CHAPTER XI. —MODE OF LIFE OF THE BACTERIA, 485 
which to ground the assumption ; but enough is known for the determination of the 
practical question of protective inoculation by means of the attenuated Bacillus. We 
cannot however enter further into this point here, but must refer the reader to medical 
works on the subject. 
Be this as it may, it is easy to conceive, in the case of a facultative parasite which 
is able to adapt itself to nutrient solutions of different concentration and qualitative 
composition at a temperature of 15°-20° C. and to the blood of a mammal at one of 
37°-40° C., that changes in the adaptation and food may be followed by changes in the 
deleterious effects, which may be supposed to be due to the production of some kind 
of ferment. An analogous though quantitatively different case is that of Sclerotinia 
Sclerotiorum described on page 380, in which the capacity for a parasitic life depends 
on the food supplied to the plant in its young state. We may also compare the 
Mucorini (page 358), which vary their form and the decomposition which they 
produce with the medium in which they live, and the Bacterium described by 
Wortmann’, which gives rise to a ferment capable of dissolving starch if it is supplied 
with nothing but starch-grains for its food, but ceases to produce the ferment if fed 
with carbohydrates in solution or with ammonium acetate. 
In the foregoing description it has been tacitly assumed that Bacillus Anthracis 
is a distinct species, and the present state of our knowledge requires the assumption. 
The Bacillus of anthrax has a resemblance to other species, and among them to 
Bacillus subtilis, which is not a facultative parasite or at least may under certain 
conditions be a harmless parasite; it varies also in the breadth and length of its cells 
and in other respects; but it always remains within the limits of the specific 
characters, the most important of which are given on page 466, and which distinguish 
it from other species and especially from B. subtilis also described above. 
Buchner has maintained, in opposition to this view, that the Bacillus of anthrax 
and the hay-bacillus may be made to pass one into the other by breeding, and that 
they are therefore only states of one and the same species. He has not supplied us 
with the strictly morphological proof necessary to establish this opinion, since he has 
not taken into consideration the behaviour of the spores of his altered forms 
in germination, at least in his published communications, and yet this is one of the 
characteristic marks of distinction. He adopted also the macroscopic mode of 
cultivation, in which it is not possible to ensure an uninterrupted control of the 
continuity of the development, or of the accidental mingling of different species. 
His transformation of the virulent Bacillus of anthrax into the supposed innocuous 
hay-bacillus was effected in cultures at a high temperature and with a more 
than ordinary supply of oxygen; the temperature was 36°C., the apparatus 
employed ensured constant shaking in air, and the solution contained 0.5 per cent. 
of meat-extract. The transformation was not obtained at a temperature of 25°C. 
and when the apparatus was not kept in motion. It was evidently Pasteur’s inno- 
cuous state which was produced in this case, but that is by no means Bacillus 
subtilis. The results of the reverse transformation appear, according to Buchner’s 
own account, extremely doubtful. Now that the facultative parasitism and the 
possible change of virulence in Bacillus Anthracis have been demonstrated, and since 

1 Zeitschrift f. physiol. Chemie, VI, p. 287. 
