4o 



PATHOGENIC BACTERIA. 



in such short individuals as to be easily mistaken for 

 slightly-bent bacilli. 



The bacteria thus far described are lower in their evo- 

 lution than the following group, because even in their 

 chains and clusters each individual is entirely inde- 

 pendent. 



The higher forms of bacteria are characterized by a 

 certain mutual dependence by which, for example, one 

 end of a filament becoming attached, growth would take 

 place at the other only. They also differ in having spe- 

 cial elements developed for purposes of reproduction. 



The higher bacteria are all characterized by filament- 

 ous forms and either real or apparent branchings. The 

 filaments are usually regularly divided transversely, so as 

 to appear as if composed of bacilli. The free ends only 

 seem to be endowed with reproductive functions, and 

 develop peculiar bodies known as conidia. 



Beggiatoa is a name given to free-swimming forms, 

 motile by undulation of the protoplasm. The division 

 of the filaments into segments is not apparent; they have 

 no special sheath ; the protoplasm frequently contains sul- 

 phur granules. 



Thiothrix differs in that an end of the filament is fixed 

 so that the plant is not free to swim. In other points it 

 much resembles beggiatoa. 



Leptothrix resembles thiothrix, but contains no sulphur 

 granules. 



Cladothrix is characterized by false branchings. There 

 are conidia formed for reproductive purposes. The parent 

 may or may not be motile, but the conidium is flagellated 

 and actively motile. 



Streptothrix is the highest form and the only one 

 encountered in animal pathology. It is best illustrated 

 by the Streptothrix actinomyces and Streptothrix Ma- 

 dura, and may possibly include the tubercle bacillus and 

 even the diphtheria bacillus if recent observations re- 

 garding them are correct. 



The characteristic of the species is a true dichotomous 



