It is curious, however, to observe how the real business of the human mind is shadowed forth in the very abuses of its powers; nothing so bad but it is charged with a certain quantity of good; no error so great but carries with it the element of its own correction. The mind in its greatest aberrations is followed by the shadow of its real duty, which as it were waits on the time when clearer views shall burst on it. Nothing shows the real tendencies of mind more than its restless desire to arrive at _some_ conclusion, _some_ tangible evidence of its highest functions. It is the impulse of this instinct—the ungoverned abuse of a high faculty, impatient for illegitimate fruition—which lies at the bottom of much false reasoning, and which blinds men, even of great power, to obstacles which are luminously evident to the most ordinary capacity. Important as the next series of illustrations cited by Abernethy are, the conclusions he deduced from them were the necessary sequences of clear and correct reasoning on familiar and established facts. The illustrations in question were those afforded by various cases of injuries of the head, in which certain consequences, however exceptional they may be, are too commonly referred to the abstract nature of the injury. We _see_ that a man has a blow, we _see_ that he does not recover in the usual way in which we have known many others to recover; but we do not, perhaps, _consider_ that if a similar—nay, perhaps an identical force produces very different effects in different cases, the cause will probably not be in the nature or direction of the force so much as the condition of the body. Now the value of these cases of Abernethy's consists, first, in impressing the influence of this condition as modifying—in other words, _sustaining_—the disturbance consequent on injuries (in their origin) purely mechanical; and secondly, in showing that, in the cases in question, _that condition_ depended on a disordered state of the digestive organs. We hardly know any cases more valuable than those in question. When a patient receives a blow, and, the _immediate_ consequences having subsided, there still remains an impairment of sense or motion, the most usual thing, and no doubt very often the true view, is to refer it all to lesion of nervous structure. It is therefore of the highest consequence to know the facts of these cases. They not only prevent the hasty institution of treatment which would be injurious; not only secure the patient from being abandoned in despair; but supply at the same time the clues to a rational treatment, and the hope of a favourable issue.