40 THE PRINCIPLE OF Chap. 1 



least use/ 4 as often as the same causes arise, which 

 originally excited them in us through the volition. In 

 such cases the sensory nerve-cells excite the motor cells, 

 without first communicating with those cells on which 

 our consciousness and volition depend. It is probable 

 that sneezing and coughing were originally acquired by 

 the habit of expelling, as violently as possible, any irri- 

 tating particle from the sensitive air-passages. As far 

 as time is concerned, there has been more than enough 

 for these habits to have become innate or converted into 

 reflex actions; for they are common to most or all of the 

 higher quadrupeds, and must therefore have been first 

 acquired at a very remote period. Why the act of clear- 

 ing the throat is not a reflex action, and has to be learnt 

 by our children, I cannot pretend to say; but we can 

 see why blowing the nose on a handkerchief has to be 

 learnt. 



It is scarcely credible that the movements of a head- 

 less frog, when it wipes off a drop of acid or other object 

 from its thigh, and which movements are so well co- 

 ordinated for a special purpose, were not at first per- 

 formed voluntarily, being afterwards rendered easy 

 through long-continued habit so as at last to be per- 

 formed unconsciously, or independently of the cerebral 

 hemispheres. 



So again it appears probable that starting was 

 originally acquired by the habit of jumping away as 

 quickly as possible from danger, whenever any of our 

 senses gave us warning. Starting, as we have seen, is 

 accompanied by the blinking of the eyelids so as to 

 protect the eyes, the most tender and sensitive organs 



14 Dr. Maudsley remarks (' Body and Mind,' p. 10) that 

 " reflex movements which commonly effect a useful end 

 may, under the chang'ed circumstances of disease, do great 

 mischief, becoming even the occasion of violent suffering 

 and of a most painful death." 



