258 PHYSIOLOGICAL CHEMISTRY 



The following bodies may be derived from hemoglobin, and each 

 possesses a specific absorption spectrum which serves as an aid in 

 its detection and identification: Oxyhemoglobin, methemoglobin, 

 carbon-monoxide hemoglobin, nitric-oxide hemoglobin, hemochromo- 

 gen, hematin, acid-hematin, alkali-hematin and hematoporphyrin 

 (see Absorption Spectra, Plates I and II). 



The relationship between hemoglobin and its derivatives may be 

 represented by the scheme shown on page 257. 



The chemical transformations which occur in the blood during respira- 

 tion are complicated and of great importance. In brief the exchange of 

 oxygen and carbon dioxide may be described as follows : Oxygen from 

 the air passes through the lungs into the blood where it is appropriated 

 for the most part by the red blood corpuscles. The hemoglobin of 

 these corpuscles possesses the property of uniting with oxygen, forming 

 oxyhemoglobin. This oxyhemoglobin possesses a red color and imparts 

 to the arterial blood its bright appearance. The oxygen is thus borne 

 by these blood cells in the circulating blood to all parts of the body. 

 As the blood passes through the capillaries it gives up the major part of 

 its oxygen which is used by the tissues in their varied activities. As the 

 blood loses its oxygen it becomes darker in color due to the fact that 

 the oxyhemoglobin has been transformed into hemoglobin (or reduced 

 hemoglobin) . At the same time in the tissue capillaries the blood takes 

 up excretory products from the tissues, the chief of which is carbon 

 dioxide. This carbon dioxide is present in the blood mainly as carbonic 

 acid and sodium acid carbonate ; a small amount is probably combined 

 with the proteins of the plasma. We now have so-called venous blood. 

 This is, in turn, carried to the lungs where the carbon dioxide is 

 exchanged for oxygen and the cycle is repeated. 



The white corpuscles (or leucocytes) of human blood differ from 

 the red corpuscles (or erythrocytes) in many particulars, such as being 

 somewhat larger in size, in containing at least a single nucleus and in 

 possessing ameboid movement (see Plate IV, opposite page 252). 

 They are typical animal cells and therefore contain the following bodies 

 which are customarily present in such cells: Proteins, fats, glycogen, 

 purine bodies, enzymes, phosphatides, lecithin, cholesterol, inorganic salts, 

 and water. Compound proteins make up the chief part of the protein 

 quota of leucocytes, the nucleoproteins predominating. Of the en- 

 zymes present the proteolytic are the most important. It is claimed 1 

 that there are two proteolytic enzymes in leucocytes, one active in 

 alkaline solution and present in the polynuclear cells, 2 and the other 



^pie: Jour, of Experimental Med. y 8; Opie and Barker: Ibid., 9. 

 2 For discussion of different types of leucocytes see "Da Costa's Clinical Hematology" 

 or some similar volume. 



