342 PROFESSOR JOSEPH LISTER. 
in full vigour and in a fluid but slightly changed from its 
original wholesome condition. It thus remains like a vigorous 
seed, ready to start into energetic growth when the con- 
ditions for its germination are supplied.! The essential 
difference between the two views may be stated shortly 
thus: M. Pasteur regards oxygen as a slow poison of the 
bacterium ; Dr. Greenfield seeks for the slow poison in the 
products of the fermentative agency of the organism. 
The time which has passed since the delivery of this 
address, has brought out facts which have led M. Toussaint 
to take a different view of the nature of the liquid used in 
his “ vaccinations ” against anthrax above referred to. In 
a letter which he had the kindness to write to me on the 
subject, he informs me that on two different occasions in- 
jections of anthrax blood treated by one of his methods has 
led to the death of the animal from anthrax; and in one 
instance, a similar injection induced a local affection which 
appeared to have the characters of malignant pustule. He 
has hence been led to the conclusion that the diseased 
blood treated by his methods, instead of being (as he at 
first believed) free from the living bacillus, contained the 
organism in an “attenuated ” form. 
Thus it would appear that the observations of Pasteur, 
Toussaint, and Greenfield, agree in ascribing the “ vacci- 
nating” influence to a modified form of the disease 
concerned. . 
At the same time some other observations have been made 
which tend to justify the original line of inquiry pursued 
by Toussaint. Chauveau has found thatif ewes inoculated 
with anthrax in the last months of gestation recover from 
the disease, not only are the mothers no longer susceptible, 
but the lambs enjoy similar immunity.? Further, it has 
been ascertained by others, including Dr. Greenfield, that 
the blood and tissues of the foetus of an animal dying of 
anthrax contain no bacilli, while those of the mother swarm 
with them. Putting these two observations together we are 
led to the inference that while the integrity of the placental 
vessels prevents the bacilli from entering the fcetal circula- 
tion, the foetus is so dosed with soluble products of the 
development of the bacilli in the maternal blood as to be 
rendered proof against the disease. 
1 See “The Brown Lectures,” by W. S. Greenfield, &c.; Lecture II, 
‘The Lancet,’ Jan. Ist, 1881. 
2 See Dr. Greenfield’s lst “Brown Lecture,” ‘The Lancet, 18th 
Dec., 1880. 
