126 



PRACTICAL PABASITOLOGY 



mediate host is usually the sheep, in the omentum of which, after 

 leaving the liver, the large bladder-worm, known as C. tenuicollis, 

 develops. T. ccenurus is another parasite of dogs, the intermediate 

 stages of which are passed in the sheep, the large Cysticerci, which 

 form many scolices, being in this case found in the brain, where they 

 originate the disease known as " sturdy." The dog also harbours 

 T. echinococcus, the Cysticerci of which are known as Echinococci. 

 These are characterized by the formation of brood-capsules containing 

 numerous scolices, which develop in the liver of domestic mammals, 



but of which man is also a 

 host. Experiments with this 

 parasite should be carried out 

 with utmost caution. 



The Cysticerci which occur 

 in crustaceans, insects and 

 worms, may also be reared 

 artificially, but the task is a 

 difficult one. The better plan 

 is to examine hosts which 

 have become infected by 

 natural means and, if a suffi- 

 cient number of individuals 

 are used for experiment, 



FIG. 47. Cysticercoid from Dipylidium cani- 

 num. Very much magnified. (After Grass! and 

 Rovelli.) 



FIG. 48. Tricho- 

 dectes canis (Deg.). 

 Male. Magnified. 

 (After Piaget.) 



Cysticerci in all stages of development will be found. The most 

 convenient subject for experiment is Dipylidium caninum, the "cucum- 

 ber " tapeworm of dogs and cats, the Cysticercoid stages of which 

 (fig. 47) occur in the dog-flea (Pulex serraticeps), and in the dog-louse 

 (Trichodectes canis, fig. 48). These insects are ectoparasitic upon the 

 bodies of dogs and cats, and, when teazed out, will frequently be 

 found to contain Cysticerci. 



Hymenolepis murina, which inhabits the intestine of rats and mice, 

 also passes through a Cysticercoid stage, though without the agency 



