288 THE BLOOD. 



ever, follow. There is no reason why many of the corpuscles 

 may not undergo, disintegration in any part of the circulatory 

 system, wherever they happen to be at the time the change takes 

 place. The large extent of blood-vessels in the liver would 

 account for the destruction that takes place there, without regard 

 to any special function of this organ connected with such destruc- 

 tion. If, as there is reason to believe, the pigment of the bile and 

 the urine are formed from that of the blood, the number of corpus- 

 cles daily destroyed must be very great. 



Function of Red Corpuscles. The red corpuscles are the 

 carriers of oxygen from the lungs, where it is received, to the 

 tissues, which appropriate it. This function is due to the hemo- 

 globin, which has a great affinity for oxygen. 



Diapedesis. In inflammatory conditions the red corpuscles 

 pass through the walls of the capillaries, constituting diapedesis 

 (p. 290). This is not an active process, as in the case of the 

 leukocytes, but a passive one ; for while the latter can make 

 their way through uninjured walls, it is only after these have thus 

 migrated that through the same opening the red corpuscles can 

 pass. 



Colorless Blood-corpuscles. These are also called white cor- 

 puscles and leukocytes. They consist of granular protoplasm, and 

 contain one nucleus or more. When in a condition of rest they 

 are spheroidal in shape, with a diameter of about 10 /^, and possess 

 the power of ameboid movement ; their shape is constantly 

 changing. 



The number of leukocytes in the blood is commonly said to be, 

 compared with the red corpuscles, as 1 to 350 or 1 to 750, or, as 

 others state it, about 10,000 in a cubic millimeter of blood ; 

 but these figures are of very little value, so greatly do the propor- 

 tions vary under different conditions. Thus Hirst found before 

 breakfast, 1 to 1800; one hour after, 1 to 700; before dinner, 1 

 to 1500; after dinner (1 o'clock), 1 to 400 ; two hours later, 1 to 

 1475; after supper (8 o'clock), 1 to 550; 12 p. M., 1 to 1200. 

 After eating the number is much increased. This increase also 

 occurs after the loss of blood, during suppurative processes, and 

 after the use of bitter tonics ; while in a state of hunger or defi- 

 cient nourishment the number is diminished. The proportion also 

 varies in different parts of the circulatory system ; thus in the 

 splenic vein it has been found to be as 1 to 60 ; in the splenic 

 artery, 1 to 2260 ; hepatic vein, 1 to 170 ; and portal vein, 1 

 to 740. 



Leukocytosis is defined as a temporary increase in the number 

 of leukocytes in the blood. It occurs normally during digestion 

 and in pregnancy, and is seen as a pathologic condition in inflam- 

 mation, traumatic anemia, various fevers, etc. Leukocythemia or 

 leukemia, on the other hand, is a fatal disease with marked 



