# Popular Science Monthly/Volume 11/July 1877/On Ground-Air in its Hygienic Relations

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* ON GROUND-AIR IN ITS HYGIENIC RELATIONS.
By Dr. MAX VON PETTENKOFER,
PROFESSOR OF HYGIENE IN THE UNIVERSITY OF MUNICH.
IF in the two preceding lectures I have tried to draw your attention to the penetration of the air into our clothing and our dwellings, I shall try in this last lecture to do the same in reference to the air which is in the ground, and to its connection and intercourse with the air above the ground. The air in the ground has been somewhat a stranger to our minds; the terms air and earth, just like air and water, implied to our mind things contrary, and exclusive of each other. The earth seemed to have its limit where the air began. Common-sense seems inclined to believe that there can be no air in that whereon we walk and stand. If we say of the surface of the earth that it is the limit of the earth and the beginning of the atmosphere, we are not correct in reference to the latter. The air begins much below the ground, and we ought to say that where the ground, which is a mixture of earth, water, and air, ends, from there the atmosphere exists alone. It is no wonder that no particular attention was paid to the air in the soil; its presence there does not make any direct impression on anyone of our senses; we infer its presence more from other experiences and consequent conclusions. 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.
We again meet here with the fact that, originally, only that calls forth ideas which impresses our senses directly. No one doubts that water penetrates the soil, and moves there according to hydrostatic laws, because we see it run, vanish into the soil, collect and run out again, or we pump it up; but hitherto not many have clearly understood that the whole surface of the earth, as far as it is porous and its pores are not filled with-water, contains air, which is also subject to aërostatic laws. And why so? One feels nothing of that air; it is always calm, it has no color, no smell, no taste, in fact we take it for nothing, I have shown you already how great an error we commit when we suppose a calm air to be motionless. This applies just as much to the air in the soil, which, if its motion were even snail-like, would still travel from a good depth to the surface in one day.
Perhaps I shall succeed in giving you a better idea of the change of the air in the ground than of that in walls. To have a correct idea ​of that air and its relations, we must know, in the first instance, its quantity in proportion to the different kinds of soil. Let us first take rubble-soil, gravel, or sand, which support the largest and heaviest edifices. Here is a bottle which holds exactly one litre (1710 pint) up to that mark on its neck. I have filled it slowly with gravel, shaking it all the while, so that the gravel settled completely. The gravel reaches up to the mark. This high cylinder contains just one litre of water, and is graduated into one hundred parts. Now I pour the water into the gravel, till I find it just coming up to its surface, and I see that of the water in the cylinder thirty-five parts have entered the gravel and driven out the air, which before had therefore taken up thirty-five per cent, of the whole mass. This is certainly a great quantity of air, and if we build a house on such a ground its weight rests, no doubt, on the gravel alone, and not on the air; but for all that, this ground, as far as it is dry, consists to the extent of one-third of air. In building on gravel, we build as well on air, just as we build on water when we build on piles driven into a swampy soil and cut off under the water. 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?
What I have shown you in regard to gravel, can, in a similar way, be proved in regard to sand, clay, and even more solid stony and rocky soils.
Most kinds of sandstone are nearly as porous as loose sand. The rock of Malta has been proved by Leath Adams to suck up water on an average to one-third of its volume; consequently, when dry it must contain air to the same extent. One would not think that this was the case with the rugged cliffs and shores of that remarkable island, which look as if they were built up from the granite of the Swiss Alps. Most buildings in Malta are built with this Maltese rock, which is much used also throughout Italy. It is not less porous than the Berlin sands; their penetrability for air and water is the same, but the grains of the Maltese rock are connected by some solid medium, while the grains of the sand are loose. In respect to their porosity they stand relatively as frozen and not frozen soil.
Many ships of the English navy have filters made of a certain kind of Maltese rock. I have tested one, and I have found that the filtering basin swallows up forty-seven per cent, of its whole contents, when used for the first time.
A soil whose pores are filled partly by air and partly by water is called damp. It can take up more water till all its pores are filled with it, when all passage of air is stopped, just as we have seen ​with regard to the mortar of the house. That degree of humidity of the soil is called ground-water; it begins at the lowest limit of the air in the soil.
