_Of the effusion of mucus and lymph from natural causes._—The abundant secretion of tough mucus in the stomach is a sign of that organ having been irritated. But the effusion of lymph is more characteristic. This may be produced by natural inflammation as well as by irritating poisons. As arising from either cause, however, it is rare; and certainly by no means so common as would be supposed from what is said in systematic works; for tough mucus has been often mistaken for it. Reticulated lymph adhering to the villous coat, and accompanied with corresponding reticulated redness of that coat, such as I have seen in animals poisoned with arsenic or oxalic acid, is an unequivocal sign of inflammation. _Of idiopathic ulcers and perforation of the stomach and intestines, and their distinction from those caused by poison._—Both ulceration and perforation may be produced by natural disease. In the ulceration produced by poisons there is generally speaking nothing to distinguish it from natural ulcers; but that caused by some poisons, such as iodine, is said to differ by the surrounding coloration of the membrane; and when the ulcer is caused by a sparingly soluble poison in a state of powder, such as arsenic, the cavity of the ulcer is sometimes filled with the powder. Perforation is a rare effect of the simple irritant poisons; but it is often caused by corrosives. It is imitated by two of the varieties of perforation from natural disease. The form of natural perforation caused by a common ulcer is precisely the same as that caused by the simple irritants, and is incapable of being distinguished, except when it is attended with scirrhus. By far the most remarkable variety, however, of spontaneous perforation is that which takes place, without proper inflammatory action, from simple gelatinizing of the coats. It is very apt to be mistaken, and in a celebrated trial, which will be immediately noticed, was actually mistaken for the effect of corrosive poison.