Structure 31 



nificance is unknown. They have been supposed to 

 bear some relationship to the biologic activity of the organ- 

 ism, especially its pathogenesis, but this is uncertain, 

 and a recent work by Gauss * and Schumburg f shows that 

 they vary with the reaction of the culture media upon which 

 the bacteria grow and have nothing to do with their viru- 

 lence. Bacillus megatherium is peculiar in having its 

 cytoplasm filled with small granules which stain deeply. 

 The diphtheria bacillus and the cholera spirillum stain very 

 irregularly in fresh cultures, as if the tingeable substance 

 were not uniformly distributed throughout the cytoplasm. 

 Vacuolated bacteria and bacteria that will not stain, or 

 stain very irregularly, may usually be regarded as degen- 

 erated organisms (involution forms) which, because of 

 plasmolysis, or solution, can no longer stain homogene- 

 ously. 



Flagella. Many bacteria possess delicate straight or wavy 

 filaments called cilia or flagella, which appear to be organs 

 of locomotion. Sometimes they are attached only at the 

 ends, sometimes to all parts of the organisms. 



Messea J has suggested that the bacteria be classified, 

 according to the arrangement of the flagella, into : 

 I. Gymnobacteria (forms without flagella). 

 II. Trichobacteria (forms with flagella). 



1. Monotricha (with a single flagellum at one end). 



2. Lophotricha (with a bundle of flagella at one 



end). 



3. Amphitricha (with a flagellum at each end). 



4: Peritricha (flagella around the body, springing 

 from all parts of its surface). 



This arrangement is, however, less satisfactory than that 

 of Migula already given. 



Motility The greater number of the bacteria supplied 

 with flagella are actively motile, the locomotory power no 

 doubt being the lashing flagella. The rod and spiral micro- 

 organisms are most plentifully supplied with flagella; only 

 a few of the spheric forms have them. 



The presence of flagella, however, does not invariably im- 

 ply motility, as they may also serve to stimulate the passage 

 of currents of nutrient fluid past the organism, and so favor 



* "Centralbl. f. Bakt.," etc., xxxi, No. 3, Feb. 5, 1902, p. 106. 

 *d., xxxi, No. 14, p. 694, June 3, 1902. 

 Rivista d'igiene e sanata publica," 1890, n. . 



