FOOT (a. W.) — ON ENTOZOA. 213 



as an independent group, being, in fact, the Tapeworm in a partially- 

 developed form.* Dujardin, in 1845, was the first to assert that the 

 cystic worms were undeveloped forms and young states of the Tape- 

 worm.f Simultaneously Von Siebold in Germany expressed the same 

 opinion. Kuchenmeister was the first, in 1851, to administer the cystic 

 worms to animals. He succeeded in rearing mature Taenioe in the dog 

 from the Cysticercus pisiformis of the rabbit, and in the cat from the 

 Cysticercus fasciolaris of the mouse. The converse of this experiment, 

 the production of cystic worms from the ova of a mature Tapeworm, has 

 since been effected by Leuckart and others. 



"When a rabbit has been fed with ripe segments of the Tcenia ser- 

 rata of the dog, in twenty-four hours a microscopic examination of the 

 blood of the portal and other abdominal veins will show an immense 

 number of minute embryos, armed with hooks, corresponding in size to 

 the ova of Tcenia serrata. About the fourth day small white semi- 

 transparent vesicles, each containing a little white embryo, make their 

 appearance in the liver. Eight days after the administration of the 

 worms the liver presents a more or less spotted appearance, conspicu- 

 ously visible to the naked eye. Soon after the passage of the six- 

 hooked embryos out of the blood into the liver the metamorphoses by 

 which the embryo is transformed into a Cysticercus appear to commence. 

 Bound the vesicle of the Cysticercus the liver forms a capsule of con- 

 nective tissue in self-defence, within which the formation of the head 

 of the larva proceeds. Many of the embryos deposited in the liver do 

 not come to maturity, but die, and undergo a change into granular 

 atheromatous masses.^ 



The cystic Entozoa have been arranged into various genera, founded 

 on peculiarities in the containing vesicle, or in the contained scolex — 

 the future head of the fully formed worm. The presence of a caudal 

 vesicle makes the genus Cysticercus, and of this genus there are several 

 species, distinguished for the most part by the forms and proportions of 

 the neck or body intervening between the head and the caudal vesicle ; 

 as, for example, Cysticercus fasciolaris, Cysticercus longicollis, Cysticer- 

 cus tmuicollis ; the genus Caenurus is so called, because the terminal 

 cyst is common to many bodies and heads. Another kind of taenoid 

 embryo becomes metamorphosed into a vesicle of larger or smaller di- 

 mensions, from whose inner surface countless scolices pullulate ; these, 

 however, become detached, and lie freely within the cavity of the parental 

 vesicle. Upon this form the genus Echinococcus has been founded ; the 

 name was given by Eudolphi on account of the cylinder of hooks which 

 surrounds the heads of the microscopic animals. These three genera of 

 cystic worms were till lately all confounded together under the name 



* " Cyclop. Anat. and Physiol.," vol. ii., p. 115. 

 t "Hist. Nat, des Helm.," pp. 554-633. 

 J Cobbold, "Entozoa," p. 110. 



