Selected Monographs.

  • New Sydenham Society.
Date:
1888
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Licence: Public Domain Mark

Credit: Selected Monographs. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    Malaria cannot originate in these superficial strata, remaining dry, but does so in the wet underlying ones, whenever the air is able to gain access to them through fissures or the porosity of surface soil, or when excavations lay them bare. In low lands these subterranean foci are sometimes formed by the old marsh bottoms covered by natural or artificial colmate* (such as, for example, the cuoraf of many places on the coast or Tuscan Maremma, and the subsoil of most of the Val di Chiana). The subterranean marshes are harmless even when they remain wet during the hot season, if the soil of the colmata covering them is deep and sufficiently compact. On the other hand, they generate malaria when only separated from the air by a thin stratum of disintegrated soil, J or when the air can reach them owing to excavations or fissures in the overlying soil. Often, however, subterranean foci have no marsh origin, are poor in organic detritus, and are found at high altitudes of mountains. The preservation of humidity in lower strata of this sort of soil is chiefly due to the sparing permeability of their subsoil and the irregular inclination of its surface impeding the escape of water. Such are frequent in Italy, and especially in the Eoman Campagna and City of Rome, as may be seen by examining a section plan of the aquiferous zone from the Jani- culan to the Porta S. Lorenzo past the Pantheon. In such soils malaria is not generated unless the access of air to them is brought about by excavations and other such means. Other hypotheses have been started unconnected with these conditions, of soil, and have become sometimes popular traditions. One of the most common is that which attributes to forests the power of generating malaria from the decomposition of the leaves and dead branches which strew the ground. This has been suggested by the existence of many forests in Europe, Africa, India, &c, &c, in which malaria attains great proportions ; and because disafforesting has had the effect of rendering many such districts salubrious. Even in the Pontine marshes an analogous fact was witnessed after the clearing made twenty years ago in the great wood * Colmata, embankment, levelling up of hollow places with earth. f Cuora, equivalent to bog or turf; the carbonized black ooze of marshes resulting from the decay of successive generations of organic materials j a term also used for marsh conduits. % Dr. G. Lindi, Paper read before the Medical Congress at Arezzo, July 10, 1877.