Spirillum Rubrum, Esmarch. 



Origin. — From the putrefied cadaver of a mouse. 



Form. — Clear, transparent, thick cells, which are 

 xisually sing-le, appearing- as large bent rods or comma 

 bacilli (vibrio). It may form spirals of three ox four, or 

 even forty windings. Involution forms are common in old 

 cultures. 



Motility. — It is actively motile. Each end of a spiral 

 has one wavy flagellum. 



Sporulation. — True spores have not been observed. 



Anilin dyes.— These stain slowly but well, especially 

 if the dye is slightly warmed. 



Growth. — This is extremely slow. 



Gelatin plates. — Owing' to the very slow development of colonies 

 ordinary plates cannot be used. In roll-tubes, colonies develop in from 

 seven to ten days, and at first are minute and grayish; later the cen- 

 ter of each colony becomes tinged with pink and eventually becomes 

 red. The edge is smooth and the contents are finely granular. 



Stab culture. — This is the most characteristic. Growth takes 

 place along the entire line of inoculation, forming a row of colonies. 

 The growth spreads slightly on the surface, and is colored a light 

 pink. The pigment formation is most marked along the line of punc- 

 ture — where oxygen is absent. It passes through a light pink to a 

 beautiful dark wine-red color. Ordinary bacterial pigments are 

 formed only in the presence of air, and are secondary products, 

 whereas this pigment is formed in the absence of air and is, there- 

 fore, a primary product. 



Streak cultv/re. — On agar, it forms moist, thick, non-spreading 

 patches, which, when old, possess a light pink or red color, especially 

 near the center. On potato, it develops slowly, foriding minute 

 deep red colonies. On blood-serum, the growth is much the same as 

 on agar. 



Milk. — In fluid media, milk, bouillon, etc., it forms long spirals 

 which show little or no motion. 



Oxygen requirements. — It is a facultative anaerobe. 



Temperature. — It grows between 16° and 40°. The 



optimum temperature is about 37°. 



Behavior to gelatin. — It does not liquefy. 



Pathogenesis. — It has no effect on animals. 



224 



