8o PLATYHELMINTHES 



The tissues of the host wall up the bladder worm and the enlarging 

 bladder worm is known as a hydatid cyst. 



Taenia saginata is a human tape worm which grows to a length 

 of forty feet, its terminal segments reaching a width of 3/16 of an 

 inch. The scolex has four large strong suckers without hooks. The 

 cysticercus stage is found in the muscles of cattle and occasionally 

 in dogs. It is more common in the United States than the pork 

 tape worm. 



Taenia solium is one of the commonest tape worms of man in 

 Europe. It reaches a length of twelve feet. Its scolex has both 

 suckers and hooks. The " bladder worm stage" Cysticercus cel- 

 lulosae, is found normally in the muscles of the pig but also occurs 

 in the dog, cat, rat and man. 



Dipylidium caninum is found in the dog and cat and occasionally 

 occurs in man. Each proglottid contains a double set of repro- 

 ductive organs. The cysticercus is extremely small, a fact cor- 

 related with its existence in secondary hosts as small as dog lice 

 and fleas. 



Taenia serrata, the common tape worm of the dog, has the rabbit 

 as its secondary host. If the rabbit swallows the eggs of the tape 

 worm, larvae develop in the alimentary canal and bore their way 

 through its wall into blood vessels which carry them to the liver. 

 From the liver the larvae migrate to the peritoneal cavity where 

 they grow into bladder worms or cysticerci. When a bladder worm 

 is swallowed by a dog the scolex attaches to the mucous lining of the 

 alimentary canal by means oi hooks and suckers and buds off a chain 

 of proglottids. 



Taenia coenurus, the dog tape worm, produces larvae {Coenurus 

 cerebralis) which infest the brain of cattle, sheep and deer and cause 

 the disease known as " staggers " or " gid." It has many segments 

 as an adult in the intestine of the dog, and the cystic form may reach 

 a size of ^ of an inch in the brain of the intermediate host. 



Diphyllobothrium latum^ the broad tape worm, causes anemia in 

 man. Its ciliated hexacanth embryo gets into the gut of a fresh 

 v/ater copepod, Cyclops strenuus or Diaptomus gracilis, then is 

 eaten by fish in whose muscles it encysts in the form of an immature 

 worm known as a plerocercoid. If eaten uncooked it becomes the 

 adult tape worm in man. Recently immigrants from Finland and 

 Baltic regions of Europe have introduced this parasite in the Great 

 Lakes region where fish have become infected. It is believed that 



