PATHOGENIC ANAEROBIC BACILLI. 



483 



Biological Characters. An anaerobic, liquefying, motile 

 bacillus. Forms spores. Grows at the room temperature, in the 

 absence of oxygen, in the usual culture media. Grows best at a 

 temperature of 36 to 38 C.; in nutrient gelatin, at 20 to 25 C., 

 development is first seen at the end of three or four days ; does not 

 grow at a temperature below 14 C. Spores are formed in cultures 

 kept in the incubating oven at 36 C. , at the end of thirty hours ; 

 in gelatin cultures at 20 to 25 C., at the end of a week (Kitasato). 

 The bacilli exhibit voluntary movements which are not very active ; 

 those containing spores are not motile. It may be cultivated in an 

 atmosphere of hydrogen, but does not grow in the presence of oxy- 

 gen strictly anaerobic or in an atmosphere of carbon dioxide. 

 The addition of one and one-half to two per cent of grape sugar to 

 nutrient agar or gelatin causes the development to be more rapid 



FIG. 159. 



FIG. 160. 



FIG. 159. Tetanus bacillus, from a gelatin culture, x 1,000. From a photomicrograph by 

 Pfeiffer. 



FIG. 160. Tetanusbacillus, from an agar culture ; spore-bearing rods, x 1,000. From a photo- 

 micrograph by Pfeiffer. 



and abundant. The culture medium should have a feebly alkaline 

 reaction. 



Colonies in gelatin plates, in an atmosphere of hydrogen, re- 

 semble somewhat colonies of Bacillus subtilis, the opaque central 

 portion being surrounded by a circle of diverging rays ; liquefaction 

 is, however, much slower, and the resemblance is lost after a short 

 time. Older colonies resemble the colonies of certain microscopic 

 fungi, being made up of diverging rays. In long gelatin stick cul- 

 tures development occurs along the line of puncture, at a consid- 

 erable distance below the surface, in the form of a radiate out- 

 growth ; the gelatin is slowly liquefied, and a small amount of gas is 

 at the same time formed. In peptonized bouillon having a slightly 

 alkaline reaction, under hydrogen gas, the development is abundant 



