Bacteriology and surgical technique for nurses

Front matter

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Chap Copyright No...

Preface

The following pages constitute the notes of a series of lectures on "Bacteriology and Surgical Technics" which followed closely upon my lectures on u Materia Medica." The first part of the book is devoted to Bacteriology and Antiseptics ; the second part to Surgical Technic, Signs of Death, Autopsies.

No attempt has been made to write a complete treatise on bacteriology, but merely to outline and simplify that branch for nurses.

It was deemed advisable to add the chapter on "Signs of Death and Autopsies," as many nurses are unacquainted with the preparations for an autopsy in private practice.

So many changes have taken place in surgery since the lectures were delivered that it has been necessary to 'rewrite many of the chapters. In this I was assisted by Dr. A. S. Allen and by Professors J. B. Murphy, Christian Fenger, and Joseph L. Miller, of the Northwestern University Medical College. I am glad of this opportunity to thank them for their assistance.

6 PREFACE.

Free use has been made of the works on bacteriology by McFarland, Crookshank, and Woodhead; of u Aseptic Surgical Technique, n by Dr. Hunter Robb ; " Operative Gynecology,'- by Dr. Howard A. Kelly; and u Aseptic Treatment of Wounds," by Dr. C. Schimmelbusch.

I am unable to express my indebtedness to Dr. Joseph P. Comegys for his valuable assistance with the manuscript and its preparation for the press.

I wish also to thank Drs. George L. Eyster and Charles C. Carter for their friendly help and interest in the work.

EMILY M. ARMSTRONG-STONEY.

September, 1900.

BACTERIOLOGY ; ANTISEPTICS.

Chapter I. History Of Bacteriology

The eye is one of the most beautiful and delicately contrived organs in the body, and yet its vision unaided is very limited in its scope. We see so much that we rarely stop to think of what an enormous world exists in and all about us which we cannot see at all — a world peopled by organisms so very small that they can be seen and studied only by the aid of the most powerful magnifying lenses, and so numerous that they are quite beyond any calculation.

Bacteria exist nearly everywhere; they are almost universal, except that they are not found deep down in the ground nor high up in the air. They and their spores, or seeds, float in the air we breathe, swim in the water we drink, grow upon the food we eat, and luxuriate in the soil beneath our feet. Wherever man, animals, and plants live, die, and decompose, bacteria are sure to be present. The surface of the body never escapes their establishment, and so deeply are some individuals situated beneath the epithelial cells that the most vigorous scrubbing and washing and the use

IO BACTERIOLOGY.

of powerful disinfectants are necessary to remove them from the surgeon's hands.

The mouth is said to be always replete with them; and, since many are swallowed, the digestive tract always contains them. The germ of pneumonia, for instance, is said to be habitually present in the mouth of almost every healthy person; consequently, its entrance into the lungs is only a matter of accident.

The existence of these bacteria has been known for many years, but it is only during the past few decades that any great advancement in our knowledge of them has been made.

Over two hundred years ago a man named Athanasius Kircher, a German, mistook blood-corpuscles and pus-corpuscles for small worms, and built up a new theory of the causes of disease and putrefaction with these worms as a basis of it. At the same time, Christian Lange, a professor in the medical school at Leipzig, expressed his opinion that the rash that appeared on the skin in the eruptive fevers, etc., was the result of putrefaction conveyed by small living worms in the body. Shortly after these observations came those of Anthony van Leeuwenhoek, a native of Delft, in Holland, who, in his early years, had learned the art of polishing lenses, and who was able, ultimately, to produce the first really good microscope that had yet been constructed. He saw, and described with astonishing clearness, various forms of bacteria found in the material taken from the teeth of an old man who never cleaned his teeth. He gave an accurate description of the rod-shaped bacteria, motile and motionless; of the longer threads, now called bacilli; of the spiral threads, or spirilla;

and of rounded micro-organisms, or micrococci. Although he did not attempt to theorize as to the meaning of these organisms in the mouth at the time, later on, in 1713, after finding similar organisms in the greenish pellicle formed on the surface of the water in an aquarium, he came to the conclusion that the various forms of bacteria found in the material scraped from the teeth found their way into the mouth through the medium of the drinking-water that had been stored in barrels, and that some of these found there a nidus in which they multiplied.

