28 THE MORPHOLOGY OF BACTERIA 



that they may be fatty or lipoidal in composition, while others are 

 probably complex phosphorus-containing compounds. 1 Not all of these 

 varieties of granules are met with in the same organism. 2 Among 

 the higher bacteria granules of sulphur or of iron are demonstrable 

 respectively in the sulphur and the iron bacteria. 



Flagella. All minute particles suspended in water or other fluids 

 of low viscosity are in constant motion. This motion, which is irregular 

 and tremulous, was first described by Brown: 3 it is variously termed 

 Brownian movement, pedesis, or molecular movement. Brownian 

 movement may be rapid or slow, extensive or circumscribed, depending 

 upon the nature of the particles and the composition and temperature 

 of the fluid in which they are suspended. This is not true motility, 

 even though each individual particle moves independently of the other 

 particles in an irregular orbit, for the particles as a whole do not 

 permanently change their relative positions. Dead bacteria and many 



FIG. 2. Flagella. 1 and 6, peritrichic flagella; 2 and 4, monotrichic flagella; 3 and 5, 



lophotrichic flagella. 



living bacteria, notably the cocci, exhibit the Brownian movement. 

 Many bacilli and spirilla, on the contrary, possess the power of 

 independent motility, that is, they can progressively and permanently 

 change their relative positions in space. Motile bacteria are provided 

 with one or more long, delicate, contractile filaments flagella which 

 are probably the organs of locomotion. These flagella cannot be 

 demonstrated on living bacteria, except possibly by dark-ground illu- 

 mination, and ordinary staining reactions usually fail to reveal them. 

 Special staining methods show them clearly. They appear to arise 

 from the cell membrane. 4 Their arrangement and number is varied 

 among bacteria in general, but relatively constant for a particular 

 variety of bacterium: they are thinner as a rule on younger bacterial 

 cells, thicker on older organisms. 5 A cholera vibrio has a single 



1 Grimme, Centralbl. f. Bakteriol., 1904, xxxvi, 952. 



2 For literature see Marx and Woithe, Centralbl. f. Bakteriol., 1900, xxviii, 1, 33, 65, 

 97; Krompecher, ibid., 1901, xxx, 385, 425; Gauss, ibid., 1902, xxxi, 92. 



3 Edinburgh Phil. Jour., 1828, v, 358; 1830, viii, 41. 



4 Schaudinn, Arch. f. Protistenk., 1903, i, 421. 



5 De Grandi, Centralbl. f. Bakteriol., 1903, xxxiv, 97. 



