942 



CENTRAL NERVOUS SYSTEM 



ticular attitude which is assumed is called a reflex figure, and is the expres- 

 sion of the complete central connections of the reflex in question. Fig. 241 

 illustrates three characteristic reflex figures obtained by applying a harm- 

 ful stimulus to various parts of the skin of a decerebrate cat. 



The reflex figure which results from such a stimulus when applied 

 to the foot of the hind leg consists in a flexion of this leg, an extension 

 of crossed hind leg (the crossed extension reflex), extension of the 

 homolateral fore leg, and flexion of the crossed fore leg. This group 

 of responses may be considered to be a compensatory reaction, inas- 

 much as the movement of certain parts is adapted to restore a balance 

 which is disturbed by the movement of other parts, and the result 

 is an orderly change in the position of the body as a whole which is 



Fig. 241. Reflex figures. A, the position of the cat in decerehrate rigidity. B, C, D, re- 

 spectively, are the reflex figures resulting from stimulating the left pinna, the left forefoot, and the 

 left hind foot. (After Sherrington.) 



significant in meeting the exigency which has given rise to the reflex 

 response. The reflex figure which we have just described might be 

 brought into play, for example, when a cat steps on some object which 

 hurts its hind foot. The hind foot is lifted from the ground by 

 virtue of the contraction of the flexors and the compensatory inhibi- 

 tion of their antagonists. The weight of the hind quarters is thus 

 thrown on the contralateral hind leg, which extends to support this 

 weight, preventing the animal from sitting on the source of discom- 

 fort. At the same time the cat must prepare to move away so that 

 the stimulus may not be encountered again, and for this act the exten- 

 sion of the crossed hind leg and of the homolateral fore-foot, with their 

 backward thrust, tend to throw the body forward and support it while 

 the flexion of the stimulated hind leg and the crossed fore leg move 



