52 PHARMACEUTICAL BACTERIOLOGY 



The cell- walls of many species undergo a gelatinous change. This 

 change may affect the outer layers only, or it may involve the entire thick- 

 ness of the wall, forming the gelatinous substances noticeable in bacterial 

 cultures and in other substances (stringy cultures, stringy milk, etc.). 

 This gelatinous substance also causes the individual organisms to cling to 

 each other, thus causing the formation of the peculiar zooglea masses in 

 in natural as well as in artificial culture media. 



FIG. 4. Illustrating the general morphology of microbes, a, showing general 

 structure of a bacillus, endospore formation, and development of new bacillus from a 

 spore; b, showing manner of transverse septation; c, arrangement of flagellae, single uni- 

 polar, single bipolar; and multiple, polar and general; d, cocci; e, flagellae of cocci;/, 

 spirillum with single polar cilia. 



The cilia or flagellae are very delicate threads, supposed to extend from 

 the cell-plasm, through the cell- wall, into the surrounding medium. The 

 delicate threads are probably cytoplasmic in nature, and by their rapid 

 vibratory motion enable the microbe to move about within liquid media. 

 Some microbes are apparently without flagellae, nor is it definitely deter- 

 mined that all motile microbes have flagellae. The attempt to make 

 generic distinctions based upon the absence or presence of few or many 

 flagellae, upon the existence of polar or non-polar flagellae, etc., is unsatis- 

 factory. Special staining methods are necessary to demonstrate the 

 presence or absence of flagellae. 



