. Des parasites animaux et la maladie humaine. Parasitologie médicale ; insectes en tant que porteurs de la maladie. L'ascaride ou Ascaris 273 nématode doré. - De la plus grande importance de ces parasites intestinaux moindre est le nématode doré, Ascaris lumbricoides (Fig. 106). Les ascaris est l'un des plus grands nématodes parasites connus, la femelle avec une moyenne d'environ dix pouces de longueur, et occasion- ally mesure d'un pied et demi de diamètre, tandis que le corps est à peu près aussi grand qu'un crayon de plomb ordinaire. Les mâles sont habituellement de plusieurs pouces de moins. Ces vers sont parmi les plus parasites humains subséquents. Ils se produisent dans toutes les parties de la wor

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. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. ASCARIS 273 Ascaris or Eelworm. — Of greatest importance of these lesser intestinal parasites is the eelworm, Ascaris lumbricoides (Fig. 106). Ascaris is one of the largest nematode parasites known, the female averaging about ten inches in length, and occasion- ally measuring a foot and a half, while in diameter the body is about as large as an ordinary lead pencil. The males are usually several inches shorter. These worms are among the most fre- quent human parasites. They occur in all parts of the world and are found, especially in children, in the majority of temperate countries, even in countries as far north as Greenland and Fin- land. In the tropics they are abundant and are almost univer- sally present in children, each individual harboring anywhere from two or three to several hundred worms. Ascaris can be recognized immediately by its large size and robust form. The males (Fig. 107) can be distinguished by the. Fig. 107. Ascaris, dissected to show anatomy; female above, male below. Note ribbon-like intestine (cross-barred) with pharynx at its anterior end; the coiled threadlike ovaries in female and testis in male; the large kinky oviducts in the female, uniting to form a vagina near the external opening on the anterior third of the body; and in the male the large sperm duct opening at the ventrally-ourved posterior end of the body in common with the intestine. sharp downward curve of the posterior end of the body, the female (Fig. 107) having a straight and rather stumpy tail. Both sexes are more slender at the head than at the tail end. The sexual organs occupy the greater part of the body. In the female theyconsist of two coiled threadhke ovaries (Fig. 107) and a pair of large oviducts in the form of kinky tubes which open about one-third of the way back from the anterior end. In the male there is a single coiled threadlike testis and a single sperm duct (Fig. 1

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