GY lllli^ij, HASTINGS liiiiilaijitiiiijito^^ Digitized by the Internet Archive in 2007 with funding from IVIicrosoft Corporation http://www.archive.org/details/agricbacteriologyOOrussrich AGRICULTURAL BACTERIOLOGY Ube Century Bgricultural Series AGRICULTURAL BACTERIOLOGY FOR STUDENTS IN GENERAL AGRICULTURE BY H. L. RUSSELL Dean of the College of Agriculture University of Wisconsin AND E. G. HASTINGS Professor of Agricultural Bacteriology The College of Agriculture rersily"ori¥4«;onsin ILLUSTRATED NEW YORK THE CENTURY CO. 1921 Copyright, 1921, by The Century Co. FOREWORD The art of agriculture has long been practised, but the science of agriculture is of comparatively recent origin. This science rests upon the fundamental sciences — chem- istrj', physics, and biology. One phase of biology, bac- teriology, has within the last three decades assumed a most important relationship. The early researches of Pasteur, Koch, and their successors opened the field of inquiry as to the. causation of animal disease. More recently, exact knowledge of the influence of microorganisms on soil pro- cesses, on dairying, and on foods in general has been greatly extended. It is of the utmost importance for the farmer and the student of agriculture to have a proper conception of these relations. The purpose of the text here presented is to give to the reader and to the student the essential facts concerning the relation of microorganisms to daily life, and especially to that of the farm, without a confusing mass of detail, both chemical and biological, the presentation of whieh often hides the essential information the student should gain. The terminology is simple. Descriptions of specific or- ganisms have been avoided; and, in general, the various phases of the subject are presented in their broad outlines in order to acquaint the student with the fundamental prin- ciples, which can be applied to subjects not considered. A full conception of the relation of microorganisms to agriculture can not be gained without working with them in the laboratory. Without such experience the organisms remain intangible to the student. Much can also be done ^oTfc VI FOREWORD by the teacher in the class-room, through the use of more extended illustrative material than it is possible to give in the text, and through examples of the practical application of the organisms, to increase the interest of the student in this subject that has so many points of contact with the daily life of every individual. CHAPTBE CONTENTS PART I PROPERTIES OF MICROORGANISMS I The Role op Microorganisms 3 Constructive agencies. Destructive agencies. Decomposition II The Development of Bacteriology .... 7 Discovery of bacteria. Spontaneous genera- tion. Pasteur. Aniline dyes. Koch and the gelatine plate III The Morphology op Microorganisms .... 12 Morpliology of bacteria. Morphology of yeasts. Morphology of molds. Protozoa IV Cultivation and Study op Bacteria, Yeasts, AND Molds 33 Culture media. Liquefiable-solid media. Ster- ilization. Isolation of pure cultures. Quan- titative methods. Microscopic examination. Systematic study of bacteria V Physiology op Microorganisms 48 Moisture. Temperature. Oxygen. Reac- tion. Light. Chemicals. Food. Metabiosis. By-products. Classes of organic matter. Distribution of microorganisms PART II SOIL BACTERIOLOGY VI The Relation of Microorganisms to Soil Fer- tility 69 Unavailable and available plant food. Soil viii CONTENTS CHAPTER PAGB as a culture medium. Moisture and air. Temperature. Reaction. Number of organ- isms in soil VII The Decomposition of Organic Matter in the Soil Humus 78 VIII The Cycle of Carbon 83 Cellulose decomposition. Retting. Oxida- tion of hydrogen and methane IX The Action of Bacteria on the Minerals of the Soil 87 Calcium. Phosphorus. Potassium. Sulphur. Iron X The Cycle of Nitrogen 94 The nitrogen of the soil. Ammonification. Nitrification. Conservation of nitrogen. Ni- trate deposits. Denitrification XI Barnyard Manures and Sewage Disposal . . 107 Manures. Sewage Disposal XII The Fixation of Nitrogen 117 The fixation of nitrogen. Leguminous plants. Inoculation of soil PART III THE RELATION OF MICROORGANISMS TO FOOD XIII The Contamination of Foods 135 Factors governing decomposition. Contami- nation of milk: from interior of udder, from air, from the animal. Influence of the milker. Contamination from utensil. Cleaning of milk utensils. Contamination from factorj^ by-products. Straining and clarifying milk. Influence of feed on contamination of milk. Contamination of other foods than milk CONTENTS IX CHAPTER XIV XV XVI XVII XVIII XIX The Contamination op Foods with Pathogenic Bacteria 154 Bovine tuberculosis. Septic sore throat and garget. Typhoid fever. Diplitheria and scarlet fever. Influence of bacterial content on healthfulness. Infant mortality. Poison- ous foods The Preservation op Foods 168 Purification of water. Inhibition of micro- organisms. Desiccation. Concentration. Preservatives. Organic acids. Silage. Low Temperature. Eggs. Heat. Pasteurization of milk. Sterilization The Fermentations Occurring in Food Prod- ucts 186 Acid fermentation of milk. Sweet curding of milk. Butyric fermentation. Slimy fer- mentation. Alcoholic fermentation. Vine- gar. Bread The Relation op Microorganisms to Butter and Cheese 202 Acid-fermentation and flavor of butter. Pas- teurization of cream. Flavor of butter substitutes. Decomposition of butter. Ab- normal flavors in butter. Cheese-making. Cheddar cheese. Gassy cheese. Swiss cheese. Mold-ripened cheese. Soft cheese The Bacteriological Control op Foods . . . 215 Municipal control of milk. Grades of Milk. Certified milk. Pasteurization of market milk PART IV TRANSMISSIBLE DISEASES The Relation op Microorganisms to Diseases OP Animals 239 The Communicable diseases. Infection. Ex- f CONTENTS IHAPTER PAGE ternal defenses. Internal defenses. Im- munity. Active and passive immunity. Persistence of immunity. Exit of organisms from the body. Necessity for correct diag- nosis XX Anthrax, Blackleg, Hemorrhagic Septicemia, AND Corn-Stalk Disease 252 Anthrax. Infection. Symptoms. Lesions. Vaccination. Disposal of carcasses. An- thrax in man. Blackleg. Symptoms. Vac- cination. Hemorrhagic septicemia. Corn- stalk disease XXI Tuberculosis 269 Animals affected. Distribution. The tu- bercle bacillus. Infection. Lesions. Distri- bution of the tubercle bacillus. Infection of the herd. Detection of tuberculosis. Free- ing the herd from tuberculosis. Vaccina- tion. Tuberculosis of hogs. Avian tubercu- losis. Joline's disease XXII Texas Fever, Contagious Abortion, and Foot- AND-MouTH Disease 295 Texas fever. Eradication. Immunization. Contagious abortion. Detection. Control, and prevention. Foot-and-Mouth disease. Nature of the disease XXIII Rabies and Actinomycosis 311 Rabies. Symptoms. Diagnosis. Preventive, treatment. Actinomycosis. Symptoms. Treatment XXIV Glanders and Tetanus 320 Glanders. Distribution. Symptoms. De- tection. Tetanus. Symptoms. Preventive measures CONTENTS XI XXV Hog Cholera '6Z6 Symptoms. Lesions. Prevention. Protec- tive treatment XXVI Diseases op Fowls 340 Chicken cholera. Roup. Fowl typhoid. White diarrhea XXVII Bacterial Diseases op Plants 34G Fenr blight. Cabbage rot. Wilts. Galls or tumors XXVIII Disinfection 351 Natural agencies. Chemical disinfectants. Lime. Carbolic acid. Coal tar disinfectants Formaldehyde. Corrosive sublimate. Sul- phur. Calcium hypochlorite. Ferrous sul- phate. Copper sulphate. Disinfection Index 363 LIST OF ILLUSTRATIONS FIG. PAGE 1. Forms of Bacteria 13 2. Cocci 14 3. Large Bacilli 14 4. Small Bacilli 15 5. Spirilla 15 6. Spirilla 16 7. Spores 16 8. Spores 17 9. Arrangement of Cocci 18 10. A Streptococcus 19 11. Bact. Anthracis 19 12. A Tetracoccus 20 13. Capsules 21 14. Yeasts 27 15. Spore-formation by molds 30 16. A Plate Culture 39 17. Effect of Acid on Bacteria and Yeasts 54 18. Effect of Light 55 19. Enzyme Action 57 20. Etching of Marble by Plant Roots 88 21. Effect of Nitrifying Bacteria on the Growth of Barley . 101 22. A Septic Tank 112 23. The Tile Drain of a Sewage Purification System . . . 115 24. Nodules on Soy Beans 121 25. Effect of Inoculation on Alfalfa 123 26. Effect of Inoculation on Peas 126 27. Effect of Inoculation on Sweet Clover 128 28. The Cycle of Nitrogen 131 29. A Section of an Udder 138 30. Contamination from the Air ........ 140 xiv ILLUSTRATIONS FIG. PAGE 31. Dirt Tests 141 32. Bacteria on Hairs 142 33. A Dirty Stable 143 34. A Clean Stable 144 35. Sanitary Milk Pails 145 36. Typhoid Fever Spread by Milk . 160 37. Typhoid Fever Spread by Water 161 38. Protection of a Well 162 39. A Home-Made Pasteurizer 182 40. Ropy Milk 192 41. Gassy Cheese 211 42. Anthrax 257 43. Tubercular Omentum 274 44. A Tubercular Spleen 275 45. Buying Tuberculosis 277 46. Tuberculosis Spread by Creamery By-products . . . 278 47. A Tubercular Animal 280 48. A Tubercular Animal 281 49. Injecting Tuberculin . 283 50. Reaction Curves in the Tuberculin Test 285 51. Avian Tuberculosis 291 52. Avian Tuberculosis 292 53. Texas Fever 298 54. Foot-and-Mouth Disease 307 55. Foot-and-Mouth Disease 308 56. Foot-and-Mouth Disease 309 57. Actinomycosis 318 58. Glanders 321 59. Glanders 322 60. Hog Cholera 330 61. Hog Cholera 331 62. Roup 343 63. Pear Blight 347 PART I PROPERTIES OF MICROORGANISMS AGRICULTURAL BACTERIOLOGY CHAPTER I THE ROLE OF MICROORGANISMS Animate nature is commonly divided into two great groups: the plants and the animals. It is possible, how- ever, to make the division of life along other lines than form and function. Every living form must have building material; the various chemical elements that are essential for its structure must be available in fitting combinations. Every living form must also have energy ; for work is being done by even the simplest forms of life, and without energy no work is possible. The sole source of energy for our world is the sun. The energy is transmitted in some inex- plicable way through the space that separates the earth from the sun. One group of living organisms is able to receive directly this radiant energy, and to use it in the work of growth and development. This power is limited to those forms that are provided with the compound known as chloropliyl, the sub- stance that gives to the higher plants their green color. They obtain their building materials from the soil, the water, and the air, in compounds that contain but little or no energy. They combine these simple compounds into complex forms that contain a great store of energy. Thus the plant uses as food carbon-dioxide, water, oxygen, ni- 3 4 AGRICULTURAL BACTERIOLOGY trates, phosphates, and sulphates, and forms from them all of the varied substances found in its tissues — the woody fiber, the sugars, the starches, the fats, the gums, the waxes, and the proteins. The green plants are builders of organic matter and storers of energy. They represent the construc- tive or the synthetic group. Living forms that do not possess this wonderful energy- receiving and -utilizing compound, chlorophyl, can not use the radiant energy of the sun directly, but must rely upon that which the green plant has stored in its structure. These forms use vegetable matter as food, and obtain therefrom their building materials and the energy neces- sary for all their life processes. They utilize the energy and leave behind simpler types of compounds than those in- gested. They break down vegetable matter, and are to be classed as destructive agents, or as analytic factors. The animal that lives upon the tissues of another animal is still relying upon the green plant for its food and energy. It is to be seen that the basis of classification is, whether the energy needed by the organism is obtained directly from the sun, or indirectly through the medium of another or- ganism. Destruction of man-made structures is as necessary as is the building thereof, and so it is in nature. The supply of plant food is limited, and it is essential that the elements in vegetable matter be returned to a form that permits of use by another plant. This is the work of the destructive group. The green plant furnishes to all other forms of life food and energy. They, in their turn, supply the green plant with food. Each group is absolutely dependent on the other for its continued existence. Not all the members of the destructive group are animals. In it are placed many forms that every one recognizes as plants, They are devoid of chlorophyl, ^n(l demand the THE ROLE OP MICROORGANISMS 5 same kind of food as does the animal ; their food must sup- ply them with both buildin^? materials and energy. The term *^ fungi" or *^ fungus plants" is applied to them. One does not think of the animals as agents in the destruction of organic matter, for our interest in them is wholly along other lines. The waste products of animal life are very simple chemical compounds. Some of the fungus plants change their food relatively little as far as its chemical complexity and energy content is concerned. Their by- products are almost as complex as is the food itself, and in many instances possess economic value. The destructive work of animals and of the fungus plants is included under the term decomposition. Other terms, such as fermentation, decaijy putrefaction^ and rotting, are synonymous. Usually, however, these expressions are ap- plied to the decomposition of certain chemical substances, or to a particular type of decomposition; for example, one says that milk ferments and that meats putrefy. The greater part of the decomposition of organic matter is occasioned by fungus plants of microscopic size that find their home in the soil and in the water. The body of an animal is buried; within a short time it completely disap- pears. An immense amount of waste organic matter may be placed in a stream — as, for example, in the great drain- age canal that receives the sewage of Chicago. Before the stream that receives the effluent of the drainage canal reaches central Illinois, the organic matter has completely disappeared under the influence of the microscopic life of the water. From this organic matter are formed carbon-dioxide, water, sulphates, phosphates, and nitrates. From organic matter minerals have been formed; therefore the term mineralization is often applied to the process. An element passes from the soil, the water, or the air into the green 6 AGRICULTURAL BACTERIOLOGY plant, and is built into some one of its compounds. These are used by some member of the destructive group, or more commonly by a series of members of this group, with the result that the element becomes again available to the green plant. This passage of the elements from one form of life to another is called the cycle of the elements. An atom of carbon may be in the air to-day in the form of carbon- dioxide; to-morrow it may be in a sugar molecule of a plant ; the next day in the tissues of an animal ; and the succeeding day it may be again present in the air in a mole- cule of carbon-dioxide; ready for another of its ceaseless passages, carrying with it a supply of energy for the animal and the fungus plant. The chief agents in the decomposition of organic matter are the protozoa; or simple animal forms, and the simple plant forms, which include the bacteria, the yeasts, and the molds. The term microorganism is often applied to these various types, and microbiology to their study. It is with these forms that this volume treats, and especially with the ways in which they influence the life of man. He meets them in the soil he tills ; he makes use of them in the prep- aration of foods and products of industrial value ; he is con- stantly striving to protect his food supplies from their ac- tion, and to protect himself and his animals from the diseases that they cause. They present themselves to him at every moment of his life, to his benefit or his injury. He must employ them, and fight them, either conscious or unconscious of the nature of his acts ; and he who has intel- ligent acquaintance with them will certainly fare far bet- ter than one ignorant of the part they play. A knowledge of the role of microorganisms in nature is as essential as knowledge concerning the higher plants and animals. CHAPTER IT THE DEVELOIWIENT OF BACTERIOLOGY Discovery of bacteria. — The study of bacteria is one of the most recent developments of biologic science. The facts that had been gathered concerning the bacteria were not grouped into an independent phase of biology until about 1880. It was not until 1882 that the new science received its name, bacteriology. The bacteria had first been seen in 1688 by Leeuwenhoek. Apparently he was the first to use an instrument of sufficient magnifying power in such a way as to make the bacteria visible. The compound microscope was first made by Johannes Janssen and his son, in Holland, in 1590. The objects to be examined by such an instrument were illuminated by light coming from above, and reflected from the surface of the object into the lens of the microscope, and thence to the observer's eye. With such an arrangement the bacteria could not be seen. Leeuwenhoek used a simple microscope in his work, of lower power than others had employed. He, liowever, examined his objects by placing them between the source of light and his lens: he used transmitted light, or the kind one uses when he wishes to determine the free- dom of a liquid from suspended matter, and places it be- tween his eye and the window. The solid objects refract the rays of light, and thus their presence in the liquid is made evident to the eye. This simple modification of his microscope made Leeuwenhoek the discoverer of many mi- croscopic objects, among them the yeasts and the bacteria. He is frequently called the father of microscopy. 7 8 AGRICULTURAL BACTERIOLOGY Decomposition and its cause. — From 1683 to 1850 little was learned concerning the importance of the bacteria in nature. The biologists of those days were more interested in classifying and naming the various plants and animals than in studying what they were able to do. They were interested in morphology rather than in physiology. It had been known to man ever since he attempted to preserve plant or animal matter that change in it was in- evitable. The microscope revealed in decomposing material an immense number of microorganisms, among which the bacteria predominated. It was believed by many that these organisms were the cause of the decomposition. Justus yon Liebig, the founder of organic and agricultural chemistry, believed that decomposition was purely a chemical process that in some way occurred in matter brought in contact with the decomposing material. He was the dominant figure in the chemical world from 1840 to 1860, and when he stated that 'Hhose who pretend to explain the putrefaction of animal substances by the presence of microorganisms reason very much like a child who would explain the rapidity of the Rhine by attributing it to the violent motion imparted to it in the direction of Bingen by the numerous wheels of the mills of Mayence," there were few bold enough to con- tradict him, and none whose reputation carried conviction. Spontaneous generation. — Numerous experiments had shown that an infusion of meat could be boiled for some time and sealed immediately thereafter in the vessel in which it had been heated, and yet it would often undergo de- composition, and would be found teeming with microscopic life. Such experiments had given rise to what seems now a curious theory, that of spontaneous generation of life; that is, the creation of life from dead matter. The scien- tists of those days could not imagine that any living form could endure the temperature of boiling water for even the DEVELOPMENT OF BACTERIOLOGY 9 briefest period of time. The infusion of meat had been protected from the entrance of bacteria after it had been heated; therefore it was believed the forms found in the decomposing infusion must have arisen in some way from the lifeless material. Many experimenters tried to disprove this theory. Schultze, in 1836, heated infusions to the boiling-point, and the air tliat entered his flasks when removed from the fire was passed through strong acid or alkali. In 1837, Schwann passed the air that entered the flasks through tubes heated by a direct flame. Schroeder and von Dusch, in 1853, plugged the tubes leading from the flasks with cotton wool, which filtered the air as it was drawn into the flasks when they cooled. Usually infusions thus treated did not decom- pose. The adherents of the theory claimed that the exposure of air to the high temperature of the heated tube, to acid or alkali, or even to cotton wool, removed some life-maintaining principle therefrom. It was not possible by such experi- ments to disprove the theory. In 1860, the Paris Academy of Science ottered a prize for an attempt to throw new light by suitable experiments on the question of spontaneous generation. Pasteur, the father of bacteriology. — Louis Pasteur was born in the Jura district of France in 1822. He was a dili- gent student of chemistry, and became interested in the ef- fect of certain crystalline substances and their solutions on polarized light. Among the substances he studied was tar- taric acid and its salts, products of one of the great fermen- tation industries, the wine industry. In 1854 he was made a member of the Faculty of Sciences in the University of Lille, a great industrial city. He began the study of the manufacture of alcohol from beet-sugar. In 1857 he read a paper on the lactic-acid fermentation. He had discovered 10 AGRICULTURAL BACTERIOLOGY in sour milk a trace of grayish substance, and had proved it to be a ferment of milk. He had before him one of the most important of the bacteria. This work was the begin- ning of the new science of bacteriology. Pasteur accepted the challenge of the Paris Academy, and on April 7, 1864, he gave his results to the world in a famous lecture at the Sorbonne. He showed that if any solution containing organic matter is heated long enough, and protected from the microorganisms in the air, it will remain unaltered. He avoided the objections that had been urged against the experiments of others by allowing air to pass in and out of his flasks through long curved tubes, on the walls of which all dust and bacteria would be deposited. He showed for all time that life comes from life, that every form is the progeny of preexisting forms of like nature. The importance of this work of Pasteur can not be over- estimated, for it led him to continue the study of microor- ganisms until his death, in 1895. Pasteur's influence on the material side of human life has probably been greater than that of any other man. Aniline dyes. — The discovery of the bacteria by Leeu- wenhoek, and the recognition of their relation to decompo- sition by Pasteur, are two great landmarks in the history of bacteriology. Another was the accidental discovery of the aniline dyes by Perkin in 1856. The recognition of the bac- teria, as they occur in many places, especially in the fluids and tissues of the animal body, is impossible unless they can be difl'erentiated by stains from the other materials. The aniline dyes were first used for the staining of bacteria by Weigert in 1876. Another great advance in the progress of the science was the development by Robert Koch, a German physician, of a method of separating one kind of bacteria from other kinds with which it might occur. His work enables the DEVELOPMENT OF BACTERIOLOGY 11 activities of a single kind of organism to be studied, and its power for the good or ill of man determined. The de- velopment, in 1882, of the gelatine-plate method for the separation of kinds of bacteria, enabled Koch and his fol- lowers to prove the bacterial nature of the cause of many of the most important diseases of man and the lower animals. Scarcely a year has passed, since 1860, that has not been marked by discoveries of the greatest importance to human- ity in bacteriology and its related sciences. Bacteriology has revolutionized the life of civilized man. Without it our great cities would be impossible, for they could not be provisioned. It has doubled the average span of human life. It has made surgery possible. It touches the life of every one of us in a multitude of ways, each day, from birth to death. CHAPTER III THE MORPHOLOGY OF MICROORGANISMS The cell. — The unit of life is the cell, which consists of a limiting membrane inclosing semi-liquid contents. Within the cell are carried on all of the activities of the organism : herein the food is assimilated, by-products are formed, and energy is liberated for all of the vital processes. The higher plants and animals are constructed out of great numbers of these unit cells, which, however, are col- lected into groups that are so related to each other as to form tissues. These tissues are often so differentiated in their physiological activity that they may perform a limited and highly specialized function. With the simpler forms of life, such as the bacteria, all of the complicated chemical processes essential to the life of the organism take place within the limits of a single cell. Between the two ex- tremes there are to be found organisms in all degrees of complexity as to structure and function. The types that are of greatest importance in the decomposition of organic matter are either unicellular or the simpler multicellular forms. With the multicellular organisms, variation in structure of the individual is limitless; consequently, morphology, or the science that describes the variation in form, is of major importance. The simplicity of the one-celled plants, the bacteria, and the yeasts, makes a description of their mor- phology much less complex. The division of life into plants and animals, so advanta- geous in the study of the higher forms, is not especially help- 12 MORPHOLOGY OF BACTERIA 13 ful when the lower forms are under consideration. The or- g^anisms most important in decomposition processes are morpholog:icalIy more closel}' related to the plants than to the animals; physiologically, they are more directly allied to the animals. It is customary, however, to consider the bacteria, yeasts, and molds as members of the plant king- dom. Morphology of bacteria. — The bacteria may be defined as unicellular plants, devoid of chlorophyl, and reproduc- ing by division of the cell into two daughter cells. This mode of reproduction has given to them the name of schiz- omyceteSy or splitting fungi. The lower or the true bacteria occur in three form types : spheres, rods, and spirals. A spherical organism is termed a coccus (plural, cocci) ; a rod is designated as a bacillus (plural, hacilli) ; a spiral organism is called a spirillum Q Fig. 1. Forms of Bacteria A spherical organism is termed a coccus; a rod-shaped one a bacillus; a spiral cell is called a spirillum (plural, spirilla). The spheres can vary only in size; the rods may vary in the ratio of the two axes, being either long and slender, or short and plump. If the two axes are of almost equal length, the rod will approach a sphere in appearance. Confusion, therefore, may develop in such cases; as, for instance, in the lactic-acid organism, which is so short a rod as to be called a coccus type by some writ- ers. The ends of the rods may vary, being rounded or square cut, or even in a few instances concave. The spiral types may present all the variations of the rods, and may vary in the extent to which the cell is bei^t. The Qur- 14 AGRICULTURAL BACTERIOLOGY vature may be very slight, or it may be a true spiral. The rigidity of the bacterial cell is well illustrated in the spiral forms. It is evident that there may be a gradual gradation in form from the round- ed coccus type through to the spirilla. Frequently under the conditions of growth in the laboratory and less frequently in nature, cells of abliormal shapes are noted, known as in- volution forms. It is Fig. 2. Cocci A. spherical organism in which the cells occur in irregular shaped masses is called staphylococcus After Giinther. commonly believed that these cells are degenerate forms and are not capable of reproduction. The de- viation from normal cell type is probably occa- sioned by growth under unfavorable conditions. Reproduction. — The bac^terial cell divides into two daughter cells by an infolding of the protoplasm in the mid- dle of the cell until the protoplasm is completely divided. The cell wall is then formed, and fin- ally splits, forming the opposing ends of the new cells Fig. 3. Large Bacilli A rod-shaped organism in which the cells occur in chains is called a streptobacillus After Giinther. In the case of bacilli and MORPHOLOGY OF BACTERIA 15 Fig. 4. Small Bacilli After Giinther. spirilla, the division is always at right angles to the long axis. With the cocci, the plane of division may have any direction, since all axes are equal. Cell reproduction in the multicellular forms of life results in an in- crease in the size of the individual; in the uni- cellular forms it results in multiplication of the number off individuals. Immediately after cell division, the daughter cells are much smaller than the original mother cell at the time division began. They increase rapidly in size; to this process the term growth can be applied. Commonly one speaks of the growth of bacteria when repro- duction is referred to. The generation period^ in the case of bacteria, is the time required for a mature cell to divide and for the resulting cells to reach maturity. With many forms of bacteria it requires only a short time for the process of division to be completed; in some instances it Fig. 5. SjDirilla The organism causing Asiatic cholera, fre- quently called the comma bacillus After Giinther. 