Part 11

Dr. Van Rensselaer, in the Orton Prize Essay on Impure Air and Ventilation, makes the statement that statistics show that of the causes of mortality the most important and farthest-reaching is impure air.

=Amount of Air Required for one Person.= Sanitarians have agreed that each individual requires at least 3000 cubic feet of air every hour. A room 10 × 15 × 20 holds 3000 cubic feet of air, which should be changed once every hour in order that one individual shall have the required amount. If three persons are in the room, it must be changed three times.

The effect of bad ventilation is well illustrated by the condition of the horses in the French army some years ago. With small close stables the mortality was 197 in every 1000 annually. The simple enlargement of the stables, and consequent increase of breathing-space, reduced the number in the course of time to 68 in every 1000, and later, from 1862 to 1866, with some attention paid to the air-supply, the number fell to 28½ per 1000.

=Necessity for a Constant Supply of Pure Air.= When we consider that the food we eat and digest cannot nourish the body until it has been acted upon by oxygen in the lungs, and that this action must be constant, never ceasing, it will help us to understand the necessity for a constant supply of air such as shall furnish us a due proportion of the life-giving principle, oxygen, and which shall not contain impurities that interfere with its absorption.

We take into the lungs a mixture of nitrogen, oxygen, and carbonic acid. We give out a mixture which has lost some of its oxygen, and gained in carbonic acid. Now, unless the amount of oxygen is what it should be, the blood will not gain from an inspiration the amount it should receive, consequently it will be but imperfectly purified and able but imperfectly to nourish the body. So the whole system suffers, and if a person for a long time continues to breathe such an atmosphere, the condition of the body will become so reduced as to produce disease. Even though in other ways one lives wisely, all the factors of health multiplied together cannot withstand the one of impure air. We eat food three or four times daily. Some of us are very particular about its quality. We breathe air every instant of our lives, but generally we give but little consideration as to whether it is pure or impure.

=Ventilation.= No attempt will be made here to explain different devices for ventilation, but only to touch upon the principle it involves. Its objects are (1) to remove air which has been breathed once; (2) to remove the products of combustion, whether from fires, lamps, gas, or other sources; (3) to carry away all other substances which may be generated from any cause, in a room or building, as the impurities from manufacturing, those arising from decaying matter, and micro-organisms. In a climate where artificial warmth is necessary a part of the year, it is difficult to warm and ventilate a room at the same time, without causing unpleasant drafts; but with some knowledge of the necessity of ventilation, and of the properties of air, one may in some measure work out a scheme of ventilation adapted to the circumstances in which he finds himself.

There are always the doors and windows, which may be thrown wide open at intervals, and in many houses there are fireplaces. If a window be opened at the bottom at one side of a room, and another be opened at the top on an opposite side, a current of air will be established from the first window, passing through the room and out at the second. This plan will do very well in warm weather when the temperature outside is about the same as that of the room, but it would be impracticable in cold weather. Then we may resort to the very simple plan of placing a board about eight or ten inches wide across the window at the bottom and inside of the sash. Then when the lower half of the window is raised, a space is left between the upper and lower sashes, through which the air passes freely as it enters, and, being sent into the room in an upward direction, causes no draft. The board is for the purpose of closing the window below, and should fit quite close to the sash.

Fireplaces are good, though not perfect, ventilators. Then there are the preventive measures, such as burning the gas or lamp low at night, avoiding oil- and gas-stoves, etc.; the latter are the worst possible means of heating rooms, for not only do they draw oxygen for burning from the air, but they give out the polluting carbonic acid and other products of combustion, which in a coal- or wood-stove go up the chimney.

A well-ventilated room should have an inflow of warm, pure air, and a means for the removal of the same after it has been used, the current being so controlled that, although the air is kept in motion, there is no perceptible draft.

The plan for the heating and ventilation of the Johns Hopkins Hospital, Baltimore, Maryland, is a most admirable one. Air from out of doors is conveyed by a flue into a chamber in the wall, in which are coils of pipe filled with hot water. The air in passing over these becomes warm, and, rising, passes into the room to be heated through a register. On the opposite side of the room is a chimney-like flue, running to the top of the building and containing two registers, by the opening and closing of which the movements of the air in the room can be controlled. The temperature is maintained by the temperature of the water in the pipes, and the rapidity of the flow.

The ventilation by this method of heating is the most perfect known to the author, who has lived for two years in a building thus supplied with warmth and fresh air. The rooms were invariably comfortable as to temperature, and the air as invariably sweet and pure.

MILK

Milk is one of our most perfect types of food, containing water and solids in such proportions as are known to be needful for the nourishment of the body. A proof of this is seen in the fact that it is the only food of the young of the Mammalia during the time of their greatest growth. It contains those food principles in such amounts as to contribute to the rapid formation of bone and the various tissues of the body, which takes place in infancy and childhood; but after this growth is attained, and the individual requires that which will repair the tissues and furnish warmth and energy, milk ceases to be a complete food.

