I 
' 1 
I 
1 
! 
I 
070 C. FISCH. ; 
__ ______—-- I 
ered from the disease. How far this assertion is correct we will 
see later. 
Having convinced myself from a thorough study of the ex¬ 
periments of other observers, that an active immunization upon i 
a large scale was, if not impossible, certainly impracticable, I > 
endeavored to establish passive immunity by means of the serum 
of animals immunized against my virulent bacilli. But the main | 
question to solve was: To what degree is hog cholera a toxic ; 
disease ? . ! 
If hog cholera bacilli in suspension, that have been killed i 
by being heated for one hour to 6o° C., are injected into the i 
abdominal cavity of a rabbit, the animal dies in a short time ! 
from a purulent peritonitis; the exudate is always found to be j 
perfectly sterile, in cover glass specimens, no remnants of bacilli | 
can be found. On the other hand, if hog cholera bacilli are ex- i 
tracted for several days with a slightly alkaline salt solution, , 
separated from the latter by filtration and again suspended in j 
water, they now, when injected into an animal (rabbit) like be¬ 
fore, cause only a very slight disturbance. The filtrate, how- i 
ever, subcutaneously administered after being neutralized with i 
acetic acid, proves to be exceedingly toxic. ! 
Finally, if very virulent hog cholera bacilli are grown in 
peptone bouillon for about a week, the culture fluid passed i 
through a porcelain filter is comparatively harmless, large doses i 
being required to bring about any effects in animals treated j 
with it. 
From these three experiments we gather the information, | 
that our bacilli, though producing a powerful toxine (or several j 
toxines) do not excrete it (or them) into the culture medium, i 
The latter only becomes charged with it (or with them) corre- ; 
sponding to the number of bacilli dying and decaying. In ac- ; 
cordance with this assertion experience teaches us that the older ; 
the bouillon cultures, the more toxic they become ; in fact, the 
filtrate of a culture that has been kept for six weeks in an incu- : 
bator at 37° C. is so poisonous in its effect, that a few tenths of : 
sufficient to kill rabbits and guinea-pigs in a short 
a c. c. are 
