THE PRODUCTION OF IMMUNITY. 525 
only the sucholotoxins being more dull than the others. 
There was also slight swelling at the point of inoculation 
with the germ, which subsided in ten days, after which the 
animals were perfectly well, and have remained so—four 
months. 
Experiment V.—Six guinea pigs were inoculated for this 
experiment, two with solution of the sucholotoxin and four 
with a solution of the mixed sucholotoxins. The sucholotoxin 
solution produced only slight local lesions, while the mixed 
toxins caused ulceration at the point of injection which did 
not heal for two weeks. The treatment in this case again ex¬ 
tended over a period of from three to four weeks. The ani¬ 
mals having by this time recovered, the test-experiment with 
hog-cholera virus was tried. Four of the animals mentioned 
above were taken—two from each set—and also two checks, 
and the six were inoculated. The checks died in eight and 
nine days, the autopsis showing the characteristic condi¬ 
tions of death from hog-cholera. Those that had the preven¬ 
tive treatment were ill and dull for from four to six days after 
the inoculation. At the point of inoculation there was also 
some swelling and infiltration, very slight, however, compared 
with the similar swelling on the checks. In the treated ani¬ 
mals the swelling sloughed and healed, and within ten days 
after the inoculation they were perfectly well. To test the 
resistance of the animals that had been treated by this method, 
to ordinary exposure, the following experiments were con¬ 
ducted. 
Experiment VI.—Two guinea-pegs that had received the 
preventive treatment, two blanks— i. e., animals that had re¬ 
ceived no treatment—and two check animals that were inocu¬ 
lated with hog-cholera virus, were placed in one large cage. 
The checks became ill and died in eight or nine days from hog- 
cholera. During this time the cage was cleaned only three 
times, so as to give full and free opportunity for contagion. 
One week after the checks had died one of the blanks became 
ill and died within ten days. The autopsy showed hog-cholera 
lesions. The second blank became ill a few days aftef the first 
blank succumbed, and died within thirty days. The animals 
