Page:Popular Science Monthly Volume 21.djvu/194

184 function" of the spinal cord (which up to this time had been generally looked on as a bundle of nerves), that the truth of Bell's doctrine came at last to be fully established. For the movements called forth, by irritation of the posterior roots were found to be due, not to the direct transmission of motor impulses from them to the muscles, but to the transmission of a motor nerve-current through the anterior roots, in response to the stimulation given to the spinal cord itself by the irritation of the posterior; while, on the other hand, it was made clear that the indications of pain given when the anterior roots are irritated, are due to the presence, in those roots, of sensory filaments derived from the posterior, which pass inward at the point of junction between the two. But for the well-devised and carefully executed experiments by which these difficulties were cleared up, the whole matter would have remained in the state of uncertainty in which I well remember it to have been, when I first entered on the study of the subject, previously to Müller's experiments.

Having myself been afterward Sir Charles Bell's pupil (in surgery) both in London and Edinburgh, I can testify from personal knowledge that he himself never admitted that his discoveries needed any confirmation whatever; but was always strong in the conviction, not only that he had himself given all needful evidence of them, but that nothing more remained to be done in the physiology of the nervous system. It is not a little significant of his attitude of mind on this subject, that he used to declare his complete inability to understand "what Marshall Hall was driving at"; the doctrine of reflex action independently of sensation being altogether "beyond his comprehension." As this last doctrine, which forms the basis of modern neurology, is one which anatomy could scarcely even suggest, and which nothing but experiment can demonstrate, I hope that Sir C. Bell's opinion of the all-sufficiency of the study of anatomy for the advancement of physiological science may henceforth be appreciated at its true worthlessness. For I have shown, first, that Sir Charles Bell, trusting to anatomy for his guidance, went altogether wrong in the first instance; secondly, that it was by experiment on the nerves of the face that he was led into the right track; thirdly, that in regard to these, through placing too much trust in his anatomical preconceptions, and insufficiently testing them by further experiments, he was led into mistakes which were only corrected by the experiments of Magendie; and, fourthly, that the most important discovery with which he is usually credited—that of the motor and sensory functions of the anterior and posterior roots of the spinal nerves respectively—was only established in the true scientific sense by the experiments of others working on his lines. Those experiments might have issued, for any real proof ever given by Bell to the contrary, in establishing some other doctrine of the spinal nerve-roots than that to which he had been led by his study of the nerves of the face—such, for