Hoiv a Complex Aii'mial Uses Food unit iv 



Fig. 224 Ly7/iphatics in the ari)i. J^ympb glands or nodes occur at definite places. 

 Where is there a group of lyinph nodes? 



out the bacteria and other foreign bodies 

 which have been swept up by the lymph. 

 You read before that when bacteria enter 

 the body many of them are engulfed by 

 the white corpuscles and digested. Those 

 that escape are normally caught in the 

 lymph glands. They are digested there 

 by the white blood cells found in the 

 nodes in large numbers. Some kinds of 

 white blood cells are made in the nodes; 

 some kinds are brought from the spleen. 

 When these glands swell after an infec- 

 tion you may become aware of their lo- 

 cation in the neck, in the crook of the 

 elbow and knee, and in various other 

 regions. 



The spleen is an organ about the size 

 of your fist, found behind the stomach. 

 You know that by contractingr it increases 

 the amount of blood and especially the 

 number of red cells in the circulation- 

 Besides this it manufactures in larsre 

 numbers the special white cells which 

 do their work in the lymph glands. It 

 also destroys worn-out red corpuscles 

 and probably has other activities not yet 

 understood. 



Note that the blood circulatory sys- 

 tem and the lymphatic circulatory sys- 

 tem are linked so that both blood and 

 the tissue fluid, lymph, serve to keep 

 materials moving about the body. 



Questions 



1. What are the two circulatory s\'stems in man? 



2. Where and how does food enter the circulatory system of man? 

 What arc two important characteristics of capillaries? 



3. What does the circulatory system of man transport besides food? 



4. Which tubes serve for long distance transportation of blood? In 

 what three respects do they differ from capillaries? 



5. By means of a table show the composition of human blood. Show 

 also the composition of the liquid part. 



6. State facts about the size, number, composition, origin, and storage 

 of red corpuscles in man. How may anemia be caused? 



7. Describe the appearance and behavior of phagocytes. Who discovered 

 them? What is pus? What do some of the other white corpuscles do? 



