THE LOxXGEVITY OF B. TYPHOSUS OUTSIDE OF THE HUMAN 
BODY. 
By A. M. Stimson, 
Assistant Surgeon Public Health and Marine- Hospital Service. 
The important question in relation to this subject is, ‘^Can the bacil- 
lus remain viable and purulent outside of the human body and under 
natural conditions long enough to transmit the infection from man to 
man by means other than by direct contact V’ This is easil}^ answered 
positivel}^, but the subquestions of how long, and in what media, and 
under what conditions it may do so, are not so simple of solution. 
Much evidence is adduced to throw light upon these questions 
from epidemiological observations and deductions, but in the follow- 
ing discussion only such of this evidence as is supported by bac- 
teriological demonstration will be presented. Purely bacteriological 
expernnents, on the other hand, are of value only when the conditions 
at least approximate the natural, and the greatest weight should be 
given those which do so, and at the same time conform to the strictest 
scientific methods. Unfortunately such cases will be found to be 
comparatively rare ui the literature of the subject. An ideal experi- 
ment of this nature involves the following three principal steps: 
(1) Maintaining the chosen medium (water, soil, food, etc.) inocu- 
lated with B. typhosus under conditions sunulating the natural, (2) 
isolating with certainty any ty^phoid-like organism from the medium 
after exposure, and (3) identif^dng the organism isolated as surely 
B. tyq)hosus, including, if possible, a quantitative estimation. 
Most of the work reported fails in one or more of these steps. 
Failure in step 1 gives obviously misleading results. In step 2 the 
failure to isolate the bacillus, if present, gives a shorter longevity 
than really obtains. The failure to completely identify the organism 
in step 3 invalidates the entire experiment. In the present state of 
bacteriology, step 3 can be completel}^ controlled by specific cross- 
agglutination and Pfeiffer’s reaction, but step 2 unfortunately still 
fails of satisfactory technical methods. 
To show how complex experimental investigation along these lines 
becomes, and in explanation of the diverse results of different observ- 
ers, some of the influences to be reckoned vdth are given: 
1. The medium itself: As to its chemical, bacterial, and protozoan 
content, qualitative and quantitative. The amount of medium used 
also has a bearing upon the results. 
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