TABLE OF CONTENTS 



PAGE 



INTRODUCTION 5 



Historical 6 



INVESTIGATION OF YEASTS IN THE HUMAN DIGESTIVE 



TRACT OBTAINED FROM THE FECES 7 



Methods 7 



Mediums for isolation 7 



Collecting and plating samples 8 



Summary of isolations of yeasts from 175 persons examined (Table 1) 9 



Discussion of results 9 



MORPHOLOGIC, PHYSIOLOGIC, AND CULTURAL STUDIES OF 



ORGANISMS ISOLATED 12 



List of fungi used for comparative study (Table 2) 13 



The significance of budding 14 



General morphology 14 



The basis of generic and specific separation 15 



Generic separation 16 



The basis of specific classification 16 



Mediums employed for specific differentiation .' 19 



Sugar mediums 19 



Litmus milk 20 



Gelatin mediums 20 



Sugar free mediums 21 



Pellicles, rings and grease films 21 



Solid mediums 21 



Giant colonies 21 



SPECIAL STUDY OF TWENTY REPRESENTATIVE ORGANISMS. 22 



Outline of procedure 22 



Important cultural and physiologic characteristics of twenty species 



summarized (Table 3) 23 



Production of acidity and alkalinity in liquid mediums 25 



COMPARISON OF THE YEASTS ISOLATED FROM THE DIGES- 

 TIVE TRACT WITH DETERMINED PATHOGENIC AND NON- 

 PATHOGENIC SPECIES 28 



FEEDING EXPERIMENTS WITH YEASTS 30 



THE CLASSIFICATION OF THE BUDDING FUNGI 33 



Taxonomic discussion 34 



Key to the genera of budding fungi 40 



DESCRIPTION OF NEW SPECIES OF YEASTS 41 



SUMMARY AND CONCLUSIONS : 45 



Bibliography 47 



Explanation of plates 50, 52, 54, 56, 58, 60 



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