220 
Distribution of Hookworms 
Rarely however it has happened that the careful counting of hookworms 
expelled from a large number of people was necessary to the elucidation of 
some intensely interesting and very important medical and public health 
problems. Such problems were presented to me and my colleagues, Doctors 
M. B. Barber, H. P. Hacker, M. B. Barnes and W. G. Smillie. In the prose¬ 
cution of our work the drudgery of the task was alleviated by the extra¬ 
ordinary interest aroused as the solution of the problems appeared to present 
themselves. 
DISTRIBUTION OF A GCH Y LOS TOM A DUODENALE. 
A. duodenale is distributed to all those countries lying in Eurasia, south 
of 35° N. latitude and north of 20° N. latitude. In Europe, as in Cornish 
mines and in Mediterranean countries and Egypt, it may be the sole species 
found; nearer the Tropic of Cancer it is associated with increasing numbers 
of N. americanus. In warm mines the worm may be found farther north 
than 35° N. 
This species has been introduced into the American continent and the 
Antilles in historic times by coolies from India and Java, by Mediterranean 
and Levantine people into Brazil and other parts of North, Central and 
South America, and by Japanese and Chinese. 
It has been introduced into Fiji by Indian coolies, and into Polynesia, the 
Philippines, and Australia, by Chinese, Japanese and Portuguese. In Europe 
it has been encountered in Italy, Sicily, Sardinia, Spain, Austria, Hungary, 
Serbia and Bulgaria. Farther north it is common among miners as in Cornwall, 
Belgium, Liege, Mons and Charleroi. In France it occurs in the Loire Basin, 
also in the mines of Germany, Poland and Silesia. Severe infections are en¬ 
countered in Egypt. 
While in general the species A. duodenale is distributed in the cooler 
latitudes north of 20° N. latitude, there seems to be no reason other than 
the lack of opportunities for implantation, for its relative absence in equa¬ 
torial regions. 
Its absence is only relative for I encountered large numbers of this species 
in Java and Malaya among people who acquired the infection within 3° N. 
and 8° S. latitudes. It is evident therefore that there is nothing in an equa¬ 
torial climate inimical to the development of the species in the soil and that 
the incidence of each species is purely a matter of implantation on soil equally 
favourable to each. 
DISTRIBUTION OF NEGATOR AMERICANUS . 
This species is found in largest proportion in Eurasia, Africa, Indonesia 
and Polynesia, south of 20° N. latitude. 
In regions near the tropic of Cancer it is associated with A . duodenale but 
farther south, as in parts of Indonesia, Fiji and South Africa, it is encountered 
alone. 
