THE PIN WORM 279 



female 4 to 5 inches in length. The parasites are characterized by the presence of 

 wing-like projections from the anterior end (arrow-like head). 



Oxyuris vermicularis. This parasite is also known as the pin-worm 

 or seat-worm and is more frequent in children than in adults. 



The male is about 1/6 of an inch long and the female a little less than 1/2 inch 

 in length. The male has an incurved tail with a single spicule and the female a long 

 tapering tail. The vulva is in the upper third. 



These worms have a clear slightly bulbous, pipe mouth-piece-like projection 

 surrounding the three-lipped anterior extremity. There is a well-marked bulb 

 cesophagus. 



The eggs are thin-shelled plano-convex, and show a coiled-up embryo. After 

 ingestion of eggs, the adults develop in the small intestine where copulation takes 

 place; the males then die. The fertilized females go to the caecum and colon where 

 they remain until they reach maturity. At this time the females wander to the rec- 

 tum where they either expel their ova or themselves work their way out of the anus. 

 This usually occurs at night, and the scratching induced by the itching causes the 

 eggs to be widely spread about the region of the anus. The worms may also wander 

 into the vagina, urethra, or under prepuce. It will be seen that as a result of the 

 scratching, the fingers become contaminated with o^a which may be carried to the 

 mouth and so cause a fresh infection, no intermediate host being required. The 

 examination of the material under the finger nails of children harboring this parasite 

 may show eggs under the microscope. A knowledge of the life history the early 

 location in the small intestine, and later on in the large shows that treatment should 

 be dual in its direction enemata for the gravid female in the rectum and santonin 

 and calomel for the young adults in the small intestine. 



The diagnosis is preferably made by examining the stools for the 

 white, thread-like females which are expelled after a diagnostic dose of 

 calomel and salts, rather than by searching for the eggs. 



These females, which are packed with embryo containing eggs, may be seen 

 wriggling on the surface of the freshly passed fasces. In handling these worms 

 one should be careful as they are apt to cause infection should the eggs get on the 

 fingers. 



ACANTHOCEPHALA. 



These are called thorn-headed worms on account of a proboscis which projects 

 anteriorly like a little peg. 



There are several rows of hooks surrounding this projection which are directed 

 backward to enable the parasite to attach itself to the intestinal wall. The worm 

 absorbs nourishment through the general body wall, there being no alimentary 

 canal or mouth. These worms are common in hogs. The three-shelled eggs are very 

 striking and the intermediate stage is in June bugs. 



The Echinorhynchus or Gigantorhynchus gigas. This parasite is about 6 inches 

 (15 cm.) long for the male and 10 to 12 inches (25 cm.) for the female. It has 



