108 PARASITES OF MAN 



larvae subsequently develop themselves is not ascertained with 

 certainty, but it is probable that persons become infested by 

 eating imperfectly cooked fresh-water fish. Leuckart has 

 suggested that the intermediary bearers are species of the 

 salmon and trout family. Dr Knoch, of Petersburg, thought 



that there was no need of the inter- 

 mediate host. He believed that he had 

 succeeded in rearing young broad tape- 

 worms in the intestines of dogs. It 

 was Leuckart who first explained the 

 source of Knoch' s errors of interpre- 

 tation. Although Knoch administered 

 eggs of Bothriocephalus latus to dogs, 

 and afterwards found young tapeworms 

 of the species in question in the intes- 

 tines of the dogs, it did not logically 



FIG. 26. Proscolex, or six-hooked em- c .. .. , ,. , , 



bryo of Bothriocephalus, escaping from tollOW that any genetlC relation (as be- 

 lts ciliated covering After Leuckart. . ., , ., -, ,, 



tween the egg -contents and the adult 



worms) had been thereby established. The circumstance that ripe 

 ova of the Bothriocephalus always contain six-hooked embryos, 

 must alone imply that an intermediate host is necessary for the 

 formation of Cysticerci or measles. If the broad tapeworm could 

 be reared in a direct manner by the administration of Bothrio- 

 cephalus eggs, there would be no need for the presence of 

 boring booklets in the proscolex. These are necessary for 

 invading the flesh of some intermediate host. 



Dr Fock, of Utrecht, has sent me particulars of an interesting 

 case, and he suggests that infection comes from the little river 

 bleak (Leuciscus albumus) . Writing from Utrecht in December, 

 1877, Dr Fock, after referring to a former case, goes on to 

 say : - 



"Permettez moi, cher confrere, que je rappelle a votre 

 souvenir que vous avez eu Pobligeance de communiquer au 

 public une observation, de ma main, sur un cas tres rare de ver 

 rubanaire, d'un Bothriocephale, chez une petite fille juive. 

 Malheureusement je n'ai pu en donner de plus amples details, 

 parce que cette enfant n'a plus, depuis ce temps-la, rendu la plus 

 petite parcelle de ver. II y a maintenant quinze mois, et voila 

 que de nouveau un cas pareil se presente. Une femme mariee, 

 frisonne, et, cette fois-ci encore, juive, s'est adressee a moi pour 

 la debarasser de son ver. Elle me disait avoir rendu, il y a 

 quelque temps, des fragments, ou plutot un fragment de la 



