C. A. Ho ARK 
81 
Experiment 37. Newt killed after four days. Results as preceding. 
Experiment 38. Newt killed after five days. Results as preceding. 
Experiment 39. Newt was left alive. 
(b) Newts fed on H. jaculum introduced by a pipette per os. 
Experiment 40. Newt killed after 24 hours. Examined contents of the alimentary tract, 
blood, liver, spleen, peritoneal fluid. Nowhere were any traces of the flagellates visible. 
Experiment 41. Newt left alive. 
The experiments on newts show that in their organism the flagellates are 
apparently very soon disposed of, no traces of them being visible even after 
24 hours. There was no change in their condition, and two newts inoculated 
intraperitoneally and per os respectively remained living, showing no signs of 
infection. 
II. Frogs (Rana temporaria) inoculated with H. jaculum. 
Experiment 42. Young frog inoculated into the dorsal lymph-sinus on November 26th. 
Killed after 24 hours. Examination of fresh blood and fluid from the lymph-sinus, and of 
stained blood, sinus fluid, liver and spleen revealed no traces of parasites. 
Experiment 43. Young frog inoculated on the same day intraperitoneally. Results as in 
preceding. 
Experiment 44. Adult $ frog inoculated into the dorsal lymph-sinus on the same day. 
Killed after 19 days. Blood examination during the period preceding death—negative. 
Post mortem results as in Nos. 42 and 43. Blood-cultures from this frog kept at 24° C. showed 
no parasites for more than a month. 
The experiments with frogs thus also produced negative results, although 
the mode of inoculation through the lymph-sinus in two cases afforded an easy 
and natural point of access to the blood-stream of the frog. 
III. OBSERVATIONS ON THE VITALITY OF SOME INSECT FLAGELLATES. 
The degree of vitality of some flagellates when exposed to abnormal 
conditions is shown in some of the experiments already recorded. As these 
experiments have demonstrated, the flagellates can remain alive in the 
intestine of fish for five hours, and in some cases (experiment 22) for 18 hours, 
resisting the action of the digestive juices. When injected subcutaneously or 
intraperitoneally into fish, they may be found alive in the peritoneal fluid for 
four days. I have also kept insect flagellates living in sealed drops with a 
physiological solution of sodium chloride and with sterile nutritive bouillon 
at different temperatures. The results were as follows: 
Contents of the gut of the sheep-ked ( Melophagus ovinus) infected with 
Crithidia melophagia diluted with normal saline were kept at room temperature 
and at 30° C. In the portion that was placed at 30° C. the flagellates lived only 
one day, but those that were kept at room temperature lived seven days. No 
multiplication was observed, and the flagellates gradually lost their motility. 
Parasitology xm 
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