CESTODA. 



335 



The proglottides have a marginal sexual opening. The vagina is usually long, 

 separated from the uterus, and enlarged at the end to form a receptaculum 

 seminis (fig. 265). The young stages are Cysticerci or Cysticercoids, rarely quite 

 without caudal vesicle ; parasitic in warm and cold-blooded animals. 



Tcenia L. ( Cijstotcenia R. Lkt). Development takes place with large vesicles. 

 The heads arise from the embryonic vesicle itself. 



T. sollum. L. 2 3 metres long. The double circle of hooks is composed of 26 

 hooks. The ripe proglottides are 8 10 mm. long and 67 mm. broad ; the 

 uterus has 7 10 dendritic branches. It lives in the human intestine. The 

 Bladder- worms belonging to it (Cysticercus celluloses} live principally in the 

 dermal cellular tissue and in the muscles of pigs, but also in the human body 

 (muscles, eyes, brain), in which self-infection with them is possible if a 

 Tcenia is present in the digestive canal ; more rarely in the muscles of the 

 Roe-deer, the Dog, and the Cat. In the human brain the Cysticercus acquires 

 an elongated form, and sometimes does not produce a head. 



T. stiff inata GoQze=--mediocaneUata Kiichenm., in the intestine of Man, distin- 

 guished by the older helminthologists as a variety of 

 T. sollum. Head without circle of hooks or rostellum, 

 but with four more powerful suckers. The Tape- 

 worm reaches a length of four metres, and becomes 

 much stronger and thicker. The mature proglottides 

 are about 18 mm. long and 7 9 mm. broad. The 

 uterus forms 20 35 dichotomous side branches. 

 The Cysticerffus lives in the muscles of the ox (fig. 

 273). It appears to be principally distributed in 

 the warmer parts of the Old World, but is often 

 found in great numbers in many places in the north. 



T.' serrata G-oeze, in the intestinal canal of the dog. 

 The Cysticercus is known as Cysticercus plsclformis 

 in the liver of the Hare and Rabbit. T. crassicollis 

 Rud. in the Cat. with Cysticercus fascwlaris of the 

 common mouse. T. marginata Batsch. of the Dog 

 (butcher's dog) and Wolf with Cysticercus tenuicol- 

 lis from Ruminants and Pigs, and occasionally in 

 Man (Cyst, visceral is}. T. crassiccps Rud. in the 

 Fox with Cysticercus long icollis from the thoracic 

 cavity of the Fieldmouse. T. coenurus v. Sieb. in the intestine of the sheep-dog, 

 with Coenurus cerebralis in the brain of one year old sheep. The presence of 

 Coenurus in other places has been stated, as for instance in the body cavity of 

 the Rabbit. T. tcnuicollis Rud. in the intestine of the Weasel and the Pole-cat, 

 with a Cysticercus which, according to Kiichenmeister, lives in the hepatic 

 ducts of the Field-mouse. 



EoHinococcifer Weinl. The heads bud on special brood-capsules, in such a 

 way that their invagination is turned towards the lumen of the vesicle (fig. 

 269). T. echinococcus v. Sieb. (fig. 270) in the intestine of the dog, 3 4 mm. 

 long, forming but few proglottides. The hooks on the head are numerous but 

 small. Its Bladder-worm is distinguished by the great thickness of the stratified 

 cuticula. It lives as Echinococcus principally in the liver and the lungs of Man 

 (#. h-omims} and of domestic animals (E. veterinorum). The first form is also 

 distinguished as E. altricipat'iem on account of the frequent production of 

 primary and secondary vesicles ; it usually reaches a very considerable size and 



FIG. 273. Cysticercus of Tcenia 

 mediocanellata, magnified 

 about eight times. The head 

 is protruded. 



