330 THE ROUND WORMS 



The presence of eosinophilia is of great assistance in diagnosis but it should be 

 remembered that not rarely severe cases of the disease fail to show any excess of 

 eosinophiles. 



Charcot Leyden crystals are often present in hookworm stools. 



It has been claimed that where ordinary microscopical examination for ova will 

 show 40% of infections and methods involving concentration 55% that cultural 

 methods will show 99%. A convenient method of culturing is to make a pile of filter- 

 paper circles of 2 inches diameter and about Y inch high and place in the center of a 

 4-inch Petri dish. Fill the dish with water about to the height of the filter-paper 

 and spread a thick layer of faeces on the top of the filter-paper island. The larvae 

 hatch out in about six days and swim out into the clear surrounding water. They 

 are best found by centrifuging the fluid containing them. 



ASCARID.E 



These have three papillae or lips around the oral cavity, one dorsal 

 and two ventral. The male has two equal-length spicules. An in- 

 termediary host is not needed in the life history of this family. 



A 



B 



FIG. 78. Anterior extremity of Ascaris lumbricoides; A, seen from front; B, seen 

 from dorsal surface. (Tyson after Railliet.) 



Ascaris Lumbricoides. The male round or eel worm is from 5 to 

 8 inches (18 cm.) long and the female from 7 to 15 inches (30 cm.) in 

 length. They are grayish to reddish in color and are from % to Y 

 inch (5 mm.) in diameter. 



It is probably the most common parasite of man, especially in 

 children and as it does not require an intermediate host infection takes 

 place through food or drink or by fingers of children who have been 

 playing where soil pollution exists. 



The normal habitat is the upper part of the small intestine, hence the ease with 

 which they are vomited up. The three papillae-like lips with a constriction just 

 behind are easily studied with a hand glass. The very long, whitish, convoluted, 

 thread-like tubes of the uterus lead to the opening of the vulva anteriorly and ven- 

 trally. The male has two large lance-like spicules which project from a subterminal 



