The theory and practice of hygiene (Notter and Firth) revised and largely re-written / by R.H. Firth.

  • Notter, J. L. (James Lane), 1843-1923.
Date:
1908
Catalogue details

Licence: In copyright

Credit: The theory and practice of hygiene (Notter and Firth) revised and largely re-written / by R.H. Firth. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

    496/1096 (page 470)
    of those conditions which favour the Hfe of the specific organisms and bring- about their aerial diffusion. These organisms are probably aUied to the- flagellate protozoa and have been described by Laveran, Marchiafava, Celh^ Eichards, Councilman, and Osier as the plasrnodinm malarim. It is an amoeboid-like body, which appears to separate out the pigment of the red blood-corpuscles. Its spores, which eventually form, are found only in the spleen and give rise to fresh amoebae. These pass into the blood, causing renewed fever, the nature of the attack being determined by the rapidity with which the different stages take place. So far, this micro-organism has- not been found in the soil, nor indeed has it even been cultivated outside- the human body. With regard to so-called malarious soils, the following geological forma- tions are more particularly known to be associated with the evolution of the agent which causes periodical fevers. Marshes. Except those with peaty soils, those which are regularly over- flowed by the sea (and not occasionally inundated), and the marshes in the southern hemisphere, and some American marshes, which, from some as yet. unknown condition, do not produce malaria. The characters of well-marked marshes are a large percentage of water,, but no flooding; a large amount of organic matter (10 to 45 per cent.) with variable mineral constituents; siHcates of aluminum; calcium, magnesium, and alkahne sulphates; calcium carbonate, &c. The surface is flat, with a slight drainage; vegetation is generally abundant. The analyses of the worst malarious marshes show a large amount of vegetable organic matter. A marsh in Trinidad gave 35 per cent.; the- middle layer'in the Tuscan Maremma 30 per cent. The organic matter i& made up of humic, ulmic, crenic, and apocrenic acids—all substances which require renewed investigation at the hands of chemists. Vegetable matter embedded in the soil decomposes very slowly; in the Tuscan Maremma, which must have existed many centuries, if not thousands of years, mariy of the plants are stiU undestroyed. The slow decomposition is much aided by heat which makes the soil alkaline from ammonia (Angus Smith), and retarded by cold, wMch makes the ground acid, especially in the case of peaty soils. It would now seem tolerably certain that the growing vegetation cover- 'm^ marshes has nothing to do with the development of malaria. ^Alluvial Soils.—Msjij alluvial soils, especially, as pointed out by Wenzel, those most recently formed, give out malaria, although they ar& not marshy. It is to be presumed, that the newest alluvium contains more organic matters and salts than the older formations. Many alluvial soils hav& a flat surface, a bad outfall, and are in the vicinity of streams which may cause great variations in the level of the ground water. Mud banks also on the side of large streams, especially if only occasionally covered with water, may be highly malarious; and this is the case also with deltas and old estuaries. The soils of Tropical Valleys, B.avines, Nullahs.—In many cases large Quantities of vegetable matter collect in valleys, and, if there is any narrow- ing at the outlet of the valley, the overflow of the rains may be impeded Sifch valleys are often very malarious, and the air may drift up to the height 'TXvZT^'^^^^^ when situated at il.. foot of iropical him, and covered wfth vegetation, as in the case of the Terai at the base of some mits of the Himalayan range. In other cases, the sandy plains are at a distance from h lis, and are apparently dry, and not much subjected to he 1^fltiSice oHariatim in the ground water. The analysis of such sand has not yet Len P P made, but two conditions seem of importance. Soma