THE RELATIONS OF MICRO-ORGANISMS TO DISEASE. 339 
found that the bacillus lost its power of producing disease in 
an animal inoculated with it. Up to this point he is con- 
firmed 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 modifica- 
tion. 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 suc- 
cess in the following manner :—Having obtained the blood 
of a healthy animal under antiseptic precautions, and defi- 
brinated it also antiseptically, and having arranged his 
apparatus so that the pure defibrinated blood, which was to be 
the cultivating medium, should be kept in constant move- 
ment, so as to continually break up the scum, and also keep 
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 develope—he 
proceded to cultivate through numerous successive genera- 
tions. A transitional form soon made its appearance; but 
the change advanced only toa 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 induced to form spores there, the modified 
organism might yet grow in the blood of a living animal. 
The carryiug out of this idea was crowned with success ; 
and, by injecting various different quantities of the liquid 
containing the organism into different individuals, Buchner 
