8. Outline of Dr. Schaaffhausen's figure of the cranium from Plau.
9. Side view of the cranium from a submarine forest at Sennen, near the Land's End.
[The figures, with the exception of the Chimpanzee skull, are all reduced to the same scale, or to half the natural size. They are all, excepting the front view of the Engis cranium, placed as nearly as possible in the same position, so that they admit of direct comparison. The position selected is that in which a line drawn from the junction of the sagittal and coronal sutures to the middle of the external auditory openings would be vertical.]
XVIII.—The Sensory and Motor Functions of Nerves.
By G. H. Lewes.
When once a doctrine has been generally accepted, and confidently taught, it necessarily calls forth a strong conservative principle of resistance against every effort to change it. That very reluctance to change of mental attitude which made the public deaf to the voice of the original teacher, now serves to close the ears of the public against the opponents of that teacher. Bell had trouble enough to get his discovery of the sensory and motor nerves accepted; but now that the contest has long been ended, and Bell is crowned victor, all the conservatism which embittered his efforts is employed to maintain his triumph. Not only is he declared victor, but "victory along the whole line" is claimed, and his errors are consecrated with his truths.
I have alreadjr paid my small but hearty tribute to Bell's genius, and to the unimpeachable validity of his anatomical discovery; but, conceiving that he had founded on that discovery a physiological induction which was erroneous, I laid before the British Association,[1] and the public,[2] certain critical strictures, the purport of which was to show that there was no essential distinction between the two nerves: both being sensory and motor, though in varying degrees. In these strictures there may be a fundamental error; and if so, I should be glad to see it pointed out. The discussion is one which cannot be without service; and if any champion of Bell's doctrine will do me the honour to descend into the arena, he may be assured that the harder he hits (without foul blows), the more welcome he will be.
Ever since the time of Galen, it has been suspected that there were "nerves of motion," and "nerves of sensation." Latterly we have had "nerves of secretion." The question to be settled is: Are these nerves different in kind? or are they the same in kind, but differentin function,
