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788 M'Binia. He believes that in that region ''0. volvulus'' affects about 5 per cent, of the riverine population. He saw cases on the Himbri, and he refers to others on the Kibali and on several of the tributaries of the Welle. Cooke met with cases in Uganda, Fülleborn in Cameroons, Parsons in northern Nigeria. Clapier reports many cases in French Guinea.

The parasite.—According to Parsons, the adult male is 20-32 mm. in length by 0.2 mm. in breadth. The body is white, filiform, tapezing at both ends. The head is rounded and has a diameter of 0.04 mm. The cuticle is transversely striated. The mouth is unarmed. The alimentary canal is straight and ends in a subterminal anus. The tail terminates in a single spiral, and is bulbous at the tip. There are two pairs of preanal papillæ, two pairs of postanal papillæ, and an intermediate single large papilla. Two unequal spicules may be seen protruding from the cloaca. According to Braun, the adult female measures 60-70 mm. in length by 0.36 mm. in breadth; more recent measurements are much less, 35-40 mm. in length (Schafer). The head is rounded and truncated; it measures 0.04 mm. in diameter. The tail is curved. The striations of the cuticle are not so distinct as in the male. The egg possesses a peculiar striated shell. The larva measures about 300 μ. in length; it has no " sheath." The body tapers from about the last fifth of its length and terminates in a sharply pointed tail. At about the anterior fifth of the body there is a gap in the central column of cells (V spot). At least four males and two females are present in every tumour. Pathogenesis.— ''0. volvulus'' is found in peculiar subcutaneous fibrous tumours, the size of a pea to that of a pigeon's egg. The same patient may present one or several of these tumours. The regions of the body most frequently affected are those in which the peripheral lymphatics converge. Thus the tumours are usually found in the axilla, in the popliteal space, about the elbow, in the suboccipital region, and in the intercostal spaces. They are never adherent to the surrounding structures and can be easily enucleated. They are formed of a dense mass of connective tissue, which enwraps the parasites and encloses small cystlike spaces filled with a greyish viscous substance consisting almost entirely of microfilariæ. The position of the adult worms within these tumours is very remarkable. The greater length of the coiled-up