48 TAPEWORMS. 



tapeworms are known as 1ii-nio»i)^, and in some cases the disease 

 ends fatally not only in animals but also in man. A well- 

 known instance of this vermiceous group is the disease called 

 " measles in pork,'' which is produced by the cystic stage of a 

 tapeworm {Tnnia soliuiii) that invades man. The worm is con- 

 tracted by eating infested pork insufficiently cooked. Another 

 is the measles in "beef" produced by the cystic stage of the 

 human tapeworm Tcenia swjinata (Goeze), the beef tapeworm. 



Tapeworms are found in all parts of the world, and are 

 usually most destructive where insanitary conditions exist. A 

 typical tapeworm (fig. 14, c) consists of a pei-manent head, 

 known as the scolex (figs. 14, s, and 12. a), and a long segmented 

 body, each segment being known as a proglottis (b). Between 

 the scolex and the body there comes a constricted area, the nedi 

 (fig. 14, n). This is the growing area of the worm, the area from 

 which fresh segments are constantly being budded ofiF. The pro- 

 glottides increase in size towards the tail end. Each proglottis 

 is practically a perfect animal in itself, as each has a separate set 

 of sexual organs. When the segments are ripe — that is, sexually 

 mature and full of ova — they fall off : sometimes they disunite 

 separately, at others in groups of from four or more, and pass 

 out to the exterior in the animal's excrement. 



The hend or scolex (figs. 12, a, and 14, s). — This so-called head 

 has no mouth ; there are usually two or four suckers {s) upon 

 it, enabling it to become attached with the additional aid of 

 two rows of hooks (Ji) to the mucous membrane of the host's 

 intestines. Hooks may be absent. (Unarmed tapeworms, as 

 Moniezia cxpanna of sheep.) In some species the scolex is 

 drawn out in front into a kind of snout, the rvstellum, and 

 then hooks are present surrounding its apex. 



We find four chief modifications of scolices : (i) In the 

 Tamiii', in which there are four suckers and two sets of hooks 

 on the rostellum ; (ii) Botliriocephahis, in which there are two 

 suckers ; (iii) Acanfhohothnum, which are provided with a 

 complicated set of suckers and beset with numerous hooks ; and 



