JlARCH 16, 1906.] 



SCIENCE. 



405 



ripe for a rapid extension of the disease 

 after the introduction of a few eases. It 

 is to be noted that vessels were constantly- 

 arriving from Havana; cases appeared on 

 the ships during the voyage, and, until 

 suspicion was aroused, patients from the 

 vessels were treated on shore. The 

 Stegomyice introduced from the vessels, be- 

 ing house mosquitoes, remained in the city, 

 while the country districts were free from 

 them, and for that reason free from any 

 extension of the fever. The absence of the 

 proper mosquito is the only explanation 

 that can be offered, and in the light of 

 our present knowledge, it is all-sufficient. 



In the United States, both before and 

 since the epidemic at Barcelona, there have 

 been similar outbreaks, always introduced 

 by importation, though frequently regarded 

 as of endemic origin, L e., at Philadelphia, 

 Baltimore, Norfolk and New Orleans. In 

 the latter city the danger is particularly 

 great, because Stegomyia, being always 

 present, will readily spread the infection 

 if it encounter a sufficient number of non- 

 immunes. 



Another good ease in point is Petropolis, 

 twenty-five miles from Rio de Janeiro and 

 at an elevation of 3,000 feet. Yellow fever 

 is never known to occur there, spontane- 

 ously, and for that reason it has been made 

 the home of non-immunes who spend the 

 night at Petropolis and visit Rio during 

 the day, for the transaction of business. 

 While there are no Stegomyice. at Petrop- 

 olis, the French eommi.ssion showed three 

 years ago that the disease can be produced 

 there by inoculation with infected insects. 

 At the present day one who seeks can find 

 abundant evidence to show not only that 

 the mosquito transmits yellow fever, but 

 that without the agency of the mosquito 

 it is impossible to have yellow fever, except 

 by means of experimental inoculations. 

 Since the first demonstration of the mos- 



quito theory by the army board in 1900, 

 confirmatory experiments have been made 

 by Dr. John Guiteras of Havana, Ribas 

 and Lutz of Brazil, the French commission 

 from the Pasteur Institute, Working 

 Parties No. 1 and No. 2 of the U. S. Public 

 Health and Marine Hospital Service; and 

 lastly the German commission from Ham- 

 burg, admit no other possibility. The lat- 

 ter, whose report was published only two 

 months ago, lay great stress upon the neces- 

 sity for the extermination of mosquitoes in 

 localities where yellow fever appears in epi- 

 demic form, because, they say, without the 

 mosquito, extension of the disease is impos- 

 sible. They advocate complete extermination 

 of the insect, and speak with enthusiasm of 

 the success that has been attained in Rio, 

 in spite of the opposition of a number of 

 local physicians and of a rather large pro- 

 portion of the population. As a result of 

 their observations in Rio, they maintain 

 positively that the natural form of yellow 

 fever can be contracted only through the 

 bite of an infected mosquito of the genus 

 Stegomyia; they are so firmly convinced of 

 this fact that they decline to consider the 

 possibility of any other mode of infection, 

 since they could find no evidence in support 

 of it. They found the yellow-fever mos- 

 quito everywhere in the city of Rio, but in 

 Petropolis, where the French commission 

 before them could not find it and where 

 yellow fever is known never to spread, they 

 failed to discover a single specimen. If 

 one could say the same of New Orleans 

 another outbreak of yellow fever there 

 would be an impossibility, except when the 

 mosquito as well as cases had been intro- 

 duced. According to Otto and Neumann,^ 

 the authorities in Rio are about to adopt 

 the admirable system of providing a mos- 

 quito-proof barrack for laborers in the har- 

 bor and docks, and they will keep the men 



"The German commission. 