16 AGRICULTUKAL BACTERIOLOGY has been found to occur in twenty minutes. Such a rapid rate is attained only un- der the most favorable conditions of food and temperature. This cell division is termed vegetative repro- diwtio7i, in contrast to a second method that is found in a small number of the bacteria, viz., re- production by the for- mation of spares. In this process a portion of the protoplasm is con- densed in one part of the cell to form a small Fig. 6. Spirilla The organism causing recurrent fever. The cells show many turns instead of only a portion of a turn as in the cholera organism After Giinther. spherical or oval, highly refractile body, to which the term Fig. 7. Spores A portion of the content of the cell is condensed into a body which appears very bright under the microscope. On germination a rod similar to the one that produced the spore results endospore is applied. The production of the spore is fol- lowed by the death of the cell and its dissolution, so that the MORPHOLOGY OF BACTERIA 17 spore is ultimately set free. Spore formation is virtually limited to a few of the bacilli, and does not occur as Ion": as nutritive conditions admit of vegetative reproduction. It is stimulated by lack of food or by the acciunulatioli of by- products of cell activit3\ Unfavorable temperature condi- tions for growth tend to prevent the formation of spores. It is a specialized function of the organism, and, like most such functions, occurs within a narrower range of condi- tions than does reproduction. The diameter of the spore in some species is greater than that of the cell it.self, thus producing a distortion of the cell. In the case of B. tetani, the organism causing lock- jaw, the enlarged spore is at the end of the cell forming a drumstick, in which case it is called capitate. If the spore is centrally located, giv- ing to the cell a spin- dle-like appearance, it is called a Clostridium type. The spores are readily differentiated from the cell proper by their higher refractile power, which gives them the appearance of bright dots under the micro- scope. In stained preparations they still appear as bright, unstained spots in the stained ciells, since they do not t?jke the stain in the ordinary methods of treatment. The bacterial spores possess greater powers of resistance to various physical and chemical agents than any other form of life. They are especially resistant to heat. Some Fig. 8. Spores The unstained body to be noted in most ^ of the cells is a spore formed by the condensa- tion of a portion of the cell content After Giinther. 18 AGRICULTURAL BACTERIOLOGY spores will withstand the temperature of boiling water for sixteen hours. They have been found alive on dried her- barium specimens after ninety-two years, and in the au- thor's laboratory the spores of Bad. anthracis remained alive in water for seventeen years. They are also resistant to chemicals. They assume an important function in the preservation of food and in the prevention of diseases, since their destruction is often a matter of great difficulty. The spore, placed in a favorable environment, germinates and produces a cell similar to the one that formed the spore. Since a cell produces but a single spore, spore formation is. not a matter of growth, but of reproduction. The germination may result in the rupture of the spore at the end, and the young cell emerges with its long axis par- allel to that of the spore. In other types the cell may emerge at the side of the spore. In some instances the spore swells and the spore wall is absorbed in the cell substance. The tj^pe of spore germination may enable the differentia- tion of closely related morphological forms to be made. Cell aggregates. — The arrangement of the cells fre- quently makes possible the recognition of species among Fig. 9. Arrangement of Cocci Streptococci, Sarcinae, Staphylococci the higher plants and animals. Something of similar na- ture can be used in the study of bacteria. After cell divi- sion has occurred, the daughter cells may separate at once, or the cells may cohere for a time. If the cohering cells MORPHOLOGY OF BACTERIA 19 continue to reproduce may consist of a few cells or of many. If the orp:anism is a coc- cus, the term strepto- coccus (chain coccus) is applied: if a bacil- lus, streptohacUlus is used. In the case of the bacilli this is the only cell aorgregrate with rejrularity of form that can occur. It is probable that the cells in a chain are in- closed in a common sheath. Various other forms a chain of cells will result, which Fig. 10. A St Kptococcus One of the organisms concerned in the souring of milk After Orla Jensen. of aggregates are found among the cocci. If the plalies of division are always parallel and the cells cohere, a chain results, as noted above. If the tendency is for but two cells to cohere, the term diptococcus is used. If the planes of division have no definite direction, the progeny of a single cell will form an irregular cell mass. Such an organism is called a staphylococcus^ from its similarity to a bunch of grapes. Cocci may occur Fig. 11. liact. Anthracis Threads consisting of many cells charac terize this organism After Giinther. 20 AGRICULTURAL BACTERIOLOGY in bunches of fours. Such grouping is called a tetracoccus. Again, the successive planes of division may be in three dimensions of space, resulting in packets of cells, to which the name sarcina is applied. The spirilla exhibit the same cell grouping as do the ba- cilli, although, as a rule, it is less pronounced. Cell structure. — The bacterial cell wall is a relatively firm membrane, through which all food must pass by dif- fusion. Lining the cell wall is a layer of protoplasm, the ecto- plast, which has a se- lective action on sub- stances in solution in the cell sap, or in the liquid in which the cell occurs. Since the action of this cell structure determines what substances en- ter or leave the cell. Fig. 12. A Tetracoccus it is one of the most It will be noted that the cells tend to occur in imDOrtaut elements aggregates of four . After Orla-Jensen. of the CCll. If the cells are placed in a strong sugar or salt solution, the proto- plasm shrinks and the cell is said to be plasmolyzed, a con- dition in which growth is impossible. The nucleus of the cell of the higher plant and animal is a structure of the utmost importance, since it governs for the most part the physiological activities of the cell. It plays the most important role in cell division. Its impor- tance is such, in the cells of the higher forms, that it would seem impossible for any ceil to function without a nucleus. A definite nucleus is not found in the typical bacterial cell. MORPHOLOGY OF BACTERIA 21 From the relation of cells to stains, the conclusion has been drawn that the substance of the bacterial cell is essentially nuclear in character. Inclusions of various kinds are sometimes to be observed in the bacteria. These bodies, termed metachromatic granules, may react to the stains in such a way as to dif- ferentiate them from the rest of the cell contents. Granules of j?lycoo:en and of sulphur are found in some species, as are also droplets of oil. The outer layer of the cell wall is often of a gelatinous nature and more or less tliickened, form- m MTROCtn ANJ 0KIOC& or runuccN t-tCAPt | TOAiK TRLt NiTROGtN nXATON jfZZfe^: CXCRtMCNT SOLID UOWO BODY PUTREfACTlON AND DECAY AMMONiriCATKDN AMMONIA igM, DCNITRIFICATlON NITRiriCATlON -NITP1TC5 N,0. rNlTRATES N,0, ' I *l I I f — • — ■ — ■ — ' Fig. 28. The Cycle of Nitrogen After Wright. the practice of sowing a small quantity of alfalfa seed with all of their grain crops, even if the land is seeded down to red clover. In a few years this preliminary inoculation suf- fices to infect the soil sufficiently so that inoculation of the crop can be readily secured later. The matter of inoculation is especially important when a new legume is to be grown or when a legume is to be sown on a field on which it has not been grown for a number of years. The bacteria are able to grow in the soil itself. Experience has shown that they gradually decrease in num- ber, and after five or six years will be so diminished that inoculation is advisable if the legume is to be grown again. It has been shown that the composition of the plant is changed b}' the presence of the nodules in that the nitro- 132 AGRICULTURAL BACTERIOLOGY gen content of the aerial parts of the plants bearing nodules is higher than plants on which nodules are not present. The composition of non-legumes growing with legumes is also changed in the same manner. A few non-leguminous plants may bear nodules on the roots, and apparently have the same relation to free nitro- gen as do the legumes. The most important of these are the alders. The development of the nodules is very sparse, as a rule. The legume furnishes the cheapest way of preventing the rapid reduction of the nitrogen content of the soil. Where sandy lands are to be reclaimed and worn-out soils restored, the legume is to be considered a most important factor. The nitrogen thus added to the soil is estimated to cost only from one half to five cents a pound, as opposed to the usual commercial price which is from 25 to 30 cents. PART III THE RELATION OF MICROORGANISMS TO FOODS CHAPTER XIII THE CONTAMINATION OF FOODS The decomposition of organic matter is due to the action of microorganisms that utilize the various compounds as food, and leave, as a result of their life processes, more sim- ple substances, or hy -products. Since most of these changes affect the quality of foods that are used by man, or even the domestic animals, it is desirable to protect food supplies in general, so far as practicable, from the action of such microorganisms. Especially in the temperate zone is this question of food preservation of great importance, for the st'ason during which plant growth takes place is short, and vegetable matter must be stored for use during the colder period of the year. Under the complex conditions in which we now live, the question of protection of food during the process of distribution is likewise of great importance. While the action of most microorganisms in food sup- plies does not enhance the nutritive properties of foods, certain types are used to advantage in the preparation of some foods, as in the fermentation industries, in which the raw materials are transformed by the action of living or- ganisms. Some by-products are used as food, or they may be of service in the preparation of food, as is the case with carbon-dioxide, formed by the action of yeast on sugar, which serves as a leaven to ''raise" or lighten the dough in bread-making. Milk. — In the following pages the discussion is limited chiefly to milk and dairy products, as virtually all phases of the relation of microorganisms to foods are well illus- 135 136 AGRICULTURAL BACTERIOLOGY trated with milk and its products. There are special rea- sons why a detailed discussion of the action of microorgan- isms on this food product is desirable. Milk is one of the most important foods in the dietary of the American and European people. It forms about one sixth of the food of the population of this country, and for children a much greater proportion of their nutriment. One milch-cow is kept for each 4.5 persons. A large portion of the milk consumed is used as raw milk^ and hence its contamination with disease-producing bacteria is of great importance. Again, its preservation is a problem that is presented to the producer and to the consumer daily; for, in the pro- duction and handling of milk, it becomes seeded with great numbers of bacteria, which find in it a most favorable place for growth. The manufacture of butter and cheese was originally carried out on the farm. Their preparation has now been largely removed therefrom ; but the farmer is still the producer of the raw material, the quality of which de- termines the quality of the product. Factors governing decomposition. — In the decomposition of any substance the rapidity of the changes involved are determined by the number of organisms from foreign sources that are brought in contact with the material, and by the rapidity with which growth occurs, since decompo- sition processes can not occur without growth, no matter how great the initial contamination of the food. The ques- tion of food preservation, therefore, may be divided into two divisions : first, the contamination of the food ; second, the destruction of the microorganisms contained in the food or the inhibition of their growth. The first is especially important with liquid foods, such as milk, because the organisms can be uniformly incorpo- rated with the liquid, and their growth will not be limited to any one point, as in the case of solid foods. Again, when CONTAMINATION OF FOODS 137 once introduced, they can not be removed therefrom as from the surface of a solid. The source of contamination of foods in general is readily traced to contact with matter from the soil, water, or the contents of the alimentary tract of animal life. These ma- terials harbor the bacterial life that is the cause of the changes involved, and if foods can be kept from direct con- tact with such organic wastes, it is comparatively easy to prevent in large measure the decomposition changes that will otherwise occur. In the protection and care of food products, it is desirable to do only those things that are of real necessity and value, rather than to waste time and effort in carrying out a mode of procedure that is unneces- sarily refined. So much exaggeration is fre - It 08 «« O 0, 212 AGRICULTURAL BACTERIOLOGY milk with bacteria capable of fermenting the sugar, and with others that produce propionic acid and carbon-dioxide. The milk is heated to about 135° F. and the curd is removed from the whey in one mass, so as not to allow it to become cool, which checks the growth of Bad. Bulgaricum in the curd. At every step in the making of this and other kinds of cheese, the process is conducted in a manner that influences the growth of certain groups of organisms. Of course, these methods were primarily worked out entirely from the standpoint of experience; but more recently their relation to the action of certain bacterial groups has been more definitely traced. In the making of cheddar cheese the salt is added to the finely cut curd before it is placed in the press, but in the case of Swiss cheese the salt is applied to the surface of the cheese. The most marked characteristic of Swiss cheese is the presence of gas-holes, ranging from the size of a cherry to that of a walnut, which are scattered quite uniformly through the interior of the cheese. These so called eyes are formed by the fermentation of the lactates with the formation of propionic acid and carbon-dioxide, the latter causing the holes in the plastic curd, while the acid influ- ences the flavor of the cheese. These organisms can not grow in the presence of salt, and it is therefore essential that an opportunity first be given for their growth. Later the application of salt to the outside checks the development of these gas- forming organisms as the salt gi.*adually pene- trates the substance of the cheese. Mold-ripened cheese. — Roquefort, a French cheese made from sheep's milk, Gorgonzola, an Italian cheese, and Stil- ton cheese, made in England, are illustrations of hard, firm cheese that contain molds. Not only does the presence of these molds confer a peculiar flavor and appearance on the CHEESE 213 cheese, but undoubtedly the ripening or digestive changes are influenced by these types of organisms. With the Roquefort type a green-spored mold, quite similar to the ordinary bread mold, is grown on rye bread, which, after drying, is powdered and the powder sprinkled over the curd before it is placed in the press. In order that the mold may have the necessary supply of air for the matur- ing of the spores, the cheese is pierced with many small holes. The green color of the mold imparts to the cheese a marbled appearance, and the peculiar flavor is due, at least in part, to the same factor. In the other varieties mentioned, the mold is not added intentionally, reliance being placed on the contamination in the factory during the process of making. Soft cheese. — In the making of Camembert, a French cheese, the curd produced by rennet is not cut, but is placed in small molds to allow the whey to drain off. After re- moval from the press the cheeses are placed in a very moist room. The lactic fermentation goes on rapidly in the cheese, changing the curd to an acid mass that is favorable for the growth of molds. The characteristic mold of milk, O'idium lactis, and a white-spored mold, related to the mold that grows in Rociuefort cheese, are essential to the ripening and the development of the characteristic flavor. It is es- sential that a certain balance be maintained between the two types of molds, which can be accomplished only by regulation of the temperature and moisture conditions within certain limits. The inability of the maker to control these conditions makes the ripening a difficult problem, and a large portion of the cheese is of low value because of the non-development of the typical flavor. Brie, Limburger, and brick cheese are other varieties of soft cheese that are made and ripened in a manner similar to Camembert. 214 AGRICULTURAL BACTERIOLOGY The manufacture of cheese is an industry that is closely connected with the farm, and is an example of the value that microorganisms exert in the preparation of a valuable food product. It indicates how valuable the products of decomposition may be in imparting a desirable flavor to what would otherwise be a tasteless product. CHAPTER XVIII THE BACTERIOLOGICAL CONTROL OF FOODS The various American governmental units, national, State, and municipal, are all expendinjj: much effort in at- tempting to control the quality of food supplies. While national activity is confined to foods embraced in interstate commerce, and in the main is concerned with those that are preserved, yet the interstate control of fresh meats is a large factor in governmental enterprise. As far as mu- nicipal control is concerned, the re2:ulatory service includes in the main only fresh food products, and of these milk is of the most importance. With the recognition of the fact that milk is the chief food product in its relation to health, especially of children, much more attention has been given of late years to the formulation of sanitary rules than ever before. Even small cities and towns are now dealing in a direct way with dairymen, so that by far the larger part of milk supplies used for direct consumption now comes under some kind of supervision. In order to have the milk reach the consumer in the city in an unchanged condition, the greatest care must be ob- served by all who handle it. The regulations that a mod- ern city imposes on the milk dealer and on the producer are complex and cover every phase of its production and handling that can in any way affect the value of the milk as human food. A city can enforce its regulations by re- fusing to allow the sale of milk that has not been produced in conformity therewith. In order to determine whether the regulations are observed, two types of inspection are 215 216 AGRICULTURAL BACTERIOLOGY maintained: first, the examination of the milk in the city as to the number and kind of bacteria it contains ; and, sec- ond, an inspection of the dairy farms as to the methods there used and to the health of the animals. A summary of the rules imposed by the city of New York follows. It will be noted that the rules are intended to force the pro- duction of a clean and healthful milk. THE cows 1. The cows must be kept clean, and manure must not be permitted to collect upon the tail, sides, udder, or belly of any milch-cow. 2. The cows should be groomed daily, and all collections of manure, mud, or other filth must not be allowed to re- main upon their flanks, udders, or bellies during milking. 3. The clipping of long hairs from the udder and flanks of the cows is of assistance in preventing the collection of filth which may drop into the milk. The hair on the tails should be cut, so that the brush will be well above the ground. 4. The udders and teats of the cow should be thoroughly cleaned before milking ; this to be done by thorough brush- ing and the use of a cloth and warm water. 5. To prevent the cows from lying down and getting dirty between cleaning and milking, a throat-latch of rope or chain should be fastened across the stanchions under the cow 's neck. 6. Only feed that is of good quality, and only grain and coarse fodders that are free from dirt and mold, should be used. Distillery waste or any substance in a state of fermentation or putrefaction must not be fed. 7. Cows that are not in good flesh and condition should be immediately removed and their milk kept separate until their health has been passed upon by a veterinarian. CONTROL OF FOODS 217 8. An examination by a veterinary surgeon should be made at least once a year. THE STABLE 9. No stagnant water, hog-pen, privy, or uncovered cess- pool or manure pit should be maintained within one hun- dred feet of the cow stable. 10. The cow stable should be provided with some ade- quate means of ventilation, either by the construction of sufficient air-chutes extending from the room in which the cows are kept to the outside air, or by the installation of muslin stretched over the window openings. 11. Windows should be installed in the cow barn to pro- vide sufficient light (2 square feet of window light to each 600 cubic feet of air space the minimum) and the window- panes be washed and kept clean. 12. There should be at least 600 cubic feet of air space for each cow. 13. Milch-cows should be kept in a place that is used for no other purpose. 14. Stable floors should be made water-tight, be properly graded and well drained, and be of some non-absorbent ma- terial. Cement or brick floors are the best, as they can be more easily kept clean than those of wood or earth. 15. The feeding-troughs and platforms should be well lighted and kept clean at all times. 16. The ceiling should be thoroughly swept down and kept free from hanging straw, dirt, and co])webs. 17. The ceiling must be so constructed that dust and dirt therefrom shall not readily fall to the floor or into the milk. If the space over the cows is used for the storage of hay, the ceiling should be made tight to prevent chaff and dust from falling through. 18. The walls and ledges should be thoroughly swept 218 AGRICULTURAL BACTERIOLOGY down and kept free from dust, dirt, manure, or cobwebs, and the floors and premises be kept free from dirt, rubbish, and decaying animal or vegetable matter at all times. 19. The cow beds should be so graded and kept that they will be clean and sanitary at all times. 20. Stables should be whitewashed at least twice a year, unless the walls are painted or are of smooth cement. 21. Manure must be removed from the stalls and gutters at least twice daily. This must not be done during milk- ing, nor within one hour prior thereto. 22. Mianure should be taken from the barn, preferably drawn to the field. When the weather is such that this can not be done, it should be stored not nearer than 200 feet from the stable, and the manure pile should be so located that the cows can not get at it. 23. The liquid matter should be absorbed and removed daily, and at no time be allowed to overflow or saturate the ground under or around the cow barn. 24. Manure gutters should be from six to eight inches deep, and constructed of concrete, stone, or some non- absorbent material. 25. The use of land plaster or lime is recommended upon the floors and gutters. 26. Only bedding that is clean, dry, and absorbent should be used, preferably sawdust, shavings, dried leaves, or straw. No horse manure should be used as bedding. 27. The flooring where the cows stand should be so con- structed that all manure will drop into the gutter and not upon the floor itself. 28. The floor should be swept daily. This must not be done within one hour prior to milking-time. 29. If individual drinking basins are used for the cows, they should be frequently drained and cleaned. e30. All live stock other than cows should be excluded CONTROL OF FOODS 219 from the room in which the milch-cows are kept. (Calf or bull pens may be allowed in the same room if kept in the same clean and sanitary manner as the cow beds.) 31. The barnyard should be well drained and dry, and should be sheltered as much as possible from the wind and cold. Manure should not be allowed to collect therein. 32. A suitable place in some separate building should be provided for the use of the cows when sick, and separate quarters must be provided for the cows when calving. 33. There should be no direct opening from any silo or grain pit into the room in which the milch-cows are kept. THE MILK-HOUSE 34. A milk-house miist be provided which is separated from the stable and dwelling. It should be located on ele- vated ground, with no hog-pen, privy, or manure pile within 100 feet. 35. It must be kept clean, and not used for any purpose except the handling of milk. 36. The milk-house should be provided with sufficient light and ventilation, with floors properly graded and made water-tight. 37. It should be provided with adjustable sashes to fur- nish sufficient light, and some proper method of ventilation should be installed. 38. The milk-house should be provided with an ample supply of clean water for cooling the milk, and if it is not a running supply, the water should be changed twice daily. Also a supply of clean ice should be provided to be used for cooling the milk to 50° F. within two hours after milking. 39. Suitable means should be provided within the milk- house to expose the milk-pails, cans, and utensils to the sun or to live steam. 