The system of Brown, likewise, was similarly founded merely upon the state of the intellectual or nervous functions. That system, therefore, although worthy of consideration, is not founded upon a view of all the animal functions, and consequently does not rationally account for all their derangements in disease. The basis of its author’s discovery was his mistaking the mere elasticity or reaction of matter for a peculiar property of living bodies, which he termed excitability. For excitability, when it seems to have been exhausted, is apparently restored by still stronger stimuli, upon the very same principle that greater pressure brings into action the remaining elasticity of a spring which had already lost some portion of it. But what is worse, Brown totally forgot that matter has other properties, and that the constitution of animals admits of other derangements than those affecting their elasticity or their excitability. Extension, for instance, another property of matter, may be destroyed in the living body, by fracture, rupture, &c.; and there evidently it is not excitement that is first produced, or that is worthy either of the first or of the greatest consideration. Brown’s doctrine, then, refers chiefly to the state of the nervous functions. Its chief merit is, that it involves a great portion of their pathology. It is because it does so, that men of ingenuity have often embraced it; and it is in reality because it did not do more—because it did not involve the pathology of the other two classes of functions, that men of much observation opposed it; and that even many of those men of genius who, throughout Europe, had adopted it, were afterwards forced, they scarce knew why, to abandon it.