XIV CONTENTS. 



tion. Organic acids, Sources, transformation and accumulation. Protein bodies, 

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

 Ammonification, nitrification, denitrification. Analytical and synthetical reac- 

 tions, Amount of bacterial substance in the soil, availability of bacterial matter, 

 transformation of peptone, ammonia, nitrate, nitrogen. 



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



by Edwards.) 268 



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 development, resistance, 

 immunity, and physiological efficiency, mechanism of fixation, variations and special- 

 ization, relation to environment. Soil inoculation, (Methods of soil inoculation, 

 inoculation with legume earth, inoculation with pure cultures. Edwards). 



CHAPTER IV. CHANGES IN ORGANIC CONSTITUENTS 284 



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, Availa- 

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

 phur, Sulphur compounds in the soil, sulphur bacteria, sulphate reduction. Potas- 

 sium, The transformation of potassium compounds in the soil. Other mineral con- 

 stituents, Iron, aluminum, manganese, and copper. 



DIVISION IV. MICROBIOLOGY or MILK AND MILK PRODUCTS. 



CHAPTER I. THE RELATION OP MICROORGANISMS TO MILK. (Stocking). (The acid- 

 forming bacteria by Hastings.) 292 



Importance of milk as a food. Absorbed taints and odors. Changes due to micro- 

 organisms. Microbial, content of milk, Common milk, special milk, certified 

 milk. Sources of microorganisms in milk. Interior of cow's udder, (healthy udders, 

 diseased udders), exterior of cow's body, atmosphere of stable and milk house, 

 the milker, utensils, water supply. Methods of preventing contamination of 

 milk, Individual cows, care of the cow's body, dust in atmosphere, dairy utensils, 

 the milker. Groups or types or microorganisms found in milk, and their sources, 

 General significance of acid-forming bacteria, groups of acid-forming bacteria (char- 

 acteristics of the Bact, lactis acidi group, characteristics of the B. coli-aerogenes 

 group, characteristics of the Bact. bulgaricus group, characteristics of the coccus 

 group) (Hastings), bacteria having no perceptible effect upon milk, the digesting or 

 peptonizing, pathogenic organisms. Factors influencing the developing of microor- 

 ganisms in milk, Initial contamination, straining, aeration, centrifugal separation, 

 temperature, pasteurization, the use of chemicals. The normal development of 

 microorganisms in milk, Germicidal period, period from end of germicidal action 

 to time of curdling, period from time of curdling until acidity is neutralized, final 

 decomposition changes. Abnormal fermentations in milk, Gassy fermentation, 

 sweet curdling fermentation, ropy and slimy fermentation, bitter fermentation, 

 alcoholic fermentation, other fermentations. The commercial significance of mic- 

 roorganisms in milk , Relation of dirt contamination to germ content. Milk as a 

 carrier of disease organisms, Those microorganisms which are beneficial and detri- 

 mental to health, (acid forms, neutral forms, injurious organisms) Bacteriological 

 analyses of milk. Bacteriological milk standards. The value of bacteriological 

 milk standards and analyses. 



CHAPTER II. THE RELATIONS OF MICROORGANISMS TO BUTTER (Hastings) 335 



Types of butter, Sweet cream butter, sour cream butter. The flavor of butter, 

 Control of butter flavor, kinds and numbers of bacteria in cream, spontaneous ripen- 

 ing of cream, use of cultures in butter-making, commercial cultures, use of pure cul- 



