448 SCIENCE PROGRESS 



be a machine. For many of our human machines produce the 

 most widely different effects from closely similar stimuli. A 

 little button is pressed and a tiny electric bell may ring or a 

 20,000 tonner may be launched into the sea or a shock may 

 cause the death of a battalion. So also we frequently produce 

 the same result from widely different stimuli. 



But let us consider this question more closely : let us take 

 Driesch's sentence and trace its physiological effects so far as 

 our knowledge extends. The phrase " my mother is seriously 

 ill" first impinges upon the organism in the form of aerial 

 vibrations : it causes a certain specific motion of the molecules 

 of air which happen to be in contiguity with the tympanum. 

 The outer membrane is thus caused to vibrate and transmits 

 vibrations to the three auditory bones ; these act as light 

 levers and the vibrations which are carried along them cause, 

 so to speak, a tapping at the fenestra ovalis in the inner wall 

 of the tympanum. The fenestra, thus agitated, sets in motion 

 the fluid which bathes it on the inner side. The waves ensuing 

 in that fluid are propagated into the cochlea, pass through the 

 membrane of Reissner, then into more fluid, whence they reach 

 the basilar membrane. Here they produce an excitement 

 of the sensory hair-cells which gives rise to currents in the 

 auditory nerve. From the auditory nerve the currents are 

 carried away down the cochlear branch by several relays to the 

 posterior quadrigeminal and internal geniculate bodies, whence 

 fibres pass on again to the cerebral cortex. 



Now I wish to point out that the whole process \s proved to 

 be mechanical, so far as our laboratory methods enable us to 

 follow it. That difference between " mother " and " brother " is 

 in the first place represented by a different mode of molecular 

 vibration in the outer air. It is represented by a different mode 

 of vibration of the outer membrane of the tympanum, of the 

 auditory bones, of the inner membrane and of the fluids and 

 membranes of the cochlea. The nervous elements distributed 

 to the cochlea are so excessively numerous that they too record 

 the difference, which is thence carried into the brain. So far, the 

 whole process is known beyond question to be mechanical : the 

 machine to be one of almost incredible delicacy and complexity. 



But however delicate and complex the auditory apparatus 

 may be, it is infinitely exceeded by the delicacy and complexity 

 of the brain into which the stimulus is carried. Physiologists 



