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 stight 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 faces, 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 
