BLOOD. nj. 



In man and the mammals the red corpuscles present neither a nucleus nor 

 a cell wall, and are universally of a small size. They can be readily dis- 

 tinguished from the corpuscles of birds, reptiles, and fish, in which animals 

 they are larger, oval in shape, and possess a well-defined nucleus. 



The red corpuscles are exceedingly numerous, amounting to about 5,000,000 

 in a cubic millimeter of blood. In structure they consist of a firm, elastic, 

 colorless framework the stroma in the meshes of which is entangled the 

 coloring-matter the hemoglobin. 



CHEMIC COMPOSITION OF RED CORPUSCLES. 



Hemoglobin, the coloring-matter of the corpuscles, is an albuminous 

 compound, composed of C,O,H,N,S, and iron. It may exist in either 

 an amorphous or a crystalline form. When deprived of all its oxygen, 

 except the quantity entering into its intimate composition, the hemoglobin 

 becomes purplish in color, and is known as reduced hemoglobin. When ex- 

 posed to the action of oxygen, it again absorbs a definite amount and becomes 

 scarlet in color, and is known as oxyhemoglobin. The amount of oxygen 

 absorbed is 1.34 c.c. for each gram of hemoglobin. 



It is this substance which gives the color to the venous and arterial blood. 

 As the venous blood passes through the capillaries of the lungs the reduced 

 hemoglobin absorbs the oxygen from the pulmonary air and becomes oxy- 

 hemoglobin, scarlet in color; the blood becomes arterial. When the arterial 

 blood passes into the systemic capillaries, the oxygen is absorbed by the tis- 

 sues; the hemoglobin becomes reduced, purple in color, and the blood 

 becomes venous. A dilute solution of oxyhemoglobin gives two absorption 

 bands between the lines D and E of the solar spectrum. Reduced hemo- 

 globin gives but one absorption band, occupying the space existing between 

 the two bands of the oxyhemoglobin spectrum. 



The function of the red corpuscle is, therefore, to absorb oxygen and carry 

 it to the tissues; the smaller the corpuscles and the greater the number, the 

 8 



