398 ON THE RELATIONS OF MICRO-ORGANISMS TO DISEASE 
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 has had the kindness to write to me on the subject, he informs 
me that on two different occasions injections 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 ‘ vaccinating’ influence to a modified form of 
the micro-organism concerned. 
Nevertheless some other observations have been made which tend to justify 
the original line of inquiry pursued by Toussaint. Chauveau has found that if 
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.t’ 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 foetal circulation, 
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. 
? See Dr. Greenfield’s First ‘ Brown Lecture’, Lancet, December 18, 1880. 
