CHAPTER XLI 



CIRCULATORY SYSTEM 



Introduction. In plants we learned that there were 

 tubes through which liquids passed from one part of 

 the plant to another. In our bodies there are also 

 tubes through which, liquids are forced. These liquids 

 have two very important functions. First, they carry 

 food from the alimentary canal and oxygen from the 

 lungs to all parts of the body, so that each part receives 

 what it needs. Second, they carry waste materials 

 from all parts of the body to the organs from which 

 they can be removed. 



The set of organs which performs these two func- 

 tions is the circulatory system. This system consists of 

 three parts: 



1. Blood and lymph, liquids which floAV through 

 tubes. 



2. The heart, a pump for forcing the blood around. 



3. Blood and lymph vessels. 



Blood. The liquid which flows through the blood 

 vessels we call blood. It consists of a watery fluid called 

 plasma. Floating in this are very small cells called 

 corpuscles. There are three kinds of these cells: red 

 corpuscles, white corpuscles, and blood plates. The last 



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