40. Facilities consisting of wash-basins, soap, and towel 220 AGRICULTURAL BACTERIOLOGY should be provided for the use of milkers before and during milking. In the summer months the milk-house should be properly screened to exclude flies, THE MILKERS AND MILKING 41. Any person having any communicable or infectious disease, or one caring for persons having such disease, must not be allowed to handle the milk or milk utensils. 42. The hands of the milkers must be thoroughly washed with soap and water, and carefully dried on a clean towel, before milking. 43. Clean overalls and jumpers should be worn during the milking of the cows. They should be used for no other purpose, and when not in use should be kept in a clean place protected from dust. 44. The milker's hands and the teats of the cow should be kept dry during milking. The practice of moistening the hands with milk is to be condemned. 45. The milking-stools should be at all times kept clean. Iron stools are recommended. 46. The first streams from each teat should be rejected, as this foremilk contains more bacteria than the rest of the milk. 47. All milk drawn from the cows fifteen days before or five days after parturition should be rejected. 48. The pails in which the milk is drawn should have as small an opening at the top as can be used in milking, the top opening preferably not to exceed eight inches in diame- ter. This lessens the contamination by dust and dirt dur- ing milking. 49. The milking should be done rapidly and quietly, and the cows should be treated kindly. 50. Dry fodder should not be fed to the cows during or CONTROL OF FOODS 221 just before milking, as dust therefrom may fall into the milk. 51. All milk utensils, including pails, cans, strainers, and dippers, must be kept thoroughly clean, and must be washed and scalded after each using ; and all seams in these utensils should be cleaned, scraped, and soldered flush. THE MILK 52. Milk from diseased cows must not be shipped. 53. The milk must not be in any way adulterated. 54. The milk as soon as drawn should be removed to the milk-house and immediately strained and cooled to the proper temperature. 55. All milk must be cooled to a temperature below 50° F. within two hours after being drawn, and kept thereafter below that until delivered to the creamery. 56. The milk should be strained into cans that are stand- ing in ice water which reaches the neck of the can. The more rapidly the milk is cooled, the safer it is and the longer it will keep sweet. Ice should be used in cooling milk, as very few springs are cold enough for the purpose. 57. If separators are used, they should stand where the air is free from dust or odors, and on no account should they be used in the stable or out of doors. 58. Milk-strainers should be kept clean, scalded a second time just before using, and if cloth strainers are used, sev- eral of them should be provided, in order that they may be chaiged frequently during the straining of the milk. 59. The use of any preservative or coloring matter is adulteration, and its use by a producer or shipper will be a sufficient cause for the exclusion of his product from the city of New York. 222 AGRICULTURAL BACTERIOLOGY WATER SUPPLY 60. The water supply used in the dairy and for washing utensils should be absolutely free from any contamination, sufficiently abundant for all purposes, and easy of access. 61. This supply should be protected against flood or sur- face drainage. 62. The privy should be located not nearer than 100 feet of the source of the water supply, or else be provided with a water-tight box that can be readily removed and cleaned, and so constructed that at no time will the contents over- flow or saturate the surrounding ground. 63. The source of the water supply should be rendered safe against contamination by having no stable, barnyard, pile of manure, or other source of contamination located within 200 feet of it. In order that the farm inspection will be as effective as possible, and to make the work of the several inspectors as uniform as may be, the dairies are scored. A copy of the score-card follows. DEPARTMENT OF HEALTH The City of New York Division of General Sanitary Inspecton Dairy Report Inspection No Time A. P. M. Date 192. . 1 Dairyman Owner 2 P. 0. Address P. 0. Address. .. State. 3 County State Party Interviewed 4 Milk delivered to Creamery at Formerly at 5 Operated by Address 6 Distance of farm from Creamery Occupied farm since. . . . 7 No. Cows No. Milking No. Qts. Produced 8 All persons in the households of those engaged in producing or handling milk are free from all infectious disease. Weekly reports are being filed 9 Date and nature of last case on farm 10 WATER SUPPLY for utensils is from a located CONTROL OF FOODS 223 feet deep and apparently is pure and wholesome State any possible contamination lo- cated within 200 feet of source of water supply or if water sup- ply is not protected against surface drainage .192.. Result .ft. Width ft. 11 Water supply on this farm analyzed. 12 Style of Cow Barn Length... TltML'lit of ceiling ft. 13 Dairy Rules of the Department of Health are posted Dairy Herd examined by on Report 192. EQUIPMENT Perfect Allow 15 COW STABLE is located on elevated ground with no stagnant water, hog-pen, privy, uncovered cesspool, or manure pit within 100 feet 16 FLOORS, other than cow beds, are of concrete or some non-absorbent material. . . 17 Floors are properly graded and water- tight 18 Cow beds are of concrete or planks laid on concrete 19 DROPS are. . . .constructed of concrete, stone, or some non-absorbent material . . . .* 20 Drops are water-tight and space beneath is clean and dry 21 CEILING is constructed of and is tight and dust-proof 22 WINDOWS No total square feet there is 2 square feet of window light for ea(h 600 cu. ft. air space (1 sq. ft. per each 000 cu. ft — 1 ) 23 VENTILATION consists of sq. ft. muslin covered openings or sq. ft. open chutes in ceiling or which is sufficient 3, fair 2, poor 1, insufficient 0 24 AIR SPACE is cu. ft. per cow (600 and over— 3) (500 to 600—2) (400 to 500—1) (under 400—0) 25 LIVE STOCK, other than cows, are ex- 224 AGRICULTURAL BACTERIOLOGY Perfect All 26 27 28 29 30 31 32 33 34 35 36 38 "EOLUlVMEliT— Continued eluded from rooms in which milch-cows are kept There is direct opening from stable into silo or grain pit Separate quarters are provided for cows when calving or sick COW-YARD is properly graded and drained WATER SUPPLY for cows is unpol- luted and plentiful MILK-HOUSE has direct opening into cow-barn or other building Milk-house has sufficient light and ventila- tion Floor is properly graded and water- tight Milk-house is properly screened to ex- clude flies MILK PAILS are of smoothly tinned metal in good repair Milk-pails have all seams soldered flush Milk-pails are of the small-mouthed design, top opening not exceeding 8 inches in diameter. Diameter Racks are provided to hold milk-pails and cans when not in use Special milking suits are provided 40 METHODS 39 STABLE INTERIOR painted or whitewashed on which is satisfactory 3, fair 2, unsatisfactory 1, never 0 40 FEEDING-TROUGHS, platforms, or cribs are well lighted and clean 41 Ceiling is free from hanging straw, dirt, or cobwebs 42 Window-panes are washed and kept clean CONTROL OF FOODS 225 Perfect Allow 43 44 45 40 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 METHODS — Continued WALLS AND LEDGES are free from (lilt, (lust, inamirc, or coliwebs FLOORS AND PREMISES are free from dirt, rubbish or decayed animal or vegetable matter COW BEDS are clean, dry, and no horse manure^ used thereon Manure is removed to field daily 4, to at least 100 feet from l)arn 2, stored less than 100 feet or where cows can get at it 0. , Liquid Matter is allowed to saturate j^round under or around cow-barn Milking-stools are clean Cow-yard is clean and free from manure COWS have been tuberculin tested and all tuberculous cows removee prescribed by the local health authorities. 'J'lic caps or tags allixed to the containers must be white and con- tain the term "(irade C pasteuri/ed" in large red type. It is to be noted that the grades of milk are based on the bacterial content of the milk and on the opportunity for the milk to become contaminated with pathogenic organ- isms. From the statements made in a previous chapter, it is evident that the number of bacteria in any sample of milk is dependent upon the original amount of contamina-. tion and the extent to which the introduced bacteria have grown. The latter is dependent on the age of the milk and the temperature at which it has been held. A high bac- terial content is indicative of poor milk, while a low bac- terial content can be obtained, in the case of raw milk, only where due attention is paid to cleanliness and cooling. This relation between the quality of milk and its bacterial content has led many cities to adopt numerical bacterial standards, even when grades of milk have not been estab- lished. Boston requires that the milk shall not contaifi more than 500,000 bacteria per cubic centimeter; Rochester, New York, has a standard of 100,000 per cubic centimeter; 232 ACailCULTURAL BACTERIOLOGY while Chicao^o requires that the milk on arrival in the city shall contain not more than 1,00(),()00 per cubic centimeter from ^lay first to September thirtieth, and not more than 500,000 between October 1 and April 30. The sale of milk containing more than 3,000,000 bacteria per cubic centi- meter is prohibited. It has been urged that bacterial standards are not of value since the healthfulness of milk depends on the kind of bacteria present rather than on the number. It is well recognized that milk containing millions of acid-forming organisms, buttermilk, is a healthful food, while that con- taining many less fcacteria may harbor some disease-produc- ing organisms. It has been urged that a ([ualitative stand- ard should supplant the quantitative. The consumer de- sires milk that has been produced under clean conditions and which has good keeping qualities. The harmless forms of bacteria exert the greatest influence on the keeping qual- ity. Experience has shown that the quantitative examina- tion of the milk supply as it comes from the farm is the most feasible method of determining, in the laboratory, whether the farmer has obeyed the rules with reference to cleanliness and cooling of the milk. The bacteriological ex- amination also gives an indication as to whether the large number of bacteria is due to gross contamination of the milk with mud and manure, or actual growth of bacteria, as in old milk. In the latter case the ordinary acid-forming bacteria will usually predominate in the milk, while in the former the number of kinds of bacteria and the proportion between the kinds will be changed. It is, of course, evi- dent that the quantitative standards should be applied with judgment. It is also claimed that the delay in securing the results in the quantitative examination of milk is an objection to the bacterial standard, since the milk is consumed before CONTROL OF FOODS 233 the laboratory findings can he obtained. It is true that it does not protect the community as far as the particular sam- ple is concerned, but it is also true that the examination is not made for the purpose of determining the condition of the particular sample, but rather to determine the methods that are employed on any particular farm. These do not vary widely from day to day. Thus if the bacterial con- tent of a number of samples from a particular source is uni- formly hijrh, it is evident that conditions surrounding pro- duction need investigation. If the milk is well cooled on the farm, and kept cold while being shipped, the growth of bacteria will be slow, and the condition of the milk, as far as keeping quality is con- cerned, much better than if less care is used. Some cities have temperature standards; New York requires that the milk shall be cooled to 50° F. on the farm, and shall not be above 50° F. on arrival in the city. Others require that it shall not be above 50° F. on delivery to the consumer. Certified milk. — In many cities the medical societies have appointed milk commissions, which adopt rules and regula- tions concerning the production of milk that shall receive the certificate of the commission. Producers who desire to have their milk thus certified must satisfy the commission that they are able to conform to the rules. The commission appoints a physician to examine the personnel of Ijie farm, a veterinarian to make frequent examinations of the herd, a chemist to examine the milk as to its content in fat and other solids, and a bacteriologist to determine the bacterial content of the milk. The rules are very stringent, and cover every point that may in any way influence the value of the milk as human food. In order to conform to these requirements, a heavy expenditure must be incurred, and the business must pay for such expert service — hence certi- fied milk must be sold at high prices. This price makes it 234 AGRICULTURAL BACTERIOLOGY a special product, and its use is confined mainly to infant feeding. The bacterial standard for certified milk is usually 10,000 bacteria per cubic centimeter. It is only by the exercise of the greatest care at every point that the bacterial content can be kept below this maximum. The term ''certified milk" has been registered by Mr. Francisco of New Jersey, who was the first to engage in the production of such milk under the direction of the IVfedical Milk Commission of Essex County, New Jersey. The use of the term is allowed when the milk is produced under the regulation of any medical milk commission. Most certified milk is now produced on fancy dairy farms conducted by wealthy men. The barns and other equip- ment are the best that can be obtained, and the methods employed, as far as cleanliness is concerned, are extreme. In some of the dairies the bacterial content is reduced to a few hundred per cubic centimeter, or to that which is de- rived from the interior of the udder. Such milk will, when well refrigerated, keep for long periods of time. It is a not uncommon thing for such milk to keep perfectly sweet for from ten to fifteen days. Pasteurization of market milk. — Milk may become con- taminated with pathogenic bacteria from a multitude of sources, none of which can be guarded against perfectly. It is estimated that at least one person in each thousand is a ''typhoid carrier." It is impossible to detect which in- dividuals are a menace to their fellow men in this respect. Even when a typhoid carrier is detected, it is difficult to control his movements so that he will not present a danger to those with whom he may be, directly or indirectly, as- sociated. The larger cities have realized the impossibility of using the tuberculin test as a means of protection against bovine CONTROL OF FOODS 235 tuberculosis. The magnitude of the task of testing all of the milch-cows each year, the expense connected therewith, and the imperfection of the protection have led to the abandonment of the demand for the tuberculin testing of all cattle. The presence of dangerous cases of udder inflam- mation may never be recognized until the epidemic of septic sore throat is well under way. Under the most ideal system of inspection, the safety of large supplies of milk can not be assured. The pasteur- ization of the milk offers an effective solution of this prob- lem of healthfulness of market milk. The process is almost a necessity under modern conditions as a preservative meas- ure. Without it the provisioning of our great cities would be most difficult, and in some cases impossible. For all of these reasons the introduction of the pasteurization process has been rapid, until more than 90 per cent, of the milk sold in large cities is now pasteurized. As previously mentioned, heating causes certain changes in milk. In the treatment of market milk it is desirable to use as low temperatures as will suffice to destroy the disease-producing bacteria. It is fortunate that tempera- tures that will insure this result have little effect on the milk. The State of New York requires that the milk shall be subjected to a temperature of from 142° to 145° F. for not less than thirty minutes, and immediately cooled. The acid-forming bacteria are not completely destroyed, and the pasteurized milk as a rule will undergo the same type of fermentation as raw milk. It is, however, deemed essen- tial that all pasteurized milk be sold as such; that it be delivered to the consumer within twenty-four hours after pasteurization ; and that no milk be pasteurized a second time. The continuous pasteurizing machines have the disadvan- tage that a small portion of the milk passes through so 236 AGRICULTURAL BACTERIOLOGY quickly that all pathogenic bacteria therein might not be destroyed (p. 181). This has led to the use of the "hold- ing" process, in which the milk is heated to the desired temperature and then placed in tanks, where it remains at this temperature for any desired time. Every portion is thus treated in a uniform manner. If the milk is bottled after pasteurization, there remains opportunity for reinfection, possibly with typhoid bacilli. Pasteurization in the final container, the bottle, is being recommended. This is possible only when a special bottle is used, having a metal cap lined with paper, or some other special appliance. PART IV TRANSMISSIBLE DISEASES CHAPTER XIX THE RELATION OF MICROORGANISMS TO DISEASES OF ANIMALS Communicable diseases. — The diseases of animals may be divided into two classes: the organic or constitutional, which are due to the faulty operation of some organ; and the communicable, which are caused by the invasion of the body by some organism and the growth thereof with the formation of substances that have a harmful action on the body. The latter are termed communicable diseases, be- cause the passage of the causal organism from the diseased to the healthy animal is sufficient to spread the trouble. The organic diseases can not be thus transmitted, for they are not due to the presence of a living organism in the body. The communicable diseases are also termed infec- tious, contagious, and preventable, since the prevention of their spread can be accomplished by stopping the trans- mission of the organism. In some instances the knowledge of the manner of transmission is so complete that if stock- men could be induced to put that knowledge into practice the diseases would soon disappear, while in other cases the information is not yet sufficiently complete to enable their spread to be prevented. Such transmissible diseases as tuberculosis, contagious abortion, hog cholera, Texas fever, and glanders entail an enormous tax on the livestock industry of the world, as will appear in the discussion of the specific diseases. Since the prevention of disease is a problem that must always rest in the hands of the farmer himself, rather than in any 239 240 AGRICULTURAL BACTERIOLOGY professional aid he may employ, it is desirable that every stockman be acquainted with the salient facts concerning the more important of the transmissible diseases of domestic animals, just as everyone should know something of the im- portant transmissible diseases of man, so that he may intel- lig-ently protect himself from them. Infection. — In order to produce disease the organism must invade the body, must grow therein, and its by-pro- ducts must exert an injurious effect on the body tissues. This sequence of events is known as infection. The severity of the attack of any communicable disease may vary from one animal to another, owing to the difference in resistance of the host and to a difference in the virulence of the or- ganism, which may be defined as the power of the organism to multiply within the body and produce disease. Little is known of the conditions that increase or diminish the virulence of organisms in nature. The resistance of the host may be impaired by any condition that tends to weaken the bod}^, such as fatigue, exposure to cold, heat, or damp- ness, improper diet, thirst, age, wounds, and other dis- eases. Neither the invading organism nor the host are to be considered as passive agents. The relation between them is a true struggle, a fight to the finish. In the strug- gle the host seeks to overcome the parasite by means that will be discussed later, and the organism protects itself in the progress of its growth and development. In so doing the perpetuation of the species is accomplished. The portals of entry into the body are the broken skin, or an injured mucoias membrane, the alimentary tract, the respiratory tract, the genital tract, and the conjunctiva, or the mucous membrane of the eye. Many organisms have specific, definite methods by which they enter the body of the host; for example, the hog cholera organism enters by way of the alimentary tract, while the tubercle bacillus INFECTION 241 enters in a variety of ways, as through wounds, by inhala- tion, or by ingestion. The tetanus or lockjaw bacillus is always introduced through wounds of the skin or of the mucous membrane. The original or initial infection is called the primary in- fection, and may be followed by a second invasion with another kind of organism which may have been present in the body, but which was unable to multiply until the re- sistance was first lowered by the primary infection. Infec- tion is usually due to a single specific organism, but some troubles are due to a mixed infection with two or more or- ganisms. When the body has been weakened by organic diseases, it is sometimes more susceptible to invasion by certain disease-producing organisms, or the results of such invasion are more likely to be serious. The original trouble might have resulted in death, but the end is hastened by the terminal infection, as it is called. The invading organisms injure the tissues by the pro- duction of poisonous substances known as toxins. In some cases the organisms grow in a limited area, and do not cause any great destruction of the tissue at the point of growth ; but the toxin is so active that a minute quantity is suffi- cient to cause death. Such a disease is known as toxemia, in contradistinction to the hacteremia or septic(Bmia, in which the entire bod}^ is invaded by the organism, as in the ease of anthrax. Examples of toxemias are lockjaw and diphtheria. In still other instances the invasive powers of the organisms are not great, but the tissue is destroyed at the point of growth, as in the case of the pus-producing organisms. It is evident that the symptoms of any disease can not appear until the organism has had time to multiply and to form sufficient toxin to have a visible effect on the body of the animal. This period which may vary from a few 242 AGRICULTURAL BACTERIOLOGY days to several months is called the period of incubation of the disease. The changes in the various tissues due to the action of the organism are called the lesions of the dis- ease. With some diseases they are very characteristic, in others not. The external defenses of the body. — There are many means by which nature has sought to protect the body against the invasion of microorganisms. The surface of the body is covered by the skin, and all of the cavities of the body that are in contact with the exterior are provided with a mucous membrane. The bacteria normally gain entrance with but few exceptions through these protective mem- branes, only as they are injured. The mucous membranes are always bathed with the products of glandular activity, which possess a more or less marked germicidal or antiseptic action. By reason of this many of the organisms that come in contact with these fluids are thus destroyed. Wounds in the mouth and in the intestine must of necessity frequently occur, especially with animals that feed on coarse, dry fodder. Yet a harmful effect from such a source is rarely noted. The lungs and air passages are constantly exposed to dust laden with adherent bacteria. These foreign bodies are removed by the action of the cilia of the cells lining the air-passages. The hairlike appendages are constantly in motion and tend to move any foreign particle outward. The internal defenses. — After the microorganisms have invaded the tissues, their development can not go on un- hampered, for the body has a number of internal defenses that must be overcome before growth and disease produc- tion can occur. An animal is said to be immune to a dis- ease when it resists the development of the organism, or is not injured by the poison that the organism produces. Various explanations have been offered to explain the im- munity of animals. The white blood corpuscles possess IMMUNITY 243 amoeboid properties, and are able to ingest solid bodies like the bacteria and digrest them. This process is known as phagoc3'tosis, and such devouring cells are called phag- ocytes. Whenever any portion of the body is invaded by a foreign agent, or when any abnormal condition arises, the phagocytes are attracted to this point as a result of a chem- ical stimulus. This causes them to accumulate at or near the point of invasion, where they soon engulf and destroy many of the invading organisms. If these white blood cor- puscles are able to overcome the harmful bacteria, the ini- tial infection may .be rendered of no importance. Again, the organism may multiply and form poisonous products which may injure the body to the extent that death is caused, or, under the stimulus of these harmful products, the body cells may react and form substances that neutralize or nullify in some way the poisonous effects of the pt*oducts of the organism. These antagonistic and protective pro- ducts are diffused through the liquids of the body, especially in the blood serum and form the. basis of the anti-serums that are used for protective purposes. Immunity. — A specific disease may occur only in a single host species, as in hog cholera, or it may be capable of spreading throughout a variety of different animals. Black- leg affects only cattle and sheep, while the anthrax bacil- lus produces a characteristic disease in man as well as in many of the lower animals. Numerous diseases affecting man, such as typhoid fever, diphtheria, yellow fever, and cholera, are limited to this host alone. Other warm-blooded animals are naturally insusceptible to these maladies; they possess a natural immunity. The term natural immunity is applied to that condition which enables an animal to resist the natural invasion by organisms that attack other varieties or species of animals. It is a condition that is present at birth, continues through- 244 AGRICULTURAL BACTERIOLOGY out life, and is transmitted to the offspring. A striking example of natural immunity is that of Algerian sheep to anthrax, while other varieties are very susceptible to this disease. Immunity to a disease may be established in the indi- vidual after birth. It is then called acquired immunity. The lessened susceptibility to certain diseases with increas- ing age is an example, as is noted in measles, chickenpox, and whooping-cough in human beings, and with blackleg in cattle. The immunity that is conferred by resisting successfully an attack of infectious disease is another example. In- stances of this type of acquired immunity are noted in smallpox and yellow fever in man, in Texas fever in cattle, and in cholera in hogs. The period of persistence of the acquired immunity is variable, sometimes extending through the remainder of the life of the individual, or again persist- ing but a short time. A successful recovery from some diseases does not seem to convey any immunity against second attack. Acquired immunity may also be produced artificially in a