Handbook of practical hygiene

Preface

The lack of a convenient handbook for the guidance of students in the sanitary analysis of air, water, soil, and the principal food materials, and in testing the ventilation of buildings, is my apology for the preparation of this little work. There are several excellent handbooks in German that cover about the same field, as well as a number of general treatises on hygiene in English that contain some of the methods incorporated in this work, but there is no short and concise* laboratory guide, in the English language, that satisfactorily meets the wants of the student in practical hygiene.

I have felt this want as a student and as an instructor and I trust, therefore, that this work may be a means of lightening the labor of others in this line of study.

As a general rule only the more simple and ready methods now in use have been here incorporated as it is expected that when once a good foundation for research has been laid the student will be stimulated to make use of the more extensive treatises relating to the subject.

The subject of food analysis has been gone into just far enough to permit of the detection of the more common forms of adulteration that are likely to be encountered, while the subject of general food analysis has been omitted entirely because, as a rule, medical students are not prepared to take up such a difficult subject in chemistry. For the same reason the subject of examination of clothing has been omitted.

Philadelphia, Pa., May 25, z8pp.

Introduction

The practical hygiene of to-day is the logical outgrowth of observations in sanitary science as the result of the experiences of the peoples of different countries, cities, and towns. These observations were made chiefly during the present century since sanitary science had made very little progress from the empirical procedures of the ancients until these procedures had been tested through the means and measures afforded by modern chemistry and physics.

It will be of interest to trace briefly the more important steps in the development of sanitary science which gave rise to what is known as practical hygiene to-day, before taking up the various steps in the development of practical hygiene. The earlier discoveries which have been of immense value to sanitary science are those of Jenner with regard to vaccinia ; those of Howard with regard to the relation of filth and insufficient air-supply to the high death-rate in prisons ; those of Bowditch, of Boston, and Middleton, of England, with regard to the relation of dampness of the soil of a locality to the prevalence of tuberculosis; those of Gerhard, of Philadelphia, with regard to the differentiation between typhus and typhoid fever; and those of von Pettenkofer, of Munich, with regard to the relation of ground-water to the prevalence of typhoid and cholera.

The discovery of the etiological factors in infectious diseases, the definite determination of the relation of certain diseases to polluted water-supplies, and of the intimate relation of certain respiratory diseases with the ventilation and general sanitary condition of buildings, mark the beginning of the practical application of scientific methods to sanitary science. Practically all of these discoveries have been made within the last two or three decades. The influence of the several sanitary commissions of England, as the Health of Towns Commission, the Barracks Commission, and the Rivers Pollution Commissions, in stimulating investigations and in the collection of valuable data, has been very great.

The discoveries made during this period w T hich stand out prominently and mark important steps in the development of practical hygiene, are those of Pasteur, of Paris, and of Koch, of Berlin, upon the relation of micro-organisms to disease; those of Lister upon the aseptic treatment of wounds ; the experiments of Paul Bert on the influence upon life and health of various atmospheric conditions ; those of von Pettenkofer and Voit on expired air, and the latter's accurate methods for the determination of carbon dioxid in air.

Of the discoveries and adaptations of methods employed in chemistry and physics to sanitary science which mark the rise of practical hygiene, it is impossible to speak with any great definiteness, since the advancement has been so gradual that it would be difficult to trace out the various steps in order to make special mention of them. Several of these methods, however, stand out quite prominently, in addition to those already mentioned, so that it is possible to

