The Uncinaria (Anchylostoma) Duodenalis is a small round worm found in the upper intestine of man. The male is from 7 to 11 mm. long and 0.46 mm. wide, the female from 7 to 16 mm. long and 0.63 mm. broad. The head of the worm is cylindric and bends backward. The mouth has three pairs of sharp incurved hooklets and opens directly into an esophagus that occupies the anterior third of the worm.

The posterior end of the female is pointed and has two openings, the excretory and the genital pore. The tail of the male is expanded and is arranged like a three-leaved cup.

The eggs appear in the feces as oval, thin-shelled, and doubly contoured bodies about 0.36 to 0.63 mm. long. The number of eggs is enormous. Has been estimated that more than four millions may occur in a single stool. After exposure to the air the embryos escape from the eggs in about six days and continue their existence in the water. They may gain entrance by means of drinking-water or, as has been shown, the embryos may penetrate the skin of the feet.

The adult worm may occur in small or large numbers. It attaches itself to the wall of the intestine and sucks the blood for its nourishment. If the worm lets go, there remains an area of ecchymosis with a small point of hemorrhage in the center. It is thought that the parasite may inject into the wound some substance that interferes with the coagulation of the blood.

Uncinaria Duodenalis (von Jaksch).

Fig. 122. - Uncinaria Duodenalis (von Jaksch).

a, Male, natural size; b, female, natural size; c, male, magnified; d, female, magnified; e, head, greatly magnified; /, /, /, eggs.

If the organisms occur in great numbers, the loss of blood may be so severe as to cause a very marked anemia.

This condition exists in Egypt, southern Europe, and Brazil.