97 



been considered insufficient to hold the two worms apart. Looss has 

 tried to infect rats with the dwarf tapeworm found in man in Egypt, 

 but his results have been negative. Here in Washington Stiles has 

 repeatedly attempted to infect rats with the dwarf tapeworm found 

 in man in the United States, but thus far no positive infection has 

 occurred in the rodents. In Italy, Grassi attempted to transmit the 

 rat form to six persons, and in one case he found tapeworms, but in 

 view of the frequency of H. nana in Italy the significance of this one 



FIG. 23. Longitudinal sec- 

 tion of the intestinal villus of 

 a rat, containing cystic stage 

 of dwarf tapeworm. En- 

 larged. (After Grassi & Ro- 

 velli, 1892a, pi. 3, fig. 25.) 



FIG. 24. Adult 

 dwarf tapeworm 

 (Hymenolems nana) 

 of man. Enlarged. 

 (After Leuckart, 

 1863, p. 393, fig. 112.) 



instance has been questioned; Grassi was not successful in trying to 

 infect rats with H. nana of man. 



Thus at present the evidence is to the effect that rats and mice are 

 not to be viewed as the source or reservoir for the dwarf tapeworm 

 (//. nana} of man. 

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