52 TROPICAL MEDICINE AND HYGIENE 



the intestinal wall, losing its booklets and developing into 

 the larval form in the muscles and tissues of the host. 

 It there grows, develops the bothridia, and becomes an 

 elongated, unsegmented worm-like body the plerocercoid 

 larva (fig. 21, c). When this larva is swallowed with the 

 flesh of the host fish by the definitive host man the 

 larva is set free and attaches itself to the intestinal wall 

 and develops i'nto the adult form. 



The genera into which the Dibothriocephaloidea are 

 divided are not numerous. 



(i) Dibothriocephalus. The type of the order, in which 

 each proglottis has a single complete sexual apparatus 

 consisting of two ovaries, testes, and a single genital pore, 

 and single uterus with its uterine opening. 



The species found in man is the Bothriocephalus lalus, 

 and in the Arctic regions other bothriocephali are found 

 in dogs, in seals and other fish-eating mammals. Some 

 species are found in the Tropics in dogs, and in man in 

 Japan. 



The Bothriocephalus latus is not usually a tropical 

 parasite, as it is most common in Arctic and sub-Arctic 

 regions, as Lapland, Finland, Iceland, around Swiss 

 lakes, &c. In many parts of Germany it is also common. 

 It occurs in Japan. In all cases it is associated with the 

 consumption of imperfectly cooked fish. 



The interest in connection with this parasite is the 

 occurrence of anaemia of an intense form in some of the 

 persons harbouring the parasite. 



Drugs, such as iron and arsenic, have little or no effect 

 on this anaemia, but rapid improvement and complete 

 recovery result from the removal of the parasites. 



As this worm, though it fixes itself on to the intestinal 

 wall, does not live on blood, but entirely on the food 

 absorbed from the intestinal contents, the anaemia pro- 

 duced must be due to some toxin formed and excreted 

 by the parasite, and absorbed by the host from the 

 intestinal contents. Fatty substances have been isolated 

 from the bodies of these worms which produce anaemia 



