222 



grass and other vegetation in the drains, and resists the scouring 

 action of heavy rains. Sanitary oil was found to be suitable for spraying 

 pools and cesspits, and retains its efficacy for some time. Pools that 

 could not be drained have been lined in the same way and spraj^ed at 

 intervals with sanitary oil. By this method the mosquitos have been 

 exterminated and the cost of the upkeep of drains greatly reduced. 

 Drains in which there is a continuous flow of water throughout the 

 year cannot be lined in this way unless the water can be temporarily 

 diverted. This method is also not applicable to drains in towns and 

 village streets owing to the danger of fire. 



The commonest Anopheline in the district is Anopheles tarsimaculatus, 

 Dyar, the only other species being A. argyritarsis, R.D., and 

 A. apicimacula, D. & K. The breeding-places of A. tarsimaculatus 

 are peculiar to the district, and owe their existence to an asphalt 

 lake and to numerous outcrops of asphalt for a distance of half to 

 one mile or more from it. These pitch holes are of two varieties and 

 are very numerous, forming permanent Anopheline breeding pools. 

 Attempts to fill them in have failed, and their drainage also offers 

 great difficulties, in view of which the only alternative method is to 

 clear the holes of all grass and to rely on the fish they contain to 

 destroy the larvae. The fish occurring in the lake are Rivulus harti, 

 which is a voracious feeder on the larvae, millions {Lebistes reticulatiis) 

 and Polycentrus schomburghi. 



Seepages were dealt with by the usual method of intercepting drains, 

 and in some cases b}^ the free application of sea sand, which, besides 

 being economical, acts by destroying the algae and other vegetation 

 and by absorbing the water. 



During 1920 adult Anophelines were found almost everywhere, but 

 now they are very seldom seen in the treated area in spite of a most 

 favourable rainy season. 



By the application of the methods described it is thought that 

 malaria control in Trinidad is quite possible, and there is no reason 

 why individual efforts, apart from Government measures, carried 

 along the same lines should not be successful at comparatively small 

 expense. 



HoARE (C. A.). Trypanosomiasis in British Sheep. (Preliminary 



Gom.m.miication.) — Trans. R. Soc. Trop. Med. & Hyg., London, 

 xvi, no. 3, 22nd June 1922, pp. 188-194, 11 figs. 



Previous work on trypanosomes of sheep and their probable 

 transmission by the Hippoboscid, Melophagus ovinus, is reviewed. 

 The present observations prove definitely that the sheep trypanosome 

 is transmitted by M. ovinus, though not by biting ; this is contrary to 

 Kleine's statement {Deutsch. Tierdrztl. Wochenschr., xxvii, no. 38, 

 1919, p. 408) that the flagellates found in the proboscis are the 

 important factors in transmission, and that the gut forms are of no 

 importance. Sheep may be bitten by infected flies without acquiring 

 infection, but as a result of the sheep nibbling the flies off their bodies, 

 the flagellates are released and penetrate through the mucous membrane 

 into the blood. In the absence of the fly, sheep remain free 

 from trj^panosomes. 



There is no doubt that the flagellate, Crithidia melophagi, is the 

 invertebrate stage of the sheep trypanosome. It occurs in the mid-gut 

 of the fly, but in the hind-gut it is transformed into a small trypanosome, 

 a fact that appears to have been overlooked and even denied by some 



