494 



PATHOGENIC ANAEROBIC BACILLI. 



affected areas have a dark color and contain a bloody serum in 

 which the bacillus is found. 



Morphology. Bacilli with rounded ends, from three to five /* 

 long and 0.5 to 0.6 /< broad ; sometimes united in pairs, but do not 

 grow out into filaments. The spores are oval, somewhat flattened on 

 one side, thicker than the bacilli, and lie near the middle of the rods, 

 but a little nearer to one extremity. The bacilli containing spores 

 are somewhat spindle-formed (Kitasato). "Involution forms " are 

 quite common in old cultures or in unfavorable 

 media ; in such cultures variously distorted and 

 often greatly enlarged bacilli may be seen, some 

 being greatly swollen in the middle spindle- 

 shaped. When properly stained, by Loffler's 

 method, a number of flagella are seen around the 

 periphery of the cells. 



Stains with the aniline colors usually em- 

 ployed, but not by Gram's method. Spore-bear- 

 ing bacilli may be double-stained by first stain- 

 ing the spores by Ziehl's method, and then the 

 bacilli with a solution of methylene blue. 



Biological Characters. An anaerobic, liq^- 

 uefying^motilebacillus. Forms spores. Grows 

 at the room temperature in the usual culture media, 

 in the absence of oxygen, in an atmosphere of hy- 

 drogen, but not in carbon dioxide. This bacillus 

 grows more rapidly and abundantly in nutrient 

 agar or gelatin to which 1.5 to 2 per cent of 

 grape sugar or five per cent of glycerin has been 

 added. Colonies in gelatin, in an atmosphere of 

 hydrogen, are at first spherical, with irregular out- 

 lines and a wart-like surface ; later the gelatin is 

 liquefied around them, and radiating filaments 

 grow out into the gelatin, so that by transmitted 

 light they present the appearance of an opaque 

 central mass with an irregular surface surrounded 

 by rays. In stick cultures in nutrient gelatin, at 

 20 to 25 C., at the end of two or three days 

 development occurs at the bottom of the line of puncture to within 

 about two fingers' breadth of the surface ; the gelatin is slowly 

 liquefied and considerable gas is formed. In old cultures the 

 growth and liquefaction of the gelatin extend nearly to the sur- 

 face. In agar stick cultures, in the incubating oven, develop- 

 ment begins within a day or two and extends to within one 

 finger's breadth of the surface ; considerable gas is evolved, and 



FIG. 169. Bacillus 

 of symptomatic an- 

 thrax; long stick cul- 

 ture in nutrient gela- 

 tin, ten days at 18- 

 80 0. (Kitasato.) 



