The Guinea-worm is a curious parasite, which is found burrowing under the skin, and finds an exit through the opening formed by a sort of boil. It very rarely attacks Europeans, as it may be avoided by the most ordinary care in the matter of water used for drinking and bathing.

Another curious malady caused by one of the round-worms is the blood-worm disease, or filariasis. In this the parent worm is found embedded in the tissues of the host, and periodically discharges into the blood enormous numbers of its embryonic offspring. As this disease is undoubtedly communicable through the agency of mosquitoes alone, its prevention may obviously be secured by the adoption of the same measures that serve to protect us from malaria.

Tape-worms have a very curious life-history. The long, flat, jointed strip is really a chain of sexually mature individuals, but when their eggs are swallowed by an animal there is hatched out from it, not another tape-worm, but a minute embryo, which has the power of boring through the tissues of its host till it reaches some favourable resting-place, where it settles down, protected by a capsule, forming what is known as a bladder-worm. It may live for years in this condition, but cannot reach maturity until the capsule has been swallowed by some carnivorous animal, though some species can multiply non-sexually and so cause terrible damage to the animal that harbours it. Both stages of several species of these parasites infest man, but fortunately their prevention is a very simple matter, at any rate as far as the adult strings of worms are concerned, as infection is impossible provided all meat and fish eaten be thoroughly cooked. The mature stage of the bladder-worm which is found infesting man inhabits the intestine of the dog, and as it is capable, in this stage, of non-sexual multiplication, may give rise to large tumours, the effects of which may be most serious if a vital organ be invaded. Though almost a medical curiosity in Europe, it constitutes a really serious danger in certain pastoral colonies, such as Australia, where large numbers of dogs have to be kept for herding sheep, and are allowed unrestricted access to the offal of carcases, which is, of course, very abundant where meat-preserving is an important industry. The disease might be guarded against by preventing the dogs having access to anything but thoroughly cooked meat, and by avoiding undue fondling and too close association with these animals.

The third important class of parasites, the flukes, but rarely infest man, but in Egypt and, in fact, throughout Africa, a peculiar fluke, the Bilharzia, is found infesting the blood-vessels, especially those of the kidney, and gives rise to the appearance of blood in the urine. It is extremely common amongst the natives of Egypt, but it very rarely attacks Europeans, and though we are quite in the dark as to its life-history outside the human subject, there is little doubt that moderate care as to the water used for drinking and bathing is sufficient to afford complete protection against the disease.

PART II.
OUTLINES
OF
TROPICAL CLIMATOLOGY

ERRATA.

p. 9, line 9 from foot, for “Camerun” read “Cameroon”; and line 12 from foot, for “Shilling” read “Shillong.”

p. 58, line 11 from foot, for “Sangor” read “Saugor.”