THE MOSQUITO THEORY OF MALARIA. 43 



mosquito theory of malaria; by Dr. ISTuttall, of the Hygienic In- 

 stitute of Berlin, who has made a special study of the relations 

 between insects and disease; and, I understand, by M. Metchnikoff, 

 Director of the Laboratory of the Pasteur Institute in Paris. 

 Lately, moreover, Dr. C. W. Daniels, of the Malaria Commission, 

 who has been sent to study with me in Calcutta, has confirmed 

 my observations in a special report to the Royal Society; while, 

 lastly. Professor Grassi and Drs. Bignami and Bastianelli, of Rome, 

 have been able, after receiving specimens and copies of my reports 

 from me, to repeat my experiments in detail, and to follow two 

 of the parasites of human malaria through all their stages in a 

 species of mosquito called the Anopheles claviger. 



It may therefqre be finally accepted as a fact that malaria is 

 communicated by the bites of some species of mosquito; and, to 

 judge from the general laws governing the development of para- 

 sitic animals, such as the parasites of malaria, this is very probably 

 the only way in which infection is acquired, in which opinion sev- 

 eral distinguished men of science concur with me. 



In considering this statement it is necessary to remember that 

 it does not refer to the mere recurrences of fever to which people 

 previously infected are often subject as the result of chill, fatigue, 

 and so on. When I say that malaria is communicated by the bites 

 of mosquitoes, I allude only to the original infection. 



It is also necessary to guard against assertions to the effect that 

 malaria is prevalent where mosquitoes and gnats do not exist. In 

 my experience, when the facts come to be inquired into, such asser- 

 tions are found to be untrue. Scientific research has now yielded 

 so absolute a proof of the mosquito theory of malaria that hearsay 

 evidence opposed to it can no longer carry any weight. 



Hence it follows that, in order to eliminate malaria wholly or 

 partly from a given locality, it is necessary only to exterminate 

 the various species of insect which carry the infection. This will 

 certainly remove the malaria to a large extent, and will almost 

 certainly remove it altogether. It remains only to consider whether 

 such a measure is practicable. 



Theoretically the extermination of mosquitoes is a very simple 

 matter. These insects are always hatched from aquatic larvae or 

 grubs which can live only in small stagnant collections of water, 

 such as pots and tubs of water, garden cisterns, wells, ditches and 

 drains, small ponds, half-dried water courses, and temporary pools 

 of rain-water. So far as I have yet observed, the larvae are seldom 

 to be found in larger bodies of water, such as tanks, rice fields, 

 streams, and rivers and lakes, because in such places they are de- 

 voured by minnows and other small fish. 'Nov have I ever seen 



