250 



BACILLI PATHOGENIC IN MAN. 



Characters of 

 the cultiva- 

 tions of 

 typhoid 

 bacilli. 



Growth on 

 potatoes. 



the characteristic bacilli by means of plate cultivations 

 from typhoid stools, and from the intestinal contents of 

 typhoid bodies. 



When sown on gelatine plates the colonies of the 

 typhoid bacilli form, after about 86 hours, minute white 

 points ; when magnified 80 times these appear as irre- 

 gular, oval, and even whetstone or citron-shaped plates 

 of a light yellow or yellowish-green colour, with sharp, 

 smooth borders, and an indistinct granular character. 

 In the course of 86 to 48 hours more the colonies have 

 spread out to form a roundish greyish-white flat deposit 

 1 to 1J mm. in diameter ; these do not form any knob- 

 like elevation, and project very slightly above the gelatine. 

 The contour of this layer is irregular, indented, and at 

 times distinctly branched ; under a low power the 

 colony, with the exception of the central part, is colour- 

 less, and shows on the surface numerous lines and 

 furrows. Liquefaction of the gelatine does not occur at 

 any stage. On agar plates at a higher temperature the 

 characters are similar ; after about 20 hours the young 

 colonies have the appearance under a low power of pear- 

 or citron-shaped brownish plates with sharp borders. 



In puncture cultivations in gelatine a thin whitish 

 thread forms along the line of puncture ; at the surface 

 a greyish-white flat layer is constantly formed, at first 

 small, but later reaching almost to the margin of the 

 glass; the outline of the growth shows in the later 

 stages numerous projections and irregularities. In 

 stroke cultivations a similar greyish-white layer forms 

 on the surface of the gelatine. 



The typhoid bacilli can also grow on blood serum, 

 fluid and solid, in meat infusion, and on other nutrient 

 substrata. In milk the bacilli grow actively but with- 

 out causing any noticeable alteration of the milk. 

 Their growth on boiled potatoes is extremely charac- 

 teristic, and of special importance for the distinc- 

 tion of the typhoid bacilli from all other forms of 

 bacteria as yet known. Slices of potato inoculated with 

 small quantities of typhoid bacilli appear almost com- 

 pletely unaltered after two or three days ; at the most 