It is well known that water becomes solid at a temperature below freezing-point. In becoming ice it changes its consistency totally, but its volume not very much, increasing it by about six per cent., one hundred volumes of water becoming one hundred and six of ice. In a frozen soil there must have been a certain quantity of water. This water in freezing has become a kind of cement for the particles of the soil, and gives it a solidity which the liquid water could not
Fig. 1.
impart. Although such frozen soil is as hard to work as stone, we have no right to assume that it is impermeable to air or gases of any kind.
Those pores of the soil which were free from water cannot be narrowed much by the expansion of the neighboring pores through the ​freezing of their water. It would be just as incorrect to deny the permeability to air of the frozen soil as that of the Maltese rock. Still, the most erroneous views have been formed on this subject, even by men distinguished in other branches of science.
Having given you an idea of the quantity of air in a porous soil, I have to give you a correct idea of the mobility of this air and of its change, and I shall try to do this in a roundabout way, as I cannot do it by direct impression on your senses.
There are things of whose existence we become only aware when they are absent. Probably the fish is as little aware of the water he lives in as we of the air, till he finds himself on the dry land. The creatures living in the air know nothing of its oxygen, but, when we place them in an atmosphere which has none or too little of it, or too much carbonic acid, they will feel and behave like the fish out of water. There is a difference in the want of oxygen between different animals; birds want a good deal proportionately, A canary-bird takes about one and a third cubic inch of oxygen from the air in one hour. In one litre of air there are about thirteen cubic inches of oxygen, which the bird would have consumed in ten hours. But he would be dead long before, as he could not live in an air deprived of one-half of its oxygen. The bird in this glass cylinder has been shut up between gravel for the last ten hours, and you see he is quite well. The cylinder is shut at its lower end by a wire netting, on which a stratum of gravel rests. The bird stands on the gravel, and above him there is another wire netting, which supports a stratum of gravel. The free space for the bird contains about one litre of air.
This bird is shut up in the same way as workmen sometimes are, digging at a well or at some kind of shaft. If accident does not kill them at once, they seldom die from want of air, even if it takes some days to dig them out, although man's consumption of oxygen is about a thousand times as great as that of the canary-bird. Some years ago, in Saxony, two men who were shut up in the shaft of a well for ten days kept alive, and were not much the worse for it when they came out again. I may mention here that the celebrated Fraunhofer, when still apprenticed to a glazier at Munich, was buried for several days under the ruins of his master's house, which had fallen in.
I expect Fraunhofer's luck will be shared by this bird, whom I intend removing to-morrow to his old cage.
You cannot longer have any doubt about the motion of the air through gravel: but I want to convince your senses; I want you to see the motion of the air, and to see that motion taking place through a much thicker stratum of gravel than the strata shutting in the bird.
You see this high glass cylinder (Fig. 2), with a smaller glass tube inside, open at both ends. The cylinder is filled with gravel, and the glass tube connected with a manometer by some India-rubber tubing. ​As soon as I blow gently on the upper surface of the gravel, you see the liquid in the manometer moving. The motion of the air which I produce acts in the first instance on the surface of the gravel, propagates itself through the same to the bottom of the cylinder, enters
Fig. 2.
the lower end of the tube, rises through it and through the tubing into the manometer, where it presses on the column of liquid, and sets it in motion.
Why does the liquid move in the manometer? Because the air, after the migration just described, presses with greater weight on the ​surface of the column it arrives at than the outer air on the surface of the other column. If there were no liquid in the manometer, the moved air would finally flow out of the manometer, and, as you see, now that I have emptied the manometer, nearly blow out this candle.
In this way I believe that I have convinced your senses that the air can move through porous soils.
If the air in the ground can be set in motion by the pressure of air or wind against its surface, there can be no doubt that the same can be effected by differences of temperature, and by diffusion, and generally by all causes which can produce movement of gases. As long as the air in the ground is of a different temperature or composition from the free atmosphere, there must be exchange and motion. I will only, in order to leave no doubt on your mind, direct your attention to several well-known facts, which can only be explained by the change of the ground-air.
