142 TROPICAL MEDICINE AND HYGIENE 



progressive anaemia of a severe type, associated with fatty 

 degeneration of the heart, liver and kidneys, and of the 

 mucosa of the alimentary canal. It may terminate fatally 

 from the anaemia, from cardiac failure, or from inter- 

 current diseases, such as dysentery. In early cases recovery 

 is rapid and complete when the worms are expelled. 



These two species of worms appear to produce the same 

 effects, and therefore the term Ankylostomiasis is used 

 indifferently whether the A. duodenale or the N. ameri- 

 canus is responsible. 



These worms belong to the division in which there 

 is a deep oral capsule. In this division the mouth opens 

 into a cavity and in this the opening of the oesophagus 

 is situated. There are frequently armatures, such as 

 teeth, thickenings, or spines, at the orifice of the 

 buccal or oral capsule, and sometimes of the orifice of 

 the oesophagus as well. 



In most of the genera the lips of this oral capsule are 

 symmetrical, but in the Ankylostomes the ventral side is 

 longer than the dorsal, and in addition the head is bent 

 towards the dorsum so that the opening of the oral 

 capsule is directed dorsally. 



The opening of the female genital organs is near the 

 middle and in the female the anus is subterminal, the tip 

 of the tail being bluntly pointed. 



The male is smaller, the cloaca is terminal and sur- 

 rounded by four membranous flaps strengthened by 

 chitinous ribs forming the copulatory bursa. There are 

 two long equal spicules. 



Ankylostomum duodenale. Female, 10 to 13 mm., by 

 i mm. in breadth. Occasionally larger specimens up to 

 20 mm. are met with. Male, 9 to 12 mm., and 0-5 mm. in 

 breadth (figs. 63 and 64). 



Necator americanus is smaller and more slender. 

 Female, 9 to n mm., by 0*5 mm. in breadth. Male, 7 to 

 9 mm., by 0*35 mm. in breadth. 



They can be distinguished without measurements by 

 the naked eye, as in Necator the head is more abruptly 



