3o THE BLOOD 



cent, solids. The principal solid constituents are (a) hemo- 

 globin (oxyhemoglobin) 87-95 P er cent., (b) stroma, com- 

 posed of fat, lecithin, and cholesterin, and (c) salts, princi- 

 pally potassium chloride, and potassium phosphate. 



Hemoglobin. Hemoglobin is the coloring matter of the 

 red cells, and is composed of (i) hematin, a pigment con- 

 taining iron, and (2) globin, a proteid. Hemoglobin is of 

 great physiological importance because of its ability to unite 

 with oxygen and thus form oxyhemoglobin. By it the blood 



A, human colored blood corpuscles i, on the flat; 2, on edge; 3, rouleau of 

 colored corpuscles. B, amphibian colored blood corpuscles i, on the flat; 2, on 

 edge. C, ideal transverse section of a human colored blood corpuscle magnified 

 5,000 times linear a, b, diameter; c, d, thickness. (Landois.) 



carries its oxygen from the lungs to the tissues. It also 

 unites to some extent with carbon dioxide and it is thus that 

 carbon dioxide is brought from the tissues. We find oxy- 

 hemoglobin chiefly in the arterial blood, while in venous 

 blood we find both hemoglobin and oxyhemoglobin. In as- 

 phyxiated blood we find only hemoglobin. 



The stroma is the colorless framework of the corpuscles 