All Christian nations bury their dead in the earth, to give back to dust what came from dust. There are burial-grounds in which a corpse decays completely in six to seven years, and others in which it takes twenty-five to thirty years. The regulations about a second occupation of a ground depend on this difference, and therefore towns with an equal population may be obliged to have burial-grounds of very different sizes. There are other circumstances of some influence on the process of decay, but the principal one is the amount of, and the facility for, the change of the air in the soil. Rubble and sandy soils do the work much quicker than marl and clay soils. Striking experiences in this respect have been made on the French battlefields, chiefly near Sedan, where a Belgian chemist, Louis Creteur, had to disinfect the large dead-pits. The bodies were buried in chalk, quarry, rubble, sand, argillite, slate, marl, or clay soils, and the sad work lasted from the beginning of March to the end of June. In rubble the decay had taken place fully, but in clay the bodies were surprisingly well kept, even after a very long time, and even the features could be identified.
As the processes of putrefaction and decay are intimately connected with the activity of certain lower organisms, which prey upon the dead, it is sufficiently clear that these organisms must thrive differently in different kinds of soil. A lively change of air and water in the ground appears to be of great influence in this respect; the more air in the ground the richer the underground life.
Remarkable testimony as to the permeability of the ground, and of the foundations of our houses, has been given by gas emanations into houses which had no gas laid on. I know cases where persons were poisoned and killed by gas which had to travel for twenty feet under the street, and then through the foundations, cellar-vaults, and flooring of the ground-floor rooms. As these kinds of accidents happened only in winter, they have been brought forward as a proof that ​the frozen soil did not allow the gas to escape straight upward, but drove it into the house. I have told you already why I take the frozen soil to be not more air-tight than when not frozen. In such cases the penetration of gas into the houses is facilitated by the current in the ground-air caused by the house. The house, being warmer inside than the external air, acts like a heated chimney on its surroundings, and chiefly on the ground upon which it stands, and the air therein, which we will call the ground-air. The warm air in the chimney is pressed into and up the chimney by the cold air surrounding the same. The chimney cannot act without heat, and the heat is only the means of disturbing the equilibrium of the columns of air inside and outside the chimney. The warm air inside is lighter than the cold air outside; and this being so, the former must float upward through the chimney, just like oil in water. It continues to do so as long as fresh cold air comes into its neighborhood from outside. As soon as we interrupt this arrival, the draught into the chimney is at an end. Any other way of looking at the action of chimneys leads to erroneous views, which have many times stopped the progress of the art of heating and ventilating.
Thus our heated houses ventilate themselves not only through the walls but also through the ground on which the house stands. If there is any gas or other smelling substance in the surrounding ground-air, they will enter the current of this ventilation. I have witnessed a case in Munich, where not the least smell of gas could be detected in the street, but a great quantity of gas found its way into the ground-floor room of a house where no gas was laid on. In another case the gas always penetrated into the best heated room and produced an illness of its inmates, which was taken for typhoid fever.
The movement of gas through the ground into the house may give us warning that the ground-air is in continual intercourse with our houses, and may become the introducer of many kinds of lodgers. These lodgers may either be found out, or cause injury at once, like gas; or they may, without betraying their presence in any way, become enemies, or associate themselves with other injurious elements, and increase their activity. The evil resulting therefrom continues till the store of these creatures of the ground-air is consumed. Our senses may remain unaware of noxious things, which we take in, in one shape or another, through air, water, or food.
We took rather a short-sighted view all the while, when we believed that the nuisances of our neighbors could only poison the water in our pumps; they can also poison the ground-air for us, and I see more danger in this, as air is more universally present, and more movable, than water. I should feel quite satisfied if, by my lectures, you were convinced of this important fact, if of none other.
