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XLV] ascertained to exist in North and South Queensland, Australia, and in several of the islands of the Pacific. So prevalent is it in many parts of India that, according to Dobson, quite 75 per cent. of the inhabitants are affected. In Egypt it is found at nearly every post-mortem examination; and there the anæmia it gives rise to is one of the most common causes for the rejection of recruits for the army. Thornhill regarded its ravages in Ceylon as far more serious than those of cholera; this, not on account of the number of deaths it causes directly, but on account of the vast numbers affected, the chronic nature of the disease, and the aggregate mortality, direct, and especially indirect, for which it is responsible.

The parasite (Fig. 175).—The normal habitat of A. duodenale is the small intestine of man, particularly the jejunum, less so the duodenum, rarely the ileum or lower reaches of the alimentary canal; very occasionally it is found in the stomach. In these situations it attaches itself by means of its powerful buccal armature to the mucous membrane, from the blood of which it obtains a plentiful supply of nourishment. It is supposed to shift its hold from time to time, the abandoned bite continuing to ooze blood for a short period. It is said to be very prodigal of the blood it imbibes, the red corpuscles passing through its alimentary canal unchanged, the plasma alone being utilized.

The male and female ankylostomes—present generally in the proportion of one of the former to three of the latter—do not differ so much in size as is the case with many of the other nematodes. The male (Fig. 177) measures from 8 to 11 mm. in length by 0·4-0·5 mm. in breadth; the female (Fig. 176) 10-13 mm. in length by 1 mm. in breadth. Both sexes are cylindrical in form, white when they are alive, grey when dead, reddish brown when full of blood. In both sexes the posterior end is the broadest part, whence the body tapers forward to a narrow neck ending in a powerfully armed, bulging, and distinct mouth capsule (Fig. 178, ). The margin of this remarkable organ is furnished with four strong, clawlike hooks—two on each side of the ventral line, and two conical teeth one on each side of the dorsal line. The tail of the female is conical, ending in a short delicate spine; the anus is subterminal, and the vagina opens on the ventral surface