This was the real beginning of bacteriology; and from this origin the study advanced with considerable rapidity in spite of ridicule and much opposition. Various opinions regarding the connection of these germs with disease and putrefaction, w 7 ere put forward; but it was not until 1831 that any important advance was made in our knowledge of this connection. Previous to that time a large mass of facts in regard to these little living organisms was being gradually accumulated, and fresh discoveries were constantly made by various workers; but since no systematic attempts to classify the newly observed facts were made, the scientific results were very small.

The first real advance made in our knowledge of the presence of a " contagium vivum," or living contagious element in the production of disease and fermentations, was made by Frederick Miiller, of Copenhagen, and was the result of a systematic attempt to arrange the knowledge which had been accumulated during all those years. From that time to the present, the science has made great strides; so that we have now an accurate knowledge of the bacteria which cause a number of different diseases. The knowledge of methods and details of work is now so general that the science of bacteriology is rapidly growing, and has revolutionized already very many branches of medicine.

In 1840, Henle was led to believe that the cause of miasmatic, infective, and contagious diseases must be looked for in living fungi, or other minute living organisms. Unfortunatelv, at that time the methods of study employed prevented him from demonstrating the accuracy of his belief. It was left for Pasteur and Koch to complete the work. Davaine, in 1848, was the first to see and to recognize disease-producing bacteria — he saw anthrax-bacilli in the blood of sheep dead of splenic fever.

Pasteur then took up the work; and in 1857 his faultless demonstration of the germ-theory of disease was brought out as a result of his experiments on fermentation and putrefaction, and on the bacteria of wine and those of the silkworm. He showed that the acetic fermentation, viscosity, bitterness, and turning flat of wines are due to the action of certain organized ferments, and demonstrated a causal relation between certain lowly-organized parasitic organisms and special diseases in animals and insects. Upon Pasteur's observations Lord Lister based his successful system of the treatment of wounds, known as u antiseptic surgery. ' '

We all know of the wonderful success which now marks the operations of major surgery, and of the daring boldness of operators who attempt what was utterly impossible as long as antiseptic surgery was unknown. Lister, accepting the truth of Pasteur's

statement — that germs are the producers of fermentations — concluded that germs entering wounds from the outside might be the cause of suppuration; and since germs are always and everywhere floating in the air, suspended in water, and attached to the surgical instruments, dressings, and sponges used in operations, he judged correctly that it was highly advantageous to employ an antiseptic agent in order to kill any of the suspended or adherent organisms before any materials could be allowed to come in contact with wounded tissues; consequently, the hands of the operator and his assistants, the surgical instruments, sponges, dressings, sutures and ligatures, were kept constantly saturated with a solution of carbolic acid (1 : 40), and the operation was performed under a spray of carbolic acid (1 : 20). Carbolized dressings were used; and if the discharge was profuse, the dressings were changed once in twenty-four hours under a constant use of the spray. The researches of a later date have shown, however, not only that the atmosphere cannot be disinfected, but also that the air of ordinarily quiet rooms, while containing the spores of numerous saprophytic organisms, rarely contains many pathogenic bacteria. We also know that a direct stream of air, such as is generated by an atomizer, causes more bacteria to be conveyed into a wound than ordinarily would fall upon it, thereby increasing instead of lessening the danger of infection. Lister, we must remember, was not the discoverer of carbolic acid nor of the fact that it would kill bacteria; but, convinced that inflammation and suppuration were caused by the entrance of germs from the air, instruments, sponges, and dressings, into wounds, he suggested the antisepsis which would result from the use of sterile instruments, clean hands, dressings, towels, and the like; and made applications intended to keep the surface of the wound moistened with a germicidal solution in order to kill such germs as might accidentally enter. He also introduced the practice of concluding operations by the application of a protective dressing, such as would tend to preclude the entrance of germs at a subsequent period. Listerism has spread slowly but surely to all the departments of surgery and obstetrics.

Since Lister's treatment was first inaugurated, many details of its application have been variously modified and great additions to our knowledge have been made. In bacteriology much important work has been done, and great advances are being constantly made. There are a number of diseases, each one of which has been definitely proved to be caused by a germ of its own, a germ which causes no other disease. There is also a list of diseases in which the proof is not yet conclusive, but for which the probability is that a specific germ will be found. The following data have been gathered chiefly from the works of McFarland and Woodhead.

