474 The Philippine Journal of Science 1921 
higher resistance of the cysts and the fact that a longer period 
of exogenous development is required before the cysts of Isospora 
become infective. With Eimeria this period is greatly reduced, 
for the cysts of species of this genus may be passed almost 
fully if not completely developed. Other protozoan cysts are 
usually fully developed when they leave the intestine and are 
more vulnerable to unfavorable environmental conditions. 
The self-limiting nature of intestinal coccidiosis precludes the 
occurrence of coccidia carriers. ‘This, of course, presupposes the 
avoidance of reinfections of the original host, that may operate 
to bring about the more or less constant discharge of cysts over 
periods beyond the duration of a primary infection. 
It will be a matter of interest, moreover, to watch the 
developments in the United States, for it is my belief that 
cther cases will occur there and add to the new problems 
that the home-coming soldier has brought with him. In this 
connection I am, minded to repeat certain remarks I made in 
the course of a paper published in 1917: (8) 
The importance of the protozoa as the causative factors in many grave 
diseases is thoroughly recognized today by every alert practitioner, par- 
ticularly those whose labors carry them into tropical or semitropical zones. 
There is likewise a gradual awakening to the fact that many parasitic 
protozoa do not restrict their activities to those localities, but, on the 
contrary, are exceedingly ubiquitous. With the opening up of new trade 
routes and the broadening and development of commerce to the Far East, 
South America and Africa, and as a result of conditions which are develop- 
ing with the progress of the European war, they are gradually establishing 
themselves in cooler climes. The malarial parasite has long been known 
too well in North America, and there is a growing realization that en- 
damebic dysentery is not by any means a rare malady in the same territory: 
The medical schools of the United States will have to cope with this situation 
before long, and they can meet it only by extending their curriculums 
so as to meet the protozodlogical needs, not only of the men who will have 
to deal with conditions at home, but also of the rapidly increasing number 
of medical men who are answering the call to the tropics. | 
PATHOGENICITY 
Before going into the question of pathogenicity and the 
problem of the treatment of coccidial infections in man, it may 
be well, for the benefit of those who have not had the oppor- 
tunity to study these organisms, briefly to review the coccl- 
dial life cycle. In all essential points, the life cycles of species 
of the genera Himeria and Isospora coincide with that worked 
out by Schaudinn for Eimeria (Coccidiwm) schubergi, parasitic 
in the gut of Lithobius forficatus. The parasite enters the ali- 
mentary tract of the host in encysted form. In Eimeria these 
cysts (odcysts), on full development, contain four dizoic spores ; 
