INTERNAL PARASITES. (ENTOZOA.) 223 



Dr. Cobbold : — " The largest tapeworm liable to reside in the 

 dog is a parasite chiefly derived from the sheep ; that is to 

 say, the sheep acts as the principal intermediary bearer of 

 the larval cestode, which latter acquires tapeworm maturity 

 when it is taken into the stomach and intestines of the doo- 

 along with flesh food. The entozoon in question is the mar- 

 gined tapeworm. This worm {Tania Marginatd) reaches a 

 length of from five to eight feet. It is an abundant species, 

 occurring, probably, in fully 25 per cent of English dogs that 

 are not less than one year old. In Denmark it occurs in 14 

 per cent ; and in Iceland, according to Krabbe, in no less 

 than 75 per cent of the native dogs. I have elsewhere char- 

 acterized the larva of this parasite as the slender-necked hy- 

 datid {Field, Feb. 22, 1873). The accompanying illustration, 

 from the learned Pastor Goeze's work, shows the hydatid 

 (Cysticercus tenuicoUis) of the natural size at A, Fig. 28 ; whilst 

 the letter B represents a magnified view of the head, display- 

 ing the suckers and double crown of hooks." 



Fig. 28. 

 Larva of the Makgined Tapeworm. (Goeze.) 



" The Hydatid Tapeworm. — " Of all the entozoa infesting 

 mankind and animals, the little Tcenia echinococcus is one of 

 the most remarkable. The larvae form the common hydatids 

 or bladder worms of veterinarians {Echinococcus veteri- 

 norum). 



" As in the dog the full-grown tapeworm only reaches the 

 third of an inch in length, it is difficult for the non-profes- 



