SOME FLY POISONS FOR OUTDOOR AND HOSPITAL USK. 335 



Methyl salicylate 2% (III). Failed. 



Phenyl „ (Salol) (III). Failed. 



Carvone 2% (III). Killed 50% on third day. 



Naphthalene 1% and 0.1% (III). 



Naphthylamine 2% (II). Killed 66% next day. 



Alizarin, alkaline solution, 2% (III). 



Quassine 0-4% (II) ; 60% dead. 



Cannabis indica extract 2% (III). 



Coumarin, saturated solution (III). In one case 22 dead out of 27 ; others failed. 



Conclusions. 



So far as laboratory tests can help, these show that there are substances other 

 than arsenic which wall kill flies ; and while these may not be effective in areas 

 where flies can get abundant shelter and food, as in France or England, they may 

 be very effective as outdoor poisons in Mesopotamia and Egypt. There is hope 

 that the fluorides, the iodates, the sahcylates, iron perchloride and some other 

 substances may replace sodium arsenite in these circumstances, which would be 

 a great advantage, owing to their being less poisonous and their residues forming 

 non-poisonous compounds. It would seem to be worth while testing these 

 chemicals in areas where flies are important ; and the knowledge that the 

 salicylates are good, that blue-stone is a possible poison, that iron perchloride is 

 fairly good, might enable a medical officer in a distant place to deal with flies when 

 he could by no possibility get sodium arsenite. The avidity with w^hich flies in 

 Mesopotamia take sodium arsenite makes one think that what are under laboratory 

 conditions quite second-class poisons may there be first-rate ones ; and so we 

 publish these results, hoping that they may help the medical and sanitary officer 

 in the solution of this problem. What we should like to urge is that many common 

 drugs and substances, not known to be fly poisons, may be so under conditions 

 where flies are really abundant ; and that if iodates, fluorides, salicylates, and 

 the like, are not available, the medical officer should try anything else that is 

 available. 



There will possibly be a use for these poisons in hospitals ; the fluorides, iodates 

 and salicylates are all excellent for indoor purposes, and used at 1 per cent, in 

 sugar solution are not in any way dangerous or offensive. Formaldehyde is so 

 uncertain that its use is not indicated when any other safe liquid can be employed ; 

 the reasons for the variability of its action are now under investigation. For 

 hospital use, particularly, the very small quantity needed makes even the 

 salicylates possible as useful fly-poisons ; an ounce of salicylate to five pints of 

 water would poison flies for some time throughout quite a large hospital, and this 

 amount could probably be spared. The fluorides are in use as indoor fly-poisons 

 in the Imperial College, where they successfully destroy flies that escape to the 

 laboratories from the fly rooms. 



