284 



OTHER INTESTINAL ROUNDWORMS 



cephala) which occasionally have been found in man. These 

 worms are not true nematodes but are distantly related to them. 

 They are characterized by the presence, at the anterior end of 



the body, of a prolonged proboscis which 

 is covered with thornlike, recurved spines. 

 This proboscis is sunk into the walls of the 

 intestine of the host to gain anchorage. Like 

 the tapeworms, the spiny-headed worms are 

 totally devoid of any digestive tract of their 

 own. The common species of the hog, 

 Gigantorhynchus hirudinaceus (gigas) (Fig. 

 116), is said to occur in man in southern 

 Russia. It is a large worm, the female ten 

 to 12 inches in length and about one-fourth 

 of an inch in diameter and the male about 

 one-fourth as long. The larval stage is 

 passed in certain species of beetles. 



A single case of infection with another 

 hirudinaceus spccies, EcMnorhynchus hominis, which was 



Giganto- 



FiG. 116. 



ryhnchus 



S»f "F^at'uSl": o"ly one-fourth of an inch in length, has been 

 B, X 5. (After Raiiiet recorded, also from Russia. A species which 

 rom eumann.) j^ probably more frequently a human para- 



site is Hormorhynchus (or EcMnorhynchus) moyiiliformis, normally 

 parasitic in field mice, rats and marmots in Sicily. The female 



Fig. 117. Development of spiny-headed worm of rats and mice, Hormorhyn- 

 chus (or Echinorhynchus) moniliformis. A, proboscis, X 50; B, larva from cock- 

 roach, X 23; C, egg, X 150. (After Grassi and Calaudruccio.) 



worm is a little over three inches in length, the male about half 

 this size. A species of cockroach serves as an intermediate host. 

 Grassi and Calandruccio found by experimentation that the larvae 

 in cockroaches (Fig. 117B) would develop apparently equally well 

 in white rats and in man. An allied species, H. clarki, has 



