xvi INTRODUCTION 



recognized object. I believe that it is no exaggera- 

 tion that many have not consciously observed a pro- 

 tozoan cyst, many are unable to differentiate the 

 several species when they see them, and not a few 

 are unable to differentiate that common organism, 

 Blastocystis, from them. 



In a great many instances the finding of an 

 amoeba in the stool has furnished, per se, a diagnosis 

 of intestinal amoebiasis. Correct identification of 

 the amoeba is comparatively seldom done. 



The finding of a free swimming form leads to a 

 report of a flagellate, without much regard to the 

 species. All are Trichomonas or "Cercovionas'' to 

 many medical laboratorians and practitioners. 



These practices are to some extent a convenience. 

 When the finding of protozoa fits with clinical ideas, 

 or when nothing else is found as a basis for the ill- 

 ness, or, in the hands of many physicians, regardless 

 of other conditions, the parasite is made the basis 

 of therapeutic attack. 



Many patients have been and are now under treat- 

 ment for intestinal amoebiasis who have had no path- 

 ogenic amoeba. Many people have been and are 

 now under treatment for ^'flagellosis" whose flagel- 

 lates are not concerned in their illness or, literally, 

 about the treatment. 



Protozoologists as a rule are not pathologists; 

 few pathologists and other physicians know much 

 about protozoa. Therefore the errors common among 

 protozoologists in evaluating disease when associated 



