94 ESSENTIALS OF BACTERIOLOGY. 



change to a longer form which occurs singly or in long chains. 

 It is stained brown by Gram's iodine solution. The bacillus 

 affords confirmatory evidence of the presence of a new growth, 

 though it may occur in benign conditions. 



CHAPTER II. 



PATHOGENIC BACTERIA. 



WE have divided this part into two portions. 



I. Those bacteria which are pathogenic for man and other 

 animals. 



II. Those bacteria which do not affect man, but are patho- 

 genic for "the lower animals. 



Here again it will only be possible to give the more impor- 

 tant bacteria ; there are many diseases in which micro-organisms 

 have been found, but they have not yet been proven as causa- 

 tive of the disease, and have also been found in other diseases. 

 We cannot treat of them here. 



Bacillus Anthracis. (Bayer and Davaine.} Kayer and Da- 

 vaine, in 1850, first described this bacillus; but Pasteur, and 

 later Koch, gave it the importance it now has. 



Synonyms. Bactericie du charbon (Fr.), Milzbrand bacillus 

 (German) ; bacillus of splenic fever, or malignant pustule. 



Origin. In blood of anthrax-suffering animals. 



Form. "Rods of variable length, nearly the size of a human 

 blood-corpuscle, broad cup-shaped ends; in bouillon cultures, 

 long threads are formed, with large oval spores. 



Properties. Liquefies gelatine ; immotile ; the spores are very 

 resisting, living twenty years, and resist boiling for five minutes. 



Growth. Grows rapidly, between 12 C. and 45 C., and re- 

 quires plenty of oxygen, but may be classed as a facultative 

 anaerobe ; grows well in all media. 



Plates of Gelatine. Colonies develop in two days, white shiny 

 spots, which appear under microscope as slightly yellowish 

 granular twisted balls, like a ball of yarn ; each separate string 