number of wa^^s which may be summarized as follows : By inoculating the individual with such a small number of organisms that a fatal attack of the disease will not result. This method is used in the case of Texas fever. By inoculating with an attenuated or weakened organism. This is practiced in anthrax, blackleg, rabies, and bubonic plague in man. By inoculating with an organism that has been modified by passage through another species of animal. This method is illustrated by vaccine for smallpox. By the injection of toxins. This is used in the immuni- zation of animals against the virus of a disease for the pur- IMMUNITY 245 pose of securing antitoxins from their blood, as in the prep- aration of diphtlieria antitoxin. By the injection of antitoxins. These are used to pro- tect against toxins and natural infection, as in the case of diphtheria. By the injection of blood serum from immune or hyper- immune animals for preventive purposes. The serum used in the case of hr>i: cholfTci is an example. Active and Passive Immunity. — If the organism of the disease is concerned directly in the process of bringing about the production of the anti-bodies, the immunity is termed active. An immunity that is due to recovery from a natural attack is active, as is that produced by injecting the organism or its toxins into the body. Active immunity is slow in its development, is somewhat dangerous, and is always attended with some discomfort to the person or ani- mal in which it is produced. It persists, as a rule, for a considerable period, varying from a few weeks to several years. If the blood serum of an animal that has an active im- munity to a disease is injected into an animal that is sus- ceptible to the disease, an immunity is produced which is called passive immunity. It involves no activity of the tissues of the immunized animal. The passively immunized animal is simply the recipient of substances formed in the bodies of other animals and transferred to it. Passive im- munity is rapidly produced, and is attended with little danger and discomfort. The period of protection is meas- ured by a few days or weeks. The most extensive use of passive immunity is in hog cholera, tetanus, and diphtheria. It is a well known fact that some outbreaks of a disease are very severe in that many of the infected die, while in another outbreak of the same disease practically all of the 246 AGRICULTURAL BACTERIOLOGY infected individuals recover. This can not be explained by the greater resistance of the second group over the first, but rather the explanation is to be sought in the diminished virulence of the organism. As has been stated, the causes that induce such changes in nature are not known. The first effort to impart immunity by artificial means was by the intentional inoculation of individuals with ma- terial taken from mild cases of smallpox. The mild attack thus induced afforded protection to the individual against the more severe form of the disease. Later it was noted by Jenner, an English surgeon, that those individuals that had acquired cowpox by milking a cow suffering from this trouble were thereby protected against smallpox. Follow- ing this observation, the inoculation of human virus against smallpox was superseded by vaccination with material taken from the pustules of the animal disease, cowpox, or vaccinia, as it is called. It is now known that the organism causing cowpox is a modified form of the smallpox virus. In some manner its residence in the body of cattle has so changed its properties that it is no longer able to produce a dangerous form of the disease in man, but it is able to stimulate the tissues to manufacture sufficient anti-bodies to protect the body for a number of years against a natural attack. The vaccine used for inoculation contains the virus of smallpox, the na- ture of which is unknown. All vaccines that are used as a protective measure against any contagious disease contain the virus of the disease against which protection is sought. The virus may be viru- lent ; it may be attenuated or weakened ; or it may be dead. The degree of protection afforded by the vaccination pro- cess will depend on the extent to which the organism has been attenuated. Thus the protection afforded by ''killed" organisms is not so great as when the weakened organisms IMMUNITY 247 are used. In the case of human vaccination, "killed" cul- tures are usually employed, because of the possibility that the virulence of the weakened org:anism may accidentally be regained. The organisms are killed in such a way as to de- stroy their reproductive power, but not to change them chemically to such an extent that when introduced into the body they will not stimulate the cells to the production of the anti-bodies. The manner in which the different vac- cines are made will be discussed in the treatment of the specific diseases. Vaccines are used not only to prevent but also to cure disease. In the production of passive immunity the anti-bodies are transferred from the body of the animal in which they have been actively formed to the animal to be protected. This transfer is accomplished by withdrawing a portion of the blood from the immune animal and injecting it into the animal that it is sought to protect. Since the blood serum is used, the term protective serum or anti-serum is often used. In many instances the anti-serum contains I)rimarily a substance that neutralizes the toxin. The term antitoxin is therefore often used. The blood of a hog that has recovered from hog cholera will contain sufficient anti-bodies to protect the individual against a subsefjuent attack, but not a sufficient amount so that the ])lood would bestow any marked degree of protec- tion on another animal when inoculated with an amount that would be practicable to use. In order to make the method of practical value, the immune animal is forced to manufacture a larger amount of the anti-bodies than would normally be produced. An animal so treated is said to be hyper-immiinized. In preparing hog-cholera serum, this is accomplished by injecting into the body of the immune hog a large quantity of blood from a hog that is already sick with hog cholera. The specific organism causing hog 248 AGRICULTURAL BACTERIOLOGY cholera is yet unknown, although it can be transferred by the use of blood from a sick hog. The introduction of a large quantity of the virus into the body of the immune hog causes the formation of an increased amount of the protective bodies. The immunizing process is thus repeated until the blood contains such a quantity of protective sub- stances that, when transferred in practicable amounts, it imparts a considerable degree of immunity. The disease virus is obtained from a sick hog by bleeding from the throat. This virulent blood is usually introduced into the blood vessels of the animal to be hyper-immunized, which, when its blood is sufficiently high in the protective bodies, is bled for the anti-serum by cutting off a piece of the tail. The animal can be bled several times in this way, a fresh cut being made each time until this appendage is too short for further use. The final bleeding is then made from the throat. In the preparation of diphtheria antitoxin the horse is used to produce the anti-bodies. The animal is not suscep- tible to diphtheria; hence, the organisms themselves can not be employed to stimulate the production of anti-bodies. The horse is, however, susceptible to the toxin of the diph- theria organism. The organism is grown in the laboratory in beef broth, which is tittered through porcelain to remove all the bacteria, and gradually increasing doses of this fil- trate are then injected into the body of the horse. At first only very small doses can be administered without killing the animal; but after recovery from the first injec- tion, repeated doses of increasing amounts are applied, the effect of which is to produce the protective anti-bodies in the blood of the animal. The blood is then drawn from the jugular vein ; it is allowed to coagulate in order to remove the clot, and the blood serum is used. Not only does this serum protect an individual from acquiring diph- IMMUNITY 249 theria by rendering him artificially immune, but it acts as a curative agent in neutralizing the poison of the disease if applied in the earlier stages of the disease. The blood serum of animals hyper-immunized against hog cholera or diphtheria varies greatly in the amount of anti- bodies formed. Before it is used it is necessary to know something of the strength or potency of the serum, so that the proper quantity to be used in the animal to be pro- tected may be determined. This is accomplished, in the case of hog cholera, by inoculating a number of young pigs with a definite (piantity of the disease virus and a varying amount of the protective serum, noting the amount which is required to protect the animal against the artificial in- oculation. In the case of diphtheria and tetanus antitoxin a num- ber of guinea-pigs are inoculated with a definite amount of toxin and with varying amounts of antitoxin. If the antitoxin administered to a particular individual is suffi- cient to neutralize the toxin, the animal remains alive. If the toxin is in excess, the animal dies. Persistence of immunity. — Passive immunity, produced by the transfer of the anti-bodies, is always of short dura- tion as compared with the active immunity produced by ar- tificial means, while the active immunity produced as a re- sult of the natural cause of the disease persists for a still longer period. The variation in time during which pro- tection persists must be taken into account in the practical employment of serums and vaccines in the prevention of an- imal diseases. Exit of organisms from body. — Almost without excep- tion, the pathogenic organisms grow only in the bodies of susceptible animals. Their continued existence in nature is therefore dependent upon their expulsion from the dis- eased body, and the opportunity for introduction into a 250 AGRICULTURAL BACTERIOLOGY new susceptible host. The exits from the host by which or- g-anisms find their way to new hosts vary in the different diseases. In intestinal diseases, as hog cholera, the excreta serve as a mode of exit. In tuberculosis the secretions, as milk and saliva, function as carriers of contagion. In some diseases the blood from wounds caused by biting in- sects or the discharges from abscesses on the surface of the body serve as channels of transmission. The transfer of the causal organisms from one animal to another may take place in a multitude of ways. In the same herd a healthy animal easily comes in direct contact with the infectious material from a diseased animal. The spread of the disease to other herds may take place through the transfer of an infected animal or of infectious material, such as milk or contaminated objects. The direct methods of transfer can be readily guarded against, but the more indirect modes of transmission are much more difficult to detect. Thus hog-cholera virus can be readily transferred by dogs, crows, or persons carrying the virus on their feet. The opportunity for the transfer of organisms for any considerable distance is dependent on the resistance of the organism, w^hich is largely determined by the fact as to whether it produces spores or not. Most of the non-spore- forming organisms can not persist for any long period out- side the animal, since they succumb quite readily to such unfavorable environmental influences as drying, sunlight, and the action of saprophytic bacteria. The spore-forming organisms, on the other hand, can persist for long periods, owing to the resistance of the spores to all ordinary environ- mental conditions. The prevention of the transmissible diseases involves the keeping of the causal organisms from coming in contact with healthy animals. This can be accomplished by isola- tion of diseased animals, by the disinfection of their secre- IMMUNITY 251 tions and the objects with which they have been in contact, and by the proper disposal of tlieir bodies. A personal knowledge of the nature of the organism and of its method of distribution is the only thing that enables one to protect himself or his herds and flocks. Necessity for correct diagnosis. — It is very essential that a correct diagnosis of any of the transmissible diseases be made, for the methods that will prove effective against one may have no effect against another. Especially is this true when serums or vaccines are to be used in preventing fur- ther spread, for these substances are specific in their action. The farmer must usually rely on the experienced veterin- arian for a proper diagnosis of any transmissible disease, and the veterinarian is fre(iuently forced to call to his aid the facilities of a bacteriological laboratory. The use of drugs in the treatment of the transmissible diseases is usually without any curative effect. The farmer must exert himself to prevent the disease, and especially to prevent their introduction on his farm. CHAPTER XX ANTHRAX, BLACKLEG, HEMORRHAGIC SEPTICEMIA, AND CORN-STALK DISEASE Anthrax. — The disease commonly known as anthrax is one of th*e most interesting of the transmissible diseases of man and the lower animals. The causal organism is large, and is found in great numbers in the tissues of the dead animal. It grows profusely on many kinds of culture media of both animal and vegetable origin. These facts led to its discovery and cultivation early in the develop- ment of bacteriology. The information gained from a study of this organism was of the greatest importance in the study of other and more obscure diseases. In 1849 Pollender noted the organism in the blood of animals that had died from the disease. This observation was confirmed by others. Robert Koch, in 1876, cultivated the organism on artificial media. He proved that its arti- ficial cultivation could be continued for long periods of time, and that on reintroduction into the body of a suscep- tible animal, a disease identical in symptoms and lesions with the naturally occurring cases would be produced. The causal relation of bacteria to the production of disease was thus proved where previously it had been suspected, but not established with certainty. In 1881 Pasteur published the results of his researches on a method of protecting ani- mals against anthrax by vaccinating them with weakened cultures of the organism. This work was the starting-point for the development of vaccines and other biological pro- 252 ANTHRAX 253 ducts that have been of inestimable value in the prevention and euro of many transmissible diseases. The organism. — The anthrax bacillus is one of the largest of the disease-producing bacteria. The rodlike cells have square-cut ends. In liquid media the cells appear in chains of great length, giving to the growth the appearance of a tangled mass of cotton fibers. The growth is rapid on all of the ordinary types of culture media. It grows under both aerobic and anaerobic conditions. In the presence of air, spores are formed quickly and in great abundance. The spores are not especially resistant to heat, being killed in a few moments at 100° C. They are, however, extremely resistant to desiccation, and also live for years in water. In the author's laboratory some spores were still alive after eighteen years' residence in a sample of water collected from a pond in a pasture in which a number of animals had died of anthrax. The rapidity and profuseness with which spores are produced when the vegetative cells are exposed to air is of thp greatest importance in the distribution and persistence of the disease. The disease is said to be the most widespread, geograph- ically and zoologically, of all the transmissible diseases. It has been present in Europe for hundreds of years. In 1613 it is asserted to have caused the death of fifty thousand people in southern Europe. In still earlier times the Arab physicians called it "Persian fire." As the civilization of Europe has spread to other lands, anthrax has been one of its gifts, until to-day no part of the world in which stock- raising is important is free from it. In this country it has been reported in many of the States. The organism is one that is easily transported over long distances in time and space, due to its resistant spores, which are likely to be present on many articles of commerce, such as hair, wool, bristles, and hides. Many of the out- 254 AGRICULTURAL BACTERIOLOGY breaks in both animals and man in this country have been caused by animal products from the Orient and South America. The disease is primarily one of cattle, sheep, goats, horses, and less frequently hogs. The other common domestic an- imals of our country, cats, dogs, and fowls, are relatively immune, acquiring the disease only when exposed to large doses of the organism, as is the case when meat from an anthrax carcass is eaten. Man is also susceptible to the disease. He is, however, more resistant to it than are the ruminants, both domestic and wild. The disease is variously known in its several forms. The old English term for it was murrain. Splenic fever refers to the enlarged condition of the spleen, while malignant carbuncle refers to the appearance of large swellings on the surface of the body, a common manifestation of the disease in man when the organism has been introduced into wounds. Infection. — In the case of cattle, sheep, and horses, the portal of entry is most frequently the alimentary tract. It is supposed that the compound stomach of the ruminating animal gives opportunity for the growth of the organism and for the more frequent infection of this type of animal. It seems probable that the organism can, in many cas' c pass through the uninjured wall of the intestine. It is cer- tain that its entrance is made more easy and certain by the presence of woui.ds in any part of the alimentary tract. It is probable that abrasion of the mucous surfaces in the mouths of grazing animals or those fed on dry fodder read- ily permits of the entrance of the organism. The transfer- ence of the organism from infectious material and its intro- duction into the body may be accomplished by b'ting flies. It is believed that this is the chief way in which the horses and mules of the plantations in the Mississippi delta region ANTHRAX 255 become infected. The infection may occur by grazing on infected pastures and by the use of contaminated dry fod- der, the spore enabling the organism to persist on the dry material. Before the development of the procedure for protective vaccination, the disease occurred yearly on many farms in France. These were known as "anthrax farms." The continued persistence of the organism in the soil of a con- taminated field is usually ascribed to the resistant powers of the spores. It may be that growth may occur each sum- mer in the soil, a new crop of spores being thus produced to favor the continued existence of the organisms. Its more frequent and constant appearance in stock pastured on low, moist land is evidence of the growth of the organ- ism under these conditions. The contamination of stables, yards, or fields with anthrax bacilli is certain to make them unsafe for a number of years. Symptoms. — The rapidity of progress of the disease in the individual has led to the division of the various cases into three types: the peracute, the acute, and the subacute. In the first the animal may show no visible symptoms until a few hours before death. Indeed, so rapid is the progress of the disease that the usual yield of milk may be obtained at one milking and death occur before the next milking- time. An artificially infected guinea-pig may show no vis- ible symptoms two hours before death. The temperature may reach 106° F. in the absence of all other symptoms. With such a temperature the respiration will be increased and the heart-beats so pronounced that they may be heard. Later the animal becomes weak and stupid, and the temper- ature falls to subnormal. In the acute type sj'mptoms of nervousness are present, manifested by kicking and convulsions. The visible mucous membranes become bluish and the urine is often bloody. In 256 AGRICULTURAL BACTERIOLOGY the subacute type the duration of the disease is from one to seven days. Tumors or carbuncles are quite common. They usually appear on the shoulders and neck, and are due to the bruising of the parts, which injury gives rise to a collection of the bacilli within the blood-vessels of the parts, inducing inflammation, followed by the development of the tumor. Carbuncles may also be occasioned by in- fection through a wound. The subacute type is the most common, and is the only form that can be treated. It is also the type noted in most isolated cases of anthrax. At the beginning of an outbreak the first animals lost usually show few or no symptoms. This rapid progress of the disease may be due to the lack of resistance of the animal. Such rapid progress of the disease often leads to suspicion of poisoning, or to death by lightning. Such conclusions as to the cause of death may lead to the careless disposal of the carcass, thus endangering human life as well as causing a widespread outbreak, not only on the farm but in the neighborhood. It is well to consider all cases of sudden death in an animal, especially when no definite cause can be given, as due to dangerous causes, and to act accordingly in the handling and disposal of the carcass. The slower process of the acute and sub- acute types of anthrax and the evident symptoms give greater opportunity for the recognition of the nature of the trouble. The mortality from the disease is from 70 to 80 per cent. Lesions. — The lesions are usually so characteristic that they enable the recognition of the disease^ or at least arouse suspicion as to its probable cause. The most marked is the dark blood, which may appear almost tar-like and which does not coagulate as does normal blood. The spleen, or milt, is usually greatly increased in size; it is dark red in color instead of the grayish color of the normal organ. The ANTHRAX 257 258 AGRICULTURAL BACTERIOLOGY interior has a semi-liquid consistency due to the breaking down of its structure. Hemorrhages or areas in which the blood has passed from the blood-vessels into the tissues are often noted in the internal organs and on the membranes. Blood often issues from the natural openings of the body. The carbuncles are at first hard, hot, and painful, but later, due to the death of the tissue at the center, the fever subsides, and no pain is evidenced by the animal when the carbuncle is opened. The exudate is tarlike in color and consistency. Gangrene, due to a secondary invasion of the abscess with putrefactive bacteria, is often noted. In the case of the hog, swelling of the tissues of the throat is commonly present. The carcass does not become rigid; bloating and decomposition occur more quickly than in the case of death from other causes. The sudden death of cattle or sheep, accompanied by black non -coagulating blood and an enlarged darkened spleen, should always lead to a suspicion of anthrax. The absence of these typical lesions is not to be considered proof of the absence of anthrax. The disease is a true septicemia in that the organisms are to be found in great numbers in every portion of the body at the time of death. The absolute diagnosis of the disease is made by finding the anthrax bacillus in the tis- sues, and, in some cases in which the post-mortem changes are not typical, this is the only way in which the diagnosis can be made with certainty. Whenever an animal has died and anthrax is suspected, the temperature of each animal in the herd should be taken. All that show a temperature of 104° F. or above should be allowed to remain in the infected quarters ; the remainder of the animals should be at once removed. Before the transmissible nature of the disease was rec- ognized, extensive epidemics were common. Prompt sep- ANTHRAX 259 aration of the animals, and care in the disposal of the car- cass and in disinfetion will do much to prevent continued loss. It has been shown that the loss of one or two animals from a herd by anthrax* is a more common occurrence than is a more extensive outbreak. Carelessness, however, may result in - ■V-"//CS?/ 1 KANS. hiO. st^ -^T^y r.^^\.~—^ ^r K> .f*OXLA V ^ }fff ^v / r" -nyw^ p- — -"^V^ ^\^ •& c f ' . M r^ wVs ^\ J -J rS^M I n MISS. pjJ! ^m • < m\ -if Jl "tpT^ ^^ ^m^^ J ^» ^^ TJ Fig. 53. Texas Fever The heavy black line bounds the area in which the disease-transmitting tick was present in 1906. The white areas below this line have been freed from the tick and the disease between 1906 and 1918 under the burdensome regulations that so hamper the tick- infested areas. The total area rendered free from the tick since the be- ginning of the work in 1906 to December, 1918, embraced 458,529 square miles. It seems reasonably certain that within a few years Texas fever will be eradicated from this country. The work of eradication should progress rapidly when the stockmen realize the great economic advantages that will accrue to the industry from the eradication. Texas fever is a disease the eradication of which simply awaits the practical application of knowledge already ac- quired ; while, in the case of other important communicable TEXAS FEVER 299 diseases, the information is not yet sufficiently complete, so that effective measures can be carried out, or else the nature of the diseases is such that there seems little hope of getting rid of them in the near future. Immunization. — The youn^r animal is not very susceptible to Texas fever, and can be readily immunized by introduc- ing into the blood a small number of the causal organisms that will not produce a fatal form of the disease, but will cause a sufficient degree of immunity to protect against natural infection. The requisite number of organisms may be introduced by transferring blood from an infected ani- mal to the animal to be immunized. The amount of the blood to be thus transferred depends on the susceptibility of the animal. If an old animal is to be immunized, one cubic centimeter of the blood is used, but if a yearling is to be treated, three cubic centimeters of the blood may be employed without danger. Again, the tick itself may be allowed to infect the ani- mal, the number of organisms introduced being governed by the number of ticks placed on the animal. The method of immunization with blood is very successful, about 3 per cent, being lost by vaccination and 7 per cent, by subse- quent infection. The 10 per cent, loss, when compared with the 90 per cent, loss that resulted when non-immunized cattle were placed on tick-infested pastures, is a measure of the success of the treatment. Certain cattle, as those of India, are resistant to the dis- ease, and attempts have been made to breed strains that possess such an immunity. Contagious abortion. — The term abortion signifies the premature discharge of the fetus. If the abortion occurs late in the gestation period, so that the young may live, it is often termed premature birth; there is, however, no es- 300 AGRICULTURAL BACTERIOLOGY sential difference, as far as the cause is concerned, between abortion early in the gestation period and that which occurs later. Causes of abortion.