BACILLUS MURISEPTICUS 281 



decomposing fluids, Koch found minute immotile rods 

 resembling the bacilli of swine erysipelas, but somewhat 

 thinner and smaller. They look at first sight like fine needle- 

 shaped crystals, and their true nature can only be recog- 

 nised by staining. They retain their colour when treated 

 by Gram's method. Gelatine is not liquefied, and indis- 

 tinctly defined colonies occur on the plate and spread out 

 over it in the form of delicate whitish nebulosities. In 

 thrust-cultures in like manner there appear bluish-grey 

 turbid clouds, which permeate the entire gelatine (fig. 99). 

 On agar round isolated yellowish-brown colonies develop 



FIG. 100. SPIRILLA OP RECURRENT FEVKR. (After Jakscli.) 



along the needle-track. Inoculation causes death in house- 

 mice in two or three days, but field-mice and guinea-pigs 

 are immune. The bacilli are found in the vascular system, 

 and the white corpuscles are often found to be totally 

 destroyed. The blood of the dead animals proves very 

 virulent. 



Spirochetae Obermeieri. In recurrent fever Obermeier 

 found spirilla in the blood at the time of the attack. They 

 are about six times as long as the diameter of a red cor- 

 puscle, and move in a very lively manner (fig. 100). They 

 show themselves readily amenable to staining with the 

 ordinary basic aniline dyes, but give up the colour again 



