PROBLEMS IN HOST-PARASITE RELATIONS 



in this introductory chapter so far as the material is 

 available. In doing- this many problems that are awaiting 

 solution are indicated. An examination of these groups 

 abundantly demonstrates that the ratio between what we 

 know and what we do not know about the host-parasite 

 relations between man and these intestinal protozoa is 

 decidedly in favor of the latter. Furthermore, a survey 

 of the literature shows that contributions to our knowl- 

 edge of this subject are due largely to chance and not to 

 concerted activities and without any well thought-out 

 program in mind. As a rule, the investigator uses the 

 material that happens to be available at the moment and 

 undertakes the study of problems that occur to him with- 

 out respect to any of the larger questions involved. This 

 situation is, of course, due partly to the fact that most 

 investigators are able to spend only part of their time 

 on research and that very seldom are more than one or 

 two investigators at work at the same institution along 

 similar lines. The adoption of a program, such as that 

 discussed in this book, by a group of protozoologists 

 variously trained in zoology, medicine and public health 

 would without doubt be most helpful and economical, 

 since it would furnish a general objective and at the same 

 time allow as much individual initiative as any investi- 

 gator could desire. It is perhaps too much to expect a 

 combination of circumstances to arise that will put into 

 effect such a Utopian situation as that described, but at 

 any rate it can do no harm to provide a program that 

 presents the problems involved according to a logical 

 plan. The subjects that especially need investigation are 



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