CHAPTER III 



DEVELOPMENT 



N view of the present vast extent of knowledge 

 concerning the minute structure of animals 

 and plants, it seems almost incredible that the 

 beginnings of such studies had hardly been 

 made within the lifetime of persons now living. It was 

 not until nearly four decades of the nineteenth century 

 had passed, that the epoch-making fact was established 

 that the bodies of all organisms were composed of living 

 units which were, and still are, called cells. 



The term cell is really a misnomer, for it implies an 

 investment or wall enclosing an empty space. The older 

 observers discovered that the stems of woody plants 

 were composed of bodies having thick walls that in each 

 case surrounded an empty cavity. These bodies they 

 properly called cells, but the units of structure which 

 they had discovered were really only walls, the essential 

 or living parts within having disappeared. Such empty 

 spaces are not found in animal bodies or in the living 

 and growing parts of plants. 



Cells that compose the body of an animal or plant are 

 not all of the same sort, as are the bricks of which a 

 building is constructed. Some are nearly spherical, 

 others are flattened or are elongated into fibers. Most 

 of them are minute, but there is a great variation in their 



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