In 1845, Langenbeck discovered that the specific disease of cattle known as actinomycosis could be communicated to man. His observations, however, were not given to the world until 1878, one year after Bollinwr had discovered the cause of the disease in animals.

In 1847, Semmelweis, on the basis of his own observations, formulated the precept that puerperal fever is the result of the introduction of organic ferments into the puerperal genital tract. This discovery, established by himself and confirmed by the observations of many others, marked an era in obstetrics. The organic ferments have since been identified as specific bacteria. Semmelweis, in this way, anticipated in practical antisepsis the discoveries of Lister and Pasteur; while the late Oliver Wendell Holmes, in a paper entitled " Puerperal Fever a Private Pestilence," published in 1843, and republished in 1855, in treating of its prophylaxis, anticipated the teaching of Semmelweis. Semmelweis was first led to recognize the source of puerperal infection by the case of Prof. Koletschka, of the University of Vienna, who, having received a dissection-wound, became thereby fatally infected. In consequence of this, Semmelweis concluded that there was an identity between this infection and that of which so many hundreds of puerperal women died. In the school for instruction in practical obstetrics, with which he was connected, there were two departments, one for medical students, the other for mid wives; the students going as a rule directly to the obstetric w 7 ard from the autopsy-room. He first noted the much greater mortality in the students' ward, and in May, 1847, began to require the students to wash their hands in chlorin-water before making vaginal examinations, thereby reducing the puerperal mortality to a point lower than had been ever before reached.

In 1863, Davaine established by experiments the bacterial nature of splenic fever, or anthrax.

In 1869, the first complete study of a contagious affection was made by Pasteur, in two diseases affecting silkworms — pebrine and flacherie — which he showed to be due to micro-organisms.

In 1875, Koch described more fully the anthrax-bacillus, gave a description of its spores and the properties of the same, and was enabled to cultivate the germ on artificial media; and, to complete the chain of evidence, Pasteur and his pupils supplied the last link by reproducing the same disease in animals by artificial inoculation from pure cultures. The study of the bacterial nature of anthrax has been the basis of our knowledge of all contagious maladies; and most advances in technic have been made first through the study of the bacillus of that disease.

In 1879, Hansen announced the discovery of bacilli in the cells of leprous nodules. They were subsequently clearly described by Neisser. From the nature of the symptoms and from the course of the disease, leprosy up to this time was long considered to be a disease similar to tuberculosis, and the discovery of the bacillus paved the way for the reception of Koch's discovery of the tubercle-bacillus.

In the same year Neisser discovered the gonococcus to be the specific cause of gonorrhea.

In 1880, the bacillus of typhoid fever was first observed by Eberth, and independently by Koch.

In 1880, Pasteur published his work upon u chicken-cholera," an epidemic disease which affects turkeys, pigeons, chickens, ducks, and geese, and which causes almost as much destruction among them as the occasional epidemics of cholera and small-pox produce among man.

In the same year Sternberg described the pneumococcus, calling it " Micrococcus Pasteuri," which he secured from his own saliva; and in the same year Pasteur also found the same organism in saliva; though it is to Fraenkel, Talamon, and particularly YVeichselbaum, that we are indebted for the discovery of the relation which the organism bears to pneumonia.

In 1882, Robert Koch made himself immortal by the discovery of and work upon the bacillus of tuberculosis, one of the most dreadful, and unfortunately most common, diseases of mankind. While great men of the earlier days of pathology clearly saw that the time must come when the parasitic nature of this disease w r ould be proved, and some, as Klebs, Villemin, and Cohnheim, w^ere u within an ace " of the discovery, it remained for Koch to succeed in demonstrating and isolating the specific bacillus, and to write so accurate a description of the organism and the lesions it produces as to render the discovery one of the most complete ever made in the history of medical science.

In the same year Loeffler and Schiitz reported the discovery of the bacillus of glanders, an infectious disease almost confined to certain of the low T er animals; although occasionally persons whose habitual association with and experimentation upon animals bring them into frequent contact with such as are diseased, have become accidentally infected.

In 1884, Koch discovered the " comma-bacillus," the cause of cholera.

In the same year Loeffler discovered the diphtheria-bacillus, and Nicolaier that of tetanus.

On October 26, 1885, Pasteur made the first application to human medicine of his method for the 2 cure of hydrophobia, nearly ten years before the time we began to understand the production and use of antitoxins.

