Generally speaking, "a tape-worm" in Western Europe will prove to be _Taenia saginata_ Goeze (the beef tape-worm, Fig. 39, A), exceedingly prevalent also in the East, and indeed cosmopolitan, occurring wherever the infected flesh of the ox is eaten in a raw or half-cooked state. Its attacks are fortunately not usually severe. _Taenia solium_ Rud. (the pork tape-worm) is found wherever the pig is kept as a domestic animal, and has consequently a world-wide distribution. Its size (6-9 feet long) and powers of adhesion would alone render _T. solium_ a formidable parasite. But the danger of its presence in the body of man, or in the flesh of pigs, lies in the fact that the larva or bladder-worm (known as _Cysticercus cellulosae_) can live in the most varied organs. Thus if by accident a mature proglottis be eaten, the embryos escape, bore their way into the wall of the stomach, and entering the portal vein, may reach in time the muscles, the brain, the eye, or even the heart itself, and attain the cystic condition. Even more disastrous may be the result, should some ripe joints of a mature worm work their way from the intestine back towards the stomach. Should this happen (and though it has not been directly proved, the possibility is to be reckoned with), the result would be the release of vast numbers of embryos capable of inflicting fatal injury on the host. An abnormal _Cysticercus_ of this species is probably the _Taenia_ {80}(_Cysticercus_) _acanthotrias_ Weinl. (see, however, Leuckart, _loc. cit._ p. 711). _Taenia_ (_Hymenolepis_) _nana_ v. Sieb.[101] is found in man in Egypt, Italy, England, Servia, Argentine Republic, and the United States. Though small (¾-1 inch long), its numbers usually excite digestive and nervous disorders of considerable severity, more serious, indeed, than those caused by the commoner tape-worms. _H. diminuta_ Rud. (_flavopunctata_ Weinl.), normally found in Rodents, has been rarely recorded in man. _Taenia_ (_Dipylidium_) _caninum_ L. (= _T. cucumerina_ Bloch = _T. elliptica_ Batsch), the commonest parasite of pet cats and dogs, and _T._ (_Davainea_) _madagascariensis_ Davaine, have occasionally been recorded from infants and young children. But the attacks of these species are insignificant in comparison with those of the cystic stage (_Echinococcus polymorphus_) of a tape-worm (_T. echinococcus_ v. Sieb.) which lives when mature in the dog.