25 ANIMAL PARASITES. 



cercus, a view which has also been erroneously supported by 

 Huxley, in the ' Annals of Natural History/ vol. xiv, p. 383. 



This was the aspect of affairs when, in the year 1851, the 

 thought already expressed, although with other views, by Goeze, 

 which, however, was still unknown to me, suggested itself to 

 my mind, of purposely administering various cystic worms to 

 different animals. For this purpose, I selected one of the most 

 easily accessible cystic worms, which Von Siebold had expressly 

 omitted from amongst those which he supposed to be capable of 

 becoming converted into matuj-e Teenies, or, as he said, " again 

 becoming healthy," namely, the Cysticercus pisiformis of the 

 rabbit, and also the C. fasciolaris (' Prager Vierteljahrsschrift/ 

 1852, " Ueber die Umwandlung der Finnen in Tsenien"). In 

 this way I succeeded in rearing Tanice, rapidly approaching 

 maturity, from Cysticercus pisiformis in the intestine of the clog, 

 and from C. fasciolaris in that of the cat. Supported by these 

 facts, I expressed the following opinions with regard to the nature 

 of the cystic worms ( f Ueber den Cestoden im Allgemeinen/ &c., 

 Zittau, 1853). 



1. If the caudal vesicle were a morbid structure, this would 

 say little for the wise arrangement of Nature, in undertaking 

 nothing without an object. 



2. The similarity of the dwelling-place of millions of cystic 

 worms indicates a general plan, and the idea of a systematic 

 infliction of disease is too unnatural to be admitted. 



3. The caudal vesicle occurs in all individuals, of all species of 

 cystic worms, even though they live in the most various zones and 

 different animals. Even in the greatest epidemics and epizootics 

 some individuals and districts are spared, but here none. 



4. The universal loss of the caudal vesicle has its analogue in 

 the metamorphoses of many animals. 



5. It would be a forced assertion to say that the dropsy is 

 cured simply by casting off the caudal vesicle ; something like 

 curing ovarian dropsy by extirpation. 



6. In the cystic worms, there is no nutritive fluid between 

 the worm and the cyst, which, however, is never deficient in 

 encysted Helmintha of other classes. (See Luschka, ' Ueber 

 Trichina spiralis.') 



7. All cystic worms, in the earliest period of their existence, 

 have the head constantly inverted towards the caudal vesicle. 



8. The state of rest in which the cystic worms must live 



