334 PROFESSOR JOSEPH LISTER. 
ther, by the circumstance that such chickens as fail to take 
the disease when fed with the infected food are liable to it 
when inoculated, implying that it was merely some acci- 
dental circumstance which secured their previous immunity. 
This disease has been made the subject of special investiga- 
tion by M. Pasteur. He found that the micro-organism 
could be readily cultivated outside the body of the fowl. It 
was, indeed, somewhat particular as regards the fluid in 
which it would grow; thus yeast-water, in which the 
Bacillus anthracis grows readily, proved an unsuitable 
medium for this organism, but it grew luxuriantly in 
chicken broth, and, indeed, in infusion of other kinds of 
meat; but chicken broth proved peculiarly convenient for 
the purpose. M. Pasteur has been so kind as to send me 
some tubes in which the organism has been cultivated, and 
a drop of the liquid has been placed under a microscope on 
the table. It will be seen that the organism is a minute 
form of bacterium, oval-shaped, tending to multiplication by 
transverse constriction, and very frequently seen in pairs, 
and occasionally in chains. Its transverse diameter is from 
1-50,000th to 1:25,000th of an inch, so that it resembles very 
closely the Bacterium lactis. The woodcut d represents a 
camera lucida sketch of the organism sent by M. Pasteur. 
So far as I am aware, this is the first time this bacterium 
has been shown in this country. Now, it was found by 
Pasteur that the organism could be produced in chicken 
broth in any number of successive cultivations, and to the 
last retain its full virulence, so that, if a healthy chicken be 
inoculated with it, the fatal disease was produced as surely 
as by inoculation with the blood of a fowl that had died of 
the complaint. This was pretty conclusive evidence that 
the organism was the cause of the disease, and that it con- 
stituted the true infective element ; because any other mate- 
rial that might be supposed to accompany it in the blood of 
the diseased animal must have been got rid of by the suc- 
cessive cultivations in chicken broth. 
The growth of the organism occasions no putrefaction in 
the liquid; so that this is a good example of a bacterium 
which is most destructive as a disease, but which is at the 
same time entirely destitute of septic property, in the primi- 
tive sense of that term as equivalent to putrefactive. After 
