BACILLUS MURISEPTICUS. 311 



of double staining used for demonstrating the bacilli of 

 swine erysipelas can be employed. 



In the preparations from the blood of the heart the 

 bacilli show a very characteristic arrangement : they lie 

 in part in the interior of the white blood corpuscles. 

 When this is the case the latter are generally much 

 swollen ; in some of the cells the protoplasm takes on the 

 stain only very feebly, and the outlines are indistinct ; in 

 other cases the whole body of the cell consists solely of 

 thickly aggregated bacilli, which here and there project 

 from the surface of the disintegrating cell mass. By exami- 

 nation of the various stages which can usually be recog- 

 nised in the same specimen we obtain the impression 

 that the cells are destroyed by the bacilli in their interior, 

 and not that the bacilli undergo destruction in the cells. 



.A 



Fig. 87. Bacilli of mouse septicaemia (after Koch) X 700. 

 A , blood of a septicaemic mouse, red corpuscles with bacilli between 



them. 

 P, white corpuscles containing bacilli. 



The bacilli can be readily cultivated, and grow on the Cultivations, 

 various nutrient substrata exactly in the same manner 

 as the bacilli of swine erysipelas (except with the slight 

 differences mentioned above). On gelatine plates they 

 form bluish-grey cloudy flakes lying underneath the 

 surface, which are resolved, under a low power of the 

 microscope, into a network of delicate threads ; in 

 jelly puncture cultivations a very delicate bluish-grey 

 cloud forms around the track of the needle, and this 

 cloud gradually extends outwards from the line of 

 puncture till it almost reaches the wall of the vessel 

 (fig. 86). . 



The minutest trace of blood containing bacilli or of a Inoculation on 

 cultivation is sufficient to set up the disease in mice. 

 Field mice and guinea-pigs are completely immune ; 



