Some Variations in Hynicnolc/^is diniinnta 3 



vember. The male hosts captured from month to month always 

 outnumbered the females by a few individuals. Nematodes in 

 the bladder were not found during September and October but 

 were abundant in December, when I found 9 rats infected with 

 42 worms, while the nematodes were present in small numbers 

 (i to 5) during the other months. 



The blood of the rats was examined for trypanosomes, begin- 

 ning with host No. 44 and extending to the end of the series. 

 Thirteen were found to be infected, eight abundantly and five less 

 so. Seven rats infected with trs'panosomes in December are closely 

 seconded by "five in November with one case in January follow- 

 ing. Examinations for this parasite were not made until No- 

 vember 24. In all, this makes 13 cases in 46 rats (28.2 per cent) ; 

 among these rats nematodes were found in the small intestine in 

 five cases, one or two worms in each, in all seven. One case was 

 found in September, three in October, one in November, and 

 none during December, January, and February. 



But one cysticercus was found in each case infected, the organ 

 concerned being the liver. Four cases in September were fol- 

 lowed by three in October and one in November, after which 

 none were found. From October to December inclusive ripe 

 proglottides of Hymoiolcpis were occasionally found in the large 

 intestine, in three cases even one or two cestodes, which, how- 

 ever, were minute, except one specimen of about five centimeters 

 in length and without a scolex. These would soon have passed 

 to the outside. 



While keeping the rats for examination, I have usually fed 

 them with shelled corn, and fearing lest this should aid in ex- 

 pelling the cestodes from the intestine, I have recorded the length 

 of time the animals have been kept before being killed, for the 

 purpose of comparison. In those animals which were killed on 

 the day when caught, I obtained an average infection of 26 ces- 

 todes, in those kept alive for i day an average of 2, for 2 davs an 

 average of 14. for 3 days 31, for 5 days 49, for 6 days 41, for 7 

 days 55, and for it days 137. There is thus nothing to justify 

 the suspicion. Corn may then be regarded as one of the verv best 

 foods for rats captured alive and retained a while before exam- 



137 



