may depend upon the slight difference in the proportion of water of crystallization which has been found to exist. The crystals, when examined with the microscope, are of a bright scarlet, like that of arterial blood when viewed with the naked eye, but when the crystals arc in mass they have a darker, more purplish appearance; but a solution in water has the seine tint as arterial blood. Examined with the spectroscope, a dilute solution is observed to absorb certain rays of light iu a peculiar way, a portion of the red end of the spectrum being absorbed, and a larger portion of the blue end; but the most characteristic phenomenon is the appearance of two strongly marked absorption bands between the letters D and E on Fraunhoffer's scale, the narrow baud being the most intense, and in extremely dilute solution the only one visible. By increasing the strength of the solution the bands are intensified and broadened, and the absorption spaces at each end of the spectrum also increase, and by further increasing the strength of the solution the bands may be brought together, so as to form one broaeband, when the only rays of light which pass through the spectrum will be in the green and red portions, on either side of the combined bands. By still increasing the strength of the solution the green light becomes absorbed, leaving only the red rays to pass through, these being the last to disappear, which accounts for the natural red color of the solution when seen by transmitted light.. Carefully prepared crystals of hemoglobine when placed in the vacuum of an air-pump part with a certain quantity of oxygen and change color. The quantity of oxygen given off is definite, 1 gramme of crystals parting with 1.76 cubic centimeters of oxygen. This oxygen is held in a rather loose state of combination, not forming a part of the permanent hemoglobine crystal, as in the following analysis by of the crystals taken from the blood of the dog; carbon 53.85; hydrogen 7.32; nitrogen 16.17;
oxygen 21.84; sulphur 0.39; iron 0.43, with 3 or 4 per cent of water of crystallization. An ordinary solution of hetnoglobine contains also a definite quantity of oxygen in a loose state (added to the quantity given in the above analysis), and which under the air pump is yielded up, the color passing from scarlet to purple (oxyhemoglobine passing to reduced hemoglobine). This excess oxygen may also be discharged by passing hydrogen gas, which causes dissociation between the permanent hernoelobine and the loosely held oxygen. It may he also expelled by the use of reducing agents; such as ammonium sulphide, or an alkaline solution of sulphate of iron. When a reduced solution of hemoglobine is examined by the spectroscope the spectrum is changed from that of the unreduced solution which contains the excess of oxygen. The two absorption bands are absent, their place being occupied by a single, broader, though fainter band, and there is also less absorption at the blue end of the spectrum. Even in strong solutions much bluish light passes through,which explains the bluish color of reduced hemoglohine. When reduced hemoglobine, either in solution or in crystals, is exposed to the air it immediately absorbs oxygen, and if sufficient is present it returns to the state of oxy hemoglobine, each gramme 1.76 cubic centimeters of the gas. If this propor tion of oxygen is not present the reduced hemoglobine takes up all there is, regaining the scarlet of oxyliemoglobine in proportion to the amount of oxygen absorbed. If oxy hemoglobine has been deoxidized by a reducing agent, and this latter is in excess, curious phenomena of alternate change of color will be observed on letting the tube stand for a time and then shaking it with air. When it has become purple, the act of slinking will be immediately followed by a change of color to scarlet. On standing a short time the solution will resume its purple color, again to be changed to scarlet on shaking. This experiment explains the change of color which takes place in the blood while perform ing its physiological functions in the system and in the lungs, parting and combining with oxygen alternately. The venous blood which is thrown from the right ventricle into the lungs has lost much of its excess of oxygen; its oxyhemoglobine is reduced to permanent hemoglobine, and it has a dark purplish color. It is only in asphyxiated blood, however, that the excess oxygen is wholly discharged, when the opaque blood looks almost black. In the lungs, where the blood meets with the inspired air, the carbonic acid gas which had been held in solution is given off, and the reduced hemo globine receives again a quantity of excess oxygen and becomes scarlet in color. The oxygenated blood returns to the heart, whence it is thrown into the arteries, and thence into the capillaries, where an interchange takes place between their contents and the outlying tissue fluids which results in the reduction of the oxyhemoglobine to permanent hemoglobine, and of course a return to the purple color of venous blood. See RtsrinA TION and NUTRITION.