Vol. XVII. No. 412. 



THE AGRICULXUJIAL XEWS. 



4S 



1. Sweet potatoes should not be plauted ou the same 

 laoil in two successive seasons, and the ditt'erent sweet potato 

 .patches should be separated from e^icb other as widely as 

 possii'le. This makes it (iitticult foi- the insects to spread 

 from one potato field to another. 



2. When planting, be very careful to use only those 

 plants which are known to have come from a locality where 

 the weevil does not occur. 



3. When harvesting the crop, great care should be 

 taken to remove all portions of the sweet potato plants from 

 the land. All vines, damaged tubers, pieces of root, etc., 

 should be collected and burnt, otherwise they will only serve 

 as breeding places for the weevil. 



i. Infested or damaged sweet potatoes should not be 

 thrown out, but should be burnt. If they are needed for 

 feeding stock they should first be boiled. This will destroj' 

 any infesting grubs or weevils, and prevent the infestation 

 of new areas. 



If these measures are practised thoroughly it will be 

 possible to reduce the damage done by the scarabee at a time 

 ■when every available sweet potato is needed. 



.J.C.H. 



MOSQUITOES AND MALARIA. 



In the /ihiiJesia Agricultural Journal, October 1917, 

 there is printed a lecture on malaria and black-water fever, 

 by Dr. A. M. Fleming, t'.MG., M.B., C-M., Medical Direc- 

 tor. Although the cause of malaria has been so absolutely 

 proved by medical research in the last few years, there are 

 still some people in the West 1 ndies who do not believe that 

 to mosquitoes, and mosquitoes alone, the infection of n,alaria 

 is due. The lecture in question so clearly states the present 

 knowledge on the subject, and the means to be taken for the 

 prevention of mal >ria, that it is worth reproducing largely. 



Malaria as a disease has been known and described from 

 time mnnemorial. Long ago it was recognized that it was 

 associated with residence in or near low-lying, marshy 

 ground, and it was for centuries a.scribed to some poisonous 

 miia^ma or exhalation arising from such swampy ground 

 as the result of decomposing vegetable matter. The 

 breathing in of these mists or miasmas was supposed 

 to infect human beings with malaria. In 1880, how- 

 ever, a French scientist discovered that in the blood 

 of persons suti'ering from malaria there were invariably to be 

 found minute organisms in the corpuscles of the blood. 

 These organisms gradually grew in size, and subdivided 

 into numerous little particles or spores. The corpuscles 

 burst, and these spores were poured out into the blood 

 streams, and found their way into other corpuscles where 

 they went through the same process. Further he .showed 

 that the various stages of ague, high tetiiperature, and 

 ■excessive sweats, were coincident with the growth and the 

 breaking up of these organisms in each successive cycle. 

 Still it remained to find out how these organisms got into 

 the blood. Thirteen or fourteen years later, Sir I'atrick 

 Manson suggested that in the case of malaria the organisms 

 laiight be carried by some variety of mosquito. Major 

 Ronald lioss, working in India, took this up, and was able 

 to prove in a short time that the mosquito theory was 

 correct, that the malaria parasite was taken up by the . 

 "Jsind of mosquito known as anophele.s, and that in the 

 mosquito's body it went through various changes, and when 

 mature was injected into healthy persons along with the 

 saliva of the mogquito. 



To prove this, numerous e.^perimeut-* were carried out. 

 For instance. Doctors Sambon and Low spent three of the 



inost unhealthy months of the year in a spot in Italy ?<>- 

 infected with malaria that no oue living under ordinary- 

 conditions ever escape.s the disea-e They lived in mosquito- 

 proof houses, and were careful never to He bitten by a mos- 

 quito, the result being that neither of them was infected, 

 although the inhabitants around were scourged with the fever. 

 Again, some mosquitoes were allowed to feed on the blood of 

 a person suffering from malaria in Italy, These mo-quitoe*. 

 were then brought to England and allowed to feed on two- 

 healthy persons who had never been in a malarial country ia 

 their Itves, the result being that both had an attack of malaria. 

 The success of the anti-malariil crusade in the Panama Zone» 

 undertaken by the Americans under the direction of Colonel 

 Gorga.s, has proved abundantly what can be attained by- 

 systematic effort to prevent malaria. A region which for 

 centuries was considered one of the most pestilential spots ia 

 the world is now a country where white men, women, andt 

 children can live and enjoy health. 



So much for the cause of malaria. But how is malaria^ 

 to be avoided? Four methods have been laid down: — 



(1) By the e.Kterminition of niilarial parasites by 

 'juinine. 



( 2) By the extermination of mosquitoes. 



(.3) By the protection of healthy persons from the bites 

 of mosquitoes. 



(4) By the isolation of malarial pitient?, s? .is to prevent 

 them from affecting rao.squitoes. * 



Theoretically, the strict observance of any sae of thsst 

 methods should be sutficient to prevent infection, bat ia 

 practice it is impossible to ensure absolute observance in 

 every case. What therefore is to be aimed at is a combina- 

 tion of these methods. In other words, as far as possible, 

 destroy the parasite in the system, and keep do-wn mosquitoes 

 in and around houses. 



Firstly, i|uinine is the one drug which ha? proved itself 

 ti;. be a direct poi.son to the parasite. It is, however, difficult- 

 to take, with any degree of regularity, sufficiently large 

 doses of quinine altogether to prevent an attack of malaria. 

 in cases of severe infection. As a preventive in malarial 

 districts, the best method is to take -5 grains nightly, 

 10 grains on Svturday nights, and 10 grains on Sunday 

 nights; and for a child, from ^ to 3 grains nightly, asoording 

 to age. 



Secondly, there is the extermination of the mosqititc. 

 Depressions of soil where water might collect, should ba 

 drained, tanks sh'Hild be mosquito-proof, and al! rabbish. 

 like tins and bottles should be cleared up. 



Thirdly, protection of individuals from mos'iuitoes. 

 There are two methods for this purpose — the use of 

 mosquito nets, and the building of mosquito-proof houses. 

 The chief disadvantage of nets is that they are used only an 

 night time, but the unfailing use of mosquito nets will do 

 much to reduce the possibility of infection. I'robably, how- 

 ever, the best method of protection is to have the house 

 itself rendered mosi|uit3-proof by affixing wire-gauze screens 

 to all doors and windows. 



Fourthly, the segregation and isolation of infeccei 

 persons. This is not only a practical step, but fortunately 

 also a simple oue. Persons infected with malaria, or tho39 

 likely to harbour infection should always sleep ande/- 

 a mosquito net, and should endeavour to a%'oid being bitten, 

 as far as possible. 



These four methods for the prevention o: aiaUrii ara 

 not in themselves either uitticidt to follo»% or costly to. 

 practice, and yet how few living in nn'arial d'stri't? p^y thet 

 attention to them that they deserve. 



