Chapter II 

 Bacteria 



MANY bacteria differ from the yeasts and moulds in being 

 capable of independent motion, which is accomplished by means 

 of fine threads, known as flagellce, growing from the protoplasm. 

 The monotricha have a single flagellum growing from one end, 

 and the lofotricha a tuft of flagellae similarly situated ; the peri- 

 tricha have flagellse all round the cell. Motility may be restricted 

 to certain stages of development, chiefly the period of active 

 growth ; on the other hand, a large number of bacteria appear to 

 be non-motile at all stages, and on this account it may be presumed 

 that they are without flagellse ; unfortunately these extremely 

 fine thread-like structures can only be rendered visible by means 

 of complicated methods of staining which sometimes fail. There 

 is, however, no doubt that the disposition of the flagellse affords 



, 



FIG. 25. Racterinm pyocyaneum, monotrich. FIG. 26. Bacterium syncyaneum, lo/o 

 (After Migula.) ' X 1,000. trich. (After Migula.) X 1,000. 



the most important of the morphological methods of distinction, 

 and one on which the classification of the bacteria should primarily 

 be based. Thus the monotricha and the lofotricha require com- 

 paratively simple nutrient material, being chiefly water bacteria, 

 while the peri trich bacteria are typical fermentation organisms l . 

 According to their shape the bacteria are divided into sphere, 

 rod or screw forms. As the first-mentioned have no axis of length, 

 division is possible in three dimensions, and, as a matter of fact, 

 cases are known where division takes place in either one, two or 



1 Orla Jensen. " Hovedlinierne i det naturlige Bacteriesystem." Viden- 

 skabernes Selskabs Oversigter, 1908, No. 5. Die Hauptlinien des Natiir- 

 lichen Bakteriensystems. Verlag von Gustav Fischer, Jena, 1909. 



