457 



invasions having occurred on the 22nd, 26th, August, 9th, 19th, and 

 20th of September on her way to Cayenne where the vessel arrived on the 

 8th of October. The explanation of the above occurrences, according to the 

 mosquito theory, would be as follows : the Anne Marie when she left Havana 

 on the 13th of June must have liad three of her crew recently infected 

 with the disease, the same who were taken sick on the 1st and 2nd of July. 

 During the operations of taking on cargo, provisions and drinking water, it 

 is next to impossible, at that season of the year, that a number of mosquito 

 larvae (rigglers) should not have been introduced into the vessel; with the 

 calms, hot weather and rains that followed, the larvae must have produced 

 a whole brood of mosquitoes by the time when the first cases of yellow fever 

 declared themselves on the 1st and 2nd of July; these young mosquitoes 

 by stinging those patients became contaminated, some of them 

 transmitting the disease in a milder form, to the six men who fell sick 

 between the 4th and the 8th of July. 



As the vessel moved more rapidly into the open sea, with a fair wind, 

 and attracted may be by the sugar, the contaminated mosquitoes, and others 

 free from contamination must have sought shelter by penetrating into the 

 hold through chinks in the wooden partition between that of the vessel 

 and the quarter where the sick men lay. There mosquitoes remained feeding 

 on the sugar and sugar cane of the cargo, the germs continuing to develop 

 on the stings of the contaminated insects and increasing their virulence 

 until the hold was opened on the 27th of July. The virulent mosquitoes 

 then commenced their yellow fever inoculations upon all the susceptible 

 persons who came within their reach, in the hold of the Anne Marie. The 

 temperature at St. Nazaire from the 23th of July to the 4th of August 

 gave daily maxima between 69° and 77° F. (the latter only on the 1st of 

 August), and minima between 53° and 63° F., from which it must be 

 understood that the mosquitoes would only leave the hold or fly out on 

 deck or in the immediate vicinity of the vessel during the hotter hours of 

 the day ; at other times they would be benumbed in the open air and might 

 easily be conveyed in bundles by the workmen or other visitors. At the 

 same time the range of temperature was such that the reproduction of those 

 including the metamorphosis of their larvae, would scarcely be possible. 

 Hence all the mosquito inoculations at St. Nazaire must be referred to 

 insects that had become contaminated on board of the Anne Marie as 

 far back as the 1st or 2nd of July. The extreme term of their existence 

 being reckoned at 35 or 40 days, all those mosquitoes would have died by 

 the 7th or 12th of August. In point of fact no instance of infection 

 occurred that could be carried back beyond the 10th more likely the 6th 

 or 7th. 



Dr. Chaillon's case may be explained on the supposition that some 

 mosquitoes having been conveyed in bundles or otherwise, by the workmen 

 to their homes, became contaminated from the yellow fever patients and 



