REFLEX FUNCTION OF THE SPINAL COED. 503 



we are justified by analogy in assuming that the will of 

 the frog cannot act more than the will of man, through 

 the spinal cord separated from, the brain, then it must be 

 admitted that many more of the natural and purposive 

 movements of the body can be performed under the sole 

 influence of the cord in the frog than in man ; and what 

 is true in the instance of these two species, is generally 

 true also of the whole class of cold-blooded, as distinguished 

 from warm-blooded, animals. It may not, indeed, be 

 assumed that the acts of standing, leaping, and other 

 movements, which decapitated cold-blooded animals can 

 perform, are also always, in the entire and healthy state, 

 performed involuntarily, and under the sole influence of 

 the cord ; but it is probable that such acts may be, and 

 commonly are, so performed, the higher nerve-centres 

 of the animal having only the same kind of influence in 

 modifying and directing them, that those of man have in 

 modifying and directing the movements of the respiratory 

 muscles. 



The fact that such movements as are produced by irri- 

 tating the sko of the lower extremities in the human 

 subject, after division or disorganization of a part of the 

 spinal cord, do not follow the same irritation when the 

 mind is active and connected with the cord through the 

 brain, is, probably, due to the mind ordinarily perceiving 

 the irritation and instantly controlling the muscles of the 

 irritated and other parts ; for, even when the cord is per- 

 fect, such involuntary movements will often follow irritatio^ 

 if it be applied when the mind is wholly occupied. When, 

 for example, one is anxiously thinking, even slight stimuli 

 will produce involuntary and reflex movements. So, also, 

 during sleep, such reflex movements may be observed when 

 the skin is touched or tickled ; for example, when one touches 

 with the finger the palm of the hand of a sleeping child, 

 the finger is grasped the impression on the skin of the 

 palm producing a reflex movement of the muscles which 