England has given proof how the public health can be improved, ​by keeping the soil clean through good drainage, abolition of cesspools, and abundant water-supply. It would carry me too far if I were to analyze now to which of these measures the lion's part belongs; I should have to enter upon many controversies, which I have no time to fight out in this place; but this is my conviction, which I want to impress upon you, that cleanliness of the soil and diminution of organic processes in the ground of dwelling-houses are most essential.
Many have considered these processes, and their effects on the ground-air, to be a mere hypothesis. This view lies now behind us, and facts have been found proving their reality. Stimulated by the investigations of Huxley and Haeckel, further researches have followed, and shown that not only at the greatest depth of the sea, but also in every porous soil, there are everywhere those beginnings of organic life, belonging neither to the animal nor vegetable kingdom, mucous formations, which are called Moneras and Protistes. When I wrote my part of the report on the cholera in Bavaria, in 1854, I pointed out already that the air, not less than the water in the soil, ought to be drawn into the circle of experimental investigations. Neither others nor myself acted at once upon my suggestion, and it is only during the last eighteen months that I have examined the ground-air in the rubble-soil of Munich, regularly twice a week, for its varying amount of carbonic acid. The results are surprising, and for the future I shall have to trouble others and myself, not only with groundwater, but also with ground-air.
The place where the examination of the ground-air of Munich is being carried on is rubble, without any vegetation, and the carbonic acid increases with the distance from the surface. Agricultural chemistry has been aware, for a long time, that a clod of arable earth which is rich in humus is a source of carbonic acid, but no one expected that, at times, so much carbonic acid should be met with in sterile lime-rubble. A few feet under the surface there is already as much carbonic acid as in the worst ventilated human dwelling-places.
I have found that the quantity of carbonic acid is smaller at fifty-eight inches than at one hundred and fifty-six inches throughout the year, the months of June and July excepted, when an inverse proportion arises. But then there begins also, in the lower stratum, a considerable increase, so that the upper stratum soon finds itself behind again. This large quantity of carbonic acid in the ground-air of Munich has been far surpassed in Dresden. Examinations have taken place in that town under the authority of the Central Board of Public Health. Prof. Fleck's diary proves that, at least at that spot where his examinations took place, the quantity of carbonic acid was in winter already nearly twice as great as in Munich in the month of August. I might become jealous of Dresden, but we must often, ​in life, put up with being left behind, although we had the first start, and I have no choice left but to resign myself.
The presence of carbonic acid in the soil and its periodical motion are for the present a bare fact. Other places, with different soils, must be examined under varying circumstances, and for longer periods, before an explanation can be attempted.
The first question which naturally meets us is that about the origin of this gas. It cannot spring from the humus of the surface, because at Munich and Dresden its quantity is smallest in the immediate neighborhood of the surface, where the humus lies, and increases in proportion to the distance thence. As the amount of carbonic acid in the ground-air generally increases the nearer this is to the ground-water, we should be at first sight inclined to assume that it evaporates from it. Is it not a fact that the ground-water which feeds wells and sources contains this gas? And is it not well known that many a well's shaft contains so much carbonic acid as to extinguish a burning candle at the distance of a few feet only from its opening? This assumption, however, is not justified for several reasons, according to the researches and experiments made at Munich: 1. There are two months in the year when the amount contained in the upper stratum, which is at the greatest distance from the ground-water, is larger than in the lower. 2. I have examined simultaneously, at given places, the amount of the gas both in the groundwater and in the ground-air, and have investigated whether, according to the laws of diffusion and absorption, either had a surplus of the gas, and was accordingly in a condition to receive or yield some of it. In every case the amount of carbonic acid in the ground-air was larger by fifty per cent, than in the ground-water, so it is clear that it is the water which receives its carbonic acid from the air, and not vice versa.