In 1890, Koch issued to medical men what is now known as tuberculin, a brownish, syrup-like fluid used in the diagnosis and treatment of tuberculosis.

In 1892, Canon and Pfeiflfer discovered the bacillus of influenza.

In the same year Canon and Pielicke first found a bacillus now thought to be the specific cause of measles.

In 1894, Yersin and Kitasato independently isolated the bacillus causing the bubonic plague then prevalent at Hong-Kong, and now threatening Europe.

Sanarelli, in 1896, reported the discovery of the micro-organism of yellow fever. His conclusions were based on the presence of a certain germ in 58 per cent, of cases examined, and the production of symptoms and pathologic changes in the lower animals resemble those present in man. Sanarelli' s observations have been confirmed by a commission of the U. S. Marine-Hospital Service; but Sternberg and his assistants doubt the specific relation of the Bacillus icteroides, as it is called, to yellow fever.

Epidemic cerebrospinal meningitis, or spotted fever, is now known to be caused by a specific germ present in the cerebrospinal fluid of patients suffering from this disease. The route of infection is not fully determined, but it is probably through the nose.

Malta-fever, a disease of the Mediterranean islands, and occasionally of the Antilles and Central and

South America, is due to a micrococcus discovered by Bruce, and called Bacillus melitensis.

Malarial fever is an infectious disease; but, unlike those mentioned, it is not caused by a vegetable germ, a bacterium, but by a microscopic animal, the Plasmodium malaricz, which is found in the blood of the afflicted individual. How it enters the blood is not definitely known, but the best authorities hold that its entrance is brought about by the stings of mosquitoes.

There is a widespread belief that malignant tumors — cancers and sarcomas — are due to infection with parasites. The nature of the parasite is as yet unknown; but the latest researches point to a tiny organism, a yeast-plant or blastomycete.

Chapter II. Bacteria As The Causes Of Disease

Diseases may be divided into two great classes — the constitutional, which are due to such causes as errors in diet, alcoholic excesses, overwork, or age; and the infectious or contagious, which are due to the introduction into the body of a living poison. We no longer look upon infectious and contagious diseases as due to an unexplainable something, whose source we cannot know, whose course w 7 e cannot predict, and whose end cannot be hastened by any efforts on our part. Investigation has shown that we are no longer fighting an unknown enemy in the dark, but that we have before us a definite, living thing, whose part in the plan of creation is as surely fixed as our own, whose life-history can be told, and whose growth is as dependent on the right amount of light, food, heat, and air as that of the rose in our garden.

The word bacteria is a general name for all the plant micro-organisms. Of these there are many different classes with different names. They vary much in shape and size, some being round, some thread-like, some rod-shaped, and some of a spiral form. Each single organism consists of a small speck of protoplasm or vegetable albumin, to which maybe given the name of a cell; and these cells are so minute that they can be seen only with the aid of the best 20 microscopes at our command. The rounded organisms, or micrococci, as they are called, are seldom more than 25-J^o °f an mc ^ ^ U diameter ; the elongated cells average a little more perhaps, and are from x^Jou

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n ° p IG< x —Various forms of bacteria: i and 2, round and oval micrococci; 3, diplococci; 4, tetracocci, or tetrads; 5, streptococci; 6, bacilli; 7, bacilli in chains, the lower showing spore-formation; 8, bacilli showing spores, forming drumsticks and Clostridia; 9 and io, spirilla ; n, spirochete (McFarland).

to g^ of an inch in length. Different forms naturally vary from this standard of size; but these figures will give a good idea as to the actual size of the forms under consideration.

The fungi connected with disease in man are divided into three classes :

1. Moulds, or hyphomycetes.

2. Yeasts, or blastomycetes. 3/ Bacteria, or schizomycetes.

Some bacteria, or schizomycetes, induce the various fermentations; while others are productive of putrefaction, and are called saprophytes. Others, again, known as the pathogenic bacteria, are the cause of various diseases; while those which do not ordinarily cause disease are known as the non-pathogenic bacteria. The chief forms of bacteria are :

1. The coccus — berry-shaped or spherical bacterium.

2. The bacillus — rod-shaped bacterium. 3 The spirillum — corkscrew bacterium.

And these, which are species relatively monomorphous — i. c., preserve their shape — are practically the only ones with which we have to do.