— The expulsion of the fetus may be due to slipping, injury by another animal, or other me- chanical causes, and to feeds that have a specific action on the pregnant animal, such as grains and fodders that con- tain large amounts of smut or ergot. It is quite certain, however, that abortion as it is observed in cattle is almost wholly due to the invasion of the animal by a specific or- ganism which may pass from animal to animal, producing what is commonly known as contagious abortion. The dis- ease is of the greatest economic importance in cattle. A similar trouble, caused, however, by a different organism, is noted in mares, and a third organism is responsible for abortion in sheep. The disease as it appears in cattle has spread rapidly in recent years, owing to the great increase in the sale of breeding animals. It is now rare to find a herd of any considerable size that has an entirely clean record. The losses it occasions are felt especially bj^ the breeder who relies on the progeny of his herd for a large share of his returns, much more than by the farmer who is primarily in- terested in the production of milk. In the beef districts the disease, of course, becomes of major importance to the farmer. The loss is not wholly confined to that incurred from the death of the calf, for if the abortion occurs early in the gestation period, the animal will rarely prove a profitable producer of milk during that lactation period. If the abor- tion occurs late in the period, the flow of milk will be nor- mal. In economic importance the disease ranks with tu- berculosis, Texas fever, and hog cholera. Against these the farmer has much hope of making a successful fight with ABORTION 301 the knowledge that is already available, but against con- tagious abortion the case is far less hopeful. The cause of bovine abortion is a small bacillus that does not form spores and is relatively non-resistant to disin- fectants. It is called B. abortus, or the Bang organism, after the Danish veterinarian who first discovered it. The organism has been found widely distributed in all parts of the world, and there is no doubt concerning its causal rela- tion to the bovine form of the disease. Nature of the disease. — The disease is one that has a spe- cific action on the pregnant animal, causing an inflamma- tion of the uterus, with injury to the fetus or causing its death. The general health of the animal is not affected to any noticeable extent. The organism is eliminated at the time of abortion, and for an indefinite period thereafter in the discharges from the uterus. It has also been found in the milk. The organism may be present for months before abortion actually occurs, indicating that it is to be looked upon as a chronic disease. Again, an animal may continue to elimi- nate the abortion bacilli in the milk years after the last abortion occurred or wh'en no abortion has been known to occur. The infection of an animal does not necessarily pro- duce abortion, since this will depend on the extent of in- jury to the fetus. The infected animals that do not abort may be as dangerous to healthy animals as those that have aborted. The fact that some unsuspected animals may thus act as bacillus carriers makes it an especially difficult dis- ease to control in a herd. The natural manner of infection is not known with cer- tainty. It has been shown by experimental methods that the infection may occur through the genital passages. It is probable that, if infection occurs in this manner, it must take place before or very shortly after conception, as, after 302 AGRICULTURAL BACTERIOLOGY the uterus is closed, no invasion can occur through the blood. It is believed by many that the male is one of the common agencies in the transmission of the organism from the infected to the healthy animal. It has also been shown that infection may occur through the alimentary tract by the ingestion of contaminated food. By some it is thought that this is the most important if not the sole way by which the organism enters the body under natural conditions. Infection in this manner may occur after conception. It will be evident that if the disease is introduced into a herd, there will always be ample opportunity for it to spread, whatever the method by which the organism invades the individual animal, since the stable and fodder is certain to be contaminated with the organism. The disease may be introduced into the herd by the pur- chase of an infected animal, and probably by the feeding of mixed creamery and cheese factory by-products. While this last method of spread has not been proved, the pres- ence of the organism in the milk of a considerable propor- tion of the infected animals, and the fact that infection can occur by way of the alimentary tract, would lead to the conclusion that this may be one method by which the disease is being distributed from farm to farm. This method of distribution can easily be avoided by pasteuriz- ing the factory by-products, a method equally effective against both tuberculosis and foot-and-mouth disease. Detection of the diseased animal. — Among the anti- bodies formed by the cells of an infected animal are sub- stances to which the term agglutinin has been applied. These substances possess the property of causing the bac- teria producing the disease to clump or to come together in large aggregates. The clumping of the cells may be deter- mined by examining the solution under the microscope or by the unaided eye. ABORTION 303 The actual tests are made by preparing a uniform sus- pension of the cells of the causal organism in a salt solu- tion. A small quantity of blood is drawn from each ani- mal to be tested, the blood is allowed to clot, and the serum removed, which is then added in var^-ing proportions to the suspension of bacterial cells. If the blood is free from the specific agglutinin produced by the animal on invasion by ihe organism of abortion, the cells remain in suspension. If the specific agglutinin is present, the cells clump and the masses soon settle, leaving a clear liquid. The agglutinin can be developed only as the host has been invaded by the organism. A positive test does not imply that the animal at the moment the blood was drawn was harboring the organ- ism, for the anti-bodies persist Ion*: after the organism has disappeared from the body. Similar tests are used in the detection of typhoid fever in man, glanders in horses, and white diarrhea in chickens. A test for another of the anti-bodies is also used in the detection of animals that are or have been affected with B. abortus. The test is so complicated that it can not be described here. It is similar to the Wassermann test used for the detection of syphilis in humans. It is also known as the complement fixation test. It involves the use of the blood corpuscles or serum from three different species of animals other than the bovine animal that is being tested. The organism causing the disease is also used. It is an example of the progress that has been made in the detection of the most minute quantities of specific substances of un- known nature formed by the bod}' cells of an animal in- vaded by a parasitic organism. The stock-owner must rely for protection very largely on the information he can secure as to the health of the herd from which he intends to purchase. Control and prevention. — It is not usual for an animal 304 AGRICULTURAL BACTERIOLOGY to#abort more than once or twice, and such condition is fre- quently interpreted as an indication that a certain degree of immunity has developed as a result of the earlier attack. It seems probable that this is not the case, but that there is an age immunity, since the greatest number of abortions occur with heifers during the first and second pregnancies. It is not good practice to sell aborting animals with the hope of getting rid of the disease, since it will rarely if ever succeed. The replenishing of the herd by purchase will serve to continue the trouble, either by the addition of healthy animals to become infected, or by the introduc- tion of new centers of infection. IMany treatments have L?en devised and recommended for the prevention and cure of abortion. For example, the internal administration of carbolic acid, both with the feed and by hypodermic injection, has been widely used. There is little reason to believe that it has any favorable effect. The use of vaccines has been attempted, but without suc- cess. It seems evident that the breeder and farmer must rely entirely on sanitary precautions to prevent the spread of the disease. He must seek to destroy the organism in the infectious material discharged by the animal. The dead fetus and also the afterbirth should be buried ; the contami- nated litter should be destroj^ed ; and the aborting animals should be flushed out with a 0.5 per cent, solution of some of the soapy, coal-tar disinfectants, such as l^^sol, or with a 0.5 per cent. LugoUs solution, which consists of one part of iodine and two parts of potassium iodide dissolved in three hundred parts of water. The solution should be warmed to 100° F. The treatment should be continued daily until no discharge is to be noted. This procedure will not only serve to limit the distribution of the organism, but will be of some service in the prevention of sterility, which is a frequent sequence of abortion, and an important factor in FOOT AND MOUTH DISEASE 305 its economic importance. It is also well to disinfect the bull after each service. A separate maternity stall should he provided, to which all animals that are to calve at the normal time should be removed. This stall should be kept clean, and supplied with an abundance of clean bedding. Animals that show signs of aborting should not be placed in this stall, but re- moved from the stables to a separate building. Foot-and-mouth disease. — There are a number of trans- missible diseases of domestic animals prevalent in Europe that are not found in this country. Among them are con- tagious pleuro-pneumonia of cattle, hog erysipelas, and foot- and-mouth disease, which affects the cloven-hoofed animals and man. All domestic animals imported from Europe must be kept in quarantine for a considerable period in order that there may be time for them to develop symptoms of any disease with which they may be infected, and to permit of a detailed examination as to their health. These precautions are taken primarily to prevent the introduction of diseases that are not known in this country. Even with all precaution, there is always opportunity for some of these diseases to be introduced and to spread rapidly. Foot-and-mouth disease forms a striking example. There have been six outbreaks of this disease, as follows: 1870, 1880, 1884, 1902-3, 1908-9, 1914-15. The disease has, how- ever, been eradicated at each appearance. The method fol- lowed has been to slaughter not only the diseased animals, but all other susceptible animals on the farms on which the outbreaks occurred. In 1902-3 4,461 animals were killed; in 1908-9 3,636 animals were slaughtered. The cost of the eradication of each of the outbreaks in 1902-3 and 1908-9 was approximately $300,000. Not a large amount to pay as insurance of the entire stock industry of this country against this disease for ten years. 306 AGRICULTURAL BACTERIOLOGY The disease is like other acute communicable diseases in that it has an ebb and flow. These waves occur at intervals of several years. The reason for this variation in severity is not known. In Germany, after a period in which the disease was not especially important, it began its ravages, and in 1911, 3,000,000 cattle were affected, 1,000,000 sheep, and 2,500,000 hogs. The loss from death of animals is not great, only about 1 per cent. The economic losses are due to the loss of flesh, to diminished milk production, or to loss of reproductive power. It has been estimated that for cattle this loss ranges from seven to twenty dollars a head, and proportionately less for smaller animals. It is thus clear that the disease imposes a great economic burden upon stockmen, and if by the expenditure of reasonable sums the country can be protected from it, it is certainly wise to spend the money. The disease presents an excellent example of the influence of modern commercial conditions on the rate of spread. The infection of the great shipping-yards is an especially important factor in the distribution. The outbreak of foot- and-mouth disease of 1908-09 was due to the importation from Japan of vaccine virus that was used in one of the vaccine establishments in Pennsylvania. Some of the virus was sent to a Detroit establishment that rented calves from a dealer for the manufacture of smallpox vaccine. After the animals had been used for this purpose they were re- turned to the dealer and resold by him to farmers. Bovine animals inoculated with the mixed virus of cow- pox and foot-and-mouth disease develop symptoms of cow- pox alone, but when brought in contact with healthy ani- mals the virus of foot-and-mouth disease may spread from the animals that show no symptoms. The calves in ques- tion were placed in pens in the Detroit stockyards, and from there distributed as shown in the diagram. Four days FOOT AND MOUTH DISEASE 307 later a shipment of cattle was placed in the same yards, a portion of the shipment was reshipped to Buffalo, and from there a number of animals were sent to two towns in Penn- sylvania in the neighborhood of which outbreaks of the Fijj. .'54. Foot-and-Mouth Disease The rapid spread of disease is made possible by modern commercial conditions disease occurred as illustrated in the diagram. In ten days the disease had traveled hundreds of miles. The rapid and effective work of government officials saved the country at that time from the permanent introduction of the disease. The outbreak of 1914-15 was of unknown origin. It was first noted in Michigan on October 15, 1914. Within ap- proximately one month it had invaded nineteen States from Washington in the AVest to Massachusetts in the East. Some weeks later three additional' States were invaded by the disease. This unparalleled rapidity of spread was due to the fact that the great stockyards of Chicago became infected early in the outbreak. The stream of animals into the stockyards is continued by a much smaller stream of animals leaving the yards to be sent to all parts of the country. No more ideal way of spreading an acute disease could be devised, and no more marked example of the role of modern commerce in the distribution of disease has ever 308 AGRICULTURAL BACTERIOLOGY been offered than the outbreak of the foot-and-mouth dis- ease in 1914-15. The number of animals slaughtered was 152,157 in 3,021 herds. The total loss occasioned by the outbreak amounted to $5,619,346. The greater part of this sum was paid to Fig, 55. Foot-and-Mouth Disease Sharply delimited eroded areas on the tongue form one of the characteristic lesions of the disease farmers to recompense them for the animals slaughtered. This amount, large as it may seem, is not much to pay to insure the United States against the ravages of a disease that caused an estimated loss of $5,000,000 to the stock in- dustry of England in one year, 1883. FOOT AND MOUTH DISEASE 309 Nature of the disease. — The causal organism is an ultra- microscopic one. In from three to six days after the animal is exposed to the infection, the disease makes its appearance. The onset af the trouble is marked by chills, followed by fever which may cause the temperature to rise as high as 106° F. In one or two days blisters or vesicles about the size of a hemp-seed or a pea are to be noted on the mucous ¥\fr. 5fi. Foot-and-Mouth Disease Ulcers between the toes are also charattcristic of this disease membranes of the mouth, tongue, and gums. The vesicles are filled with a yellowish, watery liquid in which the causal organism is present. Similar eruptions appear on the feet between the digits and above the coronet. They may also appear on the udder and teats. The milking process rup- tures the vesicles, and the organism finds its way into the milk, by which it spreads from one animal to another and from farm to farm when mixed cheese factory or creamery products are fed. The vesicles increase in size until they 310 AGRICULTURAL BACTERIOLOGY reach the diameter of a dime or even larger. They rupture soon after their appearance, leaving reddened sensitive spots or erosions behind. Food is refused, and a ropy saliva drools from the mouth. The soreness of the feet often ren- ders it impossible for the animal to stand. The disease spreads with great rapidity in the herd. The chance that all of the herd will acquire it has led to the inoculation of the animals by the transfer of some of the saliva from the diseased to the healthy animals, with the idea of shortening the period of trouble in the herd. In cases of doubt as to the nature of the disease, the inoculation of a calf should give definite information, since the inocu- lation should result in the characteristic vesicles in from twenty-four to seventy-two hours. There are a number of diseases that somewhat resemble foot-and-mouth disease. Cowpox forms similar vesicles, but the inoculation does not result in symptoms of fever and eruption for at least ten days. In mycotic stomatitis, or inflammation of the membranes of the mouth, the entire mouth cavity is inflamed and vesicles are rare; if present, they do not increase in size. The thin skin between the toes may be inflamed, but the vesicles do not appear, nor is the udder affected. The disease does not spread and the inoculation of calves is not successful. In foot-rot the in- flammation of the foot is general, and the mouth remains unaffected. In ergotism, or trouble due to the eating of too great quantities of smut, the mouth is not affected, and the tissue changes are to be noted at the tips of the ears, end of the tail, and upon the lower part of the legs. Foot-and-mouth disease is transmitted to man by the use of infected milk. It causes eruptions in the mouth and on the fingers, but is seldom fatal, except in the case of weakened children. In man it is known as aphthous fever. CHAPTER XXIII RABIES AND ACTINOMYCOSIS Rabies. — As has been shown, the losses from Texas fever are needless, since ways are known by which it can be com- pletely eradicated. Rabies is a disease that likewise could be made to disappear, if simple procedures that could easily be carried out were enforced. The disease is primarily one of the flesh-eating animals, but is transmissible to all mammals through the bite of a rabid animal. In reality it is transmitted almost wholly by dogs, since the dog is the only animal that is allowed to run about freely. It is found in most parts of the world ; Australia and England are the only countries that are known to be free from it, and they, are kept so through, the rigid enforcement of wise quarantine regulations with refer- ence to the importation of dogs. In the United States it has spread rapidly in the last few years, until at present it is found from the Atlantic to the Pacific. In 1908 it is know:n to have caused the death of 111 people. It is also of considerable economic importance because of the loss of domestic animals. The sanitary and economic aspects of the disease are small when compared with some others, but all loss is so unnecessary that it seems advisable to discuss the disease in some detail, especially since there are so many misconceptions concerning it. The virus, of unknown nature, is known to be present in the saliva, the vitreous humor of the eye, lymph, milk, urine, and the peripheral nervous sj^stem. The presence of the virus in the saliva is the explanation of the transmission 311 312 AGRICULTURAL BACTERIOLOGY by the bite of an infected animal. Many times the saliva is so completely removed from the teeth of the rabid animal that none of the organisms is introduced into the wound. Especially is this likely to be true when the wound is in- flicted through the clothing, through the coat of a long- haired dog, or through the wool of a sheep. This is one of the reasons why only a small proportion of the human be- ings and animals that are bitten by rabid animals develop the disease, even though no protective treatment is em- ployed. The virus is known to be present in the saliva from two to five days before the symptoms of the disease are evident. The wounds in which the infection is most likely to be of a serious nature are those inflicted on the head and face rather than on the extremities. The virus develops in the nerves, and is more likely to establish itself in tissues that are rich in nerves than in those deficient in these structures. The extent of the bites is also an important factor in determin- ing whether infection is to occur, since the amount of virus introduced will be in proportion to the number of bites inflicted. The tissues seem to have the power of destroy- ing a limited number of the organisms. Again, if the wounds are such that bleeding is marked, there will be a tendency for the organisms to be washed out. The deep puncture wounds are likely to be more serious than a tear in the flesh. It is commonly believed that there is a seasonal distribu- tion of rabies, that it is more common during the so-called dog days of late summer. There is little or no basis of fact for this belief. There is, however, more opportunity for the rabid dog to come in contact with human beings and with animals in the summer than in the colder months when there is less out-of-door life. The regulations that require the muzzling of dogs for a few weeks in the summer have RABIES 313 no justification unless the period is extended to include the entire year. The incubation period varies considerably in length, de- pending upon the location and extent of the bites. The symptoms are not apparent until the central nervous system is involved. The rapidity with which this will occur is de- pendent on the distance of the bite from the lirain. The extent of the bite is also of importance in determining the rate at which the disease progresses. The average periods of incubation are as follows: Man 40 days Dog 21-4S days Horsps 2«-.')6 days Cats 14-28 days Pigs 1 4-21 days Sheep 21-28 days The virus may remain dormant after its introduction into the tissues for a varying period of time, thus delaying the development of the symptoms for months and possibly years after the bite is inflicted. Symptoms. — Rabies is generally divided into two forms, furious and dumb. In the first the animal is irritable and bites nearly every object with which it comes in contact; in the second the muscles of its jaws are paralyzed early in the attack, and, being unable to bite, the animal remains more quiet. The two forms of the disease represent the ex- tremes, and all gradations are to be noted between them. The saliva from a case of dumb rabies is just as dangerous as that from a case of the furious type. The furious type passes into the dumb type as the disease progresses, owing to the paralysis of the muscles. The furious type is marked by symptoms of nervousness. The animal may be more restless or more affectionate than usual, seeking to lick the hand or face. If an abrasion of 314 AGRICULTURAL BACTERIOLOGY the skin is present on the part licked, inoculation with the virus may result. More frequently the dog seeks to be alone, but it does not remain quiet ; it often acts as if it were being annoyed by something, snapping and howling at some imaginary object. The animal often leaves home^ and on its journeyings is likely to infect animals and human beings. It does not usually go out of its way to bite. There is ample opportunity for other dogs to be bitten by it, because of the canine custom of seeking to extend ac- quaintances. Frothing at the mouth often occurs, and the voice is more of a howl than a bark, due to the atfected muscles of the throat. The rabid animal has no fear of water, as is ex- pressed by the common name of the disease, hydrophobia. Attempts to drink cause a paroxysm of the affected mus- cles of the throat. The animal can not swallow. The pa- ralysis of the muscles gradually extends itself, and death finally brings relief. Much the same symptoms are noted in man. In the dumb type the nervous symptoms are lacking and the paralysis appears very early in the course of the disease. It may easily be mistaken for choking. The furious form is the usual type noted in the case of man and in most ani- mals other than the rabbit, which is used extensively in the detection and prevention of the disease. Diagnosis. — It was stated that only about 10 per cent, of human beings bitten by known rabid animals develop the disease, owing to the non-introduction of the organism into the tissues, or to the destruction of the organisms by the tissues. Death from rabies presents a series of horrible symptoms, and if a person is severely bitten, the preventive treatment should be applied without delay. It is, however, highly advantageous to know for a certainty whether the dog that has inflicted a wound is actually rabid or not. RABIES 315 The quickest way to determine with certainty the nature of the trouble is to confine the dog and note the symptoms. The disease is invariably fatal, and death is commonly pre- ceded by a definite sequence of symptoms, so that there can be no mistake in the diagnosis. The diagnosis should be made as quickly as possible, for if preventive treatment is to be applied, it must be administered without delay, since it is of no avail if not begun until the symptoms appear. If it is impossible to secur,e and confine the dog alive, the diagnosis can be made by a microscopic examination of the brain. The head should be removed, packed in ice and sawdust, and sent to the laboratory that is maintained by most States and large cities for such work. In killing the dog, care should be taken not to injure the brain or spinal cord. Preventive treatment. — The treatment used to prevent the development of the disease in persons bitten by a rabid animal was one of the triumphs of Pasteur. The organism found in ordinary cases of rabies can be increased in viru- lence for rabbits by passing it through a series of animals. The so-called fixed virus will kill a rabbit in seven days, when introduced beneath the membranes of the brain. If the cord is removed from the animal immediately after death and allowed to dry over caustic potash, the virus be- comes attenuated, the extent of the attenuation depending on the length of the drying process. The preventive treat- ment consists in giving hypodermic injections of a' suspen- sion of the dried cord. The first injections contain mate- rial that has been dried for about two weeks, while the sub- sequent injections are made with material that has been dried for a shorter period, until at last an injection of the fresh cord can be given without danger. Injections are made for a period of twenty-one days. Of all the persons known to have been bitten by rabid animals, to which the 316 AGRICULTURAL BACTERIOLOGY preventive treatment has been administered at the Pasteur Institute in Paris, but one-half of one per cent, have died of rabies, while the mortality records of those that did not receive the treatment are approximately ten per cent. Wounds inflicted by a dog known to be rabid, or suspected of the disease, should be cauterized as soon as possible by the application of concentrated nitric acid, strong carbolic acid, or by a hot iron when the chemical agents are not available. This strenuous treatment will destroy the tissue about the wound, together with the virus that has been introduced by the animal. The quicker the cauterization is carried out, the more effective it will be. The cauterization, if it does not completely destroy the virus in the tissue, will prolong the period of incubation and thus give a better opportunity for a careful diagnosis to be made and for the preventive treatment to be applied in time to be successful. The treatment was first applied to a human being by Pas- teur in 1886. Between 1886 and 1917, 48,107 people were treated at the Pasteur Institute in Paris. From experience it is known that at least 10 per cent, of this number would have died from rabies