THE CENTRAL NERVOUS SYSTEM 867 



which causes fear or rage, ' and that our feeling of the same changes 

 as they occur is the emotion ' (James). Sherrington, however, has 

 shown that in dogs in which, by transection of the vagi and the 

 spinal cord, all sensation of viscera, skin, and muscles behind the 

 level of the shoulder was eliminated, no obvious emotional defect 

 was caused. Notwithstanding the immense abridgment of the field 

 of sensation, anger, joy, fear, disgust (as on being offered dog's flesh, 

 which most dogs refuse to eat), were as marked as ever, and were evoked 

 by the same objects as before the operation. When the afferent 

 field is still more restricted, as in the head of a dog grafted on the 

 circulation of another dog by anastomosis of the bloodvessels, with 

 precautions to avoid interruption of the blood-flow, not only does the 

 respiratory centre continue to discharge itself with a regular rhythm, 

 but cortical volitional movements persist (Guthrie, Pike and Stewart), 

 and, so far as can be judged, sense perception, emotional, and even 

 intellectual, processes continue. In one case the picture presented 

 by the engrafted head was essentially the same as that presented by 

 the head of the 'host ' for over two hours. In a transplanted head 

 from a younger dog in which the circulation had been interrupted 

 for twenty-nine minutes, a remarkable return of cerebral function 

 was observed (Guthrie). 



Localization of Function in the Central Nervous System. 

 Let us now consider a little more closely the real meaning of 

 this localization of function. Scattered all over the grey matter 

 of the primitive neural axis, and, as we have seen, over the grey 

 mantle of the brain as well, are numerous ' centres ' which seem 

 to be related in a special way to special mechanisms, sensory, 

 secretory, or motor. The question may fitly be asked whether 

 those centres are really distinct from each other in quality of 

 structure or action, or whether they owe their peculiar properties 

 solely to differences in situation and anatomical connection. It 

 is clear at the outset that the nature of the work in which a centre 

 is engaged must be largely determined by its connections. The 

 kind of activity which goes on in the vaso-motor centre in the 

 bulb, for example, may in no essential respect differ from that 

 which goes on in the respiratory centre. The calibre of the 

 bloodvessels will alter in response to a change of activity in the 

 one because it is anatomically connected with the muscular coat 

 of the bloodvessels. The rate or depth of the respiratory move- 

 ments will alter in response to a change of activity in the other 

 because it is connected with muscles which can act upon the 

 chest-walls. 



Recent experiments afford a very interesting illustration of 

 the determining influence of their peripheral ' connections on 

 the function- of nerve-fibres. It has, in fact, been shown that 

 the central end of any efferent somatic fibre i.e., any fibre 

 running from the central nervous system and ending in striated 

 muscle can make functional connection with the peripheral 

 end of any other efferent fibre of the same class, whatever be 

 the normal actions produced by the two fibres. Advantage has 



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