2 The Story of the Bacteria 



various tissues and organs are securely and 

 compactly grouped. When we have learned 

 the size, shape, number, relations, and names 

 of all these parts, our study of macroscopic or 

 general anatomy is done. If, however, enter- 

 ing that department of science known as 

 histology, or minute anatomy, we trace the 

 manner in which these parts are made beyond 

 the point where the naked eye can avail us, 

 we find that they are all composed of certain 

 tiny organisms called cells, and that these 

 cells are held together and associated by cer- 

 tain materials which lie between them. 



Just as the chemist has his atoms and 

 molecules, to which in the last analysis he re- 

 fers the properties which all known substances 

 possess, and explains by differences in their 

 nature and movements the various chemi- 

 cal phenomena which matter exhibits, so we 

 may refer both the structural features and all 

 the activities of the animal body back to the 

 structure and activities of our elements the 

 cells. While the chemist, however, must infer 

 the existence of his atoms from their deeds, 

 armed with the microscope we can see our 



