Xo. 49S] 



PHYSIOLOGY 



111 



hypothesis after hypothesis, which smell of the lamp- 

 fabrications of the philosopher's cell rather than of the 

 physiologist's laboratory. Almost without exception 

 they are elaborate exercises in dialectics, rather than real 

 portrayals of the nature of that most striking of phys- 

 iological phenomena. To the physiologist they are 

 almost without exception arid and unsatisfying. 

 ' i Words, words, words," replies Hamlet to the question 

 of Polonius. At first thought, the theories of dualism 

 and interaction seem best adapted to the obvious facts of 

 human experience: the brain and mind are two distinct 

 entities usually intimately associated, and each capable 

 of inducing phenomena in the other. But deeper brood- 

 ing, and especially a recognition of the mode of action of 

 the non-psychic portions of the nervous system and the 

 close dependence of psychic on cerebral phenomena, of 

 "how at the mercy of bodily happenings our spirit is," 

 make us seek a more genuinely physiological explanation. 



The physiologist recognizes as the morphological basis 

 of nervous actions the neurone or nerve cell, consisting of 

 a compact cell body, from which radiate outward fila- 

 ments, the nerve fibers. He finds in the nervous system 

 of the higher animal or man millions of such neurones 

 and many more millions of nerve fibers. These constitute 

 seemingly a confused and inextricable mass, but by care- 

 ful study he has been able to discover an exact and 

 definite, though excessively intricate, nervous architec- 

 ture. He finds that the bodies of neurones act as central 

 stations, to which and from which flow the nervous im- 

 pulses along the nerve fibers : the incoming impulses con- 

 stituting the centripetal, or afferent, or sometimes sen- 

 sory, impulses; the outgoing constituting the centrifugal, 

 or efferent, or sometimes motor impulses. He recognizes 

 as the physiological basis of nervous action, the reflex 

 action, consisting of an afferent impulse, a central 

 process, and an efferent impulse. He sees reflex acts 

 combined in innumerable ways, and augmented and de- 

 pressed by other reflex acts. He sees many of the most 



