REFLEX ACTIONS OF THE COED. 575 



squat on its belly instcad_of_ assuming the more erect posi- 

 Tiion of the uninjured animal; its respiratory movements 

 cease_^ (their centre being removed with the medulla); the 

 hind legs at first remain sprawled out in any position into 

 which they may happen to fall, but after a time are drawn up 

 into their usual position, with the hip and knee joints flexed; 

 having made this movement the animal, if protected from 

 external stimuli, makes no other by its skeletal muscles; it 

 has lost all spontaneity, and only stirs under the influence 

 of immediate excitation. Nevertheless the heart goes on 

 beating for hours; the muscles and nerves, when examined, 

 are found to still have all their usual physiological proper- 

 ties; and, by suitable irritation, the animal can be made to 

 execute a great variety of complex movements. But it 

 is no longer a creature with a will, doing things which we 

 cannot -predict; it is an instrument which can be played 

 upon, giving different responses to different stimuli (as dif- 

 ferent notes are produced when different keys of a piano are 

 struck), ajid always the same reaction to the same stimulus; 

 so that we can say beforehand what will happen when we 

 touch it. Such actions are called reflex or excito-motor and 

 fall into two groups; (1) orderly or purpose-like reflexes, 

 which are correlated to the stimulus and are often defensive, 

 tending, for instance, to remove an irritated part from the 

 irritating object; (2) disorderly or convulsive reflexes, not 

 tending to produce any definite result, and affecting either a 

 limited region or all the muscles of the body. 



In higher animals similar phenomena may be observed. 

 If a rabbit's spinal cord be divided at the bottom of the neck 

 the animal is at first thrown into a flaccid limp condition 

 like the frog, but it soon recovers. Voluntary movements 

 in muscles supplied from the spinal cord behind the section 

 are never seen again; but on pinching the hind foot it is 

 forcibly withdrawn. Men, whose spinal cord has been 

 divided by stabs or disease below the level of the fifth cervical 

 spinal roots (above which the fibres of the phrenic nerve, 

 which are necessary for breathing, pass out), sometimes live 

 for a time, but can no longer move their legs by any 

 effort of the will, nor do they feel touches, pinches, or hot 



