10 APPLIED PHYSIOLOGY 



forms of life. Only man presents the most perfect combi- 

 nation of these processes. 



2. The ameba. One of the simplest animals lives in 

 stagnant water and is called the ameba. It is only a lump 

 of jelly about yoVo f an ^ nc ^ * n diameter, yet it is a com- 

 plete animal, for it moves, and eats, and grows, and pro- 

 duces other amebas. It has no arms, or legs, or head, but 

 all parts of its body seem very nearly alike. It puts out 

 little fingers from its body and then rolls its whole body 

 into the fingers. In this way it is continually rolling about. 

 When it finds a particle of food it wraps itself around it 

 just as a baker rolls a mass of bread dough around a 



An ameba, sketched at intervals of ten seconds ( x 400) . 



raisin. That part of the body which is in contact with 

 the food digests as much as is needed, and then unwraps 

 itself away from the waste. It has no choice as to what 

 part of its body it shall use for any given purpose. But 

 man uses each part of his body for only definite purposes. 

 He has arms which get food, a mouth which eats it, and a 

 stomach which digests it. The arms cannot eat food, 

 neither can the mouth digest it, but each part does only 

 its own kind of work. 



3. Man like an ameba. Each part of a man's body is 

 made of multitudes of living beings, each of which eats 

 and grows like an ameba. Each tiny being is called a 

 cell. One collection of cells forms the skin, another the 

 muscles of the arm, and another the stomach, and so on 



