while between 1795 and 1802, their number had increased to 57,213. The mortality was very great, especially in 1799, when the Marquis de Branciforte the viceroy, dreading a disembarcation of the English on the eastern coast, ordered a number of troops to be cantoned in a very unhealthy place, at Aroyo Moreno, two leagues and a half from Vera Cruz. We must observe that in the period which preceded the epidemic of 1794, the yellow fever never ceased to rage at the Havanah, and in the other West India Islands, with which the merchants of Vera Cruz constantly kept up commercial relations; and several hundreds of vessels annually came from these infected places without going quarantine, yet the vomito never appeared among the Europeans. I examined in the meteorological registers of M. Orta, month by month, the temperature of the year 1794; and far from being higher, it was acBefore the commencement of the epidemic of 1794, the mortality was only 2% per cent. and now it is from six to seven per cent, and it would be still greater if this hospital did not receive, like every military hospital, many seamen whose diseases are not severe. . In the civil hospitals of Paris, in a hundred patients, generally from fourteen to eighteen die; but we must not forget that these hospitals

tually less than that of the preceding years, as is proved by the following table:

Mean temperature of Vera Cruz, (centigrade

thermometer.)
No vomito Epidemics of

Months. prieto. vomito prieto.
1792. 1793. 1794. 1795.
January . . 21. 5 20, 8 20, 6 20. 7.
February . . 21. 5 22. 3 22.8 21. 0
March . - * 23. 7 22.8 22. 6 22. 5
April . - 24. 2 26. 1 || 25. 3 24. 0
May . - - 27. 3 27. 9 || 25. 3 26. 3
June . - - 28. 5 27. 8 27. 5 27. 2
July . - 27. 5 26. 9 || 27. 8 27. 7
August . . 28. 3 || 28. 1 || 28. 3 27. 8
September . 27. 5 28. 1 27. 1 26. 1
October . . 26. 3 || 25. 5 26. 1 || 25. 0
November . . 24. 7 || 24. 4 || 23. 0 || 24. 3
December . . 21. 9 22. 1 21. 7 || 2:1. 9

- i

Mean temperature -
of the year }|25. 2 25. 2 24, 8 24.5

The heat and humidity of the air may influence in two very different manners the developement of epidemics. They may favour the production of miasmata, or simply increase the irritability of the organs, and act as predisposing causes. From the facts which we have already related, it is impossible to deny the influence of the temperature on the progress of the vomito at Vera Cruz; but nothing proves that when the malady has ceased to prevail for several years, a very warm and very humid summer is sufficient to re-produce it; and the heat really does not alone produce what is very vaguely designated by the name of bilious constitution. Notwithstanding the yellow colour which the skin of the patient assumes, it is nowise probable that the bile passes into the blood *, and that the liver and the system of the porta act the principal part in the yellow fever, as has been frequently supposed. The black matter in the vomito prieto bears a feeble analogy to the bile; it resembles coffee grounds, and I have sometimes seen that it left indelible stains on linen, or on the wall. It disengages itself from the sulphuretted hydrogen when slightly heated. According to the experiments of M. Ffirth f, it contains no albumine,

* Human bile abounds in albumine: in 1100 parts, it contains 42 of albumine, 58 of resin, yellow matter, soda and salt, and 1000 of water. Thenard in the Memoires d’Arcueil, t. i. p. 57.

t From the experiments made with great care by M. Thenard, there is no bile in the blood of persons attacked with the icterus. M. Magendie, who has enriched physiology with ingenious experiments on the action of poisons, has observed that a dog of a moderate size dies if more than seven grammes of bile is injected into his veins. In this case the serum does not assume a yellow colour, and the

but a resin, or oily matter, phosphates and muriates of lime and soda. The same anatomist has proved, from the opening of dead bodies in which the pylorus was totally obstructed, that the matter of the vomito is not furnished by the hepatic canals, but is poured into the stomach by the arteries diffused throughout the mucous membrane. He asserts, and the assertion is very remarkable, that we find, after death, the black matter still contained in these same vessels. * - - * : ' ' ...” Some of the physicians of New Spain admit that the epidemics of the vomito, as well as the small pox, are periodical in the torrid zone, and that the happy time already approaches when Europeans may land on the coast of Vera Cruz, without incurring greater risk than at Tampico, Coro, Cumano, or wherever the climate is excessively warm, and at the same time conjunctive of the animal remains white. Immediately after the injection, the bile is not recognized in the blood by its savour, although the smallest quantities of bile are sufficient to give a bitter taste to a considerable mass of water. M. Autenrieth has observed that in man the serum of the blood becomes yellow in diseases which announce no bilious complications (Physiologie, b. ii. p. 93. Grimaud second Memoire sur la nutrition, p. 78.) We know also that the skin becomes yellow in a state of health, with old men, and that it takes a yellowish tint in contusions, and wherever there is extravasated blood. * Stubbins Firth, p. 37 and 47.

very healthy. If this hope is realised, it will be of the greatest importance carefully to examine the modifications of the atmosphere, the changes which shall take place at the surface of the earth, the draining of marshes, and in a word, all the phenomena which shall coincide with the termination of the epidemic. I should not be surprised, however, that these researches led to no positive result. The beautiful experiments of M. M. Thenard and Dupuytren, have taught us that extremely small quantities of sulphuretted hydrogen mixed with atmospheric air, are sufficient to produce asphyxia. * The phenomena of life are modified by a great number of causes, the most powerful of which escape our senses. to We see dis. eases arise wherever organized substances, impregnated with a certain degree of humidity and heated by the sun, come into contact with the atmospheric air. Under the torrid zone the smallest marshes are the more dangerous, being surrounded as at Vera Cruz and Carthagena with an arid and sandy soil, which raises the temperature of the ambient air. We may conjecture some of the conditions under which the gaseous emanations which are designated