306 NEBVOUS SYSTEM. 



The animal thereupon rubbed the irritated surface with the 

 foot of the same side, apparently appreciating the locality of 

 the irritation, and endeavoring, by a voluntary effort, to re- 

 move it. The foot of this side was then amputated, and 

 the irritation was renewed in the same place. The animal 

 made an ineffectual effort to reach the spot with the ampu- 

 tated member, and, failing in this, after some general move- 

 ments of the limbs, rubbed the spot with the foot of the 

 opposite side. 1 Although this experiment does not always 

 progress precisely in the manner described, it has succeeded 

 perfectly in so many instances as to lead some physiologists 

 to conclude that sensation and volition are not entirely abol- 

 ished by removal of the encephalon, at least in frogs. 2 



The remarkable phenomena just detailed are to be re- 

 garded from two points of view : first, with reference to 

 their bearing upon the question of the existence of percep- 

 tion and volition in the spinal cord of the frog ; and second, 

 the question of the application of these phenomena to the 

 physiology of the cord in man and the higher classes of ani- 

 mals. The conditions of the experiment in the frog are sim- 

 ply these : Instead of exposing the surface to a single and 

 instantaneous stimulation, the excito-motor effects of which 

 are observed as a direct response to the irritation, and im- 

 mediately cease, we have, by the application of acetic acid 

 to the surface, a prolonged impression upon the sensory 

 nerves, which, by virtue of the anatomical connections be- 

 tween the different parts of the cord, is proba'bly dispersed 

 throughout the entire spinal axis. That powerful impres- 



1 PFLUGER, Die sensorischen Functionen des RuclcenmarTcs der Wirbelthiere, 

 Berlin, 1853, S. 124," et seq. 



2 Observations of very much the same character as those of Pfliiger were 

 published by Patqn, in 1858. He refers to experiments showing the perceptive 

 power of the cord, by Dr. Dowler, of New Orleans, but does not allude to the 

 experiments of Pfliiger. (PATON, On the Perceptive Power of the Spinal Cord 

 as manifested by Experiments on Cold-blooded Animals. North American Medico- 

 Chirurgical Review, Philadelphia, 1858, vol. ii., pp. 467, 703). These obser- 

 rations have been repeatedly confirmed by other physiologists. 



