102 ELEMENTARY PHYSIOLOGY. 



Number (7) gives us a view of the 

 thl JLunss^r). stru cture of the lungs. As you know, 



the lungs are composed chiefly of cells 

 in which the imparities are exchanged for fresh 

 supplies of life-giving oxygen. Here these cells and 

 blood-capillaries are seen. 



capillaries of * ** e P ar tid, the principal one of the 

 the Parotid salivary glands, is also composed mostly 



r (8), . , , , 



Brain (9) and * a capillary net-work, as shown here 

 cellular (g). At (9) we see the capillaries of 



Tissue (1O). 



the brain, with red and white corpuscles, 

 or blood-discs, passing through them, carrying 

 nourishment to the brain. 



(10) shows how cells grow in length and then 

 split into .tissue-forming fibers. The cell, you will 

 remember, is the smallest possible part of the body, 

 and is the most important structure of the system, 

 since all tissues and organs are made up of cells, just 

 as sandstone is made up of millions of small grains 

 of sand. But sand is lifeless, while, in the living 

 body, life resides in the cell. 



Under the microscope the muscular 



Elastic Tis- ',.., t 



sues (ii),iius- fiber has the appearance as shown at 

 ?S"* (12). It consists, of course, of many 



(12), and Bone- ^ ' J 



Corpuscles cells joined together, as will be seen 

 by carefully examining this cut. The 

 structure of the bones, with their canals and little 

 lakes, through which their nourishment is carried, is 

 nicely shown at (13). Examine it carefully, and 

 then procure, if possible, a bone cut crosswise, and 

 compare. 



