TYPHOID FEVER. 381
Kolle, cannot be separated from the bodies of the bacilli
Animals can easily be immunized to this bacillus, and
then, according to Chanternesse and Widal, develop in
their blood an antitoxic substance capable of protecting
other animals. Sternl has also found that in the blood
of human convalescents a substance exists which has a
protective effect upon guinea-pigs. His observation is in
accordance with a previous one by Chantemesse and
Widal, and has recently been abundantly confirmed.
The immunization of dogs and goats by the introduc-
tion of increasing doses of virulent cultures has been
achieved by Pfeiffer and Kolle2 and by Loffler and Abel.3
From these animals serums were secured not exactly an-
titoxic, but anti-infectious or anti-microbic in operation,
and possessed of marked specific germicidal action upon
the typhoid bacilli when simultaneously introduced into
the peritoneal cavity of guinea-pigs.
The action of the typhoid serum is specific, and exerts
exactly the same action upon the typhoid bacilli as the
cholera serum exerts upon the cholera spirilla, killing
and dissolving them (Pfeiffer's phenomenon).
So far, no serum has been produced that is efficacious
in human medicine.
The specific reaction of the serum can be used to dif-
ferentiate cultures of the colon and typhoid bacilli, the
typhoid bacilli alone exhibiting the specific effect of the
Christophers4 found that the serum from typhoid
patients occasionally caused agglutinations in cultures
of the colon bacillus, but concludes that this does not
lessen the specificity of the reaction, as there may be
two combined specific actions of these serums. Experi-
ments on rabbits established that typhoid and colon
serums could be produced, each specific in its agglutin-
1 Zeitschrift fur Hygiene, xvi., 1894, p. 45$. 2 Ibid"> l896-
3 Centralbl.f. Bakt. u. Parasitenk., Bd. xix.,]STo. 23, p. 51, Jan. 23,1896.
* Brit. Med. Jour., Jan. 8, 1898.