78 



MORPHOLOGY AND CULTURE OF MICROORGANISMS 



^' 



\l dy 



VWT/l,v~ 



^ 



Fig. s8. — Types of spirilla. {After Williams.) 



Gradations. — The difference between these fundamental form 

 types is frequently very sUght. It becomes a very difficult matter, 

 for instance, to distinguish at times between the micrococcus and the 

 bacillus. There is a number of bacteria, and among them the well- 

 known example of B. frodigiosus, that are described at one time by one 

 investigator as micrococci and at another time, or, by another inves- 

 tigator, as bacilU. The pneumonia germ is also another illustration 

 of an organism that occupies a dual position. Migula has suggested 

 a method of differentiating these which will be discussed under a 

 later head. The bacilli pass almost imperceptibly into the spirilla. 

 The cholera bacillus of Koch is in reality a spirillum. 



Fig. sg.— Involution forms. Here are illustrated unusual forms of B. subtilis 

 water bacteria, Bact. aceti, Bact. pasteurianum, bacteroids in root nodules Bact 

 tuherculosis, Bad. diphtherial. {After Fischer from Frost and McCamphell.) ' 



