No organ in the animal economy acquires by inflammation, so great a size in so short a time, and such excessive weight, as the lungs. All who open dead bodies know this. Observe the lungs of one dead of pneumonia; cut them, and you would say at first that they were solid; they often look like liver, they exhibit the appearance of such a heavy mass; but macerate them and soon the whole will escape in fluids. Now examine comparatively the skin, the stomach, the liver, the kidnies, &c. when they have been the seat of acute inflammation, that has destroyed the patient; they have nothing approaching to this enormous increase of fluid, which is seen in the substance of inflamed lungs. Not only the cavity of the cells is full, but the organ is also much dilated. I have often had occasion to open those who have died of pneumonia, in whom one of the lungs was entirely sound; now, the disproportion of weight between it and the affected one, was incomparably greater than that between an inflamed kidney and a sound one. This phenomenon evidently arises from the fact, that the lungs alone receive as much blood as the whole body, so that when an inflammation of this viscus interrupts the course of the fluids, a very great quantity of them can accumulate there in a given time. It is not however, properly speaking, the blood that is found crowding the lungs in pneumonia; the fluid appears whitish when pressed out; we should say that it was a kind of pus. Much has been said of vomicæ after pneumonia; but they are extremely rare; there is almost always effusion in the lungs; the fluid is not collected in a sac. In pulmonary inflammation, does the blood pass through vessels that do not ordinarily circulate it, as happens so evidently upon the serous surfaces, or conjunctiva, &c. when inflamed? I do not think it does, for we do not know any vessels in the lungs, except the sanguineous. It appears evident that the blood or the other fluids are effused into the pulmonary texture, in which they are deposited by exhalation. There is no doubt that in some phlegmons, this fluid passes, as I shall say, into the cells of the cellular texture; now it appears that it happens here in the same way. By breaking or cutting inflamed lungs, we see clearly that its whole texture is crowded, and filled; whereas in examining an inflamed serous surface, we see that the blood is evidently contained in the capillaries. It is a great mistake to try to represent inflammation as being everywhere the same, as exhibiting always the fluids, like their vessels, in the same state. Boerhaave for example thought, that there could be no inflammation without an _error loci_. There is according to the state of the parts, their structure, their vital properties, a thousand different modifications in the new anatomical order that this affection gives to the organs.