VARIOUS FORMS OF TAPEWORMS. 



61 



These are called colloid cancers, but Virchow showed some time 

 ago their true formation. 



The secondary internal vesicular formation is chiefly found in 

 man, the pig, and the horse, where huge hydatids are produced. 

 Secondary external vesicles are more general in ruminants, but 

 they also occur in the pig and in man. This disease is found 

 wherever dogs exist. One-sixth of the population in Iceland 

 have suffered from this plague.-' It is also abundant in 

 Australia,^ India, and elsewhere. It is by no means uncommon 

 in Great Britain. 



Other Tapeworms. 



Numerous other tapeworms exist in domestic animals and 

 man. At least fourteen are found in the dog and ten in man. 

 Tmnia serrata (fig. 18) is often very common. Its cystic stage 



Fig. 19. — T.ENIA HERBATA. 



a, Young Cysticercus ; &, same dividing; d, mature Cysticercvs ^isiformis ; c, scolex 

 and hooks of T. serrcUa ; g, h, j, various segments ; /, scolex in Cysticercus, 



(fig. 19, d), known as Cysticercus pisifoi'mis, is found in the 

 peritoneal cavity of rabbits and hares. Dogs obtain this worm 



1 Dobell, Report on Iceland. (1879.) 

 '^ Thomas, Hydatid Disease in Australia. 



Adelaide (1884). 



