EXPERIMENTAL PSYCHOLOGY 



vestigations in allied fields. Nevertheless, a full dec- 

 ade elapsed before another discovery of comparable im- 

 portance was made. Then Marshall Hall, the most 

 famous of English physicians of his day, made his 

 classical observations on the phenomena that hence- 

 forth were to be known as reflex action. In 1832, 

 while experimenting one day with a decapitated newt, 

 he observed that the headless creature's limbs would 

 contract in direct response to certain stimuli. Such a 

 response could no longer be secured if the spinal nerves 

 supplying a part were severed . Hence it was clear that 

 responsive centres exist in the spinal cord capable of 

 receiving a sensory message and of transmitting a 

 motor impulse in reply a function hitherto supposed 

 to be reserved for the brain. Further studies went to 

 show that such phenomena of reflex action on the part 

 of centres lying outside the range of consciousness, 

 both in the spinal cord and in the brain itself, are ex- 

 tremely common ; that, in short, they enter constantly 

 into the activities of every living organism and have a 

 most important share in the sum total of vital move- 

 ments. Hence, Hall's discovery must always stand 

 as one of the great mile-stones of the advance of neu- 

 rological science. 



Hall gave an admirably clear and interesting ac- 

 count of his experiments and conclusions in a paper 

 before the Royal Society, " On the Reflex Functions of 

 the Medulla Oblongata and the Medulla Spinalis," from 

 which, as published in the Transactions of the society 

 for 1833, we may quote at some length: 



" In the entire animal, sensation and voluntary 

 motion, functions of the cerebrum, combine with the 



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