GENERAL PROPERTIES: THE CORPUSCLES. 425 



which gives to hemoglobin its power of combining readily with oxy- 

 gen and its distinctive absorption spectrum. On the basis of facts 

 such as these, hemoglobin may be defined as a compound of a protein 

 body with hematin. It seems, then, that, although the hemochro- 

 mogen or hematin portion is the essential constituent, giving to the 

 molecule of hemoglobin its valuable physiological properties as a 

 respiratory pigment, yet in the blood corpuscles this substance is 

 incorporated into the much larger and more unstable molecule of 

 hemoglobin, whose behavior toward oxygen is different from that 

 of the hematin itself, the difference lying mainly in the fact that 

 the hemoglobin as it exists in the corpuscles forms with oxygen a 

 comparatively feeble combination that may be broken up readily 

 with liberation of the gas. 



Hemoglobin is widely distributed throughout the animal king- 

 dom, being found in the blood corpuscles of mammalia, birds, 

 reptiles, amphibia, and fishes, and in the blood or blood corpuscles 

 of many of the invertebrates. The composition of its molecule is 

 found to vary somewhat in different animals; so that, strictly 

 speaking, there are probably a number of different forms of hemo- 

 globin — all, however, closely related in chemical and physiological 

 properties. Elementary analysis of dogs' heznoglobin shows the 

 following percentage composition (Jaquet) : C, 53.91; H, 6.62; N, 

 15.98; S, 0.542; Fe, 0.333; O, 22.62. Its molecular formula is 

 given as C.^JI^^^^'N^^.S^FeO,,,, which would make the molec- 

 ular weight 16,669. Other estimates are given of the molecular 

 formula, but they agree at least in showing that the molecule is of 

 enormous size. The hematin that is split off from the hemoglobin 

 is a pigment whose constitution is relatively simple, as is indicated 

 by its percentage formula, Cg.Hg.N.FeOg (Kiister). It contains 

 all of the iron of the original hemoglobin molecule. The exact 

 amount of hemoglobin in human blood varies naturally with the 

 individual and with different conditions of fife. According to 

 Preyer,* the average amount for the adult male is 14 grams of 

 hemoglobin to each 100 grams of blood. It is estimated that in 

 the blood of a man weighing 68 kilograms there are contained 

 about 500 to 700 grams of hemoglobin, which is distributed among 

 some 25,000,000,000,000 of corpuscles, giving a total superficial 

 area of about 3200 square meters. Practically all of this large 

 surface of hemoglobin is available for the absorption of oxygen 

 from the air in the lungs, for, owing to the great number and the 

 minute size of the capillaries, the blood, in passing through a 

 capillary area, becomes subdivided to such an extent that the red 

 corpuscles stream through the capillaries, one may say, in single 

 file. In circulating through the lungs, therefore, each corpuscle 

 * Preyer, "Die Blutkrystalle," Jena, 1871. 



