Vascular System • 



CHAPTER IX 



VASCULAR SYSTEM; THE BLOOD AND LYMPH 



It is helpful to remember that the body consists of an enormous 

 number of individual cells, and that each cell must be supplied 

 with materials, to enable it to carry on its activities, and at the 

 same time it must have the waste materials that are the result of 

 its activities removed. Many cells are far from the source 

 of supplies and the organs of elimination ; hence the need of a 

 medium to distribute supplies and collect waste, and the need of a 

 system so that the distribution will be orderly and systematic. 

 These two needs are met by the vascular system, the divisions of 

 which may be outlined as follows : — 



Circulating fluids I ^ , 



„ , I Blood vascular 



Systems 1 t i i 



•^ I Lymph vascular. 



THE BLOOD 



Characteristics. — ■ The most striking external feature of the 

 blood is its well-known color, which is bright red, approaching to 

 scarlet in the arteries, but of a dark red or crimson tint in the veins. 



It is a somewhat sticky liquid, a little heavier than water; 

 its specific gravity is about L055. It has a peculiar odor, a saltish 

 taste, a slightly alkaline reaction when tested with litmus, and a 

 temperature of about 100° F. (37.8° C). 



Quantity of blood. — The quantity of blood contained in the 

 body is estimated to be about 2V of the body weight. This pro- 

 portion was formerly said to be about -5^3, but later experiments 

 seem to place the figure at aV- This, in an individual weighing 

 160 pounds, would weigh about 8 pounds, or measure 4 quarts. 



Functions of the blood. — Blood is commonly spoken of as 

 the nutritive fluid of the body. This is quite correct, but it is 

 more than a nutritive fluid, as will be seen from the following 

 list of its more important functions : — 



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