INTRODUCTION 3

trace their birth and evolution. Among others the following should receive special mention : The method for the determination of organic matter in water by means of potassium permanganate, published by Forehammer, of Copenhagen, in 1849, and modified since by Kubel and by Tiemann, and others; the method for the determination of the hardness of water by means of an alcoholic solution of soap, published by Mm. Boutron and Felix Boudet in Comptes rendu s, March 26, 1855, and elaborated by Dr. Thomas Clark, of Aberdeen ; the perfection of Levol's method of determining chlorin, by Mohr, in 1856, by the use of potassium chromate solution as indicator and the application of the method to the determination of chlorin in water ; the discovery of a delicate reagent for the detection of ammonia, by Nessler, in 1 856; the method for the determination of the nitrogenous organic matter in water as free and albuminoid ammonia, published by YVanklyn, Chapman, and Smith before the Chemical Society, of London, June 20, 1867; the discovery of a satisfactorv method for the determination of nitrogen as nitrites in water, by Griess, in 1881, and its improvement by Warrington ; the discovery of a delicate test for nitrates in water, by Grand val and Lajoux, in 1885. The methods in use for the determination of organic matter in air had their origin in the ingenuity of Augus Smith, Chapman, Moss, and Remsen.

The evolution of practical hygiene has been very rapid during the last two or three decades, so much so that the student of to-day rarely realizes how recently all of the different methods employed in the analysis of water have come into use. If we go back to the year 1855 we find that the only chemical methods known by means of which organic contamination of water could be detected were : Loss on ignition ; Forehammer's permanganate test ; the distillation of enormous quantities of water, as much as 50 gallons, in order to estimate the ammonia, which was done by titration with standard acid. This procedure has long since been very much simplified through the introduction of the Nessler process and the Wanklyn method of distillation. The development of practical hygiene has been of such recent date that so far it has failed to receive the consideration in educational institutions which it really merits from its immense practical utility.

The opinion that the medicine of the future must be largely preventive medicine is rapidly gaining ground, consequently the study and application of all the preventive measures known becomes of the greatest importance in the training of medical men.

Since pure air, pure water and food, and sanitary habitations and environment are of primary importance in the maintenance and restoration of health, the study of the character and sources of impurities in these, of whatever nature, is highly essential in the practical training of the physician of to-day.

The testimony of experts before recent sessions of government and legislative investigation commissions, has shown that food adulterations of a character which is as yet practically unknown to the general public are becoming quite frequent. Such disclosures as

INTRODUCTION 5

those made by Dr. Wiley, chief chemist of the Department of Agriculture, before the Senatorial Pure Food Investigation Committee, in which he stated that articles of food were imported from abroad, adulterated to such a degree that they would not be used in the countries where they were produced, should arouse us to more active supervision of the character of the food materials exposed for sale in our markets. While many of the adulterations specified in the testimony before these investigation commissions are not necessarily dangerous or even injurious to health, they are nevertheless fraudulent and should not be tolerated under any circumstances. On the other hand the use of highly injurious food preservatives is far from uncommon and is rarely suspected. Some of these preservatives act in such a manner as to render the food practically indigestible aside from any injurious effect which they may exert upon the digestive organs themselves. In order to properly control the healthfulness of food supplies it is necessary to have more general investigation into the nature and composition of the different food materials offered for sale in the markets. In order to make such a supervision feasible it is necessary to have a considerable force of trained analysts in all the larger cities and towns, in addition to a more general supervision of the mode of preparation and system of marketing of the different forms of prepared foods. In this manner it would be possible to protect the common people, at least more effectually than is done at present, against gross fraud and against injury to health from adulterated food.

Part I Atmospheric Air

The air, when pure, is composed of 20.99 per cent, by volume of oxygen, 0.03 to 0.04 per cent, of carbon dioxid, about 78 per cent, of nitrogen, 1.0 per cent, of argon, and varying proportions of watery vapor. Traces of ammonia and organic vapors are also generally present. The relative proportion of the two principal gases, oxygen and nitrogen, remains quite constant in all portions of the globe, while the carbon dioxid, aqueous and organic vapors, and the ammonia vary quite perceptibly in different localities and under various modifying influences.

For the hygienist, therefore, the constituents of the atmosphere which vary in their relative proportions, the carbon dioxid, aqueous and organic vapors, and ammonia, are of primary interest. It is these constituents, along with the temperature, barometric pressure, and the force and direction of the wind, that will engage our attention.

The nitrogen serves merely as a diluent for the oxygen of the air, and, so far as known, has no other influence upon man. The amount of aqueous vapor in the air of dwellings is a most important factor in relation to the comfort and health of the occupants.