TAPEWORM. 225 



The head and neck are often termed ' scolex,' the joints, ' proglottides, 1 

 and the whole Tapeworm, ' strobila.' 



There are five Tapeworms ordinarily found in the intestines of the dog. Of 

 these, Taenia Echinocoaus, derived from the cystic form Echinococcus veterinorum, 

 which occurs in a variety of Mammals, consists as a rule only of a head and neck 

 with three or, at the utmost, four joints. It is not much longer than an intestinal 

 villus. Taenia elliptica, derived from the Cysticercus T. ellipticae, which inhabits 

 the dog-louse (Trichodectes Cam's), is recognisable at once by the elliptic shape 

 of its ripe joints and the two pori genitales, one right and the other left. It also 

 possesses a peculiar round rostellum beset with four irregular rows of sixty small 

 hooks. The other three Tapeworms are not so easy to distinguish. They are 

 T. serrata, derived from the C. pisiformis of the Rabbit ; T. marginata, from the 

 C. tenuicollis of the Sheep, &c. ; and T, coenurus, from Coenurus cerebralis of the 

 Sheep, and perhaps of the Rabbit. 



T. serrata has the largest head (1.3 mm.), and a circle of 38-48 hooks, 

 alternately large and small, the large hooks being 25 mm. long, and the length 

 of the anterior branch of their forked roots very great ; the proglottis, when ripe, 

 is 8 mm. long and 3 mm. broad ; the uterus, when full of ova, has 8-10 main 

 lateral branches beset with numerous short ampullae. There are about 325 joints 

 between the neck and the first ripe joint. 



T. marginata has scarcely any constriction behind the head : the number 

 of hooks is 22-42, the hooks being smaller than those of T. serrata: the 

 proglottis is larger and longer; the uterus has about eight side branches which 

 are much branched laterally. There are about 510 joints in front of the first 

 ripe joint. 



T. coenurus has a pyriform head ; 24-32 hooks, which are small ; the proglottis 

 is smaller than that of T. serrata ; the uterus has 20-25 simple branches. There 

 are about 200 joints before the first ripe joint. 



The egg-shell of all three is about -027 mm. in diameter, but in T. serrata 

 it rarely bears processes as it does in T. marginata, 



The rostellum of Taeniae often attains a greater size than it does in T. serrata. 

 It has a special system of muscles. The same is true of the suckers which are 

 composed of radial and equatorial fibres almost exclusively. The former deepen 

 the cup, the latter contract its margin. 



The surface of a Tapeworm is bounded by a vertically striated cuticula which, 

 according to Griesbach, is a product of the gelatinous connective tissue of the 

 body. The striae are due to pores 1 . Beneath the cuticle is a system of transverse 

 or circular fibres which Leuckart considers to be muscular ; Griesbach as elastic. 

 The substance of the body in Soknophorus consists of a gelatinous matrix which 

 forms a system of trabeculae with lacunar spaces representing the coelome. The 

 matrix contains elastic fibres and nuclei, small rounded, as well as stellate cells, 

 and therefore closely resembles the connective tissue of Mollusca (Griesbach). 

 A fine granular protoplasm with nuclei (? cellular : see infra under T. lineatd) covers 

 the trabecula immediately below the cuticula, but does not appear to extend 



1 It has been said that protoplasmic processes extend into these pores from the granular proto- 

 plasm covering the subjacent connective tissue trabeculae. 



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