58 MORPHOLOGY 



toplasm at the poles of the cell. When stained by the various 

 bacteriological stains, these granules of condensed protoplasm 

 stain deeply and are well differentiated from the rest of the 

 cell. These granules are known as polar granules (methylene 

 blue stain on B. pestis). Frequently due to the accumulation 

 of the granules in certain parts of the cell the remaining slightly 

 stained protoplasm gives the appearance of vacuoles. These 

 vacuoles appear to contain a clear substance, in all probability 

 cell sap. As to the significance of both metachromatic and 

 polar granules there is still doubt. Obviously, it is necessary 

 to determine whether there is any consistency in their develop- 

 ment in certain species of bacteria under any and all conditions. 

 It may be stated that certain bacteria show a slight granular 

 condition of their protoplasm at all times (Bact. diphtheriae), 

 while others do not show such structures with consistency. 

 It is frequently observed when the bacteria are grown under 

 unsatisfactory conditions of temperature, moisture, or food 

 supply. It has been stated that this granular formation 

 within some bacterial cells precedes reproduction. They were 

 supposed by some to be similar to gonidia. They are also 

 known as Babes-Ernst granules. It has not been positively 

 proved that these granules have anything whatever to do 

 with the process of reproduction. Some writers have claimed 

 that they were food products, but this is an erroneous con- 

 ception. In all probability they are produced artificially in 

 the cell by plasmolysis. As mentioned above, when bacteria 

 are placed in a media of greater density (hypertonic) than 



