INTESTINAL WORMS IN TYPHOID FEVER. 213 
we may divide our 136 white cases by 2.45® in order to bring them 
on approximately the same comparative basis as the negroes. 
Thus we have 136-^-2.45 = 55.5 white cases to compare with 64 
negro cases of typhoid (compared on approximately the same basis), 
despite a whipworm infection of 3.75 per cent in nontyphoid whites 
and 9.79 per cent in nontyphoid negroes in the statistics quoted 
above (p. 212). 
Accordingly a comparison of our 200 cases of typhoid with whip- 
worm and the general infection in the District of Columbia vdth 
respect to the race of the patients shows that there was a very slight 
excess (in proportion to inhabitants) of typhoid among the negroes 
we examined over this disease among the whites. This excess in no 
way compared, however, with the mathematical probabilities of whip- 
worm infection or of helminthiasis in general, and it is therefore 
possible that it was due to some other cause. Considering, now, the 
change in our summer population, whereby the negroes form a 
greater percentage, it seems possible that the typhoid excess in 
negroes may have been due, at least to some extent, to that factor. 
The board had records of a total of 866 cases reported as t}q)hoid. 
Of these, 588 were whites and 278 were negroes. Reducing these to 
a basis for approximate comparison (588 2.45 = 240) we have for 
the entire outbreak 240 cases of typhoid among the whites to be 
compared with 278 cases among the negroes. If the proportion 
obtained from the cases examined for worms (55.5 to 64) is extended 
to the entire number of cases we should expect 241.08 white cases to 
278 negroes — figures which are approximately the same as those 
actually obtained (240 to 278). The 200 cases examined for worms 
form, therefore, a fair basis for testing the theory of inoculation by 
worms. 
It may be frankly admitted that the indirect evidence submitted 
in the foregoing in reference to age, sex, and race of the patients is 
,open to the criticism that it is onl}^ approximate. Were the results 
of the microscopic examinations themselves less at variance with the 
theory under discussion, it would be incumbent upon me to work out 
the indirect evidence on a stricter mathematical basis, but with such 
strikingl}^ negative results in the microscopic work the indirect evi- 
dence seems very secondary, and on this account approximate 
statistics wiW suffice. 
Date of manuscript, December 13, 1906. 
^^29 [per cent negroes]: 71 [per cent whites]=100 [negroes]: 245 [whites], in popula- 
tion; hence divide white cases (136) by 2.45 to reduce white and negro cases to a 
comparison on basis of relative population. 