The cocci are named according to their arrangement with one another; if, for instance, they are in pairs, they are called diplococci; if in a chain, they are

Fig. 2. — Diagram illustrating the morphology of cocci : a, coccus or micrococcus ; b, diplococcus ; c, d, streptococci ; e, f y tetragenococci or merismopedia; g t h, modes of division of cocci; i, sarcinse ; y, coccus with flagella ; k, staphylococci (McFarland).

called streptococci; if in a cluster, like a bunch of grapes, they are called staphylococci; and if in an irregular mass, stuck together by a thick substance, they constitute a zooglea. Those developing in fours are called tetrads; in eights, sarcinse.

The cocci are also named according to their functions, as, for instance, u pyogenic," or pus-forming; the specific name also describing the form, arrangement, color, and function; for example, Staphylococcus pyogenes aureus signifies a spherical colorless micro-organism forming a yellow pigment, arranging itself with its fellows into the form of a bunch of grapes, and producing pus.

Bacteria reproduce in two ways : By direct division (fission) and by the development of spores or seeds

(sporulation). The most common mode is by binary division, one body dividing itself so as to form two other bodies; these two re-dividing, and so on, It can readily be imagined how quickly an appalling increase in their numbers can be thus brought about; but fortunately this multiplication only takes place to advantage under certain favorable conditions; if these are not present, the bacterium begins to degenerate, but usually does not die until it has left behind a spore. When the formation of a spore is about to commence, a small bright point appears in the protoplasm, and increases in size until its diameter is nearly or quite as great as that of the bacterium. As it nears perfection a dark, highly refracting capsule is formed about it. As soon as the spore arrives at perfection the bac-

a b c d e f

FlG. 3. — Diagram illustrating sporulation: a, bacillus inclosing a small,

oval spore; b, drumstick-bacillus, with terminal spore; c, Clostridium, with

central spore ; d, free spores ; e and f t bacilli escaping from spores

(McFarland).

terium seems to die, as if its vitality were exhausted in the development of the permanent form. As soon as the young bacillus escapes it begins to increase in size, develops around its soft protoplasm a characteristic membrane, and having once established itself presently begins the propagation of its species by fission. In those forms of organism in which spores are not found the germs die very rapidly unless the conditions for their nutrition and multiplication remain very favorable. If all bacteria were of this kind, it would be possible to exterminate them with considerable rapidity. Spores will survive a great heat, a heat which will kill the organism from which the spore came; they will also live under a treatment with germicidal solutions which renders the bacteria inactive. In other words, the spores are much more resistant to the effect of germicides than the bacteria themselves. Cold does not kill them; they live through it and develop whenever favorable surroundings for their growth present themselves. They may lie dormant in the system for years, waking into activity only when they come into contact with some damaged, weakened, or diseased part which affords them a nest in which to develop and multiply, the cellular activity of the weakened part being unable to cope with the organisms.

The conditions which influence the growth of bacteria are, first, a temperature ranging from 85 to 104 F. , some forms requiring a higher and some a lower temperature. Some forms of bacteria are not influenced in their growth by the presence or absence of light. To some, sunlight is destructive. A few hours' exposure to the sun is fatal to the anthrax-bacillus and to cultures of the Bacillus tuberculosis. The rays of the sun, however, must come into contact with the germs and are usually active only on the surface of cultures.

The majority of bacteria grow best when exposed to the air. Some develop better if the air is withheld; some will not grow at all if the least amount of oxygen is present. Those that grow in oxygen are called the aerobic bacteria, and those that will not grow in the presence of oxygen are the anaerobic bacteria.

A certain amount of water is always necessary for the growth of bacteria, though the amount required may be very small. If dried, no form will multiply and very many forms will die.

A soil consisting of highly organized compounds is also necessary for their growth and multiplication, and slight modifications in it may prove fatal to some forms of bacterial life, but be highly advantageous to others.

With age bacteria lose their strength and die. So we see that a suitable soil, and a proper amount of light, heat, and air are absolutely necessary for the growth and development of bacteria, for they carry on all the functions of a higher organized life; they breathe, eat, digest, excrete, and multiply.

The disease-producing bacteria effect entrance into the interior of the body through the skin and superficial mucous membranes, wounds, alimentary canal, respiratory tract, and placenta.

The entrance of bacteria into the tissues through the sound skin is very rare indeed, although some authorities claim that infection has taken place through the rubbing of bacteria or their spores upon the skin. The dangers of infection through the broken skin are well recognized; hence every wound, no matter how slight, should be protected as soon as possible.

