. The animans and man; an elementary textbook of zoology and human physiology. very smallworm lives in its adult con-dition in the intestine of manas well as in the pig and othermammals. The young,which are born alive, burrowthrough the walls of theintestine, and are either car-ried by the blood, or forcetheir way, all over the body,lodging usually in the mus-cles. Here they form forthemselves little cells orcysts in which they forming of these thou-sands of tiny cysts injuresthe muscles and causesgreat pain, sometimes deathto the host. Such infestedmuscle or flesh is said to be trichi
. The animans and man; an elementary textbook of zoology and human physiology. very smallworm lives in its adult con-dition in the intestine of manas well as in the pig and othermammals. The young,which are born alive, burrowthrough the walls of theintestine, and are either car-ried by the blood, or forcetheir way, all over the body,lodging usually in the mus-cles. Here they form forthemselves little cells orcysts in which they forming of these thou-sands of tiny cysts injuresthe muscles and causesgreat pain, sometimes deathto the host. Such infestedmuscle or flesh is said to be trichinosed, and the fleshof a trichinosed human subject has been estimated to con-tain 100,000,000 encysted worms. To complete the devel-opment of the encysted and sexless Trichinae the infestedflesh of the host must be eaten by another animal in whichthe worm can live, , the flesh of man by a pig or rat,and that of a pig by man. In such a case the cysts beingdissolved by the digestive juices, the worms escape, developreproductive organs and produce young, which then migrate. FIG. 60. Tapeworm; head, magni-fied, at left; the whole wormmay be several yards long.(After Leuckart.) 148 THE ANIMALS AND MAN into the muscles and induce trichinosis as before. But,however badly trichinosed a piece of pork may be, tho-rough cooking of it will kill the encysted trichinae, so thatit may be eaten without danger. Some people, however,are accustomed to eat ham, which is simply smoked pork,without cooking it, and in such cases there is always great danger. CHAPTER XIV THE INVERTEBRATES (continued): ARTHROPODS AND MOLLUSCS The jointed-legged animals.—None of the invertebrateswe have studied so far has any organs which are really ofthe nature of legs, in the meaning commonly ascribed to theword. In fact the animals of only one out of the eleveninvertebrate branches have organs which show any analogywith the jointed legs of our own body and of the other ter-restrial vertebrates. This branch is t
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