CHAPTER XI 



EFFECTS OF CHANGES IN THE DIET OF THE 

 HOST ON INTESTINAL PROTOZOA 



By 

 Herbert Ratcliffe 



School of Medicine, University of Pennsylvania 



INTRODUCTION 



The purpose of experiments on diets and intestinal protozoa is 

 to determine something of the relation of an animal's food to its 

 susceptibility to infection with protozoan parasites. If mammals 

 are divided into three general groups according to food habits — 

 (i) meat eaters, (2) vegetable eaters, and (3) an intermediate 

 group that eats both meat and vegetables — it will be found, upon 

 consulting a comprehensive check list, that protozoa have been 

 reported rarely from the first group; that strictly herbivorous 

 animals have a distinct and specialized protozoan fauna, while the 

 omnivorous animals are parasitized by more general types of pro- 

 tozoa, some of which occur in both of the former groups. The 

 majority of animals do not, however, lend themselves to definite 

 experimentation which must be conducted under controlled con- 

 ditions in the laboratory. There are several primary considerations 

 which must be taken into account in planning studies upon the 

 relation of diet to infections with intestinal protozoa. In the opinion 

 of the writer these are (i) methods for determining the species 

 and numbers of protozoa present in the intestine of an animal, and 

 the conditions under which these organisms live, (2) diets and 

 experimental animals, and (3) intestinal protozoa of experimental 

 animals. 



METHODS 



I. Intestinal Protozoa — Numbers and Conditions in Intestine. 

 Fecal examination over a period of several days is usually suf- 

 ficient to determine the species of protozoa present in animal's 



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