1 16 LIFE AND HABIT. 



body may be thrown into sudden action, which sud- 

 denly subsides again." (How does this quiescence 

 when it no longer feels anything show that the " leg 

 or whole body" had not perceived something which 

 made it feel when it was not quiescent ?) " Again we 

 find that such movements may be performed not only 

 when the brain has been removed, the spinal cord 

 remaining entire, but also when the spinal cord has 

 been itself cut across, so as to be divided into two or 

 more portions, each of them completely isolated from 

 each other, and from other parts of the nervous centres. 

 Thus, if the head of a frog be cut off, and its spinal 

 cord be divided in the middle of the back, so that its 

 fore legs remain connected with the upper part, and 

 its hind legs with the lower, each pair of members 

 may be excited to movements by stimulants applied 

 to itself ; but the two pairs will not exhibit any con- 

 sentaneous motions, as they will do when the spinal 

 cord is undivided." 



This may be put perhaps more plainly thus. If 

 you take a frog and cut it into three pieces say, the 

 head for -one piece, the fore legs and shoulder for 

 another, and the hind legs for a. third and then irritate 

 any one of these pieces, you will find it move much as 

 it would have moved under like irritation if the animal 

 had remained undivided, but you will no longer find 

 any concert between the movements of the three 

 pieces ; that is to say, if you irritate the head, the 

 other two pieces will remain quiet, and if you irritate 

 the hind legs, you will excite no action in the fore legs 

 or head. 



