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X] the disease-producing trypanosomes. It is to be noted that the trypanosome at intervals, not as yet

Fig. 47.—General view of digestive tract of Glossina palpalis. (After Minchin, Report on Sleeping Sickness to the Royal Society.)

ascertained, is incapable of infecting the fly. For this observation also we are indebted to Miss M. Robertson.