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This whole process of decay of organic life is one in which bacteria play the most important part. In the case of the decomposition of the woody matter of the tree trunk, the process is begun by the agency of moulds, for this group of organisms alone appears to be capable of attacking such hard woody structure. The later part of the decay, however, is largely carried on by bacterial life. In the decomposition of the animal tissues, bacteria alone are the agents.

PREFACE The rapidly growing interest in home economics is caus- ing this subject slowly to assume the aspect of an exact science. At the present time it is becoming necessary for those expecting to become housewives to understand at least the elementary phases of a number of sciences, most prominent among which are chemistry and bacteri- ology. The relation of microorganisms to household affairs has only been recognized in the last few years, but is now felt to be one of the most important phases in the study of the problems of the household. The present work is therefore designed for all interested in household affairs, including not only students of household economics but all persons who have practical charge of homes and are interested in keeping them in the best and most healthful condition. 238904 iii CHAPTER I. INTRODUCTION TABLE OF CONTENTS SECTION I MOLDS PAGE II. THE GENERAL NATURE OF MOLDS . . . 12 III. CONDITIONS FAVORING MOLD GROWTH . . . . 32 IV. THE DECAY OF FRUIT USEFUL MOLDS MOLD DISEASES . ., . . 40 SECTION II YEASTS V. YEASTS AND THEIR DISTRIBUTION . VI. YEASTS IN THE HOUSEHOLD. VII. BREAD RAISING FERMENTED LIQUORS . SECTION III BACTERIA VIII. THE GENERAL NATURE OF BACTERIA . . . 100 IX. BACTERIA WHICH LIVE UPON DEAD FOOD . . 124 X. THE PRESERVATION OF FOOD DRYING COOLING 139 XL THE USE OF PRESERVATIVES . V . . . 157 XII. PRESERVATION BY CANNING . . ... . 169 XIII. MILK EGGS PTOMAINE POISONING . ... I 56 68 86 . . 182 XIV. DISEASE BACTERIA 203 Vi CONTENTS CHAPTER PAGE XV. PREVENTION OF DISTRIBUTION OF CONTAGIOUS DISEASES . ... . . . .212 XVI. PRACTICAL SUGGESTIONS . . . . . 241 XVII. DISINFECTION . . . . . . . . 255 APPENDIX DIRECTIONS FOR LABORATORY EXPERIMENTS . . .267 INDEX . ........ 287 BACTERIA, YEASTS, AND MOLDS CHAPTER I INTRODUCTION Bacteria, yeasts, and molds comprise a series of plants commonly known as microorganisms, or more popularly as microbes. It has for some time been recognized that together they form a group of the utmost importance not only to the physician but also to the agriculturist. that their rela- To-day it is beginning to be appreciated tion to the ordinary household, and hence to the housewife, is even more intimate than to the physician. We are learning that many of the tasks of the housekeeper, some of which may be more or less unpleasant, have their foundation in bacteriology, and we are beginning to recognize that these microorganisms constitute the foundation of the demand for cleanliness so forcibly emphasized in modern times. In the household microorganisms have an important bearing in three directions 1. They are the cause of the decay and spoiling of foods and many other products. 2. They are sometimes of value in the preparation of foods. 3. They are the cause of contagious diseases. Although household duties are varied in character, the larger part of them concern the preparation and the pres- ervation of foods. The preparation of food belongs pri- marily to the department of cooking, although certain other factors are concerned. But the science of cooking has little to do with the preservation of food. This latter problem is intimately related to modern bacteriology. It is largely for this reason that the study of bacteriology and kindred subjects has in recent years come to be looked upon as a part of the necessary training of the housewife...

PREFACE The rapidly growing interest in home economics is caus- ing this subject slowly to assume the aspect of an exact science. At the present time it is becoming necessary for those expecting to become housewives to understand at least the elementary phases of a number of sciences, most prominent among which are chemistry and bacteri- ology. The relation of microorganisms to household affairs has only been recognized in the last few years, but is now felt to be one of the most important phases in the study of the problems of the household. The present work is therefore designed for all interested in household affairs, including not only students of household economics but all persons who have practical charge of homes and are interested in keeping them in the best and most healthful condition. 238904 iii CHAPTER I. INTRODUCTION TABLE OF CONTENTS SECTION I MOLDS PAGE II. THE GENERAL NATURE OF MOLDS . . . 12 III. CONDITIONS FAVORING MOLD GROWTH . . . . 32 IV. THE DECAY OF FRUIT USEFUL MOLDS MOLD DISEASES . ., . . 40 SECTION II YEASTS V. YEASTS AND THEIR DISTRIBUTION . VI. YEASTS IN THE HOUSEHOLD. VII. BREAD RAISING FERMENTED LIQUORS . SECTION III BACTERIA VIII. THE GENERAL NATURE OF BACTERIA . . . 100 IX. BACTERIA WHICH LIVE UPON DEAD FOOD . . 124 X. THE PRESERVATION OF FOOD DRYING COOLING 139 XL THE USE OF PRESERVATIVES . V . . . 157 XII. PRESERVATION BY CANNING . . ... . 169 XIII. MILK EGGS PTOMAINE POISONING . ... I 56 68 86 . . 182 XIV. DISEASE BACTERIA 203 Vi CONTENTS CHAPTER PAGE XV. PREVENTION OF DISTRIBUTION OF CONTAGIOUS DISEASES . ... . . . .212 XVI. PRACTICAL SUGGESTIONS . . . . . 241 XVII. DISINFECTION . . . . . . . . 255 APPENDIX DIRECTIONS FOR LABORATORY EXPERIMENTS . . .267 INDEX . ........ 287 BACTERIA, YEASTS, AND MOLDS CHAPTER I INTRODUCTION Bacteria, yeasts, and molds comprise a series of plants commonly known as microorganisms, or more popularly as microbes. It has for some time been recognized that together they form a group of the utmost importance not only to the physician but also to the agriculturist. that their rela- To-day it is beginning to be appreciated tion to the ordinary household, and hence to the housewife, is even more intimate than to the physician. We are learning that many of the tasks of the housekeeper, some of which may be more or less unpleasant, have their foundation in bacteriology, and we are beginning to recognize that these microorganisms constitute the foundation of the demand for cleanliness so forcibly emphasized in modern times. In the household microorganisms have an important bearing in three directions 1. They are the cause of the decay and spoiling of foods and many other products. 2. They are sometimes of value in the preparation of foods. 3. They are the cause of contagious diseases. Although household duties are varied in character, the larger part of them concern the preparation and the pres- ervation of foods. The preparation of food belongs pri- marily to the department of cooking, although certain other factors are concerned. But the science of cooking has little to do with the preservation of food. This latter problem is intimately related to modern bacteriology. It is largely for this reason that the study of bacteriology and kindred subjects has in recent years come to be looked upon as a part of the necessary training of the housewife...

This whole process of decay of organic life is one in which bacteria play the most important part. In the case of the decomposition of the woody matter of the tree trunk, the process is begun by the agency of moulds, for this group of organisms alone appears to be capable of attacking such hard woody structure. The later part of the decay, however, is largely carried on by bacterial life. In the decomposition of the animal tissues, bacteria alone are the agents.