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What is a Ripe or Gravid Proglottis ? 



One in which only traces of the reproductive organs 

 remain, excepting the uterus which is greatly distended 

 and full of developing eggs or embryos (onchospheres) 

 within their tough " shells." The embryo, oval or spher- 

 oidal, has six chitinous hooks (hexacanth embryo). 



Describe the Life- History of Taenia solium, and state how 

 this Parasite is transmitted to Man. 



The Pork Tapeworm lives attached to the mucosa of the 

 small intestine of Man. It is white, and frequently attains 

 a length of from six to ten feet. 



The gravid proglottids are detached and pass out in the 

 faeces ; and (in places where unsanitary conditions exist) 

 the encapsuled embryos (or the proglottids containing them) 

 are swallowed by the omnivorous pig. The capsules are 

 dissolved by the digestive juices, and the hexacanth em- 

 bryos are liberated ; they bore into the wall of the intestine 

 and, entering the blood vessels, pass to the connective 

 tissue between the muscles. There they increase in size 

 and develop into hollow cysts filled with fluid. The wall 

 of the cyst or bladder becomes invaginated at one point, 

 and the bottom of this pouch is formed into a scolex which 

 is everted within the pouch. This is the asexual stage, a 

 " bladder-worm " of the kind called a Cysticercus. In the 

 pig, Cysticercus cellulosae causes the disease known as 

 " measles." 



When diseased or "measly" pork (i.e., pork infested 

 with Cysticercus cellulosae) is eaten by Man, the bladder- 

 worms are then transmitted. In the small intestine the 

 scolex is everted, and by its hooks and suckers it becomes 

 attached to the mucous membrane ; the bladder is dis- 

 solved, and, by budding out a chain of proglottides, the 

 tapeworm is formed. 



Taenia solium is also transmitted in the embryo stage 

 to Man, by drinking water or eating vegetables (e.g., salads) 

 contaminated with the onchospheres, and, frequently, 

 through habits of personal uncleanliness in defaecation. 

 The resulting Cysticercus is generally developed in the 



