504- THE NERVOUS SYSTEM. 



with the manifest purpose of pushing away the irritation. 

 It is as if the mind of the animal were still engaged in the 

 acts.* But, in division of the human spinal cord, the 

 lower extremities fall into any position that their weight 

 and the resistance of surrounding objects combine to give 

 them ; if the body is irritated, they do not move towards 

 the irritation ; and if themselves are touched, the conse- 

 quent movements are disorderly and purposeless. Now, if 

 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 skin of the lower extremities in the human 

 subject, after division or disorganization of a part of the 



* The evident adaptation and purpose in the movements of the cold- 

 blooded animals, have led some to think that they must be conscious and 

 capable of will without their brains. But purposive movements are no 

 proof of consciousness or will in the creature manifesting them. The 

 movements of the limbs of headless frogs are not more purposive than 

 the movements of our own respiratory muscles are ; in which we know 

 that neither will nor consciousness is at all times concerned. 



