Male.—25 to 30 mm. long by 0·1 mm. thick (40 by 0·1 mm. according to various authors). Probably two pairs of pre-anal papillæ, eight pairs of peri-anal, two pairs of post-anal papillæ, and one pair terminal. Tail curved. Two spicules, 0·2 and 0·6 mm. respectively, and a cup-like gubernaculum. The long spicule is cylindrical, expanded proximally and tapering distally to a filament with wings. At the tip it is spoon-like. The short spicule is of the same diameter throughout. It is gutter-like, coarsely marked. Testis uncoiled, terminating in a snowdrop-like process (Leiper).
Eggs.—40 µ by 25 µ. They do not appear to possess a true shell, but only an embryonal or vitelline membrane secreted by the ovum.
Embryos.—In the posterior part of the uterus eggs occur, in the anterior part embryos; the larvæ at birth measure 127 µ to 200 µ by 8µ to 10 µ. In the blood they measure in the fresh 260 µ by 7·5 µ to 8 µ. In stained films, owing to shrinkage, there is great variation in size, from 154 µ to 311 µ. Probably 260 µ to 285 µ is the average in stained films.
Geographical Distribution.—Europe: Two cases recorded, one from near Barcelona. The patient suffered from hæmato-chyluria and enlarged scrotum with mikrofilariæ in the blood. A second case from Siena. Africa: The filarial index has not been estimated for various parts. In Nigeria it is about 10 per cent.
Habitat.—Lymphatic glands: e.g., inguinal, femoral, iliac, lumbar, mesenteric, bronchial, superficial cervical, epitrochlear.
Lymphatic vessels: e.g., those draining into the receptaculum chyli of the spermatic cord, in the thoracic duct and in various different parts.
Organs, etc.: Testis, epididymis, spermatic cord, tunica vaginalis, mammary cyst, and in abscesses.
They may occur in masses, but usually only a few (one to eight). Females are commoner than males. Dead and calcified worms are common in the various sites.
Distribution of Larvæ in Body.—These are by no means uniformly distributed, but occur in greater number in the capillaries of the lungs. Besides the lungs they occur in the capillaries of other organs, as the following data of Rodenwaldt show:—