DIBOTHRIOCEPHALUS CORDATUS 315 



tapeworm by ingesting its plerocercoids with the previously men- 

 tioned fresh-water fishes ; the opportunity for such infection is 

 afforded the more readily by the fact that not only do the lower 

 classes not pay sufficient attention to the cooking of fish, so that 

 all the larvae that are present may be killed, but also in certain 

 localities the custom exists of eating some parts of these fishes in a 

 raw condition ; even the mere handling of the usually severely 

 infected intermediary hosts may occasionally cause infection. The 

 plerocercoids are as well known as, but differ materially in appear- 

 ance from, the cysticerci (Cysticercus celluloses) of pig's flesh. In 

 Germany the occurrence of the plerocercoids of Dibothriocephalus 

 latus has been confirmed in the pike, miller's thumb and perch of 

 East Prussia, and more particularly in those taken from the Courland 

 Lagoon. 



The life of D. latus is a very long one (six to fourteen years), 

 as is deduced from persons who have left D. latus regions after they 

 have been infected. 



According to the experiments of M. Schor, plerocercoids of 

 D. latus placed in slowly warmed water completely lose their move- 

 ment at 54 to 55 C. ; they survive the death of their host for several 

 days ; they are killed by low temperatures - 3 to + i C. in two 

 days ; strong acids and salt solutions kill them at once, also high 

 temperatures, but all the same at least ten minutes is required in 

 boiling or frying fish in order to kill the plerocercoids with 

 certainty. 



Dibothriocephalus cordatus, R. Lkt., 

 1863. 



Syn. : Bothriocephalus cordatus, R. Lkt. 



Length, 80 to 115 cm. ; the head is heart- FIG. 210. Cephalic end 

 shaped and measures 2 by 2 mm. The *l Dibothriocephalus corda- 



., - n e *us ; on the left viewed 



suctorial grooves are on the flat surface ; the sideways, on the right from 

 segments commence close behind the head and 

 increase rapidly in breadth. At only 3 cm. Leuckart.) 

 behind the head they are already mature ; the 



greatest breadth attained by them averages 7 to 8 mm., the length 3 to 

 4 mm. ; the number of proglottids averages 600 ; the most posterior ones 

 are usually square. The uterine rosette is generally formed of six to 

 eight lateral loops. The eggs are operculated and measure 75 /JL by 50 //,. 

 Dibothriocephalus cordatus is a common parasite of the seal, the 

 walrus and the dog in Greenland and Iceland, occasionally of man 

 also. No doubt its larva lives in fishes. 



