THE BIOLOGY OF BACTERIA 13 



means organisms are stained for the microscope. Besides the 

 variable quantity of nitrogen present, mycoprotein may also 

 contain various mineral salts. The uniformity of the cell 

 protoplasm may be materially affected by disintegration and 

 segmentation due to degenerative changes. Vacuoles also may 

 appear from a like cause, which it is necessary to differentiate 

 from spores. Two other signs of degeneration are the ap- 

 pearance of granules in the body of the cell protoplasm 

 known as metachromatic granules, owing to their different 

 staining propensities, and ^^^ polar bodies which are seen in 

 some species of bacteria. Surrounding the mass of myco- 

 protein, we find in most organisms a capsule or membrane 

 composed, in part at least, of cellulose. This sheath plays a 



Normal and Pleon-Forms of the Bacillus of Tubash. 



protective part in several ways. During the adult stage of 

 life it protects the mycoprotein, and holds it together. At 

 the time of reproduction or degeneration it not infrequently 

 swells up, and forms a viscous hilum or matrix, inside which 

 are formed the new sheaths of the younger generation. It 

 may be rigid, and so maintain the normal shape of the 

 species, or, on the other hand, flexible, and so adapted to 

 rapid movement of the individual. 



Here, then, we have the major parts in the constitution of 

 a bacillus — its body, my<;oprotein ; its capsule, cellulose. 

 But, further than this, there are a number of additional dis- 



