Bacteria 31 



Cytoplasm. — The cytoplasm, of which very little exists between the 

 large nucleus and cell-wall, is sometimes granular, as in Bacillus 

 megatherium, and sometimes contains fine granules of chlorophyl, 

 sulphur, fat, or pigment. 



Capsule. — Each cell is surrounded by a distinct cell-wall, which in 

 some species shows the cellulose reaction with iodin. 



The cell-walls of certain bacteria at times undergo a peculiar 

 gelatinous change or permit the exudation of gelatinous material 

 from the cytoplasm, and appear surrounded by a halo or capsule. 

 Such capsules are seen about the pneumococcus as found in blood 

 or sputum, Friedlander's bacillus, as seen in sputum, Bacillus 

 aerogenes capsulatus in blood or tissue, and many other organisms. 

 Friedlander pointed out that the capsule of his pneumonia bacillus, 

 as found in the lung tissue or in the "prune-juice" sputum, was very 

 distinct, though it could not be demonstrated at all when the organ- 

 isms grew in gelatin. 



Polar Granules. — By carefully staining an appropriate organism, 

 certain peculiarities of structure can sometimes be shown. Thus, 

 some baciUi contain distinct "polar granules" (metachromatic or 

 Babes-Ernst granules) — rounded or oval bodies — situated at the 

 ends of the cell. Their significance is unknown. They have been 

 supposed to bear some relationship to the biologic activity of the 

 organism, especially its pathogenesis, but this is uncertain, and 

 Gauss* and Schumburgf believe that they vary with the reaction 

 of the culture-media upon which the bacteria grow and have 

 nothing to do with virulence. 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 degener- 

 ated organisms (involution forms) which, because of plasmolysis, or 

 solution, can no longer stain uniformly. 



Flagella. — Many bacteria possess delicate straight or wavy 

 filaments, called flagella, which appear to be organs of locomotion. 



MesseaJ 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). 



» 

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

 t Ibid., June 3, 1902, xxxi, No. 14, p. 694. 

 % " Rivista d'igiene e sanata publica," 1890, 11. 



