ON THE RELATIONS OF MICRO-ORGANISMS TO DISEASE 303 
that the question has been answered in the affirmative ; and that one bovine 
animal, inoculated seven months ago with virus from a rodent, has proved itself, 
on repeated inoculations, entirely incapable of contracting splenic fever, remain- 
ing free from either constitutional or local manifestations of it. 
And now to return to M. Toussaint, who has made observations with regard 
to this same subject of vaccination against anthrax fraught with the very 
deepest interest. The question arises with regard to effective vaccination, 
using the term in Pasteur’s general sense: Is it essential that micro-organisms 
should develop in the blood of the animal in which immunity from further 
attacks of the disease is to be secured? Or is it possible that the necessary 
influence upon the system may be exerted by merely chemical products of the 
growth of that organism in some other medium ? With the view of approaching 
the solution of this question, M. Toussaint has performed experiments of inject- 
ing into the blood of healthy sheep blood taken from an animal affected with 
splenic fever, but deprived of the Bacillus anthracis. Taking blood from a 
sheep just on the point of death, when the bacillus has presumably produced 
all its possible effect upon the vital fluid, M. Toussaint proceeds to deprive it 
of the living bacillus in either of two 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. Never- 
theless, 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 constitution of the sheep may be brought about, the lapse 
of a certain time is essential. If a vaccinated sheep be inoculated 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 M. Toussaint’s other method, which consists of maintaining it for 
a considerable time at a temperature of 55° C. (131° Fahr.), which has the effect 
of killing the bacillus ; after which one-half per cent. of carbolic 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 centimetres 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 