Hereby the question about the origin of the gas is certainly not yet answered, and would have been left equally unsettled if we had to ask, Whence comes all the carbonic acid which is found in the groundwater? All this water is precipitated from the atmosphere, from rain or snow. In entering the soil as meteoric water its amount of carbonic acid is exceedingly small. By help of Bunsen's analytical tables it is easy to calculate, from the quantity of carbonic acid in the atmosphere, and the absorbing power of water for this gas, that one pint of rain-water at the average temperature and barometrical pressure can only contain a very small fraction of a grain of carbonic acid, and this has been proved further by analytical experience. But the analysis of the pump-water in Munich which was poorest in carbonic acid showed that it contained on an average 112 to 1910 grain of the free gas. The ground-water at the places of examination stands about sixteen feet from the surface. It is therefore evident that the meteoric water, which is the sole source of the ground-water, must more than centuple ​its original amount of carbonic acid before it reaches the wells. Thus much is certain, that the source of the carbonic acid must be sought for in the soil, and for this reason the more natural supposition is, that the soil yields the gas and gives it to the water and to the air simultaneously, but naturally with greater facility and in greater quantity to the air than to the water. The sources of the carbonic acid in the soil have now to undergo a stricter investigation; the probability is, they owe their origin to organic processes in the soil.
Allow me, now, a few more concluding and valedictory words.
In the introduction to my lectures I thought it incumbent upon me to give you my views about popular lectures in general. Those views necessarily excluded the possibility of disposing, in a few hours, of any one subject of hygiene in such a manner as to impart to my audience a thorough theoretical and practical knowledge. My hesitation in selection lasted some time. I might have collected and described the last works and tendencies in the field of hygiene, pointing out what had practically succeeded, and what ought to be aimed at further—and there is a series of interesting points and facts, forming a most grateful subject for lecturing; or I might have attempted to give you a survey, a kind of bird's-eye view of the whole domain of hygienic science. There is a charm, in the contemplation of a grand and beautiful distant landscape, in marking, first, the more interesting points; then to let the eye wander round them till it comes to the next striking point, and to enjoy to the utmost the sight of the rich view.
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; but, if we take the trouble of looking a little more closely into everything of which we make daily use, we shall soon make the humiliating discovery that we are acting preëminently according to instinct and tradition, and much less by personal understanding. Each period has its own task, to contribute and to create something by which civilization gains materially or ideally. But if at any one period we examine into the daily life of its generation, we shall find a great deal more that is inherited than self-acquired. This fact ought to make us modest and zealous, but also just and thankful toward our forefathers, who did not possess or know many things which we possess and know now.
As animals make use of Nature and her laws in a multifarious and surprisingly appropriate manner, so does man also. Each carrier on the road makes use of the laws of motion and friction, and of those ​of living force and its preservation, but he does so for the most part quite mechanically, so that he appears to think no more about it than the beaver when he builds his hut. Man also does most things long before he understands them, and this is part of his nature. If he could make use of things only after having thoroughly investigated them, his life would be a poor one, and barely possible. If we had to study the functions of our clothing and its material before we could put it on, we should be frozen to death long before, and no carrier would have attempted to horse his cart before the time of Galileo and Newton,
Here I find myself drawing a dangerous parallel. You may ask me at once whether I believe a carrier will be a better carrier for understanding the laws of motion, and whether our clothing and our dwellings will one day be superior to what they are now, because we shall then have learned to understand their functions better. I leave the answer to the future with the utmost confidence. The experience of the past sets me completely at ease. At all times and everywhere it has been the case that each progress in the recognition of laws, that each new fact established, and each new method applied by science, each new way on which science has directed us, has finally had its practical and useful consequences. Excuse me if I continue to dwell on this favorite subject of mine.
What men call useful is quite a relative term; they call a thing so as soon as they find out what use they can make of it. Of course, a thing must exist before we recognize it, and we must become aware of certain of its properties and relations before we can make use of them for any practical purpose. Certainly the recognition of the laws of motion by Galileo, Kepler, Newton, Laplace, and others, has not brought about a revolution, or made a sensation among the carriers, but from these recognized laws sprang and were evolved new ideas, purified from the gross primitive slag, and they led on to the railway, etc. Other examples demonstrate still more clearly the connection between theory and practice.
