ASCARIS LUMBKICOIDES 



, 



463 



Ascaris lumbricoides, L., 1758. 



The colouring, in the fresh condition, is reddish-yellow or greyish- 

 yellow ; the body is of an elongated spindle shape. The oral papillae 

 are finely toothed. The dorsal papilla carries two sensory papillae, 

 the two ventral papillae each one sensory papilla. The male measures 

 from 15 to 17 to 25 cm. in length, and about 3 mm. in diameter ; 

 the posterior extremity is conical and bent hook-like ventrally ; the 

 spicules measure 2 mm. in length, are curved, and somewhat broadened 

 at their free end ; on each side around the orifice of the cloaca there 

 are seventy to seventy-five papillae, of which seven pairs are post-anal. 

 The testicular tube is much folded, showing through the body integu- 

 ment, and is about eight times the length of the body. The female 

 measures 20 to 25 to 40 cm. in length and about 5 mm. in diameter ; 

 the posterior extremity is conical and straight. The vulva is at the 

 junction of the anterior and middle thirds of the body, which, at 



FIG. 341. Ascaris lumbricoides. a, posterior 

 extremity of the male with the spicules pro- 

 truding from the orifice of the cloaca (Sp.) 6, 

 anterior extremity from the dorsal surface, the 

 two lobes of the pulp of the lip separated by the 

 " saddle " ; c, anterior extremity from the ventral 

 surface; P., excretory pore. (From Glaus.) 



FIG. 342. Ovum of Ascaris 

 lumbricoides, with shell and 

 albuminous envelope. 400/1. 



this point, has a slight ring-like constriction ; the convoluted ovaries 

 measure ten times the length of the body. 



The ova are elliptical with a thick (4 //,) transparent shell (fig. 342) 

 and an external albuminous coating which forms protuberances ; the 

 ova measure 50 yu, to 70 /* in length, 40 //, to 50 //, in breadth ; they are 

 deposited before segmentation ; the albuminous coating is stained 

 yellow by the colouring matter of the faeces, but is sometimes absent. 

 The egg cell is unsegmented, it almost completely fills the shell, and 

 its nucleus is concealed by the large amount of coarse yolk granules. 



Abnormal or unfertilized eggs also occur in faeces. They are 

 distinguished by their elongated form (80 /A by 45 //,), irregularly 

 cylindrical, its contents consisting of refractive granules. 



Ascaris lumbricoides is one of the most frequent parasites of man ; 

 it is distributed all over the inhabited parts of the world, and though 

 it is particularly frequent in the warmer regions, yet it also occurs 



