104 ELEMENTARY PHYSIOLOGY. 



Red Blood ^S' (20) shows the red corpuscles 



of the blood of different animals. 



Blood consists of a countless number 

 of solid bodies floating in a liquid. Some of these 

 solids are of a red color, while others are pale or 

 white. These solids are called corpuscles or blood- 

 discs. They vary also in shape in different ani- 

 mals. In man, the discs are usually nearly or quite 

 circular, though, when seen in different positions, 

 they present different appearances; 'just as a coin, 

 looked at perpendicularly to its surface, looks cir- 

 cular, and, when we look at it edgewise, seems of 

 an entirely* different shape. These wonderful little 

 bodies are so small that, of the red discs, 3,500, laid 

 side by side, would measure only an inch, and, if 

 placed one upon another, 18,000 would be required 

 to make a column of that height. They usually 

 arrange themselves in piles, and fit in each other 

 like so many saucers or butter plates. It is the 

 great number of these corpuscles which gives blood 

 its color. 



The structure of the strong tendons by 



niter pi which the muscles are attached to the 

 Adipose Tis- bones, is shown very plainly at (21,. 

 As will be seen here they consist of 

 many longitudinal fibers. Number (22) shows us 

 how adipose cells appear under the microscope 

 (23), and gives us another view of the structure of 

 the bones. This is from the ulna of the forearm. 



