In swamps where drainage was impossible a regular level was aimed at, especially during the summer months, by the regulation of the incoming and outgoing water, and by the building of dams, since it was not the surface covered with water, but that which was alternately under water and exposed to evaporation, which was dangerous.
By colmata (Italian; Kolmatage, French), for instance, was meant the filling up of deep lying ditches or basins for the purpose of sanitary improvement and bonification. This is seldom done directly for the sake of husbandry (colmata arteficiale), but usually by permitting an inflow of water from the next stream or the sea, which is allowed to sedimentate, and repeating the process until the required level" is reached. The process is naturally slow, and requires decennia for its accomplishment. The most extensive achievements of this kind have been carried out in Italy. Historically famous is that of the Val di Chiana, between the Tiber and Arno, the colmata of which was attempted under the Medici (1525), but successfully accomplished only in this century. We may mention, besides, the Tuscan Maremma. The same has been done in England and Holland with sea water.
The cultivation of the ground from this, the old standpoint, might be designated as a second important factor in prophylaxis. It was well known that when cultivation is neglected even healthy regions pay the penalty of infection. The extensive clearing of forests especially has drawn in its wake serious results for the neighborhood.*
For the purpose of sanitary improvement the most useful plants are those which grow rapidly under the existing climatic and geologic conditions, though naturally the monetary value cannot be left out of consideration.
At one time the Eucalyptus globulus and Eucalyptus rostrata acquired considerable reputation. There are many instances where very successful results were accomplished by the planting of eucalyptus trees, as in the vicinity of the Trappist monastery, Tre Fon tana, near Rome, certain localities in Algeria (around Bona, Philippe ville) and in Corsica. Eucalyptus rostrata has recently displaced Eucalyptus globulus, on account of its greater adaptability to different soils and its resistance to extremes of temperature.
In addition to the eucalyptus tree, pines, Helianthus annuus, Acorus calamus aromaticus, have been recommended. Vincent and Burot laud especially the Coniferce filao (Casuarina equisetifolia), which has been tested at Bourbon.
It is probable that the beneficial effects of these plants has been exaggerated, and that the improvement following the planting is due to concomitant alterations in the surface level of the soil, rather than to a drying up of the ground on account of their quick growth and rapid evaporation. Unfortunately, this method, even if we grant all that has been claimed for it, is capable of improving only relatively small areas, and is of no importance in the case of immense stretches of malarial region, such as are found in Africa,
In addition to these general prophylactic measures, which were applicable to whole countries, we must consider, too, the special forms of prophylaxis which were adapted to narrower spheres.
There were cases reported in which infection took place on ships, when the holds, bunks, bilges, etc., were neglected, and we have already referred, on page 37, to the question of infection in dwel-
* The clearing of woods was apparently especially responsible for the infection of the Roman Campagna. From more recent times Mauritius (He de France) is another good example. Humboldt and Darwin found the island salubrious and flourishing, while, since 1867, the severest forms of malaria have raged as a result of clearings in order to establish sugar plantations. The removal of the trees, it was thought, was associated with a diminution of precipitation, and this allowed the river banks to become marshy with brackish water (Pellerau). [Whatever the influence of this factor, the result is now clearly attributable to the formation of numerous collections of water in which anophelines can multiply almost indefinitely.-Ed.] ling rooms. Although these cases were not absolutely determined to be malaria, the possibility of such confined foci was not beyond question. The prophylaxis consisted in keeping clean and preserving dry the ship's compartments. The question also arose whether or not the improvement of the drinking water was to be considered under the head of malarial prophylaxis.
There were not a few examples, especially from American forts (see Rupert Norton), where the introduction of the best spring water altered not in the slightest the malarial endemic. On the contrary, Fayrer asserted that good water was the first essential in malarial prophylaxis.
Individual prophylaxis, moreover, comprehended all the regulations capable of protecting the individual from infection.
It was naturally easier to find protection in a city of which only the periphery was malarial, than in the country in the midst of a severe malarial focus.
Experience taught that in cities the most thickly populated streets (therefore, as a rule, those situated centrally) are most immune, while the peripheral lying parts, furnished with ornamental and other gardens, villas, ponds, etc., are most frequently infected. In such cities it was, therefore, recommended to choose the central portion for habitation. The dwelling, it was thought, should not lie deep, nor yet be situated too high; the height of an ordinary second story seemed best. If it was necessary to occupy the first story, the bed was raised as high as possible from the floor. Moreover, it was always thought by many advisable to protect the bed by a mosquito netting [a practice which is now the pivot and basis of personal hygiene, but it is no longer the unseen miasm that is screened off, but the seen mosquito.-Ed.].
L. Colin, in a series of notes on the protection of workmen in malarial regions, mentioned the following points as the most important :