334 



THE ANIMAL PARASITES OF MAN 



body. The females measure 20 25 40 crn. in length and about 

 5 mm. in diameter, the posterior extremity is conical and straight. 

 The vulva is at the border between the anterior and middle third 

 of the body ; the two uterine tubes pass straight to the posterior 

 end of the body; the convoluted ovaries measure ten times the 

 length of the body. 



The ova are elliptical with a thick transparent shell (fig. 218), 

 and an external coating of albumen which forms protuberances ; the 

 ova measure 0*05 0^07 mm. in length, 0^04 0*05 mm. in breadth ; 

 they are deposited before segmentation ; the albuminous coating 

 is stained yellow by the colouring matter of the faeces. 



Ascaris lumbricoides is one of the most frequent parasites of 



' FIG. 217. Ascaris himbricoides. a, posterior 

 extremity of the male with the spicules protruding 

 from the orifice of the cloaca (Sp.) b, anterior 

 extremity from the dorsal surface. c, anterior 

 extremity from the ventral surface. P., porus 

 excretorius. (From Claus.) 



FIG. 218. Ovum of Ascaris 

 lumbricoides, with shell and 

 albuminous envelope. 400/1. 



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 in Finland, Greenland, &c. In temperate climates 

 Ascaris lumbricoides occurs most frequently in young children ; it is, 

 moreover, more common amongst country dwellers than amongst 

 the inhabitants of towns, but is not lacking in infants, adults and 

 aged persons. As a rule only a few specimens of the ascaris are 

 present in the intestine, but many cases are known in our zone 

 in which several hundreds of worms have been found in the same 

 patient. The ascaris is particularly numerous in the negroes of 

 Africa and America. 



The parasite was already known in ancient times ; the Greeks 

 called it eX/ui/9 arpoyyvXrj, Plinius termed it Tinea rotunda, later 

 on it was named Lumbricus teres ; the da/cap^ of the Greeks is our 

 oxyuris. 



