REFLEX ACTION 51 



tion of the reflex, since in them the stimulation is applied 

 centrally and no afferent nervous mechanism is needed. 

 Our breathing movements are determined to a great extent 

 by such chemical conditions, but it is a fact that reflex 

 disturbances of the breathing are so prevalent that it is 

 often difficult to give just recognition to the two factors. 



We are accustomed to contrast sharply actions which 

 are reflex with those which we regard as strictly volun- 

 tary or deliberate. The distinction is a convenient one 

 and not generally productive of confusion, but sometimes 

 it becomes quite difficult to draw the line. It may be 

 urged that all our conscious, intentional acts are performed 

 in answer to external conditions which have risen to make 

 an occasion for such new adjustments. So it might be 

 argued that the writing of a word from a copy should be 

 considered a reflex in which the retinal image of the copy 

 furnished the external stimulus. Such images printed 

 upon the retina of the trained pianist by the notes that are 

 before him cause his fingers to drop upon the corresponding 

 keys of the instrument. It may be claimed that this is a 

 reflex action. Without denying the force of such reasoning, 

 we shall do well to restrict the term to the class of responses 

 for which we are quite sure that attention is unnecessary, 

 and usually to those for which we have an inborn or at 

 least a very early developed capacity. When we ask 

 ourselves whether any act is really other than the result 

 of external circumstances affecting an organism with its 

 own past history registered in its structure, we find, al- 

 most with a shock, that we are face to face with philo- 

 sophic and ethical problems, responsibility and free will. 

 Most of us like to believe that a place is to be reserved for 

 a type of action, even though it may be rare and slight, 

 which is not externally caused. 



The great difficulty encountered by the beginner in 

 physiology lies in the attempt to realize the inevitable 

 character of reflexes and their structural basis. He finds 

 it hard not to read conscious purpose into acts which so 

 constantly prove advantageous to the individual. When a 



