﻿PARAGONIMIASIS IN THE PHILIPPINES. 29 



Occupation. — The majority of writers attribute very little importance 

 to occupation as a factor in the etiology of the disease. Many of the 

 reported cases have been among those whose vocation brought them in 

 contact with soil and water. My cases have all been among people of 

 the lower classes, where many of the different occupations offer similar 

 types of exposure and where the vocation is often changed from day to 

 day. Of 9 patients in my series where the occupation was given, 6 were 

 fishermen, 2 were cooks and 1 a laborer. So far as I know, fishermen 

 have not been considered especially susceptible in Japan. 



Climate. — Katsurada states that the disease is more common in the 

 mountainous region of Japan. 



Physical condition and personal habits. — Some writers have con- 

 sidered cold and other infections to be predisposing factors, while others 

 state that healthy persons are equally susceptible. 



An examination of my cases does not indicate any especial suscep- 

 tibility due to the personal habits or to the physical condition of the 

 patient. As may be noticed from the protocols, other diseases, which 

 probably antedated the fluke infection, were present in some instances, 

 while in others the parasitic disease was apparently the only contributing 

 cause of death. The association of tuberculosis, amoebiasis and other 

 diseases with paragonimiasis will be discussed in another part of this 

 paper. 



B. SPECIFIC ETIOLOGY. 



Trematodes in general. — The zoological position of parasitic flukes 

 is shown in Table No. 1, and the principal diagnostic points of the para- 

 sites and ova are given in Tables Nos. 2 and 3. In addition to this, 

 however, it seems advisable to enter somewhat more into the zoological 

 details, because of the very great importance of the infections to which 

 trematodes may give rise. 



There are two classes of the Platyhelmint'hes or fiat worms of interest 

 to medical men. These are the Cestoda, which have no digestive tube, 

 and the Trematoda, which have a more or less well-developed digestive 

 apparatus without an anus. The order Malacocotylea of the class Trem- 

 ' atoda contains 4 families and 10 genera or collective groups, with 15 

 species which interest us as medical men. There are certain more or 

 less general characteristics of the members of the order which here may 

 briefly be noticed, because they tend to simplify the study of the species 

 which directly concerns us. 



Nearly all parasitic flukes are hermaphroditic, with two important 

 exceptions, namely, the two species of the genus Schistosoma (S. hema- 

 tobium Bilharz and S. japonicum Katsurada), in both of which male 

 and female adult parasites develop. They are all rather small, nonseg- 

 mented worms of various shapes, but for the greater part they are of an 