Bacteria enter the alimentary canal through the food and drink. Typhoid infection has taken place through the rectum, its occurrence being due to the wearing of underclothing previously worn by typhoid fever patients, and to the use of enema syringe tips which had not been sterilized after their previous use.

Bacteria enter the respiratory tract through the mouth and nose, as in a deep inspiration, or an act of coughing, sneezing, or the like. Pneumonia and tuberculosis are said to be the result of inspiration of the specific organisms. The direct transmission of bacteria from a parent to the fetus has long been a disputed question, but is now generally conceded. The micro-organisms pass through the placenta and infect the fetus. Tuberculosis of the ovaries, Fallopian tubes, and uterus may originate through the blood, and infection from without through the vagina. Infection through the blood is evidenced by the general tuberculosis of all the viscera. Infection from without may result in tuberculosis of the uterus, ovaries, and Fallopian tubes.

The channels by which bacteria can enter the body are, then very numerous; and there is scarcely a moment in which some part of the body is not in contact with them. All the disease-producing germs have their favorable seat in some part of the body where they grow more or less luxuriantly, and in the secretions and excretions of which the chief source of their infection lies. The pneumonia-germ prefers the lungs; the typhoid fever germ selects the lower portion of the small intestine; the diphtheria-germ the throat; the cholera-germ the intestinal tract; the germ of tuberculosis prefers the lungs, but it is called a iC medical tramp," because it will lodge in any part of the body and make its home there. Hence we hear of tuberculous glands of the neck, tuberculous knee, intestinal tuberculosis, tuberculosis of the kidney, bladder, uterus, ovaries, Fallopian tubes, tuberculous peritonitis, etc. A tuberculous

BACTERIA AS THE CAUSES OF DISEASE. 2J

area is always a danger to the system, and may infect distant organs or give rise to a general tuberculosis. To prove that a microbe is the cause of a disease it must fulfil Koch's circuit. It must always be found associated with the disease, and it must be capable of forming pure cultures outside the body. These cultures must be capable of reproducing the disease, and the microbe must again be found associated with the morbid process thus reproduced. In other words, we must prove the bacteria to be always present; we must then isolate them, then prove that they can produce the disease in a healthy animal, and, finally, having succeeded in doing all this, we must prove that no other form of bacteria can produce the disease, and that where these bacteria cannot be obtained the existence of the disease is impossible. All these requirements have been met in many instances, and now there are a large number of diseases each one of which has been definitely proved to be caused by a germ of its own, a germ which produces that disease and no other. Most of the germs need a special train of circumstances in order that they may be active, so that, fortunately for us all, the mere presence of the germ itself is not sufficient to produce the disease. For instance, we know that diphtheria is caused by a germ of its own which causes that disease and no other; still, exposure to that germ does not invariably produce diphtheria — if it did, we should all be infected with it. This is because other conditions than the mere presence of the germs are needed to produce the disease.

The germs must be active, and they can act only under certain conditions. It will usually be found that the attack of the disease has been preceded by a local inflammation of the throat, thus making a suitable place for the specific action of the diphtheria-germs. In typhoid fever the germs require a suitable condition of the bowels before they can produce the disease. This is also true of cholera, and explains why taking care of the health makes such a difference in the taking of this disease. The germs find their way into the body through the food and drink. Cases are reported that show how the germs enter drinking-water, which is sprinkled over vegetables sold in the streets of cholera-infected districts, how they are carried about in clothing, and taken to articles of food upon the table by flies which have preyed upon cholera excrement. Healthy lungs are not a suitable location for the development and activity of the germs of tuberculosis. If we are not fully in good health, or if we inherit a tendency to this special disease, we may acquire it very readily, since we often inhale the germs of it. Should the disease take root in our lungs, it may be controlled to a certain extent by a change of climate and surroundings; by going, for example, from a low and damp locality to the mild and dry atmosphere of Colorado, the Carolina mountains, Southern California, or of the other Southwestern States, where there are few cloudy days and where violent atmospheric changes are rare. The germs there cannot be so active, for the air is stimulating, pure, and invigorating to the nervous system. The rarefaction of the air causes deep and strong involuntary respiratory movements, and there is consequently enforced a better ventilation of the lungs and a better oxygenation of the blood, in conse-