XVI CONTENTS 



higher plants, bacteria (numbers and distribution, bacteria in productive and unpro- 

 ductive soils, dist^bution at difiEerent depths, seasonal variations of bacterial num- 

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

 Quantitative relations, qualitative reaction, transformation reactions, rate of oxida- 

 tion of carbon, rate of oxidation of nitrogen, addition of nitrogen, reactions conoern- 

 ing calcium, magnesium, sulphur, phosphorus. 



CHAPTER II. — Decomposition of Organic Matter in the Soil 31S 



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, — Aniount and quality, carbon-nitrogen ratio. — Transformation of nitrogen 

 compounds,' — ^Ammonification, nitrification, denitrifioation. — ^Analytical and syn- 

 thetical reactions, — 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.) , 338 



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, resist- 

 ance,, immunity, and physiological efl&ciency, mechanism of fixation, variations and 

 specialization, relation to environment. — Soil inoculation, — Methods of soil inocu- 

 lation, — Inoculation with legume earth, inoculation with pure cultures, etc. (Ed- 

 wards.) 



CHAPTER IV. — Changes in Organic Constituents 354 



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 bacteria, suUofication, sulphate re- 

 duction.— Potassium, — The transformation of potsasium compounds in the soil. — 

 Other mineral constituents, — Iron, aluminum, manganese, and copper. — ^Antagonism. _ 



DIVISION IV. — Microbiology of Milk and Milk Products 



CHAPTER I. — The Relation of Microorganisms to Milk. (Stocking.) (The Acid- 

 forming Bacteria, by Hastings.) . . . . ... 364 



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, dis- 

 eased 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, — Gen- 

 eral significance of acid-forming bacteria, groups of acid-forming bacteria (character- 

 istics of the Bad. lactis acidi group, characteristics of the B. coti-aerogenes group, 

 characteristics of the Bad. bulgaricus group, characteristics of the coccus group) 

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

 izing, pathogenic organisms. — Factors influencing the developing of microBrganisras 

 in milk, — Initial contamination, straining, aeration, centrifugal separation, tempera- 

 ture, pasteurization, the use of chemicals. — The normal development of micro- 

 organisms in milk, — Germicidal period, period from end of germicidal action to time 

 of curdling, period from time of curdling until acidity is neutralized, final decomposi- 

 tion changes. — Abnormal fermentations in milk, — Gassy fermentation, sweet curd- 

 ling fermentation, ropy and slimy fermentation, bitter fermentation, alcoholic fer- 



