Section C. 



8 



me a vessel "infected" with yellow fever is simply one which is har- 

 boring these infected mosquitoes. Whether they came aboard already 

 infected or, being aboard, became infected by feeding on cases of yellow 

 fever developing aboard ship but contracted ashore, can in general be 

 determined from the history of the spread of the infection. Indeed, it 

 was primarily the history of these and other ships which led to the 

 (tentative) formulating of the laws of the "interval between the infect- 

 ing and secondary" cases of yellow fever and the "period of extrinsic 

 incubation of places" of that diease, which, and much else, are so 

 clearly explained by the conveyance by a mosquito host. 



The deductions as to the disease being contracted aboard the vessels, 

 when such deduction is made, are, however, independent of the assump- 

 tion of any theory of conveyance. I do assume, however, that the 

 period of incubation of yellow fever, rarely, if ever, exceeds six or six 

 and one-half days. 



1888. — SHIP ISLAND. 



I. Norwegian bark Magnolia, 946 tons, fifty-six days from Rio de 

 Janeiro via Pensacola Bar, rock ballast. Left Eio de Janeiro May 20 ; 

 left 2 men sick in hospital and had 1 aboard, considered yellow fever. 

 Master sick third day out, May 22 ; died, May 27. All well till June 1, 

 then several (3) got sick at once. First mate sick, June 11 ; died, June 

 17 ; black vomit. All were sick on the way up except 2 ; 21 on crew 

 list including the 2 men left in Rio de Janeiro. One of these who 

 escaped fever had had yellow fever, and the other was a lad from Dantzig 

 on his first deep-sea voyage. In all 17 men were sick of fever en route, 

 of whom 5 died. The last case, Elias Eliasen, developed June 14. 

 Here, save the captain, all sickened hot less than eleven days after 

 leaving Rio de Janeiro, and the first mate and Eliasen on the twenty- 

 third and twenty-sixth day, respectively. They then contracted yellow 

 fever aboard ship. 



The picture is that of an infection introduced aboard the vessel by 

 the men who sickened in Rio de Janeiro — i. e., there were uninfected 

 stegomyise aboard which were infected from these cases and conveyed 

 yellow fever to the remainder of the crew, except the captain, who con- 

 tracted it ashore. I did not record the dates of the cases of the men 

 left at Rio de Janeiro ; it was shortly before clearing. The interval 

 between an infecting and a secondary case is almost always fourteen 

 days or over. 



II. Italian bark Biagino, Rio de Janeiro, for Pensacola, fifty-one days 

 out ; rock ballast, 560 tons. No sickness in Rio de Janeiro until just 

 before leaving, then sent 2 men to hospital. Left five days after. 

 Log shows men were taken June 4 and June 6 and removed on June 6. 

 Sailed on June 10. No one had been ashore save master and steward, 

 using a harbor boat. 



First case reported sick en route June 21 ; 1 next day ; 6 sick en route ; 