if the protective inoculation had not been administered. Actually but 137 of this great number died from rabies. Pasteur has to his credit the saving in his own laboratory of 4,673 people from a most horrible death. Similar laboratories were soon established in all parts of the world. The total number of people saved from rabies reaches many thousands. Eradication. — Since the disease is transmitted almost en- tirely by the dog, it could be prevented and eradicated by keeping all dogs that are allowed their freedam muzzled at all times. The effect of such measures is shown by the history of rabies in England. The following figures repre- sent the number of reports of the disease : RABIES 317 1805 672 cases 1808 17 cases 1901 1 cases 1903-7 0 cases This reduction was due to the enforcement of muzzling laws after 1896. Rabies was reintroduced into Eno:land in 1919 by aviators who were able to disregard the quaran- tine regulations. The muzzling regulations that have been passed by governing bodies in this country are rarely, if ever, enforced in an effective manner, because many people believe it cruel to muzzle a dog. It is certain that the dis- ease could be eradicated in a short time if its transmission could be prevented. It is also certain that the muzzling of dogs for a short time would be much more humane than to have hundreds of them, as well as other animals and people, dying from rabies each j'car. Actinomycosis. — Actinomycosis, or lumpy jaiv, as it is more commonly called, is primarily a disease of cattle, al- though horses, sheep, hogs, and dogs may be affected. Man is also subject to the disease. The causal organism is usually classed as one of the higher bacteria. In the tissues the growth is often in starlike clusters. This appearance gave rise to the name actinomycosis. The*term Actinomij- cctcs is applied to the group of which the organism is a member. In this country the disease is not nearly so wide- spread as in some other sections of the world. It has been found in about one out of sixteen hundred animals killed in this country. Tuberculosis is many times more prevalent and more important in every way ; and yet, in many places, because of the appearance of the disease on the surface of the body, actinomycosis has made more of an impression on the popular mind than has tuberculosis. The disease is not one that spreads from animal to ani- 318 AGRICULTURAL BACTERIOLOGY mal, and hence, like tetanus, can not be classed as a con- tagious disease. It is believed that the organism grows on certain plants, as barley, and is introduced into the tissues by the barley awns. It may also enter through a wound in the mouth or through a hollow tooth, and possibly may be inhaled. It is rarely fatal, and when death is produced. Fig. 57. Actinomycosis The jaw bone has become spongy and a portion of the teeth have been lost due to the ravages of the disease it is due to mechanical causes, such as the interference with breathing or swallowing, or to the weakening of a blood- vessel by the constantly growing fungus. Symptoms. — The first symptom when the disease is lo- cated in the throat, as is most common, is a slight swelling, which gradually increases in size and is hard and dense. It undergoes disintegration at the center, and may dis- charge a thick yellow pus. The opening may heal over, only to break out again. The opening by which the content of the abscess finds its way to the outside may be on the surface of the body or in the mouth or throat. The sore at the point of discharge may become very large and have the appearance of a head of cauliflower. The growth of the tumor may continue for years. The tongue may be in- ACTINOMYCOSIS 319 volved, in which case the disease is often given the name wooden tongue. The organism may invade the bony part of the jaw, causing it to become spongy and enlarged. This permits the teeth to become loose, so that some of them may fall out. The internal organs may be invaded by the organ- ism. In the lungs, nodules similar to the nodules found in tuberculosis of the lungs may be formed under the stimulus of the fungus. These vary in size from mere specks to that of a pea. The spleen, liver, and udder may contain actinomycotic nodules. The organism occurs in masses in the pus discharged from the nodules. Because of the color of the organism, these masses of growth, which can be seen by the unaided eye, are often called sulphur granules. Treatment. — The disease is one of the few of those due to the invasion of the tissues by a parasitic organism that responds to treatment with drugs, the most successful of which is potassium iodide given in water as a drench. The dose is from one to two and one-half drams a day. The administration of this amount of the drug can not be con- tinued for any length of time without producing in the ani- mal the effect known as iodism. This causes the eyes to run, the skin to become dry and rough, and a loss of appe- tite. When these evidences of the drug become apparent, its use should be discontinued for a few days, and resumed later. In the case of milch-cows, the milk should be dis- carded, as the drug is excreted through this channel The drug may also cause abortion. All animals do not react fa- vorably to the drug. Where beneficial results are obtained, treatment should be successful in from three to six weeks. Man does not acquire the disease from cattle, but he be- comes infected in the same manner as cattle, viz., through wounds in the mouth. The meat of affected animals can be used as food, if the disease is localized. CHAPTER XXIV GLANDERS AND TETANUS The most important transmissible disease affecting, the horse and closely related animals is glanders, or farcy, as it is often called. The disease affects primarily horses, mules, and asses, but dogs and cats may acquire it by feeding on the carcasses of glandered animals. The disease is also transmissible to man, and usually results fatally. Distribution. — Glanders is found in nearly all parts of the world; Australia and New Zealand are the only large areas of any importance free from it. Great numbers of horses have been congregated from varied sources for war purposes, and have been transported to other lands, thus spreading the disease. It is asserted that glanders was in- troduced into Mexico at the time of the Mexican war by the American cavalry. During and after the Civil War, the distribution was very rapid in this country, owing to the sale of horses and mules by the government. At the present time glanders is most prevalent where large numbers of horses are brought together, as in lumber camps, on the ranges, and in the great stables maintained in cities. Constant change is going on in such stables, and every horse purchased may serve to introduce the disease, unless precautions are taken to determine the health of the animal before it is allowed to come in contact with healthy animals. The number of horses purchased by farmers is comparatively small, and, unless the farmer buys range animals, or those that have been in use by the large stables, 320 GLANDERS 321 little risk of acquiring glanders is encountered. Public stables and public watering-troughs are undoubtedly agents in the spread of the trouble. It is considered a wise pre- Running sores on a swollen leg are often noted with this disease After Reynolds. caution not to make use of public watering-troughs, but to employ a pail. Symptoms. — In some respects the disease reminds one of tuberculosis in that an animal may have it for a long time, and yet remain in good flesh and be able to stand a consid- erable amount of work. In other words, many glandered horses have an economic value, and yet are a constant 322 AGRICULTURAL BACTERIOLOGY source of danger to other animals with which they come in contact. It is thus considered wise that all glandered ani- mals be destroyed, and that the owner be compensated by the State for the protection of the industry in general. It is through the purchase of such chronic cases that the dis- ease may be introduced on the farm. The disease primarily affects the membranes lining the Fig. 59. Glanders Healed sores on the nose may be present in cases of chronic glanders After Reynolds. nasal passages, and one of the most characteristic symptoms is the discharge of a sticky fluid, sometimes streaked with blood, from one or both nostrils. Small nodules may form on the upper part of the nasal septum. The nodules, which are translucent and grayish in color, may break and form ulcers, which destroy the surrounding tissue to a greater or less extent, and may even cause a perforation of the nasal GLANDERS 323 septum. Similar nodules may be found in the lungs, and less often in the liver and kidneys. In glanders of the skin, or farcy, nodules are found in the skin and the underlying tissues. These nodules are usually called farcy buds. They vary in size from a hemp- seed to that of an cg^. These nodules break and form run- ning sores on the surface of the body, the discharge being yellow and sticky. The sores thus formed often heal and leave marked scars on the head and legs, in which places they are most common. The acute form of the disease is common in the mule and ass, but is rare in the horse. Death often takes place in from two to four weeks, although the disease may become chronic and the animal live for a number of years. Treat- ment is of little avail. Great precaution should be exer- cised in the care of glandered animals, since if any of the infectious material is introduced into the eyes or nose, or comes in contact with a wound, infection of the human being is likely to occur. The manifestations of glanders in man are quite similar to those noted in the case of the horse. Detection. — Glanders is often easily recognized by the characteristic lesions in the nasal passages or by the farcy buds. When the disease can not be recognized by physical examination, recourse must be had to some other method of diagnosis. The most common method is to apply the mallein test, which is very similar to the tuberculin test in the nature and manner of application. Mallein is pre- pared by growing the glanders organism in glycerin broth. The culture is then killed by heating, and the dead cells re- moved by filtration. The mallein is injected beneath the skin, and a series of temperature readings is made both be- fore and after the application of the mallein. A few hours after the introduction of the mallein there appears at the point of injection a swelling which, in the 324 AGRICULTURAL BACTERIOLOGY glandered horse, is hot and painful and continues to in- crease in size for from twenty-four to thirty-six hours. The swelling persists for several da3's, disappearing in from eight to ten days. At the time the swelling is most promi- nent, the diseased animal appears dull, breathes rapidly, and has a poor appetite. In the case of a healthy horse, the swelling is small and disappears in twenty-four hours, and no signs of illness are ta be noted following the injection of the mallein. The constitutional reaction in the diseased animal is accompanied by an increase in the temperature ranging from two to two and five tenths degrees. The in- crease begins about eight hours after the injection and reaches the maximum in from ten to fifteen hours. The fever persists for from twenty-four to forty-eight hours, instead of only a few hours, as in the tuberculin test. In the healthy horse there is no appreciable rise in tempera- ture. The test is not so accurate a method of diagnosing glan- ders as is tuberculin for tuberculosis, for some glandered horses do not react to the test; but a positive reaction is looked upon as proof of the diseased condition of the animal. Other tests are also employed, in which the blood is exam- ined for certain of the anti-bodies that will be produced under the stimulus of the glanders bacillus. These meth- ods can be carried out only in the laboratory. The farmer must seek to protect himself by the purchase of animals from known healthy sources, and by care in pre- venting his animals from coming in contact with infectious material in public places. The organism does not form spores and hence is not especially resistant. Tetanus. — Tetanus, or lockjaw, is an example of a tox- emia. It is also an example of a disease caused by a micro- organism that is not transmitted from one animal to another under natural conditions. B. tetani is widely distributed TETANUS 325 in soil, and is found in the large intestine of horses and cattle. Heavily manured soils and those with a high con- tent of organic matter seem to contain the bacilli in greater numbers than soils lower in humus. The bacillus is an an- aerobe that forms very resistant spores. The toxin it pro- duces is one of the most poisonous substances known, when it is introduced into the tissues of an animal. A man weighing one hundred and seventy-five pounds will be killed by 0.23 of a milligram. Toxins have been made of such potency that 0.00,000,002 gram is fatal to a white mouse. An or- ganism capable of producing such a substance does not need to grow extensively in the body of an animal in order to cause injury. The tetanus bacillus is usually introduced into the tissues through a puncture wound by some object that carries the infective material into the deeper lying tissues. Puncture wounds made by rusty, dirty nails are most dangerous. Horses, especially, become infected in this manner. Punc- ture wounds bleed but little, and therefore the foreign mat- ter is not likely to be washed out by the blood; nor is it easy to cleanse the wound by washing, as may be done with a more superficial abrasion. The infection may occur in such operations as docking,* castration, and through the umbilical cord of foals. The more frequent occurrence of the disease in horses, as compared to other domestic animals, is apparently due to the greater susceptibility of the horse to the toxin. It is estimated that the horse is twelve times as sensitive as the mouse and 360,000 times as sensitive as the fowl to this toxin. In man a large proportion of the disease is due to the wounds produced by Fourth of July accidents. The filling of many forms of fireworks is earth, which may contain the extremely resistant spores of the tetanus bacillus. Some portion of the filling may be blown into the skin by the 326 AGRICULTURAL BACTERIOLOGY premature discharge of a firecracker or some other form of fireworks. Symptoms. — The organism grows only at the point at which it was introduced into the tissues, and only to a small extent even there. In fact, so little evidence of its growth is shown by the tissues that it is sometimes impossible to determine the point of infection. The organism produces its powerful toxin, which is absorbed and which has a spe- cific action on the nerves, resulting in muscular contractions in various parts of the body. The tetanic spasms usually begin in the muscles of the head and neck, extending from these parts to the muscles of the throat, trunk, and extrem- ities. In the head, the muscles of mastication are first attacked, giving rise to the disease commonly known as lockjaw. In the horse, the muscles of the tail may be the first to show the spasmodic contractions. The duration of the disease in the horse may be a few days, or it may continue for several weeks. In cattle the disease is usually less rapid, but rarely runs longer than two weeks. Tetanus is usually fatal in sheep, and about 75 per cent, of the horses affected die. In man the disease manifests itself in much the same manner as in the lower animals. It was a very common disease in the early months of the Great War. In certain portions of the Western front, the soil apparently contained many tetanus bacilli. The contamination of wounds with the soil presented ample opportunity for the tetanus organism to enter. Later in the struggle, one of the first treatments each wounded man re- ceived was a dose of tetanus antitoxin. Preventive measures. — A preventive and, to some extent, a curative treatment has been developed in the tetanus an- titoxin. This antitoxin is comparable to the preventive serum used in hog cholera, and the diphtheria antitoxin- used so widely in human medicine. TETANUS 327 In the preparation of the antitoxin, it is necessary to force a susceptil)le animal, like the horse, to produce in its blood a (juantity of the protective substances, so that the blood can be drawn and the serum obtained. In producing the serum, the animal is hyper-immunized by the addition of repeated doses of the toxin or poison produced by the organism, beginning with very minute doses and gradually increasing them. This treatment with constantly increasing doses of the toxin is continued until the body of the horse has produced a large quantity of the substance that will neutralize the toxin. Fortunately, the body can produce an amount of the protective substances in excess of that which is necessary to render harmless the toxin introduced. If some of the blood of the hyper-immunized animal is carried to an animal that is just beginning to show symp- toms of tetanus, the antitoxin will be ready to neutralize the poison as it is formed by the growth of the organisms. It will tide the body of the diseased animal over the period of danger, and give it time to protect itself by the manufac- ture of its own antitoxin. The transfer of the protective substances is accomplished by drawing a small portion of the blood, allowing it to clot, and using the clear serum, which formerly represented the commercial product. AVays have now been found by which the protective substances can be concentrated by chemical means, a distinct advantage, since it avoids the introduction of large quantities of liquid into the animal to be protected. The protective serum is expensive, and hence is used only on valuable animals. Its widest use is in the preven- tion of the disease in man. The immunity thus produced is passive and persists for only a short time. CHAPTER XXV HOG CHOLERA The most important communicable disease of hogs is known as hog cholera, supposed to have been introduced from Europe in breeding animals. The first outbreak in this country of which record exists is that which occurred in Ohio in 1833. Since that time the disease has spread to all parts of the country. In the corn-growing States the losses occasioned by it are enormous. In the interval from 1894 to 1912 only eleven of the 92 counties of Indiana lost less than 5 per cent, yearly of the annual hog crop, 38 lost between 5 and 10 per cent., 30 between 10 and 15 per cent., 12 between 15 and 20 per cent., and one county more than 20 per cent. It is estimated that 85 per cent, of the losses incurred in the hog industry are due to this disease. From these figures it is apparent that hog cholera places an enormous tax on the swine industry of the country. This disease, like foot-and-mouth disease, is one that presents high and low tides. A widespread outbreak oc- curred in 1886-7, another in 1891 and in the years there- after, and still another began about 1911 and continued for several years. Its gradual spread from south to north is shown in the following figures, which present the per- centage of the annual hog crop lost through cholera: 1912 1913 Iowa IC 25.5 Minnesota 5.5 21.4 Nebraska 11 17.5 South Dakota 3.8 23.0 North Dakota 2 7.5 328 HOG CHOLERA 329 The disease is due to an ultrainicroscopic organism that {i:ains entrance to the body by way of the digestive tract or through the broken skin. The causal organism is elim- inated from the body in the feces and urine. All breeds of hogs are susceptible to the disease. It has been claimed by some that the mule-footed hogs would not acquire it, but experience has shown this statement to have no basis (»f fact. Symptoms. — The/ disease may appear as a typical blood- {)oisoiiiiig or septicemia, as an intestinal infection, as a lung trouble, or in any combination of the three. It was formerh^ supposed that there was more than one disease that affected hogs; but, as methods of prevention have been devised, it has been found that all respond to the same treatment and hence must be caused by the same organism. The symptoms vary with the different manifestations of the disease. The first hogs to die in any outbreak do so after having shown signs of illness a sliort time. It will usually be observed that the sick hogs fail to eat, are affected with chills, and huddle together in the pens to keep warm. They stand with l)ack arclied and with the hind feet close together or crossed. They sliow stiffness of the muscles and joints, and may stagger and fall from weakness. The skin of ears, nose, abdomen, and that inside the thighs may be reddened. The early stages are marked by consti- pation, followed by a profuse diarrhea in which tlie feces have an offensive odor. If the lungs are affected, a hack- ing cough is noted and an increased respiration. The eye- lids are often stuck together bj' a purulent discharge. The temperature is increased, reaching from 104° to 109° F. If the attack is of longer duration, as in the chronic form, there is more marked evidence of digestive disturbances. Animals with chronic cholera become emaciated, the hair 330 AGRICULTURAL BACTERIOLOGY may drop out, and even portions of the skin may die and slough off. As a rule, they do not become profitable feed- ing animals even after recovery. It is sometimes difficult or impossible to determine from the symptoms alone whether hog cholera is present in a Fig. 60. Hog Cholera Hemorrhages on and in the kidney are one of the most characteristic lesions herd. A careful post-mortem examination of the dead an- imals is necessary in order to make a conclusive diagnosis. This examination should be made preferably on the car- cass of a sick animal that has been killed, or on one that has just died. If the examination is delayed for a number HOG CHOLERA 331 of hours, it is likely to be of little service i i making a di- aofiiosis because of post-mortem changes. Lesions. — The extent of the changes in the oruans will depend on the length of the attack. If the animal died of acute hog cholera, the lesions will not, as a rule, be so marked as in the more chronic form. The color of the skin should be noted. Red or purDlish blotches are signi- ficant. The abdominal and lung cavities should be- care- fully opened and the following organs examined. The kidneys in the acute cases are likely to be darker than nor- Fipr. Gl. ITog Cholera Button ulcers on the intestinal wall are frequently noted in cases of chronic cholera mal, and to show small, red spots which impart to the organ a "turkey-egg'' appearance. The spleen or milt is usually enlarged, dark, and soft ; the liver is normal in ap- pearance ; and the membranes of the abdominal cavity, the stomach, aud the small intestines may show red areas, as if blood had been spattered on them. It will be found im- possible to remove the blood by washing, showing it to be iu the tissues rather than on them. The hemorrhages are to be found in many different parts of the body, and may vary in size from the pinpoint spots noted in the kidneys to areas of considerable size. The lungs may or may not be affected. If they are, the hemorrhages are present and 332 AGRICULTURAL BACTERIOLOGY portions of the lung tissue may be consolidated instead of being soft and filled with air. The surface of the heart may show the red blotches. In the acute cases the inner lining of the large intestine is frequently found to be blood- stained, and the feces may be bloody. In the more chronic cases the most characteristic lesions of the disease are found in the large - intestine, the so-called button ulcers, which are round, hard, and yellowish with a dark center. They are distinctly raised above the surrounding healthy surface of the intestine. In size they vary from a small point to the size of a twenty-five cent piece. The finding of such ulcers is to be considered as a positive indication of hog cholera, and it is the only lesion that can be regarded as absolutely diagnostic. The lymph-glands in various parts of the carcass are found upon section to be enlarged and reddened. A number of causes may produce symptoms that may be mistaken for cholera. Pneumonia due to exposure, dust, or lung-worms is sometimes confounded with cholera. Im- proper feeding may cause intestinal disturbances. Slops containing alkalies, such as soap powders, are often a source of trouble to garbage-fed hogs. Prevention. — Since but little can.be done to cure the disease after it has made its appearance in the individual animal, the farmer must direct his efforts to the prevention of the disease. It should be remembered that the organism is eliminated from the body of the affected animal in the urine and feces, and that it is present in all the tissues of the body. An animal that has recovered from the disease may still harbor the organisms in its body and eliminate them. With these facts in mind, the farmer can outline his plan for the protection of his herd. No animal should be purchased from a herd in which cholera has been present during the previous year, nor from a herd that has been HOG CHOLERA 333 subjected to the preventive treatment in which the virus has been employed within six weeks. Animals purchased should be kept in quarantine for four weeks and then al- lowed to come in contact with a small number of the herd. If these exposed animals remain healthy after two or three weeks' exposure, it is safe to place the purchased an- imals with the herd. It is not essential that a rigid quar- antine be established in the case of the purchased animals, for the prevention of intimate contact will usually suffice. The method of keeping hogs in separate houses rather than in one large house has many advantages, one being that if cholera breaks out in one of the yards, it can often be prevented from spreading to the remaining sections of the herd. Hogs that have been shown at fairs are likely to be ex- posed to infection, not only at the place of exhibition but also during shipment. Care should be taken in allowing such animals to mingle with the herd, until time has shown the animals to be free from infection. The virus of hog cholera can be carried on objects from one farm to another. It is probable that this is one of the chief wa3's in which the disease progresses in any locality into which it has been introduced. The farmer should re- member that any object transferred from an infected farm to his own may serve to carry the infection. The visiting of the hog-yards in which an outbreak has made its ap- pearance, the transfer of tools or wagons, or of animals such as dogs or cows, are ways in which the disease spreads. It seems probable that, if the farmer takes care of those factors that he can control, he will have little trouble with those he can not control. The herd should be kept in as healthy a condition as possible by providing clean, well ventilated pens, clean feeding-troughs, and proper feed, since anything that tends 834 AGRICULTURAL BACTERIOLOGY to weaken the animal makes it more likely to acquire hog cholera in case the organisms are taken into the body. It is generally believed that the feeding of new corn produces the disease. The feeding of large quantities of new corn may produce digestive troubles and make the animal more susceptible to cholera, but it can not cause hog cholera. If cholera makes its appearance in the herd, all the healthy animals should be removed at once to another field. One can not rely on the appearance of the animals to tell whether they are infected or not. A much more reliable way is to take the temperature of each animal, and to re- tain all showing any fever in the yard with the diseased animals. The normal temperature of