LIFE AND MECHANISM. 39 foot gives an involuntary jerk. In cases where from injury or other morbid conditions the physiological communication between the brain and the lower part of the spinal cord is severed, the jerking of the foot can still be elicited, and indeed is now exaggerated. It is therefore clear that the jerking is not brought about through the medium of the higher nerve- centres in the brain, but concerns only those of the spinal cord. As the jerk follows the stimulus to the skin with perfect regularity it is evident that there must be a causal connexion between the two phenomena, and it is not difficult to follow out that connexion through the afferent nerves, certain groups of ganglion-cells in the cord, and the motor nerves, to the muscles which move the foot. So far as these facts go they entirely corroborate the belief that the organism is a machine. And it is a plausible deduction from them that, since the cells of the higher nerve-centres are presumably in all fundamental respects similar to those of the lower centres, the actions in which they are concerned are in reality only very complicated reflex actions, the element of consciousness being sometimes added, but in no way altering the matter from a physical point of view. Of course it is clear that the deliberately purposive actions in which the higher nerve-centres are concerned are of the same sort as those which we have already considered in the case of the earthworm. The restoration of function which, in greater or less degree, follows cerebral lesions in man is also similar in kind to the reproduction of a limb in the case of the newt. Accordingly the reasoning of the previous part of this article may be applied to show that in the case of the higher nerve-centres in man there is something more than mechanical action. But if the matter is left there, and it be at the same time admitted that reflex action is purely mechanical in itself, the conclusion follows that the ganglion- cells of a lower centre are altogether different from those of a higher one, and manifest in themselves the life of the organism in a far less intimate manner. Such a conclusion, however, strikes one at once as being altogether contrary to biological analog}' ; and a further consideration of the facts will show that it is unnecessary. The fact that a soldier instinctively performs a certain action on receiving the word of command from his superior officer, does not imply that he is a machine. His obedience may have the appearance of being more or less mechanical, but the fact that he originally learned to obey, and was not made to do so by influences acting on him merely from without, shows that he is not in reality a machine. For in the process of
