Tropical diseases : a manual of the diseases of warm climates / by Sir Patrick Manson.

  • Patrick Manson
Date:
1907 (repr. 1912)
Catalogue details

Licence: In copyright

Credit: Tropical diseases : a manual of the diseases of warm climates / by Sir Patrick Manson. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

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    the opportunities for man to contract the common disease are most frequent, or are only found, in the tropics. Such, most probably, are some 'of the tropical ringworms. Certain parasites are so organised that before re- entermg man they must pass a part of their lives as free organisms in the outer world, where they require a relatively high temperature for their development. Such parasites, therefore, and the diseases they give rise to, must necessarily be tropical or sub-tropical. The Ankylostomum duodenale and ankylostomiasis are an instance in point. There is a class of intoxication diseases which depend on toxins generated by germs whose habitat is the soil, water, or other external media, and whose germs do not enter the human body as a necessary feature in their life histories, although their toxins may. The yeast plant and its toxin, alcohol, and the disease it causes, alcoholism, are the most familiar example of this. Such, too, are ergotism, atriplicism, and, perhaps, lathyrism. The beriberi gei-m, its toxin, and beriberi, are possibly another. These germs require certain temperatures and certain media; consequently the diseases they produce have a corresponding geographical range. If one of these conditions be a high temperature, the disease, as in the case of beriberi, is mainly a tropical one. Lastly, I can conceive, and believe, that there is another and less directly-acting set of conditions influencing the distribution of disease, conditions which as yet have been ignored by epidemiologists, but which, it seems to me, must have an important bear- ing on this subject. Disease germs, their transmitting agencies, or their intermediate hosts, being living organisms, are, during their extracorporeal phases, necessarily competing organisms, and therefore liable to be preyed upon or other^vise crushed out by other organisms in the struggle for existence. The malaria parasite is absent in many places in which, appar- ently, all the conditions favourable to its existence are to be found in perfection. Why is it not found there, seeing that it must certainly have been fre-
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