32 BACTERIOLOGY. 



As stated above, the cellular contents of most bacteria 

 appear perfectly homogenous. Certain species, however, 

 show the presence of various sized granules. These are 

 especially present in old cultures and seem to have a protein 

 composition. They may be related to the chromatin of 

 higher cells and, as pointed out above, they are believed by 

 some to represent the earliest form in the development of a. 

 nuclear body. These granules may be large or small, very 

 numerous or apparently absent. It is quite possible that 

 these are due to condensation of the protoplasm as a result 

 of plasmolytic changes. Similar bodies appear in the cell 

 contents invariably previous to spore formation, and these 

 have been termed sporogenic granules. 



In the process of drying, fixing and staining bacteria v 

 artificial changes not infrequently occur which may be con- 

 sidered as evidence of a structure which in reality does not 

 exist. For instance, a bacterial suspension is allowed to dry 

 on a cover glass. As the water evaporates the concentration 

 of the salts present is increased, and as a result marked plas- 

 molytic changes may result. The cell may then show marked 

 granules or polar bodies and vacuoles. The socalled spores 

 of the tubercle bacillus may be due to changes of this kind. 



Certain bacteria, such as the typhoid and chicken 

 cholera group, on feeble staining show well stained ends 

 separated by an almost colorless zone. This is spoken of 

 as the bi-polar stain, and is supposed to be due to the pres- 

 ence of a vacuole or cell fluid in the middle of the cell. 

 The protoplasm is consequently pushed to each side and, 

 owing to its dense condition, readily takes up the stain. 

 This may represent the normal conditions of the cell but, 

 on the other hand, it may be due to the plasmolytic changes 

 mentioned above. These polar bodies are certainly not 

 spores, as has been at one time supposed. 



The contents of the bacterial cell are, as a rule, per- 

 fectly colorless. This is true even though the organism 



