The re-connection of regenerated nerves with their terminal apparatus presents to the mind a curious problem. There is no evidence that as function is re-established the brain has to re-learn the situation of the sensory spots on the skin, or to re-acquire skill in using the muscles which again come under its control. From the moment that the outgrowing nerves have recovered their terminal connections skin and muscles have their right representation in the brain, however much the two cut ends may have been twisted in their relation one to another. It seems inconceivable that each nerve-fibre can find its way to its original station; but if it does not, our conception of the mode of working of the nervous system still needs much refining from the telephone-exchange analogy by which we naturally help out our explanations. If a telephone cable has been severed, it can be made useful again only in one of two ways. Either the two segments of every wire that has been cut must be reunited, or the subscribers’ numbers must be redistributed. The experiment of uniting the proximal segment of one nerve with the distal segment of another of a quite different function gives results which have an even more disconcerting effect upon our theory of the nervous system. The sympathetic cord of the neck and the vagus nerve lie very close together, alongside the carotid artery. The vagus is both afferent and efferent. The sympathetic is wholly efferent—_i.e._, it conducts impulses, which enter the sympathetic chain within the thorax, in the direction of the head. If both nerves are cut, and the end of the vagus turned round, so that it is in apposition with the upper end of the sympathetic, its regenerating fibres make their way along the sympathetic cord, headwards, to the superior cervical ganglion. They arborize about the bodies of its ganglion-cells, just as the sympathetic fibres used to do. The vagus is a nerve of many functions. Amongst others, it inhibits the contraction of the heart, constricts the bronchi of the lungs, dilates the bloodvessels of the intestines, and helps in regulating the movements of these viscera. After it has taken the place of the upper segment of the sympathetic it dilates the pupil, constricts the bloodvessels of the ear, erects the hairs of the head, as if to the manner born. To take another example, in a monkey the two nerves supplying respectively certain flexor and certain extensor muscles of the forearm were cut, and their ends crossed, so that flexor nerve-fibres grew down to extensor muscles, and extensor fibres to flexor muscles. There was no bungling of reflex actions or of voluntary actions when the new roads were first used. The monkey did not jerk its hand open when it tried to scratch or to grasp a nut.