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was " blown." In 18 out of the 43 cases no " blowing " occurred ; 

 the controls were all badly " blown " within 7 days ; in 15 cases the 

 treated meat was blown within 6 or 7 days ; in five cases, in 11 days ; 

 in two cases in 13 and in three cases in 17 days ; the chemicals which 

 delayed attack bv the flies longest were sulphur, /3-naphthol and 

 borax. Arsenic sulphide, nitrobenzene, eucalyptus and clove oil, and 

 oxahc acid delaved it for 1 1 days. Lavender oil, aniseed oil and ginger 

 seemed to have little effect, as the meat treated with them was attacked 

 within 6 days. The means by which immunity was conferred in the 

 case of cert"ain chemicals is not known, but the authors regard the 

 effect as being produced through the sense organs of the fly and that 

 either the smell or taste of the compounds \\as repellent or that, by 

 preventing decomposition, the attraction of the meat for the fly was 

 absent. Precipitated chalk is a very cheap and excellent vehicle 

 for such insecticides and can easily be obtained in so fine a powder 

 that it can be blown into the wool of sheep as a spray and would have 

 no harmful effect upon it. 



Experiments were made on larvae with various chemicals («) with 

 a powder basis, (6) with emulsions, (c) with vapours. Pieces of fresh 

 sheep-skin, 12 inches by 8 inches, were nailed to a large board, wool 

 uppermost, with strips of wood between them to prevent the larvae 

 from migrating from one piece to another. Although with zinc 

 oxide and arsenic sulphide nearly 70 per cent, of the larvae did not 

 pupate, the method was not successful, as the skins dried up or decom- 

 posed and the larvae bored through them and pupated underneath 

 out of reach of the powders. In another experiment, a definite 

 number of larvae were shaken with the powder so as to be well covered 

 by it and then transferred to a glass jar containing sand or sawdust ; 

 the jar was covered with muslin and the number of flies which developed 

 noted. With arsenic sulphide, 88 per cent, were killed in sawdust, 

 as against 8 per cent, in the control, and in sand, 68 per cent, as against 

 36 per cent, in the control. Other chemicals gave relatively high 

 figures, but the mortality in the control in sand sometimes exceeded 

 that of the treated larvae, and death from starvation or the varymg 

 resistance of larvae of different ages to the reagent suggested itself 

 as vitiating the result. The experiments were therefore repeated, 

 the larvae being separated into yoimg and old. The results were 

 somewhat erratic, but the young larvae were clearly much more 

 susceptible to the poison than the old. With arsenic sulphide, 100 

 per cent, of yoimg larvae died and only 16 per cent, of the old ; nitro- 

 benzene yielded the same figures ; borax killed 100 per cent, of young 

 and 20 per cent, of old larvae. The results seem to point definitely 

 to the desirability in practice of applying any poison used as early as 

 possible in the life of the larvae. It is stated that young larvae secrete 

 a fluid which digests tissue and the resulting liquid is then reabsorbed, 

 so that in their case the chemical acts in a sense as a stomach poison, 

 whereas in old larvae the action is rather by contact. In a further 

 series of experiments on old and young larvae, the chemicals were 

 diluted with sand to one-tenth the previous strength and the larvae 

 placed in it. Arsenic sulphide of only one-tenth per cent, killed all 

 young larvae, and 68 per cent, of the older ones. The same applies 

 to nitrobenzene, oil of cloves, turpentine, ^-naphthol, creosote, 