Electric telegraphy, which is not only practical and useful, but already indispensable to us, had its first origin in the observations of the anatomist Galvani, who saw the legs of frogs quiver when they came in contact with different metals. Imagine to yourself great practical men of the time, whether statesmen, or divines, or soldiers, or physicians, witnessing Galvani's experiments going on year after year; certainly every one of them would have thought that the man could apply himself to something more useful. But from that form of electricity which Galvani detected there sprung the researches and works of Volta, Sömmering, Steinheil, Morse, and Wheatstone, to whom we owe the whole of our telegraphic system. Place together in your mind the quivering leg of the frog and the transatlantic cable.
After the-discovery of Columbus the Spaniards found in the sand ​of a river grains of a white metal, which was not affected by fire, and appeared, therefore, to be a noble metal. Quantities were brought to Europe, and the new metal received the modest name of platina (low silver), this being a diminutive of la plata (silver). The masters of the Mint, the gold and silver smiths, had soon formed their ideas about the new metal; it could neither be melted by itself, nor hammered, nor rolled, nor dissolved in aqua-fortis. It was only soluble in aqua-regia and other melted metals, but the combinations were all brittle and discolored; in short, it came to be considered a perfectly useless metal, practically worth less than lead and iron. Its importation was prohibited by the Spanish Government, because there was danger of its high specific gravity leading to its use for the adulteration of gold. What platina there was in the country already was thrown into the sea by order. But Science, who makes no difference between the useful and useless, and considers everything useful which increases our insight into the things that are, has quietly held intercourse with the outcast metal; she learned how to tame the shrew, and since Wollaston platina is considered to be one of the most pliable and useful of metals; just what were originally considered its vices have enhanced its value so much in the course of time that weight for weight the "low silver" is paid seven times as much for as the "high silver."
Modern times have not ceased furnishing numerous examples of the same kind, showing that it is not the business of science to ask for the immediate profit, for the immediate practical use. They do not fail to come forth in time.
Science may point to the words of the Bible: "But seek ye first the kingdom of God and his righteousness, and all these things shall be added unto you." All sciences are provinces of God's infinite kingdom, and in them, as everywhere in God's kingdom. Justice is dealt by Truth alone. This was my standpoint, which helped me over the doubts I might have had concerning the utility of these lectures. It seemed to me that the principal thing was not to present to you a series of practical applications and contrivances, but a series of truths, which carry in themselves their use and applicability, and impose their authority in proportion as they are talked over more frequently, understood more clearly, and felt more vividly.
But I wanted to tell you the whole truth about the things which formed the subject of my lectures, and it became my duty to draw your attention not only to what is positively known, what is complete, what requires no further investigation, but also to point out to you much greater fields of hygiene, where scarcely a seed has been sown. Otherwise I should probably have jeopardized the only and immediate practical use which my lectures can have here, and which I believe to be this: that the conviction may spread and take root everywhere, that hygiene has been neglected until now, ​practically as well as theoretically, and that this neglect is a dark spot on our civilization, which has to be removed by this generation This conviction begins just now to lay hold of ever-widening circles of society, and a certain sympathy is stirring for the interests of public health, much more than formerly. The weather seems suitable for ploughing fields which have remained untouched, and for sowing good seeds where a rank vegetation has been growing.
When a current, a general motion of men's minds, sets in toward some definite goal, then it becomes the duty of all those who are their leaders to choose the proper routes with earnestness and conscientiousness. If a good intention in behalf of some object is wrongly directed, it soon turns against the object itself; all those who allowed themselves to become interested therein turn away discouraged as soon as they believe that their good intention has been wasted to no purpose, and hence those unlimited reactions and rebounds in public opinion. I believe that I am under a moral obligation to speak out in this place. I do it here, perhaps, more confidently than anywhere else, because I feel that here I am understood. I feel it, through the very fact that I have been requested to give my lectures before this audience. The request came to me from the Committee of the Albert Society, from its exalted Lady President. The existence of the Albert Society, its organization, its functions, its efficiency, and its authority, are ample proofs that the value of hygiene is understood here.
In this place I must also acknowledge that the Saxon Government was the first in Germany to establish a Central Board of Public Health; it has also included the teaching of hygiene in the teaching of military medical science. Such arrangements appear to me to be types of the two directions which must now be taken and followed out: on the one hand, investigation, observation, and experiment; on the other, systematic personal teaching. These are the only two ways which lead to the goal.
