BLOOD. 127 



The white corpuscles are far less numerous than the red, the pro- 

 portion being, on an average, about i white to from 350 to 400 red; 

 they are globular in shape, and are ^'su'o ^ an inch in diameter, and 

 consist of a soft, granular, colorless substance, containing several 

 nuclei. 



The white corpuscles possess the pawer of spontaneous movement, 

 alternately contracting and expanding, throwing out processes of their 

 substance and quickly withdrawing them, thus changing their shape 

 from moment to moment. These movements resemble those of the 

 ameba, and for this reason are termed ameboid. The white cor- 

 puscles also possess the capability of moving from place to place. 

 In the interior of the vessels they adhere to the inner surface, 

 while the red corpuscles move through the center of the stream. 



The white corpuscles are identical with the leukocytes, and are 

 found in milk, lymph, chyle, and other fluids. 



Origin of Corpuscles. The red corpuscles take their origin from 

 the mesoblastic cells in the vascular area of the developing embryo. 



In the adult they are produced from colorless, nucleated corpuscles 

 known as erythroblasts. The spleen is the organ in which they are 

 finally destroyed. 



The white corpuscles originate from the lymphocytes of the 

 adenoid tissue. 



COAGULATION OF THE BLOOD. 



When blood is withdrawn from the body and allowed to remain 

 at rest, it becomes somewhat thick and viscid in from three to 

 five minutes ; this viscidity gradually increases until the entire 

 volume of blood assumes a jelly-like consistence, which process 

 occupies from five to fifteen minutes. 



As soon as coagulation is completed, a second process begins, 

 which consists in the contraction of the coagulum and the oozing 

 of a clear, straw-colored liquid, the serum, which gradually in- 

 creases in quantity as the clot diminishes in size, by contraction, 

 until the separation is completed, which occupies from twelve to 

 twenty-four hours. 



The changes in the blood are as follows : 



Before coagulation. 



