24 MODERN BIOLOGIC THERAPEUSIS 



themselves with exceeding rapidity and grow 

 without the aid of chlorophyll. There are such 

 wonderful differences in the conditions of life 

 and nutrition which suit the different varieties 

 that bacteria are found all over the known 

 world. Wherever there is sufficient moisture, 

 one form or another will find certain conditions 

 sufficient for multiplication. The fact that each 

 bacterial variety, possible of cultivation, may 

 grow in distinctive ways upon so-called artificial 

 culture media, has been an immense aid in the 

 differentiation of these microorganisms ; for the 

 individual cell of most varieties is so minute 

 that even the highest magnification of the micro- 

 scope may show little if any morphologic differ- 

 ence between microorganisms which produce 

 distinctly different diseases, or between a path- 

 ogenic and non-pathogenic form. 



Shape The basic forms of bacteria embrace 

 the sphere, the rod and the segment of a spiral. 

 Although under different conditions the type- 

 form of any one species may vary considerably, 

 yet these three main divisions under similar 

 conditions are constant. (1) The spherical 

 form, or coccus, when seen in the process of 

 multiplication through division, is seldom 



