176 ORIGINAL AETICLES. 



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 re- 

 duced to the same scale, or to half the natural size. They are all, ex- 

 cepting the front view of the Engis cranium, placed as nearly as possi- 

 ble 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 open- 

 ings would be vertical.] 



XYIII. — 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 re- 

 sistance 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 induc- 

 tion which was erroneous, I laid before the British Association,* and 

 the public,! 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 stric- 

 tures 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 hind? or are they the same in kind, but different in function, 



* Aberdeen Meeting. 1859. f Physiology of Common Life, vol. ii. 



