Max Joseph von Pettenkofer

“ How slow is the process of the growth of wheat before it can be eaten as bread, which a man will eat, digest, and decompose, in twenty-four hours! The animal and human organism consumes and decomposes food as quickly as a stove burns the wood which took so many thousand times longer to grow in the forest.
It would scarcely be intelligible if I were to calculate how much carbonic acid and oxygen a rose, a geranium, or a bignonia, would absorb and give out in a room in a day, and to what extent the air might be changed by it, taking into account the inevitable change of air always going on. ”

“ I might, perhaps, have succeeded in satisfying your expectations up to a certain point, but I thought it preferable to direct and to concentrate your attention mainly upon one single object which is known to every one, and which seems to be so thoroughly examined that many believe that there is very little to say about it—the air, in its hygienic relations to man's clothing, to his dwelling-place, and to the soil on which he builds.
It is such a natural error to imagine that we cannot but understand everything with which we are in continual intercourse ”

“ We know well that a house standing on piles stands with its foot in water, that this water is drawn up by the walls till beyond the water-mark, that the water of the ground has a good deal to do with the house; why should we, then, refuse to acknowledge that the foot of a house built on dry gravel, stands also on the air, and that the air in the ground is in intimate relation with the house? ”

“ THE last sheet-anchor of the contagionists is always the linen of cholera-patients. But this view rests on such debatable ground that in the end it may prove to be fallacious. If cholera is really spread through human intercourse, then it is clear that the unknown specific something must accompany other vehicles, which may be man himself; and if this something can cause illness in man, then it must reside in the system of the patient, and ought to be found there. ”

“ Now the many crevices, holes, and pores in our dwellings will no longer be considered by you as unlimited means of change of the air, since you know how large that change has to be; you will rather feel anxious whence to procure such enormous quantities when you sit quietly within your four walls where you do not feel the least draught, where no curtain moves, and a feather lies quietly on the floor. This sensation of calm we owe to the insensibility of our nerves—and yet the air moves. ”

“ I consider the impression which plants and plantations make upon our minds and senses to be of hygienic value; further, their influence on the conformation of the soil, with which health is in many respects connected; and, finally, their influence upon other qualities of the air, than carbonic acid, oxygen, and ozone: among these may be mentioned, in passing, shade in summer, and decrease of wind and dust.
It is an old observation, needing no demonstration, that the cheerful and happy man lives not only an easier, but, on the average, a more healthy life than the depressed and morose man. ”

“ All human aim must be to obtain the greatest effect at the smallest expense. We ought to choose those means which attain the end without exhausting our power, which should be preserved for higher purposes. These principles ought to guide us in approaching the question. It is not only superfluous, but positively injurious, to use one's self up.
I believe that it is now evident to you that a part of the heat of our body radiates from the surface of our clothing; but we must now consider whether this radiation does not vary according to the nature, quality, or color, of the material. ”

“ The human mind formerly looked upon the air as something unsubstantial, spiritual, although men saw the effect of hurricanes; no wonder, then, that no one thought of the air hidden in the ground, which cannot even blow the hat from our head. ”

“ It is only against the deterioration of the air by respiration and perspiration, which is beyond the control of cleanliness, that ventilation can direct its power and against this deterioration this power must be chiefly directed.
Let us now consider the different causes of the motion of the air. As air in motion is wind (ventus, Latin) , ventilation is a better expression than "airing." Anything which disturbs the equilibrium of a body of air, produces motion in it. Its immobility supposes equality of temperature and specific gravity, and also of mixture in quantity and quality. ”

“ But, aside from the fact that damp houses and damp soils are positively disadvantageous to health, it would not be possible to maintain such a degree of moisture or other conditions that it should never be too dry, that there should never be any spurts of gas, and that no germs should ever be washed off. We can judge of the uselessness of such efforts from the fact that no one has ever found air, either out-of-doors when it has rained incessantly for a long time, nor in a house where it is still moist, that was free from mold. ”

“ The question we are now concerned with is not what food or what medicinal remedies plants provide us with, but the value of plants and plantations in dwellings and in the open air in conducing to health or preventing disease. We have given the subject very little consideration until quite recently, just as we have thought very little of the way in which the pleasures of the table, fine raiment, comfortable dwellings, and many other things, conduce to our well-being. Meanwhile we have been guided by our instincts, which, like Nature in general, have, on the whole, guided us rightly. ”

