490 
S. J. J. HAKGER. 
cc. (one nine-hundredth) is inactive, while the remaining two 
develop tetanus; again one cc. (one five-hundredth) is harm¬ 
less to guinea-pigs while three cc. cause tetanus. 
These experiments show that it is not a question of neutral¬ 
ization or chemical union between the toxin and anti-toxin in the 
blood, but rather the stimulating action of the former upon the 
animal cells, enabling them to resist the action of the virus of 
the disease. 
The existence of a previous disease or a previous injection 
of microbe products is not without effect. It weakens the 
animal tissues which respond less strongly to the stimulating 
action of the anti-toxin. Roux and Villard injected five 
guinea-pigs with one-half cc. of anti-toxin serum and toxin 
(one to 900) with a negative result. Five other guinea-pigs, 
which had some time before been immuned against the vibrion 
of Massaonah, developed tetanus, while the same treatment as 
the preceding five, one-third cc. only produced tetanus when 
the animal is subsequently injected with microbic product, 
coli bacilli, etc. 
In eighty days, this horse, the details of immunization of 
which I will cite at the end of this paper, received over eight 
hundred cc. of toxin without any symptons other than a slight 
local oedema and an elevation of temperature of one degree. 
The serum of a horse immunized in this manner had a pre¬ 
ventive power of more than fifty thousand; that is, a guinea- 
pig inoculated with one fifty-thousandth of its own weight of 
the serum twelve hours before will resist the action of one- 
half cc. of a virulent culture of diphtheria bacillus. One-tenth 
cc. of this serum and one cc. of diphtheria toxin does not pro¬ 
duce any oedema in the guinea-pig w r hen injected under the 
skin. 
The horse is kept in this condition of immunization by in¬ 
jections at intervals of fifteen to twenty days of diphtheritic 
toxin (about 200 to 250 cc.). 
Roux and Martin immunized a horse with 40 cc. of the 
toxin heated to 65° C. given in eight doses at intervals of ten 
days; he was then injected with 1 cc. of pure toxin repeated 
at regular intervals. The virulent bacilli are also employed for 
this purpose. 
