Page:Transactions of the Royal Society of Tropical Medicine and Hygiene, volume 2 (3).djvu/35

Rh refer Drs. Sambon and Wenyon to that paper. He would, however, make some comments on one of the so-called developmental stages of a vertebrate trypanosome. It will be remembered that Prowazek described the life-cycle of Trypanosoma lewisi in the louse (Hæmatopinus spinulosus), and according to his observations it passes through a complicated sexual cycle in the louse, so that this insect ought to be the true host of the trypanosome. No other observers, however, have been able to find these stages, and he (Captain Patton) had also searched for their developmental forms without success; recently, in Cambridge, he had had the opportunity of studying a flagellate of the rat-flea (Ctenophthahnus agyrtes), which was not unlike Prowazek's developmental forms in the rat-louse. He knew, however, that this flagellate was a true parasite of the rat-flea and belonged to the genus ''Crithidia. Herpetomonas and Crithidia'' were very like each other in their immature stages, and if this stage alone were studied it was impossible to differentiate between them. In their adult flagellate stages they were, however, quite distinct, and the occurrence of Crithidia in blood-sucking insects has led numerous observers to describe them as developmental forms of vertebrate trypanosomes; in certain stages of their development some of these flagellates were like small trypanosomes. He (Captain Patton) had not touched upon the hereditary transmission of these flagellates, but he was well aware that the flagellate of the sheep-bred Melophagus ovinus was a crithidia, and that it was transmitted hereditarily; the complete life-cycle of this parasite would shortly be described by Swingle, who would prove that it had no connection with any blood parasite of the sheep.

With regard to Dr. Sambon's remarks as to Oriental