ILLUSTRATED KEY TO THE TREMATODE PARASITES 
OE MAX. 
By Ch. Wardell Stiles, Ph. D., Chief of Division of Zoology, Hygienic Laboratory, 
TJnited States Public Health and IMarine-Hospital Service. 
INTRODUCTION. 
Upon seTeral recent occasions the writer has been called upon for 
information in regard to the treniatodes xvhich are parasitic in man, 
and it is in response to such reciuests that the present paper is pub- 
lished. This key is offered not as an exhaustive treatment of the 
subject, but as a ready reference aid in clinical diagnosis. 
To the American physician the treniatodes or flukes hax’e been here- 
tofore chiefly matters of scientific interest, most men looking upon 
them as zoological curiosities. Hepatic distomatosis, caused liy 
Fasciola hepatica and F. magna^ is known to occur in cattle, particu- 
larl}" in the Southern States; F. hepatica is also found in sheep in 
various parts of the country, and it need not be surprising if isolated 
cases of infection with this parasite should be found in man. About 
20 cases of hepatic distomatosis, caused by Opristhorchis sinensis^ hax^e 
alread}^ been found in this country, and it is strange that the cases 
thus far seen are so few in number. Parasitic hemoptysis, caused bx" 
Paragonimus icesterinanii, been found in the United States in 
dogs, cats, and swine, and one (imported) case in man has recentl}" 
been recognized in Portland, Oreg. Bilharziosis, caused by Schisto- 
soma heematoljium^ has been found in this country upon at least three 
occasions, and it is also said to occur in Cuba and Porto Rico. Thus, 
for the American physician, trematode diseases are becoming some- 
thing more than a mere matter of curiosity, and their importance is 
increased by the fact that about 120,000 of our troops have been serv- 
ing in the Asiatic quarter of the globe, or, in other words, in a part 
of the world where maladies of trematode origin are more common 
than the\" are with us. Whether the return of these troops, together 
with the return of travelers from Asia, xvill result in making these 
diseases more or less common in man in the United States can not lie 
definitelv prophesied, but the indications are that we shall not entirely 
escape infection. It is difficult to guard against the introduction of 
the parasites under consideration, and the question whether they will 
multiply here depends primarily upon two factors, namely, first. 
