THREAD WORMS. 219 



worm, seat-worm or thread-worm. The male is about 1/6 of an inch 

 long and the female a little less than 1/2 an inch in length. The male 

 has a single spicule and the female a long tapering tail. 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 copu- 

 lation 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 rectum where they either expel their 

 ova or themselves, working 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 ova which may be carried to the mouth and so cause a fresh in- 

 fection. 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. 



ACANTHOCEPHALA. 



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

 which projects like a little peg. It has several rows of hooks pro- 

 jecting backward which enable it to attach itself firmly 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 3 shelled eggs are very striking and the intermediate 

 stage is in June bugs. 



The Echinorhynchus or Gigantorhynchus gigas E. hominis 

 E. and moniliformis have also been reported for man. 



HIRUDINEA (LEECHES). 



Hirudino medicinalis. This is the leech used medicinally for the 

 abstraction of blood. They have a secretion which prevents coagula- 

 tion of the blood so that when removed the wound still continues to 

 bleed. 



Hirudo nilotica. This species has been found in many parts of 



