ON THE RELATIONS OF MICRO-ORGANISMS TO DISEASE 395 
in Professor Nageli’s laboratory, to solve the double problem of changing the 
Bacillus anthracis into hay-bacillus, and the converse. Having devised an 
ingenious apparatus by which a large reservoir of pure cultivating liquid was 
placed in communication with a cultivating vessel, so that any cultivation could 
be drawn off by simply turning a stop-cock, and further cultivating liquid 
supplied to the organisms remaining in the vessel by a mere inclination of the 
apparatus, Buchner proceeded to cultivate the isolated Bacillus anthracis in 
extract of meat for several hundred successive generations. As an early result 
of these experiments, he found that the bacillus lost its power of producing 
disease in an animal inoculated with it. Up to this point he is confirmed by 
Dr. Greenfield, who has found that, when the Bacillus anthracis is cultivated in 
aqeous humour, after about six generations it loses its infective property. Then 
as Buchner’s experiments proceeded, the appearance of the growing organism 
was found to undergo gradual modification. Instead of a cloud at the bottom 
of the vessel, a scum began to make its appearance—at first greasy-looking and 
easily broken up—constituting, so far as appearances went, an intermediate 
form between the two organisms ; and in course of time the scum became drier 
and firmer, and at length the modified Bacillus anthracis was found to be capable 
of growing in an acid hay-infusion, and to present in every respect the characters 
of the hay-bacillus. The converse feat of changing the hay-bacillus into the 
Bacillus anthracis proved very much more difficult. A great number of 
ingenious devices were adopted by Buchner, who was, nevertheless, continually 
baffled, till at last he attained success in the following manner: Having obtained 
the blood of a healthy animal under antiseptic precautions, and defibrinated it 
also antiseptically, and having arranged his apparatus so that the pure defibri- 
nated blood, which was to be the cultivating medium, should be kept in constant 
movement, continually breaking up the scum, and also keeping the red corpuscles 
in perpetual motion so as to convey oxygen to all parts of the liquid—in this 
way imitating, to a certain extent, the conditions of growth of the Bacillus 
anthracis outside the animal body, within which the hay-bacillus could not be 
got by any means to develop—he proceeded to cultivate through numerous 
successive generations. A transitional form soon made its appearance; but 
the change advanced only to a limited degree, so that further progress by this 
method became hopeless. The modified form hitherto obtained failed entirely 
to grow when injected into the blood of an animal. On the contrary, it was 
in a short time completely eliminated from the system, just like the ordinary 
hay-bacillus. It had, however, been observed by Buchner that spores had 
never been formed by the bacillus growing in the defibrinated blood ; and it 
occurred to him that, perhaps, if it were transferred to extract of meat, and 
