274 THE ROUND WORMS 



(27 mm.) with a rounded tail end. Found only once in the alimentary canal of a 

 native in the Caucasus. Leiper has recently reported a species P. mordens from 

 Uganda, one case. 



Ancylostoma duodenale (Dochmius duodenalis.) The hookworm, 

 so called from the hook-like appearance of the ribs of the copulatory 

 bursa or from the hook-like projection of the head dorsally, is probably 

 the most important of the parasitic worms. This species in Europe 

 and Africa and the Necator americanus in the New World cause an 

 immense amount of invaliding. The Egyptian anaemia and the Porto 

 Rican anaemia are caused by this parasite. 



Goeze found a hookworm in a badger in 1782. He named the parasite Ascaris 

 criniformis. Froelich, in 1789, found hookworms in the fox and called them hook- 

 worms from the hook-like ribs of the copulatory bursa. He proposed the generic 

 name Uncinaria. Therefore Uncinaria belongs to the hookworms of the fox and 

 is not valid for any human species. 



In 1838, Dubini found a hookworm as a human parasite. On account of the 

 four ventral teeth projecting from the mouth he gave it the name Agchylostoma or 

 correctly Ancylostoma. 



Bilharz and Griesinger noted the connection of the parasite with Egyptian 

 chlorosis, but it was not until the time of the St. Gothard tunnel (1880), that the 

 importance of the parasite was recognized. Grassi noted the diagnostic value of 

 the ova in faeces in 1878. In 1902, Stiles noted and described the hookworm found 

 in the United States as different and proposed the name Uncinaria americana, later 

 changed to Necator americanus. A. J. Smith had also recognized the morphological 

 differences. 



Hookworms may be found in the small intestine (jejunum) of man 

 in enormous numbers. They either produce their effects by feeding on 

 the mucosa or by causing loss of blood. 



The males are little more than 1/3 of an inch (9 mm.) long and the females little 

 more than 1/2 inch (13 mm.) in length. The male can readily be distinguished 

 by his umbrella-like expansion or copulatory bursa. The tail of the female is pointed. 

 The vulva of A. duodenale is located in lower half of the ventral surface; that of 

 N. americanus in upper half. The large oval mouth of the Old World hookworm 

 has four claw-like teeth on the ventral side of the buccal cavity and two on the dorsal 

 aspect. In N. americanus the buccal capsule is round, smaller and the ventral 

 teeth are replaced by chitinous plates. Dorsally there are two similar but only 

 slightly developed lips or plates. A very prominent conical dorsal median tooth 

 projects into the buccal cavity. Through it passes the duct of the dorsal 

 cesophageal gland. The copulatory bursa of the N. americanus is also different, 

 being terminally bipartite and deeply cleft in the division of dorsal ray rather than 

 tripartite and shallow as with the A. duodenale. 



The delicate-shelled eggs pass out in the faeces, and in one or two days a rhabditi- 

 form embryo (200X14/0 is produced. 



