122 AN INTRODUCTION TO SCIENCE 



conducting paths through the grey matter ; the protoplasmic 

 processes are supposed to retract and extend ; the proto- 

 plasm of the cells is supposed to flow out along invisible 

 nerve-fibres, and so forth ; but no one imagines that the 

 feltwork of the grey matter can in any way alter the quality 

 of the impulses which it transmits. 



If neither nerve-fibres nor grey feltwork exercise any 

 influence over the quality of the impulses which they con- 

 duct, the nerve-cells alone remain to those who wish to see 

 "the god in the machine." And it cannot be denied that 

 physiologists have taken great liberties with the machine. 

 It has turned out every kind of work which their fancy 

 exacted. They have pictured the nerve-cells as doing all 

 their thinking, and they have thought of the nerve-cells as 

 working in the way they pictured. Reading some recent 

 text-books recalls to mind the Irishman who held up the 

 plank he was sitting on. But as far back as 1877 Lewes 

 combated in vigorous language the '* superstition of the 

 nerve-cell." Yet, even now, it is not slain. Perhaps it 

 does not deserve to die. Ay, there's the rub ! Physiology 

 is the last of the sciences to render itself independent 

 <$ priori reasoning. We feel, will, enjoy, forego, therefore 

 there must be a mechanism which is capable of feeling, act- 

 ing, and, latest birth of evolutionary time, deciding not to 

 act. But this conclusion does not justify us in assigning 

 these properties to the nerve-cell. The physiologist of a 

 century ago said, with no misgivings as to the cogency of 

 his argument, ' ' I have come down this morning in a bad 

 temper. Therefore, my vital spirits are contaminated. The 

 spleen is the organ which makes black bile. Therefore the 

 spleen has poured black bile into my blood." Poor mis- 

 understood spleen ! It is busy day and night in purifying 

 the blood, ridding it of its worn-out blood-corpuscles. 



All that physiologists know about the nerve-cell is that it 

 transmits impulses and provides for the nutrition of the 

 nerve-fibres to which it gives origin. And in connection 



