222 LESSONS FEOM NATUKE. [CHAP. VII. 



embrace, just as they would do in a living and perfect frog 

 in the act of clasping the female. 



There is, however, another class of actions which in us 

 result, indeed, from sensations, but which take place auto 

 matically, and without the intervention of our will, or even 

 of our attention. 



Thus, when an object suddenly approaches our eye, the 

 eyelids may close almost simultaneously with the experience 

 of the sensation. A sudden or unwonted sound will cause 

 the whole frame to start a direct and immediate sense- 

 perception, producing a result before we have time to inquire 

 into the cause of that affection of our sense. The act of 

 swallowing an object placed far back in the mouth is probably 

 simply reflex, but, as Dr. Alison has remarked,* the initial 

 act of deglutition, that of passing the food backwards from 

 the tongue to the isthmus faueium, is due to a sometimes 

 almost irresistible propensity to swallow whatever grateful 

 food or drink is in the mouth. Again, as to the act of 

 sucking, Bichat says : 



&quot; It is instinct, which I do not understand, and of which I cannot 

 give the smallest account, which makes the infant, at the time of birth, 

 draw together its lips to commence the action of sucking.&quot; 



Indeed, actions of this kind are commonly spoken of as 

 instinctive ; and such are those we perform in walking 

 through crowded streets absorbed in a reverie, or in running 

 up or down stairs when, indeed, any direction of the atten 

 tion upon our successive actions tends but to mar them. 

 Allied to these actions, also, are the wonderful wanderings 

 of somnambulists. Dr. Carpenter givest an amusing account 

 of the spontaneous production of movements in response to 

 felt stimuli on the part of certain somnambulists. He says 

 of such that, if their arm be 



&quot; advanced forward in the position of striking a blow, .... the som 

 nambulist is very apt to put it into immediate execution.&quot; On one occa 

 sion, when Dr. Carpenter was present, &quot; a violent blow was struck, which 



* See Todd s Cyclopaedia, vol. iii. p. 4. 

 t Mental Physiology, 187-1, p. 605. 



