THE BACILLUS OF TYPHOID FEVER. 441 



Cassedebat, also, in an extended examination of the river water 

 at Marseilles with reference to the presence of the typhoid bacillus, 

 found three species which very closely resembled it, but which by 

 careful comparison were shown to present slight but constant dif- 

 ferences in their biological characters. He was not able to find the 

 true typhoid bacillus, and his researches, together with those of Babes 

 and other recent investigators, make it appear probable that numerous 

 mistakes have been made by bacteriologists who have reported the 

 finding of the typhoid bacillus in river and well water, in fa3ces, etc., 

 and who have depended mainly upon the character of invisible 

 growth upon potato in making their diagnosis. Cassedebat states 

 that all three of his pseudo-typhoid bacilli corresponded in their 

 growth upon potato with the bacillus of Eberth. They also corre- 

 sponded in their growth on gelatin, agar-agar, and blood serum, 

 which, as heretofore remarked, has no characteristic features. They 

 all gave a negative indol reaction. Like the typhoid bacillus, they 

 grew in milk without causing coagulation of the casein, but two of 

 them produced an alkaline reaction in this fluid, while the third cor- 

 responded with the typhoid bacillus in producing a decided acid re- 

 action. Differences were also observed in bouillon cultures, and in 

 bouillon and milk to which various aniline colors had been added, as 

 recommended by Holz. 



Whether the typhoid bacillus, as obtained from the spleen of a 

 typhoid cadaver, is in truth specifically distinct from these similar 

 bacilli, or whether they are all varieties of the same species, result- 

 ing from modifications in their biological characters acquired during 

 their continuous development under different conditions, is an un- 

 settled question. But, in view of the experimental evidence now 

 available, there is nothing improbable in the supposition that they are 

 simply varieties, and that, as the result of a saprophytic mode of 

 life, this bacillus may undergo more or less permanent modifications. 



In the writer's experiments (1887) the thermal death-point of the 

 typhoid bacillus was found to be 56 C., the time of exposure being 

 ten minutes ; and potato cultures containing the refractive granules 

 described by Gaffky as spores were found to be infallibly destroyed 

 by a temperature of 60 C. This result has been confirmed by Buch- 

 ner (1888) and by Janowsky (1890), and the inference seems justified 

 that these granules are not reproductive bodies, as was at first be- 

 lieved ; for spores are distinguished by their great resistance to heat 

 and other destructive agencies. According to Buchner, the bacilli 

 containing these refractive granules are even less resistant than fresh 

 cultures in which they are not present, and he is disposed to look 

 upon them as representing a degeneration of the protoplasm of the 

 cells. They do not stain by the methods which are successful in 



