viii CONTENTS 



CHAPTER X PAGE 



BACTERIA AND THE CIRCULATION OF NITROGEN IN NATURE 



1. Introduction: The Assimilation of Free Nitrogen by the Bacteria of the Root Nodules of 



Leguminous Plants, and by Bacteria in the Soil ........ 88 



CHAPTER XI 

 BACTERIA AND THE CIRCULATION OF NITROGEN (continued) 



2. The Liberation of Organic Nitrogen by Putrefaction, and its Mineralization by the Nitri- 



fying Bacteria .............. 98 



CHAPTER XII 

 THE CIRCULATION OF CARBON DIOXIDE IN NATURE 



1. Introduction; Organized Ferments and Enzymes ; Races of Ferment Organisms; Fermen- 



tation of Alcohol and of Acids; Optical Activity and Fermentation .... 107 



CHAPTER XIII 

 THE CIRCULATION OF CARBON DIOXIDE IN NATURE (continued} 



2. Bacterial Fermentation of Carbohydrates . . ...... 116 



Milk and other Dairy Products . . . . . . . . . . . 117 



Butyric Fermentation ..... .......121 



Cellulose Fermentation ....... 122 



Mucilaginous Fermentation . . . . . . . . . . . .123 



Fermentations in technical processes . . . . . . . . . .123 



CHAPTER XIV 

 THE CIRCULATION OF CARBON DIOXIDE IN NATURE (continued} 



3. The Yeast Fungi and Alcoholic Fermentation. Theory of Fermentation and Anaerobiosis. 



Concluding Remarks on the Circulation of Nitrogen and Carbon in Nature . . .126 

 Theory of Fermentation and Putrefaction .......... 133 



CHAPTER XV 



BACTERIA IN RELATION TO DISEASE 



1 . Diseases of Plants ; Harmless ' Messmates ' in the Human Body ; Pathogenic Bacteria ; 



Points of Attack and Sources of Infection 137 



CHAPTER XVI 



BACTERIA IN RELATION TO DISEASE (continued} 



2. Description of sorr.e Pathogenic Species 147 



CHAPTER XVII 

 BACTERIA IN RELATION TO DISEASE (continued) 



3. Mode of Action of Bacteria, and the Reaction of the Organism. Serum Therapeutics and 



Immunity ............... 158 



NOTES 169 



INDEX 185 



The Arabic figures inseited in round brackets in the text refer to the 

 Bibliographical Notes, pp. 169-184. 



