The tenacity with which the disease attached itself to the Eclair is sufficiently explained in the absence of due ventilation; in fact, that in the first instance there was no ventilation at all in the hold of the ship. This also the more readily affords a clue to the disaster through all its stages, first in the contraction of the disease as an endemical affection in the vessel; secondly, in the multiplication of the
germs in the damp ill-ventilated hold, in a warm climate; and thirdly, the persistence and entire localization of the disease to the vessel when it arrived in the climate of the British shores; while, fourth and lastly, in the unusually hot and damp island of Bona Vista, the seeds of the disease were sown, and, as we might expect, multiplied indefinitely.
The consecutive attacks of the crew of the Eclair shew that here a noxious gas or a vaporized inorganic poison could not have been the cause of the disease, for as I have before said, in this case the attacks should have been simultaneous; we find, on the contrary, that as the depressing effects of the melancholy condition of the crew was almost hourly undermining the health of the stoutest of them they as surely became the victims. The Kroomen, or natives on board the ship had not suffered, shewing that they were inured to the miasm, or were destitute of that condition of blood which would be favourable to a propagation of the materies of the disease.
The Eclair we learn had left Bona Vista eight days when the first victim breathed his last; this would give perhaps three or four days for the incubation of the disease in the patient, or supposing he had not contracted the germs of the disease before the crew of the Eclair left the fort, some local favouring conditions were the means of keeping the germs in a fertilizing state, for it is clear from this spot the infection spread as from a centre or focus.
Such instances as these might be multiplied to extend the length of the enquiry, but, I think, to little advantage. The chief facts to be gathered are that an endemic affection became epidemic and pestilential, contrary to its usual mode, for the Portuguese official physician, on being consulted by the Governor of the Island as to the safety of landing the contaminated crew, said, "No danger at all; I have often brought sick men on shore coming in vessels from the African coast, and I never knew any ill effects to arise." Putting the most reasonable construction on this emphatic and straightforward language, we may presume that ordinary, remittent, and yellow fever had been commonly imported into the island, for it is not to be supposed but that both forms of disease must have existed among those sick men who had "often been landed," under the sanction of the Portuguese physician.
To take another instance; intermittent fever or ague, is a disease known among almost all nations of the world, but it usually occurs in the endemic form only. It is universally supposed to depend entirely upon marsh effluvia, and we are accustomed to consider it as attaching only to low lying countries;[[40]] but this is not always the case, for disease in
this respect, like vegetation, may be found in various latitudes, to accommodate itself at varying altitudes, to the temperature and climatic relations, so as to appear indigenous. But though our prejudices are in favour of a simple miasmatic source of ague, as its sole cause, there are some who believe in its infectious nature. M. Sigaud, in his work on the Climate and Diseases of Brazil, speaks of Epidemics of grave intermittent Fever, and Dr. Copland says, that the epidemic prevalence of ague is a better established fact than its infection, and has been admitted by most writers.[[41]] We have, therefore, but to go one step further to arrive at infection, after having found that an endemic disease under peculiar circumstances, though but rarely, becomes
epidemic. The number of persons attacked by ague in a malarious district, in proportion to the population, is not so great as might be expected, considering that they are always subject by night and day, more or less, to respire the air containing the germs of intermittent fever; we might, therefore, deny the paludal source of the affection, as reasonably as deny infection, if we found that occasionally, persons, though subject to all the usual influences, yet escaped all injurious consequences.
There are grades and varieties of infectious diseases, from the most inveterate to the most mild and doubtful; but that all, without exception, which can in any way be traced to a specific generating and organic cause, may assume an exalted infectious character, and that the most inveterate, on the contrary, may more resemble the mild and doubtfully infectious forms, is a conviction that must be forced on all who pursue this enquiry with unbiassed interest.