54 MIND IN EVOLUTION CHAP. 



Understanding that this comparatively rapid process of 

 acquisition in individual experience, which we find in the 

 higher and more adaptable animals, is replaced in the lower 

 orders by natural selection acting in the course of genera- 

 tions upon the race, we have in this instance the whole 

 scheme of the development of the reflex in a concrete 

 illustration. There is a stimulus which disturbs the 

 equilibrium of the organism. A certain reaction would 

 restore that equilibrium. The first result of the disturb- 

 ance is a series of random actions. These fail to remove 

 the source of disturbance. At length one succeeds. This 

 one has an advantage subsequently over others if the 

 individual is capable of training, and in course of time the 

 tendencies to perform this act preponderate over all others. 

 If the individuals of the species are not capable of training, 

 those which in their random movements come nearest to 

 the one required will have a certain advantage in the 

 struggle for existence, and thus in a more roundabout way 

 the reflex mechanism is built up by inheritance. 



10. The random, undifferentiated actions out of which 

 we suppose the reflex to be hewn are no mere fiction 

 of the scientific imagination. The random movements 

 of internally initiated activities are matched by numerous 

 instances of quite random reflexes. The latter occur 

 in all conditions of over excitability. Great joy and 

 pain throw the whole body into motions not adapted 

 to serve it in any way unless the draining off of the 

 excitement be itself regarded as a service. If any 

 stimulus be greatly increased in intensity, it not merely 

 calls forth the movements suited to dealing with it, 

 but brings more and more muscles into action till the 

 whole body may be convulsed. 1 There is a tendency, 



1 Instances of undifferentiated or purposeless nervous discharge are 

 well seen in pathological states. In cases of injury to one hemisphere, 

 Goltz speaks of a regular " Entfesselung der reflektorischen vorgange " 

 (op. cit. p. 59). In another dog a curious special reflex putting out the 

 tongue and licking the nose appeared regularly in response to tickling 

 of the back. Evidently the response has nothing to do with the stimulus, 

 and we can only suppose that the excitation of that particular part 

 happened for some reason to find the line of least resistance in discharging 

 along the nerve paths, ending finally in the muscles of the tongue. On 

 the permanent inhibitory function of that part of the cerebrum which he 

 calls the association centres, see Flechsig, Gehirn und Seele^ p. 32. The 



