THE SOURCE OF BOTHRIOCEPHALUS LATUS IN JAPAN. 55 



be tolerably constant. Another reason for regarding 0. Perryi as at 

 least one of the chief sources of B. latus, is the undeniable fact that 

 where that fish abounds, the tnpe-worm is also abundant. Toyama 

 in the province of Ecchiu is such a place. In Yezo, especially anion o- 

 the Ainos, tape- worms are said to be common. Considering that 

 0. Perryi occurs there in plenty, these tape- worms presumably belono- 

 to the species Bothriocephalus latus. 



0. Perryi is in some parts of Japan often eaten raw (Sashimi) 

 like many other fishes. Under such circumstances, infection with 

 Bothriocephalus is highly probable and all the more so since its larvœ 

 in the flesh might easily be mistaken for a piece of fat, tendon or 

 nerve. Once a friend told me, soon after his return from a short 

 visit to Saikyö, that he had there tried the ^^ sashimi" of the fish in 

 Cj[uestion. I warned him of what change might perhaps occur in his 

 health within 3 weeks' time, little suspecting that he would, as he 

 really did, present me with a fine specimen of B. latus at the end of a 

 month. In Tokyo, where 0. Perryi is altogether scarce, its ^^sashimi" 

 is not generally indulged in, a fxct which probably explains the 

 comparative scarcity of B. latus in this city. 



The life-tenacity of Bothriocephalus -larvae seems to be of no 

 small degree. They may retain vitality for a week outside their 

 host and Braun even found them alive not only in weakly salted 

 pike but also in such that had been frozen. It is however certain 

 that the heat of thorough cooking or roasting sufiices to render them 

 harmless. At the same time it must be admitted that ordinary 

 methods of cooking do not exclude all chances of infection, as is clear 

 from the way we obtain our Tœnia from beef or pork. A naturalist 

 friend in Tokyo once discharged a B. latus, which he is inclined to 

 regard as having been received from the flesh of 0. Perryi, which he 

 had eaten roasted about one month previously. The fish had been 



