RE3IEDIES AGAINST MOSQUITOES 197 



Health Department, and by the Italians Celli and Casa- 

 grandi. 



After all, we are xiractically reduced to the use of oils 

 in this larvicidal work. The question will naturally arise, 

 ** Are there any other oils which can be used to better 

 advantage than the best petroleum oils ? " Mr. Matheson 

 suggested to me the use of corn-oil, a substance which is 

 rather extensively made in certain parts of the country and 

 which, considering the enormous crops of corn grown in 

 our Western States, which, in fact, are so great that some- 

 times in years of over-production the grain is burned as 

 fuel, might reasonably be supposed to be a cheap oil. At 

 present, however, that does not seem to be the case, and 

 its price in the ordinary market is prohibitive, as com- 

 pared with ordinary kerosene. Nevertheless, experiments 

 were undertaken with samples received from Mr. Mathe- 

 son. It was found that the corn-oil did not spread readily 

 and that it gathered together in large patches. Mosquito 

 larvge rising to the surface of the water, and finding them- 

 selves under a patch of oil, simply wriggled violently 

 until they found the s^iaces between the patches, where 

 they breathed comfortably and lived for several days. In 

 this experiment the main object was to secure a persist- 

 ent oil which Avould not evaporate, but would remain for 

 at least several weeks over the surface of the water. The 

 non-spreading qualities of corn-oil, however, as well as its 

 price, remove it from the list of good culicides. 



Although a number of proprietary and secret mixtures 

 for mosquito-breeding pools have been sent to the writer 

 for experiment, none of them have been found more satis- 



