THE RELATIONS OF BACTERIOLOGY 217 



armory of public hygiene, whether or not it prove to be the most 

 efficient one or the most economic in execution. In this same cate- 

 gory are to be put the attempts to prevent the infection of the 

 mosquito by guarding malarial patients against the bite of Anopheles. 

 It is obvious that this plan may often be difficult of execution, be- 

 cause of the impossibility of exercising efficient control over the 

 movements of individuals suffering from latent or recurrent infection. 

 A second possibility consists in the general protection against 

 mosquito bite of all persons dwelling in infected regions. The pestifer- 

 ous insect may beat its wings in vain against the windows of a mos- 

 quito-proof dwelling; if it cannot come near enough to the human 

 being to inject the contents of its poisoned sahVary gland, no single 

 case of malaria will result. In parts of Italy, it is said, this mode of 

 prevention has been practiced with brilliant success in protecting 

 railway employees, forced by the exigencies of their calling to reside 

 in highly malarious localities. 1 



A third point of attack is presented in the possibility of destroying 

 or at least arresting the propagation of the insect host of the malarial 

 parasite. The extermination of a number of species belonging to a 

 widely distributed and abundant insect genus may seem in itself a 

 gigantic task to undertake. Remembering the ambiguous success 

 that has attended the efforts of the human race to combat the ravages 

 of certain insects injurious to agriculture, it is not easy to be sanguine 

 concerning the speedy extinction of Anopheles. It is noteworthy that 

 the most considerable triumphs attained along economic lines have 

 been effected by the utilization of the natural enemies of the noxious 

 forms. Efficient foes of Anopheles have so far not been discovered. 

 There is no question, however, that in definite localities the numbers 

 of individual mosquitoes belonging to malaria-bearing species may be 

 enormously diminished by the destruction of the breeding-pools. The 

 labors, in this direction, of English health officials in various parts of 

 the \vorld, have been rewarded by a decisive decrease in the preval- 

 ence of malaria. 2 



It will not escape remark that the effect of any one or of all of these 

 protective measures is cumulative. A diminution in the number of 

 mosquitoes, or in the number of persons harboring the malarial pro- 

 tozoon in their blood, or in the number of infected or non-infected 

 individuals bitten by mosquitoes, w r ill inevitably produce a lessening 

 in the amount of malaria in a given region. This will in turn diminish 

 the opportunities for mosquitoes to become infected, and will at least 



1 Celli, A., La Malaria in Italia durante il 1902, Annali d' Igiene sperimentali, 

 13, p. 307, 1903. 



La Socic'te pour les etudes de la Malaria, Archives italiennes deBiologie (1898-1903) 

 39, p. 427, 1903. 



2 Ross, R., Report on Malaria at Ismailia and Suez. Liverpool School of Trop- 

 ical Medicine, Mem. 9, 1903. 



