284 



BAQILLI PATHOGENIC IN MAN. 



on the ordinary gelatine plates, but Loeflfler succeeded 

 in growing them by diluting a small portion of the 

 material taken from the diphtheritic membrane, and by 

 inoculating drops of the diluted material on solidified 

 blood serum ; in this way pure cultivations of the bacilli 

 Mode of com- were obtained. Wyssokowitsch recently succeeded in 

 isolating the same rods from a piece of diphtheritic 

 membrane which had been coughed up, employing agar 

 plates for the purpose, and keeping the material at 

 35 C. In order to render the isolation of the organ- 

 isms certain one must always employ a large number of 

 plates, as a large proportion of them are generally com- 

 pletely overgrown by the rapidly growing saprophytes. 

 Loeffler found that the best medium was a solid material 

 composed of three parts of calves' or sheep's blood 

 serum, and one part of neutralised veal broth, to which 

 one per cent, of peptone, one per cent, of grape sugar, 

 and a half per cent, of common salt were added. On 

 this soil the bacilli grew at 37 C. in the form of whitish 

 opaque drops, or of a thick white layer, which attained 

 the acme of its development within two days. Agar 

 jelly forms an almost equally favourable soil ; on nutrient 

 jelly growth also occurs at about 22 C., but it is slow 

 and imperfect ; no growth appears to take place on 

 potatoes. 



On agar plates the youngest colonies lying in the 

 substance of the material appear, when magnified 80 

 diameters, as round or oval, dark 

 brown, coarsely granular, and not 

 sharply outlined discs. Several 

 colonies often run together, so that 

 irregular figures are formed. The 

 superficial colonies are greyish- 

 yellow, with granular, rough, 

 almost net-like, surfaces, and with 

 the a delicate wavy border. 



The rods are immobile, the 



of majority of them are slightly bent. They vary much in 

 length, being on an average of much the same length as 

 the tubercle bacilli, but they are considerably thicker than 



Fig. 

 di 



81. Colonies of 

 iphtheritic bacilli 

 on agar plates X 

 80. 



Morphological 



agar. 

 b, those situated on 

 surface. 



