Page:Tropical Diseases.djvu/836

780 The alimentary tube begins at the oral cavity, which is funnel-shaped and surrounded by a strong muscular mass. It consists of a slender œsophagus without bulb, of an intestine attaining a width of about 65 μ towards the middle of the body, and of a short, attenuated rectum.

The male reproductive organ is first encountered about 3 mm. from the cephalic extremity, where it ends in a pointed blind sac. Anteriorly it is very sinuous and winds round the alimentary canal; posteriorly it straightens, attains a diameter of 85-105 μ, and terminates by a vesicula seminalis filled with more or less spherical spermatozoa 6-8 μ in diameter.

Fig. 154.—L. loa, female. (Partly after Looss.)

In the female the vulva forms a small eminence at about 2·5 mm. from the anterior extremity. The vagina, 9 mm. long and 95 μ wide, branches off into two long tubes extending almost throughout the entire length of the body. These tubes, the narrow ends of which are the ovaria, contain eggs in all stages of development, as well as free larvæ 0·253-0·262 mm. in length by 0·0047-0·005 mm. in breadth.

Structure of the larval form.—Microfilaria loa (= diurna) is very similar in size (298 μ by 7·5 μ) and structure to microfilaria bancrofti. Like the latter, it is enclosed within a "sheath," its tail is pointed, and it has the same V and tail spots. (Figs. 96, 97.)