=Composition of Cow's Milk.= The composition of cow's milk varies with the breed and age, care and feeding, of the animals. Cows which are kept in foul air in stables all the year, and fed upon bad food such as the refuse from breweries and kitchens, give a quality of milk which is perhaps more to be dreaded than that from any other source; for such animals are especially liable to disease, and are often infected with tuberculosis, pneumonia, and other fatal maladies. Cows are particularly susceptible to tuberculosis, and may convey it to human beings either in their milk or flesh. According to Dr. Miller, cow's milk contains the following ingredients:

Water 87.4% Fat 4.0% Sugar and soluble salts 5.0% Nitrogenous matter and insoluble salts 3.6%

Another analysis is that of Uffelmann:

Water 87.6% Albuminoids 4.3% Fat 3.8% Sugar 3.7% Salts .6%

=Characteristics.= Milk from healthy, well-nourished cows should be of full white color, opaque, and with a slightly yellowish tinge sometimes described as "cream white." It should vary but slightly in composition from the above analyses. The fat should not be less than 2.5%. The amount of fat may be easily determined with a Feser's lactoscope (Eimer and Amend, New York), directions for the use of which come with the instruments. It will generally vary from 3% to 4% in good milk. Should it fall below 2.5% the milk should be rejected as too poor for use. Such milk has probably been skimmed, or comes from unhealthy or poorly fed cows.

The specific gravity of milk should be from 1.027 to 1.033. This may be found with a Quevenne's lactometer. If it falls below 1.027, one has a right to claim that the milk has been watered or that the cows are in poor condition.

The reaction of good milk varies from slightly alkaline to slightly acid or neutral. That from the same cow will be different on different days, even under the same apparent conditions of care, varying from one to the other, probably because of some difference in the nature of the food she has eaten. However, if the reaction is decidedly alkaline, and red litmus-paper becomes a distinct blue, the milk is not good, and possibly the animal is diseased. Should the reaction be decidedly acid, it shows that the milk has been contaminated, either from the air by long exposure, or from the vessels which held it, with those micro-organisms which by their growth produce an acid, a certain amount of which causes what is known as "souring."

Milk from perfectly healthy and perfectly kept cows is neutral, leaving both red and blue litmus-paper unchanged; but as a general thing milk is slightly acid, even when transported directly from the producer to the consumer and handled by fairly clean workmen in fairly clean vessels. Such milk two or three hours old when examined microscopically is found to contain millions of organisms. Milk is one of the best of foods for bacteria, many of the ordinary forms growing in it with exceeding rapidity under favorable conditions of temperature. Now it has been found that such milk, although it may not contain the seeds of any certain disease, sometimes causes in young children, and the sick, very serious digestive disturbances, and may thus become indirectly the cause of fatal maladies.

All milk, unless it is positively known to be given by healthy, well-nourished animals, and kept in thoroughly cleaned vessels free from contamination, should be sterilized before using. Often the organisms found in milk are of disease-giving nature. In Europe and America many cases of typhoid fever, scarlatina, and diphtheria have been traced to the milk-supply. In fact milk and water are two of the most fruitful food sources of disease. It therefore immediately becomes apparent that, unless these two liquids are above suspicion, they should be sterilized before using. Boiling water for half an hour will render it sterile, but milk would be injured by evaporation and other changes produced in its constituents by such long exposure to so high a degree of heat. A better method, and one which should be adopted by all who understand something of the nature of bacteria, is to expose the milk for a longer time to a lower temperature than that of boiling.

=To Sterilize Milk for Immediate Use.= (1) Pour the milk into a granite-ware saucepan or a double boiler, raise the temperature to 190° Fahr., and keep it at that point for one hour. (2) As soon as done put it immediately into a pitcher, or other vessel, which has been thoroughly washed, and boiled in a bath of water, and cool quickly by placing in a pan of cold or iced water. A chemist's thermometer, for testing the temperature, may be bought at any pharmacy for a small sum, but if there is not one at hand, heat the milk until a scum forms over the top, and then keep it as nearly as possible at that temperature for one hour. Do not let it boil.

=To Sterilize Milk which is not for Immediate Use.= Put the milk into flasks or bottles with narrow mouths; plug them with a long stopper of cotton-wool, place the flasks in a wire frame to support them, in a kettle of cold water, heat gradually to 190° Fahr., and keep it at that temperature for one hour. Repeat this the second day, for although all organisms were probably destroyed during the first process, spores which may have escaped will have developed into bacteria. These will be killed by the second heating. Repeat again on the third day to destroy any life that may have escaped the first two.

Spores or resting-cells are the germinal cells from which new bacteria develop, and are capable of surviving a much higher temperature than the bacteria themselves, as well as desiccation and severe cold. Some writers give a lower temperature than 190° Fahr. as safe for sterilization with one hour's exposure, but 190 may be relied upon. Milk treated by the last or "fractional" method of sterilization, as it is called, should keep indefinitely, provided of course the cotton is not disturbed. Cotton-wool or cotton batting in thick masses acts as a strainer for bacteria, and although air will enter, organisms will not.

All persons who buy milk, or in any way control milk-supplies, should consider themselves in duty bound to (1) ascertain by personal investigation the condition in which the cows are kept. If there is any suspicion that they are diseased, a veterinary surgeon should be consulted to decide the case. If they are healthy and well fed, they cannot fail to give good milk, and nothing more is to be done except to see that it is transported in perfectly cleansed and scalded vessels. (2) If it is impossible to obtain milk directly from the producer, and one is obliged to buy that from unknown sources, it should be sterilized the moment it enters the house. There is no other means of being sure that it will not be a bearer of disease. Not all such milk contains disease-producing organisms, but it all may contain them, and there is no safety in its use until all bacteria have been deprived of life.

DIGESTION

=Definition.= Digestion is the breaking up, changing, and liquefying of the food in the various chambers of the alimentary canal designed for that purpose. The mechanical breaking up is done principally by the teeth in the mouth, the chemical changes and liquefying by the various digestive fluids.