TYPHOID BACILLUS 369 
The organisms were shown not to appear in tlie in-ine or feces or 
blood when introduced subcutaneously. They were unable to induce 
immunity in the chimpanzee with killed cultures of tyjjhoid bacilli 
or with autolysates of killed cultures. Having in mind the efficiency 
of living cultures, they^ attempted the vaccination of man with living 
cultures of the typhoid bacillus. They used sensitized cultures which 
appeared to cause only a feeble local reaction and no general reaction 
in the chimpanzee, in preference to non-sensitized living cultures, 
which they found produced rather intense local and general reac- 
tions. The vaccine was prepared by emulsifying agar cultures of 
typhoid bacilli in normal salt solution and permitting the organisms 
to remain in contact with antityphoid serum for twenty-four hours 
at 37° C. The organisms are then removed by centrifuging, washed 
repeatedly, then re-emulsified in normal saline solution and heated 
to 50° C. for thirty minutes, then standardized in the usual manner. 
Nearly 800 people have been vaccinated with these sensitized living 
cultures; the local reaction was slight in each instance, and only 
exceptionally was there any general reaction. A careful examination 
of the blood, urine and feces of (34 of these cases failed to show typhoid 
bacilli, which woukl suggest that individuals vaccinated with living 
typhoid bacilli neither develop typhoid fever nor becomes carriers. 
The cases are too few in number to compare statistically with the cases 
vaccinated with killed cultures. Gay and Claypole^ have taken issue 
with Metchnikoft" u])on this point and their experiments indicate that 
their sensitized dried vaccine may be equally or more efficient without 
the theoretical dangers which attend the use of living bacilli. 
Various attempts have been made to induce passive immunity to 
typhoid infection by the injection of sera obtained from horses which 
have received numerous injections of typhoid bacilli or their soluble 
products. The results have on the whole not been encouraging. Gay 
and Force^ have applied a preparation of typhoid bacilli ("typhoidin") 
made like Koch's old tuberculin, by the von Pirquet method, to 
patients that have recovered from typhoid fever and to those who 
have been vaccinated with typhoid bacilli. They find that 95 per 
cent of recovered cases from typhoid (20 cases out of 21 examined) 
gave a clear-cut cutaneous reaction. One case had typhoid forty-one 
years previously. The reaction was negative in 85 per cent of indi- 
viduals not gi\'ing a history of typhoid (and presumably not vaccinated) 
—41 cases tested. The 9 cases (15 per cent) that gave a positive 
reaction were suspected to have had a mild undiagnosed attack. Sev- 
eral, but not all, of those vaccinated within four years (9 out of 15) 
gave a positive reaction. Gay and Force suggest that the test is of 
presumptive value as an index of protection against typhoid by 
vaccination. Later observations by them tend to confirm this view. 
1 Semaine Med., July 24, 1912, p. 355. 2 Loc_ pj^. 
3 University of California Publications in Pathology, 1913, 2, No. 14; Arch. Int. Med., 
1914,13,471. 
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