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. 

 Meissneralso afterwards found (Siebold and Kolliker/s 'Zeitschr./ 

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

 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. R. 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 tier 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 cellulose, 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, celluloses. 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 Tarda 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 Taenia of the rat and mouse, which I regard as 

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

 In the meanwhile I resolved to resume these experiments with the 

 Tienia Cmnurus, in order to obtain the remarkable phenomena of the 

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

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

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



