Rural Hygiene. Henry N. Ogden
assumed to be the healthiest soil on which a house could be built, provided the ground water reaches its highest stage three or four feet below the cellar bottom.
Sand is equally desirable except in the cases where vegetable matter has been mixed with the sand, rendering decay imminent. Water drawn from such sands in the form of springs will contain large quantities of nitrates which may lead to excessive development of vegetable life and may have on the human system the same laxative effect as comes from drinking swamp water.
Clays and heavy alluvial soils are not usually considered desirable soils on which to build. Water does not run from such soils; they hold moisture, and hence are always damp, and marshes are very apt to exist in the vicinity.
Effects of cultivation.
It was formerly thought that extensive cultivation was objectionable from the standpoint of health, that manured fields in the vicinity of a house were undesirable, and that the turning up of a well-manured field with a plow in the spring was a very likely source of fever. It is a very common belief to-day that when water pipes are to be laid in city streets, thereby disturbing the soil and bringing fresh earth to the surface, typhoid or other fevers may be expected. There is, however, no ground for this belief, and the fact that laborers and their families live healthily in the midst of the thousands of acres of sewage-irrigated fields near Berlin, where the heavily manured fields are constantly being plowed, is a sure proof of this. The earlier text-books on hygiene all assert, however, the contrary; Parkes, for instance, says that irrigated lands, especially rice fields, which give a great surface for evaporation and also exhale organic matter into the air, are hurtful, and in northern Italy the rice grounds are required to be three quarters of a mile from the small towns to protect the village inhabitants against fevers. There is no ground, however, for such a requirement.
No evidence can be found that men who work in sewers and who breathe sewer air all the time are especially unhealthy. Statistics show that the laborers on the sewage fields of Paris and Berlin are actually healthier than the average person living within those cities.
No reason can be assigned, based on our present knowledge of bacteriology, why upturned earth or manured fields should be unhealthy except as the breeding of insects may be encouraged thereby. The two essentials, however, which should be considered are: first, the topography or the formation of the soil in order that the surface water may run off freely, and second, the character of the soil so that ground water may not remain too near the surface. Whether the soil is rock or gravel makes very little difference.
Made ground.
One kind of soil, however, is distinctly objectionable, although, fortunately, in the country such a soil is unusual: That is, a soil made up of refuse, whether it be garbage, street sweepings from a near-by city, or factory refuse.
The writer has in mind one enterprising landowner and farmer who offered a near-by city the free privilege of dumping the city garbage on his land. This was done for several years, and the low-lying districts of his farm were all filled to a more advantageous level. This garbage was then covered with about a foot of dirt and the land sold in building lots to enterprising laborers determined to own their own homes. According to the old theories of hygiene, the occupants of such houses should have died like rats, but no particular excess of sickness in the one hundred houses so located could be observed. One must, however, believe, as we shall see later, that the repeated breathing of air drawn from such polluted soil must be unhealthy, even though the mortality records fail to show it.
It is interesting in this connection to note that the organic matter in soil gradually disappears, just as a body buried in a grave will finally decompose. Experiments show that such organic matter as wheat straw or cloth in small pieces rots and decays in about three years. But this depends very largely on an excess of air. If the soil is open and the organic matter loose, oxidation takes place rapidly; but if a large pile of organic matter is buried in clay soil, it will take decades for it to disappear. The vegetable matter in soil is usually produced by the decay of plants which have either grown on the soil or have been washed down into its voids. A great deal was formerly written on the relation between this organic matter and the prevalence of malaria, and some earlier writers believed that the amount of malaria in a district was dependent upon the amount of vegetable débris in the soil. Since we have learned that malaria is carried by mosquitoes, we are less interested in the amount of organic matter in the soil. Its mere presence is not likely to be injurious.
Water in the soil.
Only the hardest rocks are entirely solid, the others containing a certain percentage of voids or interstices. These voids are filled with air or water, as the case may be, and we may stop for a moment to inquire the effect of the presence of this air and water. In loose sands the amount of voids is 40 to 50 per cent of the total volume, in sandstone about 20 per cent, and in other rock reduced amounts. The volume of air, therefore, in the soil under a cellar to a depth of four or five feet, amounts to a good many cubic feet and would not be worth inquiring into except for the fact that it is continually in a state of motion. When the ground water, perhaps normally five feet below the cellar bottom, rises in the spring, this ground air is forced out, and in a cellar without a concrete foundation it rises into the cellar and penetrates into the house.
A house artificially warmed by stoves is continually discharging heated air from the tops of the rooms and colder air is being brought in from below to take its place. This air comes from the ground below, and in open soil may come from a great depth. A case has been noted where gas escaping from a main in a city street twenty feet from a cellar wall was, by the suction due to heat, drawn into the cellar and thence into the rooms of the house. It is possible that air from cesspools and broken drains in the vicinity of a house may, in this same way, contribute to the atmosphere breathed within the walls of the house. Gravelly and sandy soils, therefore, in order to maintain the superiority which they furnish for building construction, should not be polluted, since any pollution in the vicinity influences the quality of air which may get into the house. The method of preventing such ingress is plainly to water-proof the outside walls of the cellar and provide an air-tight floor over the cellar bottom. Methods of doing this will be discussed in the next chapter.
Moisture in soils.
The presence of water in the soil has usually been considered to be unhealthy because of the impression that it led to certain fevers. The writer has heard, for instance, of an attack of malaria being caused by a short visit to a damp vegetable cellar; and it is one of the triumphs of the century that the malarial parasite has been discovered, and the old theory of the dangers of moisture been done away with. A damp cellar has always been considered to be undesirable, but just why nobody knows. A damp cellar causes molds to form rapidly, thus destroying vegetables and other material which might naturally be stored there, but that the presence of moisture in a cellar in itself produces any organic emanation leading to disease is not true, although dampness is essential to the growth of certain organisms.
In the latter part of the nineteenth century, Dr. Bowditch, of Boston, showed that consumption developed most where the surrounding soil was moist, and generally it is the impression that dry air is the only proper air for a consumptive person to breathe. This theory, however, is being rapidly exploded, and patients now remain outdoors in any weather, and no kind of air is objected to by physicians, provided it is outdoor air. Some little time ago the writer was called by a Board of Health to investigate a certain swamp which had some odor, was considered a blot on the landscape in an unusually picturesque village, and was said to be responsible for a long list of contagious diseases. A house-to-house inquiry in the vicinity showed that among some dozen families, only one illness in the last few years could be remembered, and that was an old lady who had been on the verge of the grave for forty years.
It is curious to note the many examples which are cited by the earlier sanitarians to prove the dangerous effect of damp soil. For example, Pettenkofer, a very prominent German hygienist, says that in two royal stables near Munich, with the same arrangements as to stalls, feed, and attendance, and the same class of horses, fever affected the horses very unequally. In one stable, fever was continually prevalent; in the other, no fever was found. Horses sent from the unhealthful to the healthful stables did not communicate the disease. The difference between