You have been enabled to see, from that single subject I have treated, how much remains to be done and created; everything is still insufficient and incomplete, and has to be developed and determined. Think of the great chapters—air, clothing, dwelling, ventilation, heating, lighting, building-places, and soil—their relation to air and water, and their influence on the course of disease; epidemics, and protection against them; drinking-water, and its distribution among the population; alimentations and articles of food; the maintaining of different classes of men under different circumstances; dietaries; public baths; gymnastics; collection and removal of excrementitious matters and refuse from households and trades; drainage; disinfection; inspection of dead bodies and their interment; unhealthy trades and manufactories, schools, barracks, asylums, hospitals and nursing, prisons, health statistics, etc.
​There is not one among these departments of hygiene in which nothing is left to be done; in most of them the work has scarcely begun. There has always been a desire for and an aiming at health; but ideas about it have changed completely. The former supports of hygiene have crumbled away in the powerful analytical solvents of modern physiology; very little has remained; everywhere new foundations are necessary. This requires workmen; the season appears favorable—do not let it pass unemployed.
It is not sufficient to build up correctly a series of hygienic truths, which might be the work of a few; these truths must be brought to bear upon life, and this requires instruments. Three professions are in real life the natural trustees and representatives of the hygienic interests of the community—physicians, architects, and engineers, and also the public administration. There must be harmonious action between them; good intentions are not sufficient; there must be knowledge and power. Only good musicians can make good music, and they must be well taught and practised. The institutions at which the members of these professions have received their education have all the while generally ignored hygiene as an independent branch of study. A vague supposition left it to the individuals concerned to take the trouble of gathering for themselves whatever was known or would be made public about matters of hygiene. Lectures on forensic medicine were supposed to be sufficient, but they have to consider facts and evidence only with regard to penal laws, which themselves result from the old and highly-cultivated science of jurisprudence. Hygienic laws must spring from hygienic science, and there was none.
Many of the existing hygienic laws and regulations cannot be kept up if examined by the light of hygienic science as it is now. It is no good going on issuing public regulations, demonstrative of good intentions, for the public health; the right thing is to create a firm basis for practical purposes and public measures. Hygiene must become an independent branch of study, to be taught by special teachers at universities, medical and polytechnic schools, not without the help of proper laboratories. Systematic instruction must be offered to students and practitioners of medicine, to members of the civil or municipal service, to architects and engineers. Books and reading can as little occupy the place of personal teaching and experimental investigation as a medical book in the library that of the physician, or a hand-book that of the public chair. The self-taught hygienist has frequently to look out for principles on which to act, while he is called upon to act at once, and routine alone is a dangerous and unreliable assistant. There are exceptions—brilliant ones even—but exceptions prove the rule.
The increasing interest taken by the intelligent and well-meaning members of society in matters of public health, which have also an ​intimate connection with the public purse, cannot fail to assist the whole movement which is taking place in favor of hygienic science and its independent and well-endowed instruction.
The whole movement is still going on, but not without resistance here and there. This resistance shields itself, sometimes, behind the pretext that there are at present not enough well-qualified teachers. Certainly the beginning has its difficulties, but everything must have its beginnings. This was the case with the first periodical in Germany for public hygiene, founded by Dr. Varrentrapp, which has achieved an entire success, in spite of all misgivings and discouraging vaticinations before it was started. Worthy representatives of the neglected science will be found for teaching it, as soon as a serious demand manifests itself. A certain species of medical men will be quite made for it, after some preparation. 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. But as the votaries of the latter sciences have never done the work of pure physiologists, so these would never have done, and never will do, the work of pure hygienists. England has preceded other countries in the creation of professorships for hygiene, I confidently believe that the proper men, in sufficient number, will also be met with in Germany in a short time.
Should my lectures in Dresden have had the effect, in some degree, of turning your hearts and minds toward the most pressing tasks of hygiene, so that every one of you may do his best for them in his own sphere, then I am sure I have done something practically useful, and have not spoken in vain.