INTESTINAL WORMS. 175 
the Scolex can gain a passive migration into the intestinal canal of 
an animal suitable for its development, that development will 
proceed ; the vesicle will be cast off: joints will be formed suc- 
cessively beneath the neck, and in thése joints the genital organs 
will be developed, the joints first formed, or nearest the posterior 
extremity of the body, being the first to become mature. Thus the 
Scolex is changed into a Tape-worm. Many naturalists now con- 
sider the Tniz to be compound animals, (which indeed was the 
opinion long ago of VALISNIERI and CouLer and. afterwards of 
BLUMENBACH,) colonies, like certain Polyps: the head and neck 
corresponding to the Polyp-stock, and the joints, under the name of 
Proglottis, to the single Polyps. By such observations as these 
Von SrEBOLD has been enabled to interpret justly those of LEBLonND 
and Mrescuer alluded to above. The Amphistoma of LeBLonD 
was the embryo of the Tape-worm, now the receptaculum Scolecis, 
the Tetrarhynchus the Scolex of a Rhyncobothrius. When the 
minuteness of these embryos is considered (they are not more in 
volume than the blood-dise of the frog) it is not difficult, as Van 
BENEDEN’ says, to comprehend that they may perforate the walls of 
the intestine to encyst themselves beneath the peritoneum, or to 
penetrate the vessels and distribute themselves with the blood in 
_ different viscera of the body, not excepting the brain itself, or the 
humours of the eye. Dr Haupner of Dresden caused six young 
lambs to swallow the living and mature joints of Twnia serrata. 
They all died of the peculiar vertiginous disease produced by 
Cenurus cerebralis. The Cenurus vesicles were found in the brain, 
and the heart, lungs, and voluntary muscles abounded with encysted 
broods of Tenia*. It would seem from this that the different forms 
of Canurus and Cysticercus assumed by the larva depend upon the 
locality occupied by the embryos, and the quantity and nature of 
the nutriment which they obtain there. And this conclusion is 
confirmed by the previous and converse experiments of Von SiE- 
BOLD. On causing young dogs to swallow Cystic. pisiformis from 
the liver of the hare, Cist. tenuicolles from the mesentery of the 
sheep, Cist. cellulosa from the muscles of the swine, Canwrus cere- 
bralis from the brain of the sheep, the same form of Teenda, viz. 
1 Van BenepEn Ann. des Sc. natur. Série 111. Zoolog. Vol. xx. PP.1329, 320 
2 Von Srenoip Band u. Blasen-wiirmer, 8vo, Leipsig, 1854, p. 106. 
