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NOTES ON TRYPANOSOMA LEW I SI AND ITS 
RELATION TO CERTAIN ARTHROPODA. 
By C. STRICKLAND, M.A. 
AND N. H. SWELLENGEEBEL, Ph.D. 
{From the Quick Laboratory, Cambridge.) 
(One Text-figure.) 
The following notes on the biology of Trypanosoma lewisi are the 
result of experiments extending over the last two years. They are 
arranged under the following heads ; 
I. The prevalence of T. lewisi in rats under natural conditions 
(a) Endemic foci ........ 
{h) Variation of incidence in endemic foci . 
II. The relation of ectoparasites to the prevalence of T. leu'isi 
in rats under natural conditions . . . . . 
III. Experiments demonstrating the part played by Arthropods 
in the transmission of T. lewisi from rat to rat. 
(i) Experiments with fleas 
(a) by previous authors ...... 
(b) our experiments ...... 
(c) on the mechanism of infection 
(d) on the relation between the developmental cycle 
of T. lewisi in the flea and infection by 
the flea ........ 
(ii) Experiments with lice 
(«) by previous authors ...... 
(h) our experiments ...... 
(c) on the relation between the developmental cycle 
in the louse and infection by the louse 
(iii) Experiments with other arthropods 
IV. Description of a peculiar form of T. lewisi 
V. Summary and Conclusions ...... 
VI. References .......... 
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