442 PROCEEDINGS OF THE 



sliady places close to fords, or drinking or washing places, and 

 after biting return to their resting-places until another oppor- 

 tunity occurs. Some trypanosomes, which do not appear to harm 

 their usual hosts, when transferred to other animals cause disease, 

 and possibly death. The tsetse flies are larvi parous, the larvae 

 being nourished in the body of the female, and pupating soon 

 after they are discharged. The disease called Ngana, which 

 affects horses and cattle, is transmitted by G. longifeymis. The 

 opening up of the African trade routes is largely responsible for 

 the spreading of sleeping sickness. The early settlers often lost 

 most of their oxen in passing through " fly-belts," and " salted " 

 animals — i.e. those which had had the disease mildly, and were 

 consequently immune — were much sought after. They used to 

 wait for dull weather or dark nights, when the flies were not so 

 active, to pass through the infested districts. 



The speaker then dealt with mosquitoes, and described the 

 ravages of yellow fever and malaria in South America and Panama. 

 The French failure to cut the Panama Canal was owing to these 

 diseases, and it was due to the researches of Manson, Ross, Bruce, 

 Grassi and others that the responsibility of communicating these 

 diseases has been traced to mosquitoes. Means having been 

 adopted to destroy these insects, not only has it been possible 

 to cut the Panama Canal without serious loss of life, but Santos 

 and Rio, where formerly yellow fever was rampant, have prac- 

 tically become health resorts. Mr. Martin Duncan recounted 

 some of his experiences in " oiling " the ponds in these districts — 

 i.e. covering the surface of the water with a film of mineral oil 

 that the air-breathing larvae are unable to penetrate with their 

 breathing siphons, and are consequently drowned. Malaria or 

 ague used to be common in the English fen districts, but now 

 most of the swamps have been drained : and, the mosquitoes' 

 breeding places having been destroyed, the disease has almost 

 died out. Some strange " cures " for ague were described, and 

 a short account given of the life-history of the anopheline 

 mosquitoes and the malaria blood- parasite. 



The human flea may transmit Kala Azar, and rat-fleas are the 

 carriers of plague. There are two ways by which inoculation 

 may possibly be effected. Faecal matter containing plague 

 bacilli is frequently discharged while the flea is sucking blood, 

 and this infected material may be rubbed into the wound by the 



