CHAPTER V 

 THE BLOOD 



THE blood, a chemically complex fluid contained within the 

 vessels of the body, ha's been recognized from the earliest 

 times as indispensable to the life of man. An excessive hemor- 

 rhage prostrates, enfeebles, and may cause death. This be- 

 comes evident when it is known that the blood carries to the 

 tissues material for their growth and repair, and removes 

 from them matters that have become effete. It equalizes the 

 temperature of the body, and maintains uniform imbibition 

 relations between the cells. It is an internal medium that 

 bears the same relations to the tissues that the outer world 

 does to the entire body. It forms in total from 5 to 7.7 per 

 cent, of the body weight, so that a man of 170 pounds will 

 possess over 13 pounds of blood, or nearly 6 quarts. In given 

 individuals it does not vary through any wide limits. Varia- 

 tions that are brought about by loss of water as by perspiration 

 or by a gain of water, as through the ingestion of excessive 

 quantities of water, are compensated for by a passage of fluid 

 from or to the tissues. In starvation the quantity and the 

 quality of the blood are maintained at the expense of the other 

 tissues. 



An estimation of the amount of blood of an animal is 

 made by measuring directly as much as will escape from the 

 vessels. The latter are then washed out with normal saline 

 solution, and the tint of the washing is matched by diluting 

 a given quantity of normal blood. This process is repeated 

 after carefully mincing the entire body. The blood in the 

 washings may be calculated by knowing the dilution of normal 

 blood required to match it. This, 'added to the amount 

 measured directly, gives the total quantity. It is distributed 

 in the body as follows: 



