Next come the nerves of the tongue; and here again, in natural conditions, there is a constant harmony between them and the stomach—that to which the taste readily gives admission being, in _undisturbed_ conditions of the economy, some guarantee that it is innoxious; but what these _functions are to the stomach_, the stomach is _to the other organs_. In the first place, in natural conditions it usually at once rejects any noxious material which, from being disguised, or from any other circumstances, may have eluded the vigilance of the sentinels I have mentioned; but it has a vivid sympathy with every organ in the body. If anything deleterious be once admitted, it has to go through various processes, which may render it a source of indefinite disturbance; therefore, if any organ in the series of the blood-manufacture be materially disturbed—that is, so as to be disabled—the stomach usually refuses food; because there is no other way of stopping the mischief. Illustrations of this occur in many disorders of the kidney, in many affections of the alimentary canal, as also of the liver, and other parts. No doubt the stomach is therefore a most important organ; but to suppose that it is therefore always the seat of disorder, is not only a most mischievous error, but a complete blind to its most beautiful and instructive relations; and as opposite to Mr. Abernethy's views as the most narrow can be to the most comprehensive. Proceeding with his illustrations, Mr. Abernethy cites a number of most instructive cases, such as palsy and other affections of most serious character, which too often result either from organic disease of some organ, or from mechanical pressure on the brain or spinal marrow, but which in the cases cited depend on disorder of the digestive organs. It is impossible to exaggerate the interest or importance of these cases; not only from the fact that they almost certainly would have led to organic disease, but also for the value of that practical discrimination which they exemplify. Again, the very treatment which would have been proper, which had sometimes been begun, and which was not inappropriate to cases of _organic_ disease, with which the symptoms were in part identical, would have inevitably, in the cases in question, only served to exasperate the very conditions they were designed to relieve, and to hasten those processes against which they were intended to guard. No one can understand the force of these cases, without recollecting the intense difficulty of ascertaining that point at which disorder ceases to be merely functional, and at which organic disease begins. This is of all things the most difficult to determine in the whole circle of physiological or pathological inquiry.