INOCtJLATION WITH DILUTED VIRUS. 
103 
animals are very closely related organisms, that the mysterious 
condition of the animal body, which we call insusceptibility, is 
comparable from all points with the insusceptibility of mankind, 
and that the methods by which we can grant immunity to animals 
are equally applicable to the human subject. From this stand¬ 
point it at once becomes a matter of importance to learn if the 
diluted virus of other contagious fevers of animals produces 
either a milder affection or a harmless local irritation also cndino- 
O 
in immunity; in other words, is our method of vaccination, with 
a small number of very virulent germs, generally applicable to the 
various diseases of this class ? 
In April, 1881 , M. Chanveau* announced the result of experi¬ 
ments made with charbon virus, by diluting virulent blood until 
each cubic centimeter contained from fiftv to one thousand rods 
•/ 
of the bacillus anthracis , and injecting this dose directly within 
the jugular vein. He did not state how the number of germs 
was estimated, and one would suppose that this would be rather a 
difficult matter to accomplish with any degree of certainty, unless, 
indeed, an apparatus similar to that used for counting blood cor¬ 
puscles was at hand. M. Chanveau believed that by introducing 
the germs directly into the blood-stream there would be less dan¬ 
ger of a fatal result—a supposition which may be contested from 
the results of my experiments. In his first experiment four sheep 
received a dose of one thousand bacilli each. All died of char¬ 
bon. In the second experiment, two sheep received about six 
hundred bacilli each. One died of charbon ; the other did not 
shew the least symptom of disease. In the third experiment, one 
animal received fifty and the other one hundred bacilli. To the 
liquid containing the larger number one per cent, of carbolic acid 
was added. No effect was produced by the carbolized virus ; the 
other animal had a very slight fever of short duration. 
The animals remaining from the second and third experiments, 
and two others, in all five sheep, received, seven days after the 
third experiment, a dose containing about one thousand bacilli. 
All died of charbon ; but the one which had showed slight. 
* Comptes Rendus, xcii., 1881, p. 844. 
