Vlll CONTENTS 



CHAPTER PAGE 



VII. FERMENTATIONS AND THE ACTION OF ENZYMES 



(continued) . . . . .100 



Putrefaction and decay, 100 ; Putrefactive organisms, 103 ; 

 Oxidizing enzymes or oxidases, 114. 



VIII. BACTERIOLOGY OF THE SOIL . . . .117 



Numbers of bacteria in the soil, 118 : Kinds of bacteria in the 

 soil, 122 ; Action of antiseptics and heat upon the soil, 130. 



IX. NITRIFICATION . . . ' . . .134 



Nitrification, 134. 



X. DENITRIFICATION . . . . .152 



Denitrification and reduction of nitrates and nitrites, 152. 



XI. THE FIXATION OR ASSIMILATION OF NITROGEN . 169 



The fixation or assimilation of the free nitrogen of the air, 168 ; 

 Clostridium pastorianum, 171 ; Species of Azotobacter, 175. 



XII. THE FIXATION OR ASSIMILATION OF NITROGEN 



(continued) . . . . .187 



The fixation of nitrogen by bacteria in symbiosis with legu- 

 minous plants, 186. 



XIII. BACTERIOLOGICAL EXAMINATION OF SOILS. . 206 



Comparison of the fermentative action of soils, 206. 



XIV. FARMYARD MANURE . . . . .211 



Nature and composition of farmyard manure, 211 ; Bacteria in 

 farmyard manure, 215; (i) The ammoniacal fermentation of urine, 

 217; (ii) Putrefaction in the manure heap, 225 ; (iii) Nitrification 

 and Denitrification, 226 ; (iv) The fermentation of cellulose, 226. 



XV. MILK, ITS ORIGIN AND COMPOSITION . . 232 



Secretion of milk, 232; Composition of milk, 234; Colostrum, 

 241 ; The enzymes of milk, 242 ; Action of heat on milk, 245. 



