STEUCTUEE AND DEVELOPMENT OE CYSTICEECUS TENUICOLLIS. 569 



take into consideration the fact that during the development and 

 gradual ripening of the proglottides a more or less extensive 

 growth takes place. In T. marginata there is between the first ripe 

 joint and the head a chain of 550 joints, of which the foremost are 

 of very inconsiderable length. In T. serrata there are about 325, 

 and in T. ccenurus hardly 200 segments. ^ 



I may now pass from the consideration of the anatomy of T. 

 Ttiarginata, especially since the character of the internal organs is 

 essentially the same as in T. solium. It is true that certain differences 

 in detail are not wanting, of which, however, I shall only mention 

 that the muscles of the body (as also in T. serrata), are more power- 

 fully developed than is the case in T. solium. Owing to this the 

 contractility of this tape-worm is much greater and more extensive 

 than that of the hook-bearing human tape-worm. The firm appearance 

 of the chain is also partly due to this circumstance. 



Structure and Development of Cysticercus tenuicoUis. 



Like Tcenia marginata, which is in many respects very nearly 

 related to T. serrata, Cysticercus temiicollis has a great resemblance to 

 C. pisiformis. This is especially true of its occurrence, and, according 

 to my investigations, of the events in its history. At first these 

 bladder- worms inhabit the liver, inside the branches of the portal 

 vein, which soon after the entrance of the embryos become choked 

 through the secretion of an exuded granular substance. Few only, 

 however, of the worms remain in this locality, most of them leaving 

 the liver before the development of the head, to remain for a time 

 free in the body-cavity, and then to become encapsuled anew, gene- 

 rally in the mesentery. " 



The youngest specimens of Cysticereus tenuieollis hitherto observed 

 are those found by Leisering in a lamb,=* which died ten days after 

 the feeding. Seen with the lens or with the naked eye, they 

 appeared as " small pale yellow points," which lay " in hundreds " in 

 the widely dilated ramifications of the portal vein. While the surface 

 was still uninjured, they could be driven out of one vessel into another 

 by careful pressure with the handle of the scalpel, and when a portion 

 of the larger branches of the portal vein was excised, they issued in 



^ These numbers differ from Kiichenmeister's statements (according to which T. mar- 

 ginata possesses altogether only 400, T. serrata 286, and T. ccenurus 150 joints), only 

 because the anterior ones, which are certainly difficult to distinguish, have been overlooked. 



" For further information regarding the developmental history and fate of Cysticercus 

 pisiformis, see "Blasenbaudwiirmer," p. 113. 



' Bericht iiber das Veterindrwesen Sachsens, p. 22, 1857-58. 



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