OUR HUMBLE HELPERS 



experiment shows it. If a dog is made to take with 

 its food some vesicular worms from a sheep's brain, 

 the animal soon gives unequivocal signs of the pres- 

 ence of the taenia: its excrement contains chaplets 

 more or less long of ripe joints. Furthermore, by 

 sacrificing the dog so as to be able to decide the ques- 

 tion more conclusively, one finds in the intestines 

 the vesicular worms converted into veritable tsenias 

 or tape-worms. So the dog gives the sheep the 

 germs that develop in the brain into vesicular 

 worms; and the sheep gives the dog back these ve- 

 sicular worms, which change into tape-worms in the 

 intestines." 



"But how," asked Louis, "can the dog become 

 infected with vesicular worms when they are not ex- 

 pressly given to it with its food, as an experiment?" 



"Nothing easier. The sheep affected with the 

 staggers is slaughtered, and its head, the seat of the 

 disease, is thrown away. The dog that finds it 

 feasts on it." 



"And there we have shepherd dogs attacked by 

 taenia," said Louis. "Their excrement will spread 

 the staggers among the flock." 



"We must, then," concluded Uncle Paul, "as is 

 recommended by those who have studied this subject 

 experimentally in veterinary schools, exercise care- 

 ful supervision over shepherd dogs and exclude from 

 the flock those that are attacked with the taenia; 

 finally, if the infection shows itself in the sheep, we 

 must bury beyond the reach of any dog the heads of 

 the slaughtered animals." 



