GIARDIA LAMBLIA: CROSS INFECTION 



of length to breadth, distance from the anterior end of 

 the body to the center of the nucleus, from the center of 

 the nucleus to the lateral shields, from the end of the 

 lateral shields to the posterior end of the body ; distance 

 across the body at the center of the nuclei and at the ends 

 of the lateral shields; the contour of the body, whether 

 narrow or broad at the anterior end and across the lateral 

 shields ; distance of nuclei from the median line and from 

 the posterior edge of the sucking disc ; size and shape of 

 the nuclei ; number, size, shape and location of the para- 

 basal bodies; staining characteristics; and infectivity 

 when cysts are fed to experimental animals. 



Cross infection. The results of cross-infection experi- 

 ments are briefly as follows: Grassi (1882) was unable 

 to infect himself by swallowing cysts from lower ani- 

 mals. Calandroncio, however, according to Piccardi 

 (1895) was more successful, since he found motile speci- 

 mens in his stools 25 days after ingesting cysts. Moritz 

 and Holzl (1892), on the contrary, did not succeed in 

 infecting a human being with cysts from mice. Results 

 just as contradictory have resulted from attempts to 

 infect lower animals with giardias from man. Perron- 

 cito (1888) claims to have infected 2 white mice and 

 Stiles (1902) a guinea-pig with human cysts. Only nega- 

 tive results were obtained by Bohne and Prowazek 

 (1908) when trophozoites and cysts from man were in- 

 jected both per os and per rectum into rabbits, rats and 

 kittens. 



The experiments of Fantham and Porter (1916) seem 

 remarkably successful. Eight kittens and nine mice pre- 

 viously found to be free from giardias were fed washed 



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