HEMOGLOBIN 79 



globin (96 per cent.), and a simpler pigment, hematin (4 per 

 cent.), together with other bodies whose nature is unknown. 

 If the decomposition takes place in the absence of oxygen, 

 hemochromogen is formed instead of hematin. It is the hemo- 

 chromogen that gives to hemoglobin its peculiar power of 

 taking up oxygen into loose chemical combination. There 

 are 14 grams of hemoglobin to every 100 grams of blood, so that 

 a man weighing 68 kilos has 750 grams of hemoglobin distributed 

 among 25,000,000,000,000 corpuscles, giving a superficial area of 

 about 3200 square meters. This is important from a respiratory 

 point of view, as the entire surface is practically exposed to 

 the absorption of oxygen. Hemoglobin will take 1.59 c.c. of 

 oxygen to each gram weight, and form in so doing a com- 

 pound known as oxy hemoglobin. The latter, if placed in an 

 atmosphere which is deficient in oxygen, will be converted 

 by the loss of oxygen to hemoglobin. Hemoglobin has the 

 power of combining with a number of other gases. With 

 carbon monoxide it unites in the proportions of one volume 

 to one of hemoglobin, forming carbomonoxide hemoglobin, 

 which is more stable than oxyhemoglobin, so that it is not 

 easily converted into ordinary hemoglobin. This explains 

 the fatal effects produced by breathing illumina ing gas, which 

 contains carbon monoxide as a constituent. The oxygen of the 

 air is prevented from uniting with hemoglobin, and thus pro- 

 duces asphyxia. Nitric oxide (NO) produces a still more stable 

 combination. Carbon dioxide (CO 2 ), however, which in its 

 reaction with hemoglobin produces carbohemo globin, unites 

 with a different part of the hemoglobin molecule, since it does 

 not interfere with the absorption of oxygen. Thus is explained 

 the action of this gas as an anesthetic. It has been suggested 

 that the carbon dioxide unites with the protein portion, and 

 it makes possible the transportation of carbon dioxide by hemo- 

 globin from the tissues, where it is given off as a waste product, 

 to the lungs, where it is removed from the body. The most 

 characteristic feature of hemoglobin is the presence of iron, 

 which amounts to about 0.47 per cent., so that an estimation 

 of the iron of the blood would be a method of determining the 

 amount of hemoglobin. This element remains a part of hematin 

 when hemoglobin is decomposed, and upon it depends the 

 affinity of hemoglobin for oxygen. One atom of iron will take 



