394 ON THE RELATIONS OF MICRO-ORGANISMS TO DISEASE 
in progress; but M. Toussaint informs me that he has already ascertained the 
existence of immunity against anthrax for three months and a half in both the 
sheep and the dog treated in this way. 
I need hardly remark on the surpassing importance of researches such as 
these. No one can say but that, if the British Medical Association should 
meet at Cambridge again ten years hence, some one may be able to record the 
discovery of the appropriate vaccine for measles, scarlet fever, and other acute 
specific diseases of the human subject. But even should nothing more be 
effected than what seems to be already on the point of attainment—the means 
of securing poultry from death by fowl-cholera, and cattle from the terribly 
destructive splenic fever—it must be admitted that we have here an instance of 
a most valuable result from the much-reviled vivisection. 
I have yet one more example to give of researches in this domain of patho- 
logy ; and this also has reference to the Bacillus anthracis. The investigator 
in this instance is Dr. Buchner, assistant physician in Munich. It is well known 
that the Bacillus anthracis is morphologically identical with an organism fre- 
quently met with in infusion of hay, which may be termed hay-bacillus. Such 
being the case, it occurred to Dr. Buchner that they might be merely one and 
the same organism modified by circumstances. For my own part, I am quite 
prepared to hear of such modifying influence being exerted upon bacteria, 
having made the observation several years ago that, when the Bacterium lactis 
had been cultivated for some time in unboiled urine, it proved but a feeble 
lactic ferment when introduced again into milk. Its power of producing the 
lactic fermentation had been impaired by residence in the new medium. In the 
case before us, indeed, the physiological difference between the two organisms 
seems, at first sight, so great as to forbid the idea of anything other than a 
specific difference. The Bacillus anthracis refuses to grow in hay-infusion, in 
which the hay-bacillus thrives with the utmost luxuriance; and conversely, 
the hay-bacillus is utterly incapable of growing in the blood of a living animal, 
whether introduced in small or in large quantities. The hay-bacillus is remark- 
able for its power of resistance to high temperatures, which is not the case with 
the Bacillus anthracis. The latter is destroyed by a very slight acidity of the 
liquid of cultivation, or by any considerable degree of alkalinity, whereas the 
former survives under such conditions. Both will grow in diluted extract of 
meat, but their mode of growth differs greatly. The hay-bacillus multiplies 
rapidly, and forms a dry and wrinkled skin upon the surface, while the Bacillus 
anthyacis produces a delicate cloud at the bottom of the vessel, increasing slowly. 
Nothing daunted by these apparently essential differences, Dr. Buchner has 
laboured with indomitable perseverance, by means of experiments carried on 
