THE NERVOUS SYSTEM 239 



been cut off. The cold-blooded animals also exhibit reflex 

 movements in an astonishing degree. A decapitated centipede 

 will run rapidly forward, and will seemingly strive to over- 

 turn, or else climb over obstacles placed in its way. A frog 

 similarly mutilated will sustain its headless body upon its feet, 

 in the standing posture, just as it might do if it were still 

 alive. If pushed over, it will regain its feet; and if the feet 

 are irritated, it will jump forward. There can be no doubt 

 that, in the lower animals, movements may take place which 

 are completely divorced from the will, sensation and conscious- 

 ness ; for in those animals, as well as in man, these faculties 

 have their principal seat within the brain. 



39. An irritation is necessary, in most instances, to awaken 

 reflex movements. In the case of the decapitated fowl, its 

 muscles are excited to convulsive action by reason of its being 

 thrown upon the hard ground and roughly handled. Let it be 

 treated differently, and the convulsions will not take place: 

 let it be laid gently upon soft cotton, and the body will remain 

 comparatively quiet. It may comfort some people to know 

 that the convulsions which follow decapitation are not attended 

 with pain, nor are they a necessary part of the " act of death," 

 as some suppose. 



40. In the human body, likewise, actions are excited that 

 are entirely distinct from the ordinary voluntary efforts. It is 

 ot permissible, desirable, nor even necessary to decapitate a 

 man that the body may be disconnected from his brain, in 

 order to test the effect of irritation upon the spinal cord 

 although the bodies of beheaded criminals have been experi- 

 mented upon, and caused to move by powerful galvanic bat- 

 teries. Such experiments are rendered unnecessary by the 

 occurrence of certain deplorable cases of disease and injury, 

 which effectually sever all communication between the brain 

 and a large part of the body. 



41. Thus, the cord by an accident may be so far injured as 



39. What is necessary in most cases to awaken reflex movements ? In the case of the 

 fowl ? Convulsions which follow decapitation ? 



40. Actions in the human body distinct from voluntary efforts ? J^^ 



41. Reflex action after Injury of the cord ? Why not due to the muscles f / Or T H E 



( UNIVERSI 



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