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with. Potassium permanganate produced but little effect except in 

 very strong solutions. During these tests the marked superiority of 

 petroleum oil soon became manifest, and there seemed to be no special 

 advantage of one petroleum product over another. The Lima oil 

 which was used in petrolising the stagnant pools and rain barrels, etc., 

 is a crude petroleum with a minimum amount of naphtha. One cubic 

 centimetre of this added to 3,500 c. cm. of water containing larvae 

 killed them in three or four hours. This is equivalent to about twenty 

 drops of oil to a gallon of water ; and, as a matter of fact, this result 

 was usually obtained by less than this amount of oil. Dr. DOTY is 

 inclined to believe that the death of the larvas is due to obstruction of 

 respiration, and also that emanation from the oil or its odours, or 

 both, is particularly repugnant, if not dangerous, to the full-grown 

 mosquito. 



There is no doubt, he says, that the best effect of the oil is gained 

 by introducing it to a considerable depth under the water. In this 

 way it is more surely brought in direct contact with the larvae, particu- 

 larly if the water is agitated. In petrolising stagnant pools it soon 

 became evident that the long grass and weeds, particularly in the 

 immediate vicinity of these places, were the abiding places of the mos- 

 quito during the day. Special attention was therefore given to the 

 removal of this growth, the ground being afterwards petrolised with 

 an ordinary sprinkling pot. The cisterns, rain barrels, and other such 

 breeding places were treated by sprinkling the inside of the woodwork 

 and the surface of the water with oil. If the boundaries of the section 

 experimented upon included all the breeding places in this part of 

 Staten Island, there is no doubt that a marked diminution in the 

 number of mosquitoes would have been apparent at once ; but, unfor- 

 tunately, many breeding places exist in the territory surrounding this 

 place. Nevertheless, the opinion expressed by the inhabitants of the 

 section indicates that there has been a positive change for the better. 

 Dr. DOTY thinks that this investigation has been of scientific value 

 because it has shown (i) the intimate relation between the mosquito 

 and malarial fever ; (2) the true breeding places of the mosquito ; and 

 (3) that petroleum oil will surely and promptly destroy mosquito 

 larvae, and, so far as careful experiments indicate, it is the only agent 

 which can be depended upon for this purpose. The suggestion that 

 birds, dragon-flies, etc., should be propagated for the purpose of 

 destroying mosquitoes is, in his opinion, not entitled to serious con- 

 sideration. He feels himself justified in saying that the continued 

 presence of mosquitoes in large numbers as a rule indicates defective 