grown animals ranges from 101° to 103° F. In young animals the tem- perature will run somewhat higher, but in separating the herd all animals having a temperature of more than 103.5° should be considered as infected. The carcasses of hogs that have died should be burned if possible. If this can not be done, they should be buried deeply. All infected litter should be burned. The care- less disposal of carcasses is one of the chief ways of spread- ing and perpetuating the disease. The hogs should be pastured in fields that do not border on the road and that are not traversed by streams, since infection may be introduced in either of these ways. The most effective way of protecting the herd against the disease is to apply the preventive treatment described later. Many cures for hog cholera have been proposed and are widely advertised. It is certain, however, that no treatment other than the administering of the protective serum is of any value. Protective treatment. — A hog that has recovered from a natural attack acquires an immunity to the disease, due to the presence in the blood of protective substances that IIOG CHOLERA 335 have been formed under the stimulus of the disease-pro- ducing organism. The amount of protective bodies that are thus produced as a result of an attack of the disease is not sufficiently great so that the blood can be drawn and introduced into the body of another animal for the pur- pose of imparting immunity. If, however, such an immune animal is injected with large quantities of the blood of a hog that is ill with the disease, the stimulus imparted by the introduction, of the virus will cause the animal to form additional protective bodies, so that it will be practicable to draw the blood and use it in protecting other animals. The hogs thus treated are said to be hyper-immunized. The protective serum is secured by bleeding the immunized hog. This is done by cutting off the tip of the tail. About five or six cubic centimeters of blood to one pound of body weight is drawn. This process is repeated three times, at weekly intervals. The animal is then given an- other injection of the virulent blood, is then bled twice from the tail, and after the usual interval is bled from the throat. The blood is beaten with a wire as soon as drawn from the animal to remove the fibrin and prevent clotting. One half of one per cent, of carbolic acid is added as a preservative. Before the serum is used in the field it is necessary to determine its protective power. This is done by injecting varying amounts into susceptible pigs that are inoculated at the same time with some virulent blood. In this manner it can be determined how much must be used in actual work to protect an animal. It will be seen that the prepa- ration of the serum is expensive because of the large num- ber of hogs that must be used and the labor involved. Many of the States have established laboratories for the preparation of the serum. By the use of the serum alone a passive immunity is 336 AGRICULTURAL BACTERIOLOGY produced that will protect the animal from a serious in- fection for from six to ten weeks. If a small quantity of virulent blood is introduced into the animal at the same time the serum is injected, active immunity will be pro- duced, which will generally protect the animal for life. The introduction of the virus at the same time as the anti- serum may result occasionally in a fatal case of cholera. In order to avoid this risk, the protective serum may be injected, and about a week or ten days later the virus may be given, together with a second dose of the anti-serum. The first method is known as the serum-alone method, the second as the simultaneous method, and the last as the double or combination method. Each has its advantages and disadvantages which must be considered in determining which to apply. The serum-alone is safe, but protects for only a short time, unless the animals coma in contact with infectious material soon after treatment, in which case the results are substantially the same as those obtained in the simultaneous treatment. The method is of small value iii the protection of breeding animals. It does allow the farmer to protect his herd for a short time when the dan- ger of infection is great. In the simultaneous method, some of the treated animals may die froin cholera, because not sufficient serum was used to protect against the virus administered. The ani- mals in which acute cholera is thus produced may serve as centers of infection from which the disease may spread to other herds. This danger has led many to advise against the use of the simultaneous method. In herds in which the disease already exists, only the serum should be used. The combination method avoids the danger of the simultaneous treatment, since rarely are any animals lost by cholera due to the treatment. It is more expensive, since serum must be given twice. HOG CHOLERA 337 Breeding herds should be protected by the use of the combination method, even if cholera is not present in the vicinity, because it enables the breeder to send, without danger, breeding hogs into infected districts and to fairs. Application of the serum. — The serum may be applied by the farmer liiniself, but if the virus is to be used, as is the case in the simultaneous or combination methods, a veterinarian should be employed, since the virus is dan- gerous material and, if handled by those who do not ap- preciate its nature, trouble may result. The animals should receive a light laxative diet for a day or so before being treated, and should be kept in clean, dry quarters. Small hogs are usually injected in the arm-pit. The animal may be held on its back between two round fence- posts joined together by cleats. Larger animals may be snubbed to a post by a rope around the upper jaw, and the serum injected in the fold of loose skin at the side of the neck. The needle of the hypodermic syringe should be thrust deep into the tissue, not simply through the skin as when tuberculin is applied. If the infection of the animal with organisms that will cause inflammation and abscesses is to be avoided, it is necessary to see that the syringe is sterilized before use, by placing it in cold water and bring- ing it to the boiling-point. If the syringe has leather washers on the plunger, its sterilization must be accom- plished by the use of chemical disinfectants, since boiling would destroy the leather. The skin at the point where the injection is to -be made should be scrubbed with a stiff brush, warm water, and soap ; then rinsed with some water that has been boiled and allowed to cool. The skin is then treated with a 4 per cent, solution of carbolic acid or tinc- ture of iodine. Care should be exercised to keep everything clean during the process. The doses of serum are as follows : 338 AGRICULTURAL BACTERIOLOGY ^eight of animal When virus is used No virus 0-20 lbs. 15 cc 10 cc. 20-50 lbs. 25 cc. 20 cc. 50-75 lbs. 35 cc. 25 cc. 75-100 lbs. 40 cc. 30 cc. 100-150 lbs. 50 cc. 35 cc. 150-200 lbs. 55 cc. 40 cc. 200-300 lbs. 65 cc. 45 cc. 300-400 lbs. 85 cc. 65 cc. 400^000 lbs. 100 cc. 85 cc. The larger quantity of serum is used with the virus in order to protect the animal against the v-irus, which by itself would cause death. The virus is usually applied at some other point than the serum, as beneath the skin at the center of the space between the fore legs when the serum is applied in the arm-pit. For a few days after the serum is administered the feed should be reduced to about one half the normal amount, gradually increasing until at the fourth week the full feed may be given. When only the serum is given, there should be little or no reaction. With the double or the simul- taneous treatment in six to ten days after the injection, the reaction fever sets in and the temperature may rise to 106° F. The animals may lose appetite, have chills, and present the symptoms of a mild case of hog cholera. The more susceptible animals may die from the effects of the virus. The hogs that show symptoms may eliminate the virus, and be the starting-point of an outbreak of cholera in case they come in contact with susceptible animals. The results that have been obtained with the serum have been such as to recommend its use. When applied in herds in which the disease had already made its appearance, more than 80 per cent, of the animals were saved, while the treatment applied before the infection of the herd took place has protected more than 90 per cent, of the animals against infection. HOG CHOLERA 339 There seems to be little doubt but that any farmer or breeder can protect his herd against loss from cholera by the consistent and careful use of the protective serum and the virus of the disease. It is a matter of some expense, and the farmer must weigh the cost of the insurance against the probable loss from cholera before deciding whether or not to apply the treatment. CHAPTER XXVI DISEASES OF FOWLS The transmissible diseases of fowls inflict a heavy tax on the poultry-raiser and the general farmer. Present knowl- edge concerning many of these diseases is far from com- plete, and in many cases so fragmentary that no definite plan for the eradication and prevention can be devised other than the customary plan applicable in most cases of transmissible diseases, viz., removal of affected individuals, 'destruction of carcasses, and general cleanliness and dis- infection. Chicken cholera. — Chickens, like swine, are subject to dietary disorders which may often simulate a true con- tagious disease in the rapidity with which it appears in the flock and in its high mortalit}^ Cholera is a term applied to many of such disorders that are not produced by a spe- cific organism. The true chicken cholera is rare in this country, and is due to the invasion of the body by a spe- cific form of bacteria. Symptoms. — The' urates, that part of the excrement ex- creted by the kidneys, in the case of healthy birds are pure white in color. In birds affected with cholera the urates are yellow, often a bright yellow, and sometimes a bright green. This change in color is not proof of the presence of cholera, but is a valuable indication of the disease. Diarrhea is usually present. The sick bird leaves the flock, becomes weak and drowsy, acts dumpish, and the feathers are roughened. Intense thirst is noted, the appetite is poor, and the crop remains distended with food. There is 340 CHOLERA 341 a rapid loss of flesh. The disease makes rapid progress in the flock, because of the short period of incubation, from one to three days. Most of the affected birds die in a short time of an acute form of the disease; others may have a chronic type; recovery is rare. On post-mortem examination the digestive organs will be found to be inflamed, and the liver is usually enlarged and softened. The presence of cholera can, however, be estab- lished only by a bacteriological examination of the blood, which will be found to contain great numbers of the causal organisms. The disease is a true septicemia. The organ- ism enters the body by the ingestion of contaminated food or water, which may become contaminated with the excre- ment of the affected birds or the material that drops from the beak. The extensive lesions in the intestine allow the excrement to become mixed with manure. The disease may be introduced into the flock by the pur- chase of a bird with a chronic form of the disease, or by doves and wild birds that fly from farm to farm. Prevention. — Nothing can be done for the birds that are infected. All efforts must be concentrated in preventing the spread of the disease. It should be remembered that every drop of blood contains great numbers of the causal organisms, and that if any portion of the carcass is con- sumed by well birds, they are certain to become infected. It is advisable to kill the birds that show any symptoms of disease. Tliis should be done in such a way that no blood is drawn. The dead fowls should be promptly disposed of; the feed and water troughs should be thoroughly disin- fected, as also the roosting houses. If possible, the still healthy birds should be removed to fresh, uncontaminated grounds. The causal organism does not produce spores and will not persist long outside the body of the bird. It is considered safe to bring new stock on the place after the 342 AGRICULTURAL BACTERIOLOGY expiration of two weeks, provided the house and other con- taminated objects have been thoroughly disinfected. Fowl typhoid. — This disease is often mistaken for chicken cholera. It is, however, produced by a different organism. The disease is less rapid in its progress in the individual bird than is cholera. The diarrhea so character- istic of cholera is absent, and the intestines are pale in- stead of deep red, as in cholera; the contents are normal in consistency, while in cholera the intestinal contents are liquid and blood-stained. The blood is free from the or- ganisms. It is not especially important that a correct diag- nosis be made as to which of these diseases is present in the flock, since identical methods of prevention should be employed with either. Cleanliness should be the chief re- liance of the poultryman against these diseases. Roup. — Roup, or diphtheria of fowls, is considered the most important transmissible disease affecting the barn- yard fowl of this country. It occurs in turkeys, ducks, pigeons, and pheasants, as well as chickens. The cause of roup has not been discovered, and it is not certain whether chickenpox and canker are different diseases from roup or different manifestations of the same disease. It has sometimes been considered that this disease has some relation to diphtheria in man. There is no reason for such belief other than that in certain forms of roup there may be formed a membrane similar to the membrane noted in diphtheria. The first symptom of roup is a watery discharge from the nostrils and often from the eyes. The bird becomes dumpish; the breathing is often noisy, due to the obstruction of the air-passages by the exudate. The fowl may be able to breathe only by opening the beak. Sneezing is frequent. The eyes may be covered with a dry discharge, or they may be forced from the sockets by the accumulation of cheesy matter in the sockets. There may ROUP 343 be found in the mouth and throat patches of grayish-yellow exudate or membranes. Death is often occasioned throu«;h suffocation due to the closing of the throat by the mem- brane. The swelling of the head caused by the accumula- tion of the exudate in the various cavities of the head has given rise to the term swell-head. It is considered that potassium permanganate is helpful i(T. 62. Roup The eye is swollen and filled with exudate as is the mouth both as a preventive and for the treatment of affected birds. It may be added to the drinking water in sufficient quanti- ties to impart a pink color to the water. The heads of the affected birds may be dipped in a 1 or 2 per cent, solution of the same substance. Roup is to be differentiated from simple catarrh, which closely resembles the human trouble known as cold-in-the- head. Simple catarrh is caused by exposure to dampness, cold winds, and by improper ventilation of the houses. It 344 AGRICULTURAL BACTERIOLOGY has been shown experimentally that it is impossible to pro- duce roup in these ways. There seems to be no doubt, how- ever, that birds suffering from catarrh are susceptible to roup. Roup may be carried from flock to flock by the transfer of birds with a mild form of disease. Fowls should not be purchased from infected flocks, and it is well to place in quarantine for some days new birds or those that have been at shows before i)lacing them with the flock. Any bird showing any discharge from the mouth or eyes should be removed at once from the flock. White diarrhea. — Of the diseases affecting young chicksy white diarrhea is the most important. It is probable that more than one trouble has been classed under this name. The white diarrhea of young chicks, caused by B. pullorum, is the most important. This disease offers an example of hereditary transmission of disease. It has been shown that the ovaries of the hen may be affected, and that the ova contain the organism. The young chick becomes infected from the yolk sac. Some of the females that survive con- tinue to harbor the germ and become bacillus-carriers. The adult females may become infected by contact with other infected adults or by infected litter. They may then be- come bacillus-carriers. The infection is in all probability acquired through the mouth. The economic importance of the disease is occasioned by its effect on young chicks. The greatest danger of infec- tion is during the first forty-eight hours. The danger of infection is very slight after four days. The affected chicks appear stupid and remain under the hover or hen much of the time. The feathers become rough, and the wings droop. There is constant loss of weight. The chicks eat little and appear unable to pick up their food. A whitish discharge from the vent soon makes its WHITE DIARRHEA 345 appearance. The discharge may be creamy or sometimes mixed with brown, and it is more or less sticky or glairy. In many cases it clings so closely to the down as to close up the vent. ]\Iany of the chicks peep constantly or utter a shrill cry, apparently of pain, when attempting to void the excrement. The abdomen is enlarged and protrudes to the rear. The post-mortem examination shows no marked lesions. The organs are all pale; the alimentary tract is usually empty except for some slimy fluid. The prevention of the disease must rest on the non-intro- duction of bacillus-carriers in the purchase of breeding stock, and by the purchase of eggs and young chicks from flocks that are known to be free from the disease. The w^idespread infection of breeding birds is shown by the fact that, in a flock in which the losses of the young chicks had been excessive, more than 80 per cent, of the laying hens were shown to have diseased ovaries. The chicks that recover from the infection do not, as a rule, grow as rapidly as do non-infected birds. It has been shown conclusively that the feeding of sour milk to young chicks is of value in preventing the spread of the disease. The dishes in which the milk, is kept should be cleaned daily and a fresh supply of milk provided. The incubators and brooders should be thoroughly dis- infected after each hatch, and extreme cleanliness should be practised in all regards in the handling of young chicks. CHAPTER XXVII BACTERIAL DISEASES OF PLANTS The most important transmissible diseases of animals are those caused by bacteria rather than by the other groups of microorganisms such as molds and yeasts, while in the plant kingdom the reverse is true. The molds are by na- ture better fitted to penetrate into the tissues of the plant than are the bacteria. Just as the increased commerce in animals has hastened and accentuated the spread of the transmissible diseases of animals, the increased sale of seeds and plants of all kinds and their shipment from one part of the country to another has led to the rapid spread of both bacterial and fungus plant diseases. At the present time about forty bacterial diseases of plants have been described. A few are wide- spread and are certain to come to the notice of every one engaged in farming, and are of great economic importance. The bacterial diseases of plants may be divided into four classes, depending on the manner in which they affect the plant: the blights, the rots, the wilts, and the galls. In the first the tissue is killed by the organism, but it is not decomposed as in the rots, in which the tissue is not only killed but decomposed; while in the wilts the passage of water to some portion of the plant is interfered with, and hence death of the affected tissues soon ensues. The complicated questions that arise in connection with the immunity against bacterial diseases of animals do not occur in the bacterial diseases of plants. There is a dift'er- ence in the susceptibility of different plants to the same 346 PEAR BLIGHT 347 organism. Efforts are being made to increase and extend this natural immunity. Much more can be done in an ex- perimental way in the breeding of resistant varieties of plants than can be done with animals. Pear blight.— The most important of the blights is that which affects the pear and apple, and to a lesser extent the quince, apricot, and plum. It was first observed in 1780 in the Hudson River valley, and as orcharding has spread Fior. 63. Pear Blight Normal fruit is shown on the right and diseased fruit on the left. In the center one of tl* i)ear8 is healthy, the other is affected westward, the disease has developed, until it is now found in all parts of this country and Canada. In Colorado it found such favorable conditions that it has caused the abandon- ment of commercial pear-growing. It has also caused great losses in California. As far as our present knowledge goes, the blight is of American origin and is confined to North America. Th^ disease is readily recognized by the' fact that the young twigs appear to have been injured by fire. This condition has given rise to the common name of fire blight. The leaves of the affected parts turn brown or black, and 348 AGRICULTURAL BACTERIOLOGY cling to the diseased twigs long after the other leaves have fallen. The twigs show a blackened and shriveled bark. The bacteria enter the tissues through the blossoms, being carried from flower to flower by bees and other insects. The immature fruit shows the disease by turning dark and gradually drying up. From the flowers the germs find their way into the cambium, or growing layer immediately below the bark. The diseased condition develops backward in the twig at the rate of an inch or more a day. The blackening of the bark does not occur as fast as the infec- tion spreads, so that infected tissue is always found sev- eral inches in advance of any outward signs. As the sea- son progresses the tissue becomes harder and less favorable for the growth of the organism, and b}^ the middle of the summer the progress of the disease has ceased. The infection may also occur through wounds in older tissue. It often reaches the large limbs and even the trunk, in which case it is known as body blight. The bacteria pass the winter in the blighted parts. These hold-over bacteria become active with the increased sap flow in the spring, and soon spread to the healthy bark, where they multiply so rapidly that at the time the blossoms open the bacterial growth oozes from the cracks in the diseased bark. In- sects attracted to this material become contaminated and thus carry the organisms to the blossoms. The bacteria multiply rapidly in the nectar of the flowers, and thus in- fection is carried from the old wood to the new. It is not rare to see a tree with almost every new twig showing symp- toms of the disease through its blackened leaves. Since the bacteria are protected by the bark, nothing can be applied to the tree that will destroy the organisms ; hence this trouble does not lend itself to such treatments as are found efl'ective in combating fungous diseases, in which the causal organism is found on the surface of the plant. The CABBAGE ROT 349 only known method of control is by the removal of all dis- eased branches as the symptoms appear. The cut should be made twelve to fifteen inches below the last visible sign of the disease. The diseased wood should be burned. Care should be exercised not to spread the infection through the prnninf>-kiiife or saw. Cabbage rot. — Of the class of bacterial diseases known as the rots, the black rot of the cabbage and related plant?? is most common ami important. The first s^^mptom is the appearance of yellow or brown areas near the margin of the leaf. The organism enters the tissues through the water pores on the edge of the leaf, and spreads along the ribs of the leaf, ultimately reaching the main stem of the plant in many cases. It causes the death and softening of the tis- sues. Invasion by other forms readily occurs in the broken-down tissue, with the result that the entire head ultimately is destroyed. The affected ribs are blackened, and on cutting across the infected stem one can see the blackened ends of the fibrous strands (the fibro-vascular bundles). The organisms may also enter the plant through wounds on the roots, such as are made when the young plants are transplanted. It has been shown that the organisms may be on the seed, and thus the soil of the seed-bed infected with the organisms, which await a favorable opportunity to pene- trate the plant. Preventive measures must consist of disinfection of the seed and rotation of crops. Rots caused by other bacteria occur in carrots, sugar- beets, muskmelons, and hyacinths. Wilts. — The wilts of the cucumber, muskmelon, squash, and pumpkin are widespread in the eastern half of the United States. The disease is characterized by a wilting of the vine, without any visible external cause. The leaves 350 AGRICULTURAL BACTERIOLOGY and runners wilt suddenly, as if from a lack of water or from too hot a sun. The whole plant may wilt, or only one runner. The disease is caused by an orojanism, the growth of which fills the water-ducts with a viscid mate- rial that prevents the rise of the water, and wilting follows. If the cut ends of a vine are rubbed together gently and drawn apart slowly, the viscid matter will string out for some distance. The infection is supposed to occur through wounds in- flicted by insects, such as the striped cucumber-beetle and the common squash-bug. A similar wilt affects the egg-plant, tomato, Irish potato, and tobacco. Galls or tumors. — Another class of plant diseases is marked by the formation of galls and tumors. Crown gall is the most important, and is peculiar by reason of the great number of plants that are susceptible to the attacks of the organism. The apple, peach, plum, prune, apricot, cherry, grape, raspberry, blackberry, rose, English walnut, chestnut, almond, white poplar, hop, sugar-beet, potato, to- mato, tobacco and Paris daisy are susceptible. The great- est economic losses are in connection with fruit trees and shrubs. It has also attracted attention because some of the manifestations of the disease are very similar to cancer in human beings. The presence of the causal organism stimu- lates the surrounding plant tissue to continued and persist- ent growth, which results in the formation of excrescences or tumors of varying size. CHAPTER XXVIII DISINFECTION In the discussion of various diseases, it has been shown that there are a number of ways by which the causal or- ganisms are eliminated from the body of the diseased ani- mal. For each disease the manner of elimination is more or less characteristic. In some it is true that the organisms ma}' be discharged in a number of ways, as in the case of tuberculosis, in which the organisms are to be found in the sputum, the feces, the milk when the udder is involved, and in the discharge from the genital passages when the repro- ductive organs are affected. In the case of Texas fever the causal organism is able to leave the body only as the blood is drawn, and under natural conditions the transmission of the organism from animal to animal is due entirely to the bite of a specific insect, one of the cattle ticks. It has also been shown that the organisms vary greatly in their resistance to environment. Those that produce spores are, as a rule, resistant to all agencies, and persist for long periods outside" the body in the dormant form. The non-spore-forming organisms differ greatly in resist- ance, some resisting certain agencies almost as long as the spore-bearing organisms, while others are so sensitive that the disease produced by them can be transmitted from ani- mal to animal only by the most intimate contact. It is fortunate that none of the important transmissible diseases in man is due to spore-bearing organisms, and but two of the diseases affecting animals, viz., anthrax and blackleg. If it were otherwise, the difficulties in combating the trans- missible diseases would be greatly increased. 