314 THE MICROSCOPICAL NEWS. 
various bacteria to which so much attention has latterly been given 
we have the true causes of zymotic diseases. Very erroneous and 
imperfect accounts of the contents of Klein’s paper have been pub- 
lished, and it is desirable that these should be corrected. For 
those of our readers who are not familiar with the subject, it may 
be explained that, broadly speaking, there are two classes of fungi, 
to which order, provisionally, the bacteria may be said to belong. 
These two classes are known as saprophytes and parasites. The 
former absorb their nutriment from the remains of dead organisms 
or from organic compounds formed by living organisms, and may 
therefore be said to fulfil an innocuous if not a useful purpose in 
nature ; the latter absorb their nutriment from living organisms 
which they thus kill, and they have therefore essentially the nature 
of disease. In the familiar vegetable world, for instance, mush- 
rooms belong to the former class, and the potato disease to the 
latter. Now the idea has been enunciated by our townsman, Dr. 
William Roberts, Von Nageli, Buchner, and others, that the 
parasites are merely “‘ sports ” from the saprophytes, resulting from 
special conditions of culture, and that the two classes are mutually 
convertible. The importance of this idea, as bearing upon the 
genesis and extinction of zymotic diseases, is obvious, and the 
primary purpose of Klein’s researches has been to test this question, 
though in the pursuit of this object he has been led to examine 
other issues which have lately been brought very prominently before 
the public, and which, apart from their general theoretic bearing, 
have a special, or, so to speak, individual importance. There are 
two bacilli which are remarkably typical of the two classes of fungi 
referred to. One is known as Bacillus subtilis; it grows in a 
decoction of hay, or in what may be spoken of, in familiar terms, as 
hay broth, and it is perfectly harmless. The other is known as 
Bacillus anthracis, and it has not only swept away enormous num- 
bers of sheep in France and elsewhere, but develops in man himself 
as the terrible “‘ woolsorters’ disease.” 
Now to all appearance these two bacilli are identical in form and 
development ; the only perceptible difference being that the harm- 
less !bacillus exhibits the power of motion in the fluids in which it 
is cultivated, while the deadly contagium is motionless. Here, 
then, apparently, there is a prima face relation involving a possibility 
of artificially converting one into the other. At this point Pasteur’s 
recent researches become suggestive. It will be remembered that 
Pasteur, having already succeeded in producing, in the specific 
microscopic organism which he found associated with chicken 
cholera, some mysterious modification which he calls “attenuation,” 
discovered that, after inoculation with such artificially cultivated 
and modified virus, fowls were protected against the ordinarily fatal 
consequences of subsequent inoculation with unmodified virus. 
