TAPEWORM IN CYSTIC STAGE. ' 229 



Coetome, Fraipont, op. cit. ; cf. Van Beneden and Ray Lankester, Z, A. iv; 

 1 88 1 ; v. 1882. Griesbach on Solenophorus (supra). 



Sexual organs of T. mediocanellata (=saginata) and T. solium, Sommer, Z.W. Z. 

 xxiv. 1874; of Bothriocephalus, Id. and Landois, Z. W. Z. xxii. 1872. 



Development of proscolex from ovum in T. serrata, E. Van Beneden, Archives 

 de Biol. ii. 1881. For general account, see Moniez, Travaux Zool. Inst. Lille, iii. 2, 

 and Leuckart (supra). 



47. TAPEWORM IN CYSTIC STAGE (Cysticercus pisiformis^ 

 s. C. Taeniae serratae), 



Mounted as a preparation for the microscope. 



THE worm has been removed from its connective tissue sac or capsule, 

 and the head with a small portion of the neck has been evaginated by 

 gentle pressure from the vesicle, or proscolex, within which it is generally 

 retracted. The vesicle has delicate walls, and in life is distended by a 

 liquid which contains only a trace of albumen and is little more than a 

 solution of salts, chiefly of sodium. 



Under the microscope, using a -inch objective, the principal features 

 of the head may be readily made out : the slightly projecting rostellum : 

 the circlet of hooks and the suckers. The hooks are arranged in alternation, 

 one large with one small. The free part of a large hook is longer and 

 somewhat straight as compared with the corresponding part of a small 

 hook. The imbedded portion or root is in both cases forked, but the 

 anterior (or rostellar) branch of the fork is of remarkable length in the 

 large hooks. 



In the neck, especially in the part not completely evaginated, may be 

 noticed numerous clear rounded bodies. These are the calcareous bodies, 

 or concretions : see ante, preceding preparation, p. 227. They do not exist 

 in the walls of the vesicle. 



The life-history of Taenia serrata is briefly as follows. The ripe proglottides 

 are scattered among the grass by the way-side, &c., and are swallowed by a Rabbit, 

 the soft tissues being digested in the stomach, and the chitinoid shells containing the 

 hexacanth embryoes or proscolices set free (cf. p. 228) : or the proglottides decay 

 naturally and set free the contents of their uteri, which are then eaten with her- 

 bage. The chitinoid shell of the proscolex, under the combined influence of 

 warmth and the gastric juice, becomes brittle, and either break up spontaneously or 

 is broken by the. movements of the embryonic hooks. The embryo, now free 

 appears to bore its way into the tissues : and it has been found in the portal blood 

 by Leuckart. The embryoes of T. marginata have been similarly found by Leis- 

 ering in the portal capillaries of the Lamb. The parasite sojourns for about four 



