Chap. XL] UNCONSCIOUS COGNITION. IGl 



corresponding limb are suddenly extended ; and *' this 

 movement of the two legs is," as Yulpian says, " that 

 which is most appropriate, either to repel the cause of 

 irritation or to shoot the animal forward, and so remove 

 it from the influence of the irritating agent." 



Again, if the skin of the side of the body is slightly 

 pinched in a headless frog, the foot of the hind limb on 

 the same side is brought up so as to endeavour to rub 

 away the irritating agent. Here also we have a complex 

 movement brought about by many muscles definitely com- 

 bined and adapted to obtain a certain result. But the 

 particular movements executed always vary in accordance 

 with the site of irritation. Thus, a pinch at the posterior 

 extremity of the trunk, evokes wholly different movements 

 from those just described. In this case, according to the 

 same authority, " There is a new combination of muscular 

 contractions, by means of which the feet are first brought 

 towards the point irritated and there pressed together, and 

 then the limbs are suddenly extended, thus giving rise to 

 the movement most suitable for repelling the cause of 

 irritation." 



In addition to the instances already cited there is the 

 celebrated experiment of PflUger still to be mentioned, in 

 which the reflex act evoked was so definite and purposive 

 as to lead him to claim for the Spinal Cord a kind of con- 

 scious perceptive power, similar to that which physiologists 

 generally restrict to the Brain. He placed a drop of acetic 

 acid on the upper part of the thigh of a decapitated Frog, 

 and the segments of the corresponding limb were quickly 

 flexed, so that the foot was made to rub the seat of irrita- 

 tion. He then amputated this foot of the headless animal 

 before reapplyiiig the acetic acid. The result was most 

 remarkable. The maimed animal began to make fresh 

 efforts to rub the irritated spot, but was unable to reach 



