486 THIRD PART.—BACTERIA OR SCHIZOMFCETES. 
it has been further established that species can be distinguished in the Bacteria 
as in other organisms, the whole controversy has lost the importance which it was 
once supposed to have. 
In Buchner’s experiments on the change of the hay-bacillus into the Bacillus of 
anthrax, Bacillifrom an infusion of hay were bred with certain precautions in fresh blood. 
The macroscopic character of the masses of Bacilli was changed, and intermediate 
forms were obtained between the hay-bacillus and the Bacillus of anthrax, and strange to 
say no reversion was obtained in the intermediate forms when solution of meat-extract 
or infusion of hay was substituted as the nutrient fluid. Mice and rabbits were inocu- 
lated with the altered matter, and some of the creatures experimented on sickened and 
died of anthrax, but much the larger number did not take the infection. Koch will not 
allow that the observed disease was true anthrax, and maintains that it may have been 
a disease which is common in mice and cannot always be at once distinguished from 
anthrax—a disease known as malignant oedema, and produced by a Bacillus morpho- 
logically very like the Bacillus of anthrax, which must have found its way into the 
culture with the hay-bacillus. If we allow that the disease in the cases actually ascer- 
tained was anthrax and disregard Koch’s doubt on the point, the things to be remembered 
are chiefly these. By far the largest part of the original material used for the experiment 
may have been ascertained to consist of Bacillus subtilis ; but we have no proof that 
other Bacilli, lost at first in the overwhelming mass of B. subtilis and practically not 
distinguishable from them, were not contained along with B. subtilis in the hay-infusion. 
It would indeed be wonderful if one species, B. subtilis, were on all occasions the 
only form obtained without admixture of any others from a material like hay treated 
according to a definite procedure, especially as the apparently exceptional security of the 
procedure, the boiling the hay, offers no certain guarantee, because the spores of other 
Bacteria as well as Bacillus subtilis are capable of withstanding that temperature. 
Bacillus subtilis then may be present in the hay-infusion in much the larger numbers, 
and the forms mixed with it may be comparatively few. But we have to ask whether 
this numerical relation may not be altered or even reversed in other nutrient fluids, for 
instance in blood, whether single spores of Bacillus Anthracis may not have been pre- 
sent in the original material and only after change of cultivation have been in a condition 
to produce a small quantity of infectious material among the individuals of the other 
species, and thus occasional cases of infection may have occurred among the instances 
of failure; to these questions the data before us afford no certain answer. Allusion has 
been already made to Koch’s views, and we will not draw attention here to other points 
of difficulty. The reader is referred for further particulars to the original publications. 
The Bacillus of anthrax has been discussed at some length because it is at 
present the best-known example of the Bacteria which inhabit the bodies of animals 
and incite disease in them. Modern pathology resting on older observations and 
experiments, among which the researches into anthrax itself occupy a prominent 
position, and supported by Nageli’s theoretical considerations, endeavours to refer all 
infectious diseases in animals, excepting the few that are caused by Fungi (p. 376) 
and some that were not formerly supposed to be infectious, to the invasion of Bacteria 
as their proximate cause. These organisms have been sought for sometimes with 
great, even with excessive zeal, and some have been found. The parasitic qualities, in 
virtue of which many of these organisms incite disease, have been sufficiently proved 
in a number of cases, for example in septicaemia, erysipelas, recurrent fever in warm- 
blooded animals, Pasteur’s fowl-cholera, the flacherie of the silk-worm, though our 
botanical knowledge of the plants themselves is still very defective. Some forms are 
still the subjects of lively discussion on the part of experimental pathologists. Bacteria 
