THE RELATIONS OF MICRO-ORGANISMS TO DISEASE. 337 
ways—by filtration, or by destroying the vitality of the 
organism. The former he effects by mixing the blood with 
three or four parts of water, and then passing it through 
about twelve layers of ordinary filter-paper. ‘The bacillus, 
in consequence of its large dimensions, is entirely retained 
by this form of filter, as is proved by the fact that the 
filtrate no longer gives rise to the organism in a cultivating 
liquid or in a living animal. Nevertheless, if injected in 
considerable quantity into the circulation of a healthy sheep, 
it produces a true vaccinating influence, that is to say, 
secures immunity from splenic fever. But, what is further 
extremely interesting, in order that this change in the con- 
stitution of the sheep may be brought about, the lapse of a 
certain time is essential. If a vaccinated sheep be inocu- 
lated with anthrax within a few days of the operation, it 
will die of splenic fever ; but if from twelve to fifteen days 
be allowed to elapse, complete immunity is found to have 
been produced. Similar results followed from the injection 
of anthrax blood treated by Mr. Toussaint’s other method, 
which consists of maintaining it for a considerable time at 
a temperature of 55° C. (131° F.), which has the effect of 
killing the bacillus; after which one half per cent. of car- 
bolic acid is added, to prevent putrefaction of the liquid. 
The blood treated in this way having been proved to be 
free from living bacilli by negative results of an experiment 
upon a rodent, about four cubic centimétres are injected into 
the venous system of a sheep, with the effect of producing 
the same protective influence against splenic fever as is 
ensured by the filtered blood. ‘These experiments are still 
in progress; but M. Toussaint informs me that he has 
already ascertained the existence of immunity against an- 
thrax for three months and a half in both sheep and dog 
treated in this way. 
I need hardly remark on the surpassing importance of 
researches such as these. No one can say but that, if the 
British Medical Association should meet at Cambridge again 
ten years hence, some one may be able to record the dis- 
covery of the appropriate vaccine for measles, scarlet fever, 
and other acute specific diseases of the human subject. But 
even should nothing more be effected than what seems to be 
already on the point of attainment, the means of securing 
poultry from death by fowl-cholera, and cattle from the 
terrible destructive splenic fever, it must be admitted that 
we have an instance of a most valuable result from the much- 
reviled vivisection. 
I have yet one more example to give of researches in this 
