7 
respectively, the following rates of infection with intestinal worms: Less than 1 year’s resi- 
dence, 12.46 infections per 100 persons; 1 to 3 years, 10.84 infections per 100 persons: 9 to 
15 years, 9.66 infections per 100 persons; more than 15 years’ residence, 12.99 infections 
per 100 persons. The rate of infection with whipworms varied in the different groups in 
much the same manner as did the rate for all infections; pinworms showed a consistent 
tendency to increase in frequency, and hookworms a consistent tendency to decrease in 
frequency, with prolonged institutional life; eelworms presented their highest rate of infec- 
tion among persons of lass than 1 year’s residence, and Cochin China worms among those 
of more than 15 years’ residence, but neither parasite shows any consistent variation through- 
out the 5 groups. 
A mathematical explanation of the variations in the amount of infection found among 
persons of different lengths of institutional life can be given only when the longevity of the 
parasite and the amount of infection endemic within the hospital are known. It would 
appear that the tendency is for high entrance infections to be lowered and low entrance 
infections to be increased until the percentage of endemic infection is reached, namely, 
until the endemic infection exactly balances the mortality of the parasites. 
Among the 3,334 adults examined, 1,023 (white) who were of foreign birth gave an 
average of 11.44 infections per 100 persons; 1,637 native-born whites gave an average of 
9.35 infections per 100 persons. Whipworms, eelworms, and the fat tapeworms gave 
higher rates of infection among the foreign born; pinworms, hookworms, and Cochin China 
worms gave higher rates among the native born. Among the foreign-born patients, those 
of German birth gave an average of 7.36 infections per 100 persons; the English born, an 
average of 10.13 infections per 100 persons; the Irish born, an average of 13.68 infections 
per 100 persons. 
Two hundred and fifty-six persons (white and negro) admitted to the Government Hos- 
pital from the District of Columbia (chiefly from city life) within 1 year prior to exami- 
nation gave an average of 8.20 infections with intestinal worms; 108 persons (white) 
admitted to the Connecticut Hospital from Connecticut (rural and city life) within 1 year 
prior to examination gave an average of 9.26 infections per 100 persons; 148 white persons 
admitted to the Government Hospital from the District of Columbia (chiefly from city life) 
gave an average of 5.41 infections per 100 persons. That the higher rate of infection among 
persons admitted from Connecticut is due to the fact that they were in part admitted 
from rural life is rendered very probable in that among the 26 of the 108 persons, admitted 
from Connecticut, who had an assured history of city life the rate of infection was only 
3.84 per 100. 
The 1,494 white males examined at the Government Hospital were divided, according to 
their history prior to admission, into 6 groups, namely, old soldiers admitted from the 
various Soldiers’ Homes, civilians from the District of Columbia, soldiers from the regular 
United States army posts before 1898, sailors from the United States Navy, soldiers from 
active service or the special reserve camps after 1898, and soldiers admitted from service in 
the Philippine Islands. These groups showed, respectively, the following rates of infection 
with intestinal worms: Old soldiers, 3.80 infections per 100 persons; civilians, 5.54 per 100 
persons; soldiers from the Army prior to 1898, 7.26 per 100 persons; sailors, 8.74 per 100 
persons; soldiers from the Army after 1898, 21.11 per 100 persons; soldiers from Philippine 
service, 45.22 infections per 100 persons. The rate of infection with whipworms varied in 
the different groups in about the same manner as did the rate for all parasites; the pinworm 
gave its highest rate of infection among soldiers admitted from the Army before 1898, its 
next highest among the old soldiers from the Soldiers’ Homes, and it did not appear among 
the soldiers returned from the Philippine Islands; hookworms presented by far their highest 
rate of infection (12.17 per cent) among the Philippine soldiers and their next highest (3.33 
per cent) among the soldiers admitted from the Army after 1898. 
The infections with intestinal worms found among our cases were very unevenly distribu- 
ted among the different buildings, sections of buildings, and wards of the two hospitals from 
which the adult subjects of our examinations were taken. At the Government Hospital 
