XV111 CONTENTS . 



CHAPTER II. MICROBIOLOGY OF SEWAGE (Phelps) 330 



Bacterial flora of sewage. Types of sewage bacteria, Putrefactive and anaerobic 

 bacteria (the liquefaction of protein, the fermentation of cellulose, the saponification 

 of fats, the fermentation of urea, the reduction of sulphates and nitrates), oxidizing 

 bacteria (the production of nitrates and nitrites, other oxidizing reactions), patho- 

 genic bacteria (prevalence and longevity, life in septic tanks and filters). The culti- 

 vation of sewage bacteria, Filters, anaerobic tanks. The destruction of sewage 

 bacteria, By biological processes, by chemical processes. 



DIVISION III. MICROBIOLOGY OF SOIL (Lipman) 



CHAPTER I. MICROORGANISMS AS A FACTOR IN SOIL FERTILITY 345 



Introduction. The soil as a culture medium. Moisture relations, The amount 

 and distribution of rain fall, range of soil moisture, effect of drouth and excessive 

 moisture. Colloidal nature of the soil. Aeration, Mechanical composition of 

 soils, aerobic and anaerobic activities, rate of oxidation of carbon, hydrogen and 

 nitrogen, the mineralization of organic matter. Temperature, Influence of cli- 

 mate and season, early and late soils, production and assimilation of plant food. 

 Reaction. Range of soil acidity, causes of soil acidity, soil reaction and hydrogen- 

 ion concentration, change of reaction produced by microorganisms in the medium, 

 effect of reaction on number and species. Food supply, Organic matter, the 

 mineral portion of the soil. Biological factors, Fungi, algae, protozoa, higher 

 plants, bacteria (numbers and distribution, bacteria in productive and unproduc- 

 tive soils, distribution at different depths, seasonal variations of bacterial numbers 

 and activities, morphological and physiological groups). Methods of study, 

 Methods for counting bacteria, quantitative relations, qualitative reaction, trans- 

 formation reactions, rate of oxidation of carbon, rate of oxidation of nitrogen, addi- 

 tion of nitrogen, reactions concerning calcium, magnesium, sulphur, phosphorus. 



CHAPTER II. DECOMPOSITION OF ORGANIC MATTER IN THE SOIL 375 



Carbohydrates, Origin, decomposition of cellulose, the production of methane and 

 hydrogen, oxidation of methane, hydrogen, and carbon monoxide, the cleavage and 

 fermentation of sugars, starches, and gums. Fats and waxes, Origin and decompo- 

 sition. Organic acids, Sources, transformation and accumulation. Protein 

 bodies, Amount and quality, carbon-nitrogen ratio. Transformation of nitrogen 

 compounds, Ammonification, nitrification, denitrification. Analytical and syn- 

 thetical reactions, Amount of bacterial substance in the soil, availability of bacterial 

 matter, transformation of peptone, ammonia, and nitrate nitrogen. 



CHAPTER III. FIXATION" OF ATMOSPHERIC NITROGEN. (Methods of Soil Inoculation, 



by Edwards.) 400 



The source of nitrogen in soils, Early theories, chemical and biological relations. 

 Non-symbiotic fixation of nitrogen, Historical, anaerobic species, aerobic species, 

 energy relations. Symbiotic fixation, Historical, modes of entrance and devel- 

 opment, resistance, immunity, and physiological efficiency, mechanism of fixation, 

 variations and specialization, relation to environment. Soil inoculation, Methods 

 of soil inoculation, Inoculation with legume earth, inoculation with pure cultures, 

 etc. (Edwards.) 



CHAPTER IV. CHANGES IN ORGANIC CONSTITUENTS 41? 



Weathering process, Origin and formation of soil, influence of biological factors. 

 Lime and magnesia, Removal and regeneration of carbonates, lime as a base, effect 

 of calcium, magnesium compounds upon bacterial activities. Phosphorous, Avail- 

 ability of phosphates, relation of phosphorus to decay and nitrogen-fixation. Sul- 

 phur, Sulphur compounds in the soil, sulphur- phosphate composts, sulphur bac- 

 teria, sulphofication, sulphate reduction. Potassium, The transformation of 

 potassium compounds in the soil. Other mineral constituents, Iron, aluminum, 

 manganese, and copper. Antagonism. Variability in soil fertility investigations. 



