76 PSYCHOLOGY. 



combinations of movement and impression the co-operatioii 

 of the hemispheres is necessary from the start. Even in 

 birds and dogs tlie power of eating properly is lost when 

 the frontal lobes are cnt off.* 



The plain truth is that neither in man nor beast are the 

 hemispheres the virgin organs which our scheme called 

 them. So far from being unorganized at birth, they must 

 have native tendencies to reaction of a determinate sort.f 

 These are the tendencies which Ave know as emotions and 

 instincts, and which we must study with some detail in later 

 chapters of this book. Both instincts and emotions are reac 

 tions upon special sorts of objects of perception ; they de- 

 pend on the hemispheres ; and they are in the lirst instance 

 reflex, that is, they take place the first time the exciting ob- 

 ject is met, are accompanied by no forethought or delibera- 

 tion, and are irresistible. But they are modifiable to a 

 certain extent by experience, and on later occasions of 

 meeting the exciting object, the instincts especially have 

 less of the blind impulsive character which they had at 

 first. All this will be explained at some length in Chapter 

 XXIV. Meanwhile we can say that the multiplicity of emo- 

 tional and instinctive reactions in man, together with his 

 extensive associative power, permit of extensive recouplings 

 of the original sensory and motor partners. The conse- 

 quences of one instinctive reaction often prove to be the 

 inciters of an opposite reaction, and hoing suggested on later 

 occasions by the original object, may then suppress the 

 first reaction altogether, just as in the case of the child and 

 the flame. For this education the hemispheres do not need 



* Groltz : Ptiiiger's Archiv, vol. 42, p. 447 ; Schrader: ibid. vol. 44, p. 

 219 ff. It is possible that this symptom may be an effect of traumatic 

 inhibition, however. 



f A few years ago one of the strongest arguments for the theory that 

 the hemispheres are purely supernumerary was Soltmann's often-quoted 

 observation that in new-born puppies the motor zone of the cortex is not 

 excitable by electricity and only becomes so in the course of a fortnight, 

 presumably after the experiences of the lower centres have educated it to 

 motor duties. Paneth's later observations, however, seem to show that 

 Soltmann may have been misled through overnarcotizing his victims 

 (Pflliger's Archiv, vol. 37, p. 202). In the Neurologisches Centralblatt 

 for 1889, p. 513, Bechterew returns to the subject on Soltmann's side with- 

 out, however, noticing Paneth's work. 



