REARING HELMINTHES FEEDING EXPERIMENTS 125 



end of nino hours, as well as at a later period, they will be found 

 free in the blood-stream in the portal vein. It is a more difficult 

 matter to catch them in the act of perforating the bowel-wall. The 

 best method is to kill the host at the end of the first, or beginning 

 of the second, day ; rapidly to sever the small intestine at the 

 mesentery ; and to prepare it in series of sections. It will be neces- 

 sary, however, to examine a large number of sections before finding 

 one which shows the oncospheres within the substance of the bowel- 

 wall. The developmental changes which the oncospheres undergo 

 in the liver, as well as the pathological changes to which they give 

 rise, are best seen by means of sections cut from the affected organ. 

 Where, however, the Cysticerci are solarge that they may be pre- 

 pared singly, it is better to examine the living object. The worm 

 is of slow growth. Thus, the head does not make its appearance 

 until twenty-five days after infection, while the suckers and hooks do 

 not appear until forty days after infection. A large number of indi- 

 viduals fail to develop and gradually perish, one worm only, though 

 occasionally more, attaining complete maturity. 



The Cysticercus fasciolaris of Tcenia crassicollis as very distinc- 

 tive. After the development of the scolex, they proceed to form a 

 chain of proglittides, which lengthens with age and which differs 

 only from that of the mature worm in having at the tail-end the 

 characteristic Cysticercean bladder. Except that they are without 

 genital organs of any description, the single segments exactly resemble 

 those of the adult worm. 



Cysticerci in this stage of development may be introduced into 

 suckling kittens or kittens which have just been weaned. This is 

 done by holding the mouth open and placing a Cysticercus at the back 

 of the tongue, when a swallowing movement on the part of the kitten 

 will propel the parasite into the alimentary canal. One cat may be 

 given several Cysticerci, either immediately following one another, or 

 at longer intervals. In opposition to the prevailing view, E. Bartels 

 maintains that the only part of the Cysticercus which perishes, is the 

 bladder. He believes that not the scolex only, but the entire seg- 

 mented body, with the exception perhaps of the end-joints, continues 

 its existence in the new host, that it becomes sexually mature, and 

 adds to its length by the formation of new proglottides on to the old 

 ones. 



Another subject for experiment, which is easily obtained and con- 

 venient to handle, is Tcenia serrata of dogs, the intermediate stages of 

 w T hich are found as Cysticercus pisiformis in the liver of rabbits and 

 hares. 1 T. marginata is also obtained from dogs, and here the inter- 



1 See B. Leuckart, B. Moniez. 



