diate contact or breath of the dying person, is
dangerous to those not seasoned to the climate,
who may attend on the patient. On the con-
tinent of equinoctial America, the yellow fever
is not more contagious, than the intermittent
fevers of Europe. -
According to the information which I ob-
tained during a long stay in America, and
from the observations of M. M. Mackitrick,
Walker, Rush, Valentin, Miller, and almost
all the physicians who have practised both in the
West India Islands and the United States,
I am inclined to believe that this disease is

not contagious in its nature, either under the

temperate zone *; or in the equinoctial regions of the New Continent. I say from its nature; for it is not contrary to the analogy which other pathological phenomena exhibit, that a malady not essentially contagious, may, under a certain influence of climate and seasons, by the accumulation of patients, and from their individual disposition, assume a new character. It appears that the exceptions, which are infinitely rare under the torrid zonet, are more particularly to be found under the temperate zone. In Spain, where in 1800 more than 47,000, and in 1804 more than 64,000 individuals fell victims to the yellow fever, “this disease was contagious, but only “in those places where it committed its ra“vages; for it has been proved by numerous “facts, and particularly from observations “made at Malaga, Alicant", and Carthagena, “ that affected persons did not communicate “the disease in the villages to which they “retired, although the climate was the same “ there as that of the contagious towns.” This opinion is the result of the observations of the enlightened commission f sent by the French government, into Spain, in 1806, for the purpose of investigating the developement of the epidemic. When we successively turn our eyes to the equinoctial regions of America, to the United States, and to those parts of Europe where the yellow fever has exercised its ra. vages, we see, that notwithstanding the equality of temperature which prevails during

several months of the year, under zones very

remote from one another, the malady assumes a different appearance. Between the tropics its uncontagious character is almost universally acknowledged. In the United States this character has been warmly contested by the faculty of medicine of the University of Philadelphia, as well as by M. M. Wistar, Blane, Cathral, and other distinguished physicians. At last, advancing north-eastwards to Spain, we find the yellow fever undoubtedly contagious, as is proved by the examples of persons who preserved themselves by shutting themselves up, although they were in the very heart of the disease. . The farm of l’Encero, near Vera Cruz, which I found to be 928* metres, elevated above the level of the ocean, is the superior limit of the vomito. We have already observed that the Mexican oaks descend no farther than that place, being unable to vegetate in a heat sufficient to develope the germ of the yellow fever. Individuals born and brought up at Vera Cruz,

are not subject to this disease; and it is the same with the inhabitants of the Havannah, who do not quit their country; but it happens that merchants, born in the island of Cuba, and who have inhabited it for a great number of years, are attacked with the vomito prieto, when their affairs oblige them to visit the port of Vera Cruz during the months of August and September, when the epidemic is at its height. In the same manner Spanish Mexicans, natives of Vera Cruz, have been seen to fall victims to the vomito at Havannah, Jamaica, or the United States. These facts are no doubt very remarkable, when we consider them with respect to the modifications which the irritability of the organs exhibits. Notwithstanding the great analogy which the climate of Vera Cruz bears to that of the . island of Cuba, the inhabitant of the Mexican coast, insensible to the miasmata of the air of his native country, falls under the exciting and pathogenical causes which, act on him at Jamaica and the Havannah. It is probable that under the same parallel, the gaseous emanations which produce the same diseases, are almost the same; but that a slight difference is sufficient to throw disorder into the vital functions, and to determine that particular succession of phenomena, by which the yel

low fever is characterized. Thus I have shewn by a long series of experiments", in which the galvanic excitations serves to measure the state of irritability of the organs, that chemical agents excite the nerves not only from the qualities which are peculiar to them, but also from the order in which they are applied after one another. Under the torrid zone, where the barometrical pressure and temperature of the air are nearly the same throughout the whole year, and where the electrical tides, the direction of the wind, and all the other meteorological variations succeed one another with an immutable uniformity, the , organs of the man, habituated from his birth in his native climate, to the same impressions, become sensible to the smallest changes of the surrounding atmosphere. From this extreme sensibility, the inhabitant of the Havannah, transported to Vera Cruz while the vomito is committing the most cruel ravages there, runs sometimes the same risk as persons not seasoned to the climate. f I say sometimes, for in ge