_Black Vomit._--In a preceding part of these observations, in alluding to the black vomit, I took occasion to express my views respecting its nature,--stating that I regard it as consisting of mucous flakes, mixed with a large proportion of altered blood. That such is the true nature of this substance, on which so much has been said and written, I have had sufficient reason to be convinced. The opinion that it consists of altered bile, I deem totally untenable, for the following reasons: The matter is occasionally voided in large quantities, in cases in which the liver is not at all affected, and in which, after death, the gall bladder is discovered to be more or less filled with _natural_ bile. Independently, of this, it may be stated, that the appearance of the two substances is very dissimilar;--the black bile vomited in bilious fever being of a homogeneous nature, and of a black or deep green colour; whilst the matter of the black vomit is, in a large majority of cases, a compound of a mucous, flaky substance, and a sanguineous matter, bearing some resemblance to the grounds of coffee, and, for the most part, of a brown tinge. When mixed with water, the two substances produce very different effects,--the bile mixing with and imparting a greenish tinge to it without difficulty, whilst the grounds of the other, float on the surface of the water, without mixing with and colouring it, in the same manner as bran, deprived of all its mucilage, or rather like mahogany saw-dust. This I consider as one of the best modes of distinguishing these two substances,--serving at the same time to establish a difference between the fevers, I was in the habit of observing in the West Indies, and the yellow fever of this country. Nor are these the only reasons for rejecting the supposition of the black vomit of yellow fever being of a bilious nature; for I have known this substance (and I suppose other practitioners have observed the same fact) occasionally to exude from surfaces, from which, in all probability, bile is excluded. I allude particularly to the skin and verous membranes. Thus it has often happened, that the application of a blister, especially in the advanced stage of the disease, has been followed by a copious exudation of a fluid, resembling, in all respects, the matter ejected from the stomach; an occurrence which was strikingly exemplified in a case, which fell under my immediate observation during the last visitation of the disease in this city, in 1820. During the same epidemic, I had occasion to attend a Mrs. H. about 70 years of age, who presented a curious example of the exudation of a similar substance from the peritoneum. She had not been exposed to the causes of the yellow fever, and indeed presented none of its ordinary pathognomonic signs. She was attacked very early in the morning with violent colic, attended with fever, great tenderness of the abdomen, and high colour of the face. She was bled at 10 o'clock; at