10 THE BIOLOGY OF BACTERIA 



Two other signs of degeneration are the appearance of granules in 

 the body of the cell-protoplasm known as metachromatic granules, 

 owing to their different staining propensities, and the polar bodies 

 which are seen in some species of bacteria. Surrounding the mass 

 of mycoprotein, we find in most organisms a capsule or membrane 

 composed, in part at least, of cellulose. This sheath plays a 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, mycoprotein ; its capsule, cellulose. But, further 



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Fig. 3.— Diagrams of ISTormal and Polymorphic Forms of Tubercle Bacilli. 



than this, there are a number of additional distinctive characteristics 

 as regards the contents inside the capsule which call for mention. 

 Sulphur occurs in the Beggiatoa which thrive in sulphur springs. 

 Starch is commoner still. Iron as oxide or other combination is 

 found in several species. Many contain pigments, though these 

 are generally the "innocent" bacteria, in contradistinction to 

 the_ disease-producing. A pigment has been found which is 

 designated bacterio-purpurin. According to Zopf, the colouring 

 agents of bacteria are the same as, or closely allied to, the 

 colouring matters occurring widely in nature. Migula holds that 

 most of the bacterial pigments are non-nitrogenous bodies. There 

 are a very large number of chromogenic bacteria, some of which 

 produce exceedingly brilliant colours. Among some of the commoner 

 forms possessing this character are Bacillus et micrococcus violacev^, 

 B. et M. aurantiacus (orange); B. et M. luteus ; M. roseus (pink) ; 

 many of the Sarcince; B. aureus; B. fluorescens liquefaciens et 



