486 THIRD PART. BACTERIA OR SCHIZOMYCETES. 



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, Bacilli from 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 