351 352 AGRICULTURAL BACTERIOLOGY The control of infectious diseases rests on the prevention of the passage of the causal organism from diseased to healthy animals. This is accomplished in part by the iso- lation of diseased animals, thus preventing contact with non-infected animals. The federal and State quarantines, and those established by other agencies, seek to prevent the spread of disease in this v^ay. Another phase in the pre- vention of disease is the destruction of the organisms in the material discharged from the body of the affected ani- mal by the use of some physical or chemical agent before any healthy animal has opportunity to come in contact with the infectious material. This method is being used with the greatest success in the prevention of human dis- eases. It is evident that, before it can be applied, definite knowledge must be obtained of the nature and resistant powers of the organism, and the ways in which it is elimi- nated from the body; otherwise all efforts are likely to be unsuccessful, for, to secure effective results, every organism must be destroyed. In the case of typhoid fever it is easy to treat all of the infectious discharges of the patient so as to prevent the spread of the disease. Indeed, the concurrent disinfection or the immediate treatment of all infectious material as soon as it leaves the body of the patient is so successful that practically all of the transmissible diseases of man are now treated in the same wards in some of the great hospitals of the world, without the various diseases spreading from one patient to another. The former plan was to pay little at- tention to the treatment of the discharges, but to attempt to destroy the organisms in the room and on the objects with which the patient had been in contact after death or recov- ery had taken place. This is called terminal disinfection, and represents that which must be employed in the control of animal diseases, together with isolation of the affected DISINFECTION 353 animals. In other words, the farmer will find it necessary to destroy the disease-producing: organisms in the stables in which diseased animals have been quartered before the stables are used for healthy stock. Natural agencies. — The two agencies of nature that de- stroy many disease-producing organisms are drying and light. The disease-producing organisms vary widely in their resistance to desiccation. Most of the non-spore-pro- ducing types endure drying for only a short time, and it is certain that this is one of nature's most effective ways of destro3'ing and limiting the spread of harmful organisms. The direct rays of the sun exert a powerful germicidal effect, and are able within a comparatively short time to destroy not only the vegetative cells of the organisms but many of the spores. The action of light as a purifying agent is, however, often overestimated. It is effective only when the direct rays of the sun strike the unprotected or- ganism. The action of diffuse daylight is so small as to have no practical importance, and when the organisms are covered with a layer of dust, or are embedded in manure or other material, the action of sunlight is of no importance. It is certain that ample provision should be made for light in our houses and stables, but not with the idea that disease-producing organisms shall be destroyed, but rather to render ourselves and our domestic animals more resistant in case they are brought in contact with infectious material. Heat is another physical agent that can be used in the destruction of organisms. It is applied either in the form of dry heat, or as steam or hot water, depending on the material to be treated. Here again the resistant powers of the organism must be considered in determining the ex- posure that must be used to be effective. All small objects of wood or iron, and all clothing, can be most easily ren- dered harmless by boiling. In the control of the trans- 354 AGRICULTURAL BACTERIOLOGY missible disease of human beings, this process is of the great- est importance. The use of dry heat is limited, except when material is to be destroyed by burning, a method that should be widely used in the disposal of carcasses of animals and litter. Chemical disinfectants. — A large number of chemicals have an injurious action on microorganisms. It is cus- tomary to divide them into two classes, which differ in the intensity of action. Those that have a relatively weak action and tend to prevent the growth of organisms rather than to destroy them are termed antiseptics, or preserva- tives when used in foods. Those that have a more pro- nounced action and destroy the organisms are called dis- infectants. It will be apparent that when a disinfectant is present in small amounts, it will have an antiseptic action, since cessation of growth will always precede death of the organism ; but certain of the antiseptics can not exert a dis- infecting action, even if used in concentrated form. For example, boric acid is but slightly soluble in water, and in a saturated solution exerts an antiseptic action; but, owing to its limited solubility, it can never be classed as a disin- fectant. Some of the disinfectants have the power of over- coming offensive odors by combining with specific sub- stances, and are often called deodorants. Some deodorants have little or no disinfecting action, and of course are of little or no value, since they do not act on the source of the trouble. Again, some chemicals used as disinfectants have an injurious action on insects, such as lice on animals. In the use of these agents the farmer should first have in mind what he desires to accomplish, and then choose the agent that is most likely to be effective as a disinfectant, a deodorant, or an insecticide. He must also have informa- tion as to the resisting power of the organisms he is attempt- ing to kill, and as to the effectiveness of the disinfecting DISINFECTION 355 agent, otherwise his work is likely to be of no avail. For example, the use of carbolic acid as a protection against hog cholera is of little or no value, since it is known that the organism will live for months in the presence of one half of one per cent, of this substance which is so effective in the destruction of many disease-producing organisms. Each class of disinfectants has its advantages and dis- advantages. A particular class can be used to advantage under certain conditions, while, under other conditions, its use may be of little value. Lime.— In the manufacture of lime, the limestone, which is a carbonate of lime, is heated to drive off the carbon- dioxide, forming calcium oxide, which on exposure to the air gradually combines, with the carbon-dioxide in the air to form the carbonate again, or air-slaked lime. If the quick or stone lime, as it is often called, is treated with six parts of water to ten of lime, a dry white powder will be obtained, called hydrate of lime or water-slaked lime. The water-slaked lime resembles air-slaked lime in appearance, but not in composition, as can be determined by placing a little of each on the tongue. The air-slaked lime has a chalky feel and taste, while the water-slaked causes the tongue to burn. It has caustic and disinfecting properties, while the air-slaked has no value whatever as a disinfectant. Lime is one of the best disinfectants that can be used on the farm for many purposes. The dry powder, produced when a proper amount of water is added to the lime, can be used or it can be applied to the walls and ceilings in the form of whitewash. The whitewash has a germicidal ac- tion, as well as a mechanical incrusting effect, thus placing the organisms under such conditions that they can not exist for any length of time. It makes the stables lighter and cleaner than would otherwise be the case. If the white- wash is prepared from good lime and properly applied, it 356 AGRICULTURAL BACTERIOLOGY is probably as effective a disinfecting agent as can be used to advantage in ordinary stable disinfection. It can be made more effective by the addition of carbolic acid or chloride of lime. In all disinfecting processes it is essential to use plenty of the agent. The cheapness of lime is thus an advantage, as is the ease with which it can be procured. It is also to be recommended when carcasses of animals that have died from transmissible diseases must be buried instead of being burned. In such cases the carcass should be well covered with lime, and then the dirt returned to the excavation. Carbolic acid. — Carbolic acid is prepared from coal-tar and is sold in the form of white crystals which melt below the boiling-point of water, and which remain liquid on the addition of 5 per cent, of water to the melted acid. It is used as a disinfectant in solutions containing from 1 to 5 per cent, of the pure acid. Its action is not greatly re- tarded by the presence of organic matter, as is the ease with so many other disinfectants; hence it can be used for the disinfection of feces from typhoid patients, and the treatment of sputum of tubercular people. Carbolic acid, or phenol as it is often called, does not find wide use on the farm, because of its expense, its cor- rosive action on the skin, and its poisonous properties. Coal-tar disinfectants. — After the carbolic acid has been removed from coal-tar, the residue still contains substances that have a disinfecting action. From this residue there is now prepared a great number of disinfectants commonly known as coal-tar- or cresol disinfeictants, a term that ap- pears in the name of many of the proprietary compounds, such as kresol, kreso, kresolig. The value of these com pounds varies widely. Some are about equal to carbolic acid, while others are ten times as effective. The great majority are from two to three times as effective as phenol DISINFECTION 357 and are used in solutions containing from 1 to 3 per cent, of the agent. They are less corrosive and less poisonous than phenol, and can be used as a dip for the destruction of insects on animals. They are usually composed of the creosote oil and soap, and when mixed with water form a milky emulsion that is very permanent. They can be em- ployed in widely varying concentrations, and their action is, as a rule, not greatly impaired by the presence of or- ganic matter. Only soft or rain water should be used to dilute the coal-tar disinfectants, because the salts present in hard water may materially reduce the disinfecting action. They are undoubtedly the best class of disinfectants for common use on the farm, especially in the treatment of animals. Formaldehyde. — This important disinfectant is sold in the form of a 40 per cent, solution of the gas dissolved in water, and is usually called formalin. Its widest use on the farm is in the disinfection of closed spaces by setting free the gas from the liquid, as will be described later, and for the destruction of smut on seed grains and scab on seed potatoes. Corrosive sublimate. — This compound, frequently known as bichloride of mercury, is one of the strongest disinfect- ants known. Its disadvantages are its poisonous properties and its greatly decreased action in the presence of organic matter such as manure. It also has a corrosive action on metals, and is irritating to the tissues. It can be used to advantage in many places as a wash or as a spray on walls. For this purpose it is used in a one to one thousand solu- tion, or one ounce of the salt to eight gallons of water. Sulphur. — AVhen sulphur is burned, irritating fumes are formed. When moisture is present in the air, sulphurous acid is formed which possesses a considerable disinfecting action. It is used in the place of formaldehyde as a gaseous 358 AGRICULTURAL BACTERIOLOGY disinfectant for such closed spaces as refrigerators and other rooms in which the bleaching action of the sulphur will be of no importance. It can not, as a rule, be used in furnished rooms because of this property, which formalde- hyde does not possess. Calcium hypochlorite. — Bleaching pow'der or calcium hypochlorite has long been used as a disinfectant and de- odorant. Under certain conditions it is one of the most effective that can be employed, as for example in the treat- ment of water and sewage. Many cities draw their water supplies from sources that may become contaminated with typhoid bacilli. It has been found that the addition of minute quantities of bleaching powder is sufficient to de- stroy the typhoid organism. Calcium hypochlorite finds its widest use as a deodorant for use in cellars, privies, and similar places. For these purposes the dry powder is usually employed. It can be used for the treatment of cisterns in which a large amount of organic matter has been carried by the wash from the roofs. During the warm weather the de- composition of the organic matter may be so marked as to impart a disagreeable odor to the water, which can be over- come by the addition of a solution of bleaching powder. The amount to be added will depend on the quantity of or- ganic matter in the water. It should be added in small quantities, as an excess will impart the characteristic odor of the hypochlorite to the water. Ferrous sulphate and copper sulphate. — These sub- stances, commonly known as green and blue vitriol, have been widely used as disinfectants in the past. It is now known that they are almost worthless and should be discarded in favor of some one of the efficient disinfectants. Disinfection. — The choice of a disinfectant for any par- DISINFECTION 359 ticular purpose will depend on the conditions under which it is to be used. If the room to be treated is so constructed that it can be made tight enougrh to retain the gas for some hours, the use of formalin or sulphur is to be recommended. The gas penetrates to every portion of the room, into cracks and crevices into which it is difficult to- force a liquid. Gas will not easily penetrate layers of clothing and bedding, so that the treatment of a living-room or bedroom with a gaseous disinfectant will often not accomplish what many conceive it will do. For the treatment of surfaces to which a liquid can not be applied it is of the greatest value. The room to be treated should be made as tight as pos- sible by pasting paper over the window and door cracks. The gas can be liberated from the liquid by the use of per- manganate of potash. One pound of formalin and one half pound of permanganate will be needed for each thousand cubic feet to be treated. The permanganate is placed in a large pail and the formalin poured over it. A violent chemical action results, and a portion of the formaldehyde is set free. The room should be warm and the air moist to obtain the best results. The room should be opened for twenty-four hours. The gas has no harmful action on objects except those of delicate leather. If sulphur is used, five pounds must be employed for each thousand cubic feet. The sulphur should be placed in an iron vessel, which should be set in a pan of water so that the heat will evaporate a portion of the water, for it is essential to have a considerable amount of moisture in the air if the sulphur is to prove effective. The powdered sul- phur is ignited by making a depression in the center of the pile and adding a small amount of kerosene, which is ig- nited. The room should remain closed for twenty-four hours. Stable disinfection. — In the treatment of stables and 360 AGRICULTURAL BACTERIOLOGY other places in which there is likely to be a large amount of material, such as manure that contains the harmful or- ganism, the first step in the disinfecting process should be the thorough cleaning of the stable walls and floor, in order to remove as much as possible of the infectious material and allow the disinfectant to come in contact with the bare surface of the walls. Dried manure is not easily pene- trated by the liquids, and the organic matter is likely to combine with the disinfectant used and thus reduce its action. The thorough cleaning will remove most of the organisms. All loose woodwork such as box mangers, etc., should be removed. The walls should be moistened with a solution of corrosive sublimate so as to prevent dust in the subsequent cleaning. The walls and floors should be scraped clean, and the material removed and all litter burned, not thrown into the yard, where animals may have access to it. The disinfectant should be applied with a spray-pump that will enable one to reach all parts and to force it into the cracks. If whitewash is used, it should be strained and made thin enough not to clog the pump. The mangers should be well scrubbed with a solution of lye and then with water. A half-hearted job of disinfection is no better than none at all. It gives a fancied but no real security against a recurrence of the disease. The disinfection of yards is something that can not be done under ordinary conditions. If a small yard is in- fected, a liberal sprinkling with dry, water-slaked lime is the best that can be accomplished. The disinfection of fields is impossible. Small areas may be limed or burned over, but neither of these methods is likely to be effective in the case of spore-bearing organisms, and all other forms will soon die. One must rely on natural agencies for the destruction of pathogenic organisms that have been brought DISINFECTION 361 in contact with the soil of yards or fields. It should be re- membered that the patliogenie organisms do not find condi- tions for growth in the soil, and hence their destruction is only a question of time, and with all except the spore-form- ing bacteria the time will be relatively short. Burning over a pasture may be resorted to in order to get rid of vegetable growth and give a better chance for sunlight to exert its influence. INDEX Abortion, contagious, 299 Acetic fermentation, 196 Acid-fast bacteria, 272, 293 Actinomyces, 26 Actinomycosis, 317 Aerobic organisms, 53 Agar, 35 Agirlutinin, 302 Air, contamination of milk from, 139 Air, microorganisms in, 04 Alcoholic fermentation, 193 Ammonification, 9() Amphitrichous l)acteria, 22 Anaerobic organisms, 52 Aniline dyes. 10, 43 Anthrax, 252 Antiseptics, 56 Antiserum, 247 Antitoxin, 248 Antitoxin, tetanus, 326 Ascospores, 28 Ascus, 28 Aspergilli, 30 Auto-intoxication, 85 Autolysis, 58 Avian tuberculosis, 291 Azotobacter chroococcum, 119 Bacillus, 13, 20; abortus, 301; botulinus, 106: Chauvei, 263; coli, 166, 188; lactis aerogenes, 166, 188; pullorum, 344 Bacteremia, 241 Bacteria, cell aggregates of, 18; coll structure of, 20; classifica- 363 tion of, 25; determination of number of, 41; discovery of, 7; involution forms of, 14; micro- scopical examination of, 42; morphology of, 13; motility of, 21; relation to animals, 85; re- lation to reaction, 53; repro- duction of, 14; size of, 22; spores of, 16; urea-fermenting, 98 Bacterial poisons, 166 Bacterial standards for milk, 231 Bacterium, anthracis, 253; Bul- garicum, 189, 210; lactis acidi, 106, 187; lactis longi, 192; tuberculosis, 272 Bacteroids, 129 Benzoic acid, 173 Berthelot, 118 Beyjerinck, 124 Bichloride of mercury, 357 Birds, tuljerculosis of, 291 Bitter milk, 193 Black leg, 263 Bleaching powder, 170, 358 Boric Acid, 173 Bread, 199 Broth, preparation of, 34 Brown ian movement, 43 Butter, abnormal flavors in, 207; control of flavor of, 204, 205; decomposition of, 206; flavor of, 203; renovated, 206; sour cream, 203 ; sweet cream, 202 Butyric fermentation, 191 364 INDEX Cabbage rot, 349 Calcium, 87; hypochlorite, 170, 358 Capsules, 21 Carbohydrates, 02 Carbolic acid, 356 Carbon, cycle of, 83 Carbon dioxide, formation of, 83 Cellulose, decomposition of, 84 Cheese, 207; brick, 213; camem- bert, 213; cheddar, 208; gassy, 209; Gorgonzola, 212; Limbur- ger, 213; mold ripened, 212; Roquefort, 212; soft, 213; Stil- ton, 212; Swiss, 210 Chicken cholera, 340 Chlamydobacteriacea, 26 Clarification of milk, 151 Cladothrix, 26 Clostridium, 17; Pasteurianus, 119 Coal tar disinfectants, 356 Coccus, 13 Colonies, 39 Commensal microorganisms, 58 Communicable diseases, 239 Concentration, effect on micro- organisms, 49; preservation of foods by, 171 Condensed milk, 172 Conidia, 29 Conidiophores, 29 Copper sulphate, 358 Consumption, 272 Contagious diseases, 239 Cornstalk disease, 268 Corrosive sublimate, 357 Cover crops, 103 Cream, bacterial content of, 203; pasteurization for butter, 204; ripening of, 205 Cresol, 356 Creosote, 174 Cultures, 40 Cycle of elements, 6 Decomposition, 5, 8, 50, 61 ; of foods, 136; in soil, 78 Denitrification, 104 Desiccation of foods, 171 Digestion tanks, 112 Diphtheria, 165 Diplococcus, 19 Disinfectants, 56, 354; coal tar, 356 Disinfection, 351, 358'; concur- rent, 352; terminal, 352 Dosing chamber, 114 Earth worms in soil, 76 Eggs, preservation of, 178 Endospores, 16 Enzymes, 56 Eubacteria, 25 Factory by-products, contamina- tion of milk from, 149 Facultative organisms, 53 Farcy, 320 Fats, 62 Feed, contamination of milk from, 157 ; influence on taste of milk, 152 Fermentation, 5, 186 Ferrous sulphate, 358 Fire blight, 347 Fire fanging of manures, 108 Flagella, 21, 44 Flax, retting of, 86 Flies, transmission of anthrax by, 254 Floats, 89 Foods, bacteriological control of, 215; concentration of, 171; contamination of, 135, 152; desiccation of, 171 ; influence of bacterial content on health- fulness of, 165; organic acids in, 174; poisonous, 166; pres- ervation of, 168; preservation of by heat, 179; preservatives INDEX 365 in, 172; tubercle bacilli in, 1.55 Foot and mouth disease, 305 Formaldehyde, 357 Formalin, 173 Fowl typhoid, 342 Fre<'/.inor, effect on micror)rgan- isms, 51 Halls, plant, 350 " Garget, J58 Gelatin, 35 Generation period of bacteria, 15 Glanders, 320 Gram's stain, 45 Haplobacteria, 24, 25 Heat, effect on microorganisms, 52; preservation of foods by, 179 Hellriegel, 122 Hemorrhagic septicaemia, 206 Hemp, retting of, 80 Hippuric acid, 08 Hog cholera, 328 Hogs, tuberculosis of, 290 House fly, 164 Humus, 80 Hydrogen, 86 Hydrogen sulphide, 91 Hyphae, 28 Immunity, 242, 243; persistence of, 249 Infant mortality, 166 Infection, 240 Infectious diseases, 239 Involution forms, 14 Iron bacteria, 92 Johne's disease, 293 Kefir, 190 Koch, 10, 252, 281 Koumiss, 195 Leeuwenhoek, 7 Legumes, 120 Legume bacteria, groups of, 127 Leptothrix, 26 Lesions, 242 Liebig, 8, 120 Light, relation of microorgan- isms to, 54 Lime, 355 Lockjaw, 324 Lophotrichous bacteria, 22 Low temperature, preservation of foods by, 175 Lumpy jaw, 317 Lupus, 2?2 Mallein, 323 Manures, 107; loss of organic matter from, 108 Meats, chopped, 153 Media, culture, 33; liquefiable solid, 35 Mesophilic microorganism, 51 Metabiosis, 59 Metachromatic granules, 21 Metchnikoff, 85, 190 Methane, 86 Microbiology, 6 Micrococcus, 25 Micron, 22 Microorganisms, distribution of, 63; role of, 3 Microscope, 42 Microspira, 26 Milk, 135; absorption of odors by, 152; acid fermentation of, 186; bacterial standards for, 231; bitter, 193; certified, 228, 233; clarifying of, 151; con- tamination of, 137, 151; cur- dling of, 187; factors deter- 'S66 INDEX mining number of bacteria in, 150; grades of, 227; pasteuri- zation of, 180, 234; rules for production of, 216; slimy, 192; straining of, 151; sweet cur- dling of, 191; taste of influ- enced by feed, 152 Milk pails, small topped, 145 Milker, contamination of milk by, 146 Milking machines, 147 Mineralization, 5 Moisture, relation of microorgan- isms to, 48 Molds, in soil, 75; morphology of, 28; relation to air, 53; re- lation to reaction, 53 Monotrichous bacteria, 22 Morphology, 12 Mucors, 30 Multicellular organisms, 12 Murrain, 254 Mycelium, 29 Nitrate deposits, 104 Nitric acid, action on calcium carbonate, 89 Nitrification, 99 Nitrogen, cycle of, 94; fixation of, 117; forms available to green plants, 90; loss from soil, 95 Nitrogenous fertilizers, availa- bility of, 97 Nocardia, 20 Nodular disease, 293 Oidia, 30 Oidium lactis, 189, 213 Oleomargarin, 200 Organic acids, 174; action on cal- cium carbonate, 89 Oxygen, relation of microorgan- isms to, 52 Osmotic pressure, 49 Oysters, 153, 164 Parasitic mcroorganisms, 58 Pasteur, 9, 179, 316 Pasteurization, 179; of milk, 234 Pathogenic organisms, 154 Pear blight, 347 Pearl disease, 272 Penicillia, 30 Pepsin, 209 Peptone, 34, 96 Period of incubation, 242 Peritrichous, 22 Phagocytes, 243 Phenol, 356 Phosphates, action of bacteria on, 89 Phosphorus, 89 Phthisis, 272 Physiological characteristics, 40 Physiological dryness, 48 Pickles, 174 Planococcus, 25 Planosarcina, 25 Plant food, available and un- available, 70; store in soil, 70 Plasmolyzed cells, 49 Plasmotypsis, 50 Potassium, 90 Preservatives, 56, 172 Preventable diseases, 239 Proteins, 62; decomposition of, 90 Proteoses, 90 Protozoa, 32, 97, 295 Pseudomonas, 20 Psychrophilic microorganisms, 51 Pure cultures, 33; isolations of, 38 Putrefaction, 5 Rabies, 311 Reaction, relation of microorgan- isms to, 53 INDEX 367 Rennet, 207, 209 Retting, S() Roup, 342 Saeeharomyctes, 2G Saprophytic microorganisms, 5S Sarcina, 20, 25 Sauerkraut, 174 Scarlet fever, 165 Sell i/omy cotes, 13 Score card for dairies, 222 Semi-permeable membrane, 49 Septic tanks, 1 1 1 Septicaemia, 241, 206 Septic sore throat, 158 Serum, protective, 247 Sewage farms, 110 Sewage disposal, 109 Silage, 175 Slimy fermentations, 192 Smallpox, vaccination against, 246 Smoking meats, 174 Soil, air in, 73; decomposition in, 78; inoculation of, 125; micro- organisms in, 63; moisture in, 72 ; number of microfirganisms in, 75; odor of, 93; reaction of, 74 ; temperature of, 74 Spices, 174 Spirillum, 13, 26 Spirochaeta, 26 Spirosoma, 26 Splenic fever, 254 Spontaneous generation, 8 Sporangia, 29 Sporangiaphore, 29 Spores, bacterial, 16, 44 Staining bacteria, 43 Staphylococcus, 19 Starters, 205 Sterigmata, 31 Sterile, 36 Sterilization, 36, 37, 179, 183; by filtration. 37; by heat, 36 Straining of milk, 151 Streptobacillus, 19 Streptococcus, 19, 25 Sulphates, 91; reduction of, 92 Sulphur, 91, 357 Sweet curdling of milk, 191 Symbiosis, 129 Symptomatic anthrax, 263 Syrups, 172 Taettemjolk, 192 Temperature, relation of .micro- organisms to, 50 Tetanus, 324 Tetracoccua, 20 Texas fever, 295 Thermal death point, 52 Thermophilic microorganisms, 51 Tick fever, 296 Torulae, 28 Toxemia, 241 Toxins, 241 Transmissible diseases, necessity for correct diagnosis for, 251 Trichobacteria, 24, 26 Tuberculosis, 269; bovine, 155 Tuberculin, 281 Tuberculin test, 283 Tumors, plant, 350 Turgidity, 49 Typhoid carriers, 163 Typhoid fever, 159 Udder, contamination of milk ' from, 137 Ultramicroscopic organisms, 23 Unicellular organisms, 12 Urea, 98 Urease, 98 Uric acid, 98 Utensils, cleansing of, 148; con- tamination of milk from, 146 Vaccination, 246; against an- thrax, 259; against black leg, 368 INDEX 265; against hog cholera, 334; against rabies, 315; against Texas fever, 299 Vaccines, 246 Vinegar, 196 Virus, filterable, 23 V^itamines, 181 Water, ground, salts in, 87; microorganisms in, 63; puri- fication of, 169; supplies, con- tamination of, 160 Weigert, 10 Wells, protection of, 161 Whey, contamination of milk from, 149 ; heating of, 149 White diarrhea, 344 Wilfarth, 122 Wilts, 349 Yeasts, 193, 199; in soil, 75; morphology of, 26; relation to air, 53; relation to reaction, 53; reproduction of, 27; spores of, 28 Yoghurt, 190 Zoogloea, 21 UNIVERSITY OF CALIFORNIA LIBRARY THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW APR 2 8 1934 JAN 2 m 16 Ai. 28 B'i' 19tt FEei 1363 F£B 4REC'D DEC 19 1969 [DEC 9RlC'D^ 5to-10,'22 >?^ So nh UNIVERSITY FARM LIBRARY