PROTECTIVE INOCULATIONS. dll 
to rabbits, and a few drops injected subcutaneously sufficed to kill a 
small bird within a few hours. In their second paper (1889) the 
authors mentioned state that so long as the reaction of a culture in 
bouillon is acid its toxic power is comparatively slight, but that in 
old cultures the reaction is alkaline, and in these the toxic potency is 
greatly augmented. With such a culture, filtered after having been 
kept for thirty days, a dose of one-eighth of a cubic centimetre in- 
jected subcutaneously, sufficed to kill a guinea-pig; and in larger 
amounts it proved to be fatal to dogs when injected directly into the 
circulation through a vein. 
The same authors, in discussing the nature of the poison in their 
filtered cultures, infer that it is related to the diastases, and state that 
its toxic potency is very much reduced by exposure to a comparatively 
low temperature—58° C., for two hours—and completely destroyed by 
the boiling temperature—100° C., for twenty minutes. It was found 
to be insoluble in alcohol, and the precipitate obtained by adding al- 
cohol to an old culture proved to contain the toxic substance. ’Loffler 
also has obtained, by adding five volumes of alcohol to one of a pure 
culture, a white precipitate, soluble in water, which killed rabbits in 
the dose of 0.1 to 0.2 gramme when injected beneath the skin of these 
animals. It gave rise to a local cedema and necrosis of the skin in 
the vicinity of the point of inoculation, and to hyperemia of the in- 
ternal organs. This deadly toxin appears to be an albuminoid sub- 
stance, but its exact chemical composition has not yet been deter- 
mined. 
Brieger and Frankel (1891) obtained results corresponding with 
those previously reported by Roux and Yersin. Their researches 
showed that the toxic substance contained in diphtheria cultures is 
destroyed by a temperature of 60° C.; that it is soluble in water, and 
insoluble in alcohol; that it does not pass through a dialyzing mem- 
brane, and has not the chemical characters of the ptomaines or toxins, 
but is an albuminous body—a toxalbumin. It was obtained by the 
authors named by precipitation with slightly acidified (acetic acid) 
alcohol; the precipitate, after being washed in a dialyzer and dried 
in a vacuum ata temperature of 40° C., was a snow-white, amorphous, 
erumbling mass. 
Wassermann and Proskauer (1892) found that the alcoholic pre- 
cipitate from diphtheria cultures contains two different substances, 
which are distinguished by their different degrees of solubility in 
dilute and absolute alcohol; both, however, give the usual reactions 
of albuminous bodies, and pass very slowly through a dialyzing mem- 
brane. Only one of these substances possesses toxic properties. : 
