ANIMAL PARASITES. 31 



the intestine, and, increasing in size, give origin in their interior 

 to the head of the tape-worm (scolex), whilst the portions of the 

 embryonal body which were not employed in the formation of 

 the head, remained attached to the head in the form of a caudal 

 vesicle. With him, therefore, the cysticercal state is the second 

 stage of development immediately following the embryonal state. 

 Meissner also afterwards found (Siebold and Kolliker's 'Zeitschr./ 

 v, p. 380) the six embryonal booklets on the Cysticercus ofArion 

 empiricorum, but did not explain the nature of the caudal vesicle 

 correctly. Without discovering the much smaller embryonal 

 booklets of those tapeworm-embryos which pass through a true 

 vesicular state, Goeze (loc. cit.) had already seen how the future 

 tapeworm-head is developed in the interior of the caudal vesicle ; 

 G. E. Wagener (loc. cit.) had proved the occurrence of this pro- 

 cess within the enlarged embryonal body (caudal vesicle) ; and I 

 myself had set about the experimental solution of this problem, by 

 the administration of the ova of tape-worms. In order to arrive 

 at a peculiarly convincing result by these administrations, 1 

 selected the dog as an experimental animal, in July, 1853, and 

 even previously, and this may, at the same time, serve the 

 reviewer of my book, ' Ueber die Cestoden im Allgemeinen/ in 

 Schmidt's ' Jahrbuch cler Medizin/ as an answer to his astonish- 

 ment on this account, and administered mature segments of 

 Tcenia solium to several of these animals. Gurlt had previously 

 stated that he had found a dog with Cysticercus celluloses, and I 

 thought that, from the rarity of the occurrence, the experiment 

 would be most convincing in case I succeeded in infecting the dog 

 with Cyst, cellulosce. In this, however, I did not succeed, any 

 more than in infecting rabbits with the same Cysticercus by the 

 administration of T. solium. The attempt, also, to produce 

 cysticercal forms in the meal-worm, by the administration of 

 Tcenia angulata of the missel thrush, and of a Tcenia from the 

 starling, an experiment upon which I have hitherto forgotten 

 to report, did not succeed ; but for about four years I have been 

 unable to find the Tcenia of the rat and mouse, which I regard as 

 the Tcenia belonging to the cysticercal forms of the meal-worm. 

 In the meanwhile I resolved to resume these experiments with the 

 Tcenia Coenurus, in order to obtain the remarkable phenomena of the 

 vertigo in sheep. On the 15th of May, 1853, I at last obtained 

 the cystic Ccenuri ; on the 25th of July mature proglottides of this 

 Tcenia were passed by the dog to which the Ccenuri were adminis- 