“ Thus by our clothes we keep the heat radiating from us somewhat longer in the immediate neighborhood of our surface. The lightest covering even makes itself perceptible by impeding radiation, the thinnest veil keeps warm in some degree. It is just the same with the earth itself. On a calm, clear night the earth's surface becomes so chilled by radiation into the colder space, that the moisture of the air precipitates itself on it as dew, and at times as hoar-frost, and even as ice, just as the moisture in a warm room does on a windowpane cooled from the outside ”

“ Each person standing in the still air of a room causes in this way an ascending current of air, just like a heated stove. A very sensitive anemometer, placed between coat and waistcoat, shows the existence of this current, which is strong enough to set the little wings of the instrument in play. The air in this room appears quite still, and yet it is in thousand-fold motion and ceaseless restlessness; but, happily, our nerves are not aware of this, just as a short-sighted person may deny the existence of some object, till his eyes get the assistance of a glass. ”

“ If we consider the minuteness of the substances left by hunted game on the soil, which it scarcely touches in its flight, and how the dog detects them even a long time after, we cannot sufficiently admire such a performance of the sense of smell. Other substances make themselves known in other ways, sometimes by some physiological effect. Oxide of carbon, for instance—a gas which is generated from burning charcoal—is not perceived by any of our senses, but if it is present in air to the extent of a half per cent, only, it destroys human life after a while. ”

“ Indeed, the great density of the population of the cities is in itself like a concentration of the filth, and the scattering of the dwellings in the country is like a dilution of it. In the villages the manure-heaps are on top of the ground and open to the air, which, ventilating them freely, effects a salutary dilution and change: in the cities we do not bring the dirt out into the yard, but we deposit it by the walls of our houses ”

“ I believe I have made you sufficiently aware of the fundamental facts and conditions as to the change of the air in our dwellings, so far even that you are now able to judge for yourselves whether a certain plan for ventilation is rational or not. We have no other motors for changing the air, but differences of temperature and motion of the air, which we can call forth either by heat or by the motion of wind-fans—or which we must make use of as far as they are preexisting in the atmosphere surrounding the house. ”

“ Besides this, shade in the open air always causes a certain draught which acts as a kind of fan. All must have noticed when walking in oppressive heat, when the air seems still as death, that a refreshing breeze arises as soon as a cloud casts a shade. The same thing may often be observed in summer in walking through a street with close rows of houses, when the air is still, and one side is sunny, the other in shade. On the sunny side there is not a breath of air, while on the other there may be a light breeze. ”

“ Hygiene is, after all, nothing but applied physiology, with particular reference to the physical well-being of mankind. According to my experience, men of science and physicians, who are specially grounded in the practical and theoretical study of physiology, chemistry, and natural philosophy, are those who can most easily fit themselves for the special work of hygienic science. It is true, physiology includes the most essential points of hygiene, and physiology is an application of natural philosophy, chemistry, and anatomy. ”

“ You readily understand how much more difficult it is to manage one's heat-household in a hot than in a cold climate. Our means for warming ourselves are better than those for carrying off our heat. Therefore the European race has a hard fight under the equator. The working power of the body depends on a certain amount of consumption, by which a certain amount of heat is necessarily created, which has to leave the body in a regular way. ”

“ WATER plays quite as important a part in the soil as air. Obviously, no organic life, no organic change, can be conceived of without water; and we ourselves consist three parts in four of water. Therefore it may be inferred that change in the moisture of the soil must have a certain influence on its organic and organized constituents, and on the organic life within it. Two degrees of moisture in the soil may be especially distinguished: one in which air and water both occupy the pores, and one in which the pores are quite filled with water excluding the air. ”

“ There is certainly and frequently danger in being exposed to a draught—a danger which has, perhaps, been over-estimated, because men have an irresistible desire to fix a certain cause for a certain evil. All collision is avoided if the proper meanings of ventilation and draught are thoroughly understood.
Ventilation is the necessary change of the air in a closed space, at which the velocity of the air is still taken for a complete stillness, and its motion takes place all round our body. ”

“ Our clothing not only renders the air still around us, but it also regulates its temperature by the heat which leaves our body; we heat our garments, and they continually heat the air passing through the meshes and pores of the texture. We may compare our clothing to a calorifer or stove, warmed by the heat emanating from our body's engine for the purpose of warming the air round our surface. ”