DIPHTHERIA BACILLUS. 365 
doses of toxin which have been previously mixed with 
an amount of antitoxin believed to be sufficient to pro- 
tect from the toxin. If the guinea-pig lives four days, 
but dies soon after, the amount of antitoxin added to 
the toxin was just 1 or 0.1 unit, according as one hun- 
dred or ten fatal doses were employed. If the guinea- 
pig dies earlier, less than 1 unit was added. 
The Use of Antitoxin in Treatment and Immuniza- 
tion. The antitoxin in the higher grades is iden- 
tical with that in the lower grades; there is simply 
more of it in each drop of the serum. In treatment, 
however, for the same amount of antitoxin we have to 
inject less blood-serum with the higher grades, and, 
therefore, have somewhat less danger of rashes and 
other deleterious results. With concentrated globulin 
solutions we may hope still further to avoid all dis- 
agreeable effects (see page 362). The amount of anti- 
toxin required for immunization is 200 units for an 
infant, 500 for an adult, and proportionately for those 
between these extremes. After the observation of the 
use of antitoxin in the immunization of several thousand 
cases, I have absolute belief in its power to prevent 
an outbreak of diphtheria for at least two weeks, and 
also of its harmlessness in the small doses required. If 
it is desired to prolong the immunity the antitoxin in- 
jection is repeated every two weeks. For treatment, 
mild cases should be given 1500 units, moderate cases 
2000 units, and severe cases 3000 units. Where no 
improvement follows in twelve hours the dose should 
be repeated. Antitoxin is useless when given by the 
mouth, as very little of it is absorbed. 
No deleterious effects are to be feared except a rash, 
with some rise of temperature, in about 20 per cent. of 
