o68 THE ALCALIGENES— DYSENTERY— TYPHOID GROUP 
protective immunization of human beings, both by the use of killed 
cultures of typhoid bacilli and by live cultures. The vaccine pro- 
phylaxis for typhoid fever is the best known and the most widely 
practised. The procedure is to grow typhoid bacilli on agar slants, 
wash them off with sterile physiological salt solution, kill them by 
heating to 60° C. for one hour, standardizing the suspension of typhoid 
bacilli, and injecting as a first dose 500,000,000 killed typhoid organ- 
isms. After an interval of five to seven days a second injection of a 
billion killed typhoid bacilli is made, and after an equal interval a third 
and last injection of 1,000,000,000 killed typhoid bacilli is made. The 
use of lipo vaccines (see page 191) has reduced the injections to one, 
a matter of prime importance both in military and civil practice. 
In about 20 per cent of the cases injected general symptoms which 
consist of a febrile reaction and malaise develop, accompanied by 
local symptoms of pain, redness and swelling at the site of inoculation. 
These symptoms may appear after the second or even after the third 
injection. It is customary to make the inoculation about four o'clock 
in the afternoon, so that the patient in the majority of cases sleeps 
through the general symptoms. 
The immunity produced is generally considered to be relatively 
complete for from two to four years. The agglutination titer of 
the serum of the vaccinated individual, when immunization is com- 
pleted (about one month), usually varies between -jho ^^^^ toVt- It 
must be remembered that for at least three weeks following the vac- 
cination there may be a diminution in the resistance of the individual 
to typhoid fever; consequently, typhoid vaccination should not be 
undertaken if there is a possibility of exposure to typhoid during this 
period. Vaccination is also very undesirable if it is performed during 
the incubation period of typhoid fever. It should be practised only 
on perfectly healthy subjects free from all general and local organic 
defects or infections, particularly tuberculosis. Nurses, ward orderlies, 
doctors and those engaged in the care of typhoid patients are particu- 
larly likely to benefit by these inoculations. Gay and Claypole^ 
have demonstrated experimentally that a satisfactory degree of 
protection may be attained in animals by three injections, at intervals 
of two days each, of a dried sensitized vaccine. Observations upon 
persons immunized with this vaccine indicate that the reactions are 
milder and the whole process can be completed within a week, thus 
diminishing very materially the time element which has been an 
important factor in the past. It is possible that the period of increased 
susceptibility to infection may be decidedly shortened as well. 
Vaccination with Lixinq CvHures.—^\i^tc\\\r\ko^ and Besredka- 
found that the subcutaneous injection of living sensitized cultures 
produced an immunity in anthropoid apes which was apparently 
as definite as that produced by an actual attack of typhoid fever. 
1 Arch. Inst. Med.. 14, 671. 
= Ann. Inst. Pasteur, 1913, 27, 597. Besiedka: Ann. Inst. Pasteur, 191.3, 27, 607. 
