CEREBRO-SPINAL NERVOUS CENTRES IN GENERAL. 



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table, which is intended to represent the ordinary course of operation when 

 the whole is in a state of complete functional activity, and the character of 

 the " reflex" actions to which each part is subservient, when it is the highest 



Intellectual Operations. 

 I 4- 



Emotions. 



WILL 



-CEREBRUM. 



centre of emotional and idea-motor reflexion. 



Sensations. - 



--{-SENSORY GANGLIA- 



centre of sensuri-motor reflexion. 



Impressions. 



-SPINAL CORP 



[ Motor Impulse. 



or SYMPATHETIC GANGLION, 



centres of excilo-ntolor re-flexion. 



j 



centre that the impression can reach. The directing power of the Will 

 eeems to be most strongly exerted over those actions which are most closely 

 connected with psychical changes, and which are exclusively Cerebral in their 

 seat. It has been already pointed out, that the Cranio-Spinal axis not 

 merely serves as the channel for the reception of the impressions which ex- 

 cite the activity of the Hemispheric ganglia, and as the instrument whereby 

 the results of their operation are brought to bear upon the muscular system; 

 but that it is also the centre of reflexion through which various automatic 

 movements are called forth, that are immediately concerned in the main- 

 tenance of the organic functions. The impressions which excite these move- 

 ments do not in general pass on to the Cerebrum ; for we only perceive them 

 when we specially direct our attention to them, or when they exist in unusual 

 potency. Thus we are unconscious of the ''besom de respirer" by which our 

 ordinary movements of respiration are prompted; and it is only when we 

 have refrained from breathing for a few seconds, that we experience a sen- 

 sation of uneasiness which impels us to make forcible efforts for its relief. 

 Notwithstanding, however, that the Cerebrum is thus unconcerned in the 

 ordinary performance of those automatic movements, yet it can exert a certain 

 degree of control over many of them, so as even to suspend them for a time, 

 though in no instance can it carry this suspension to such an extent as 

 seriously to disarrange the Organic functions ; thus, when we have volun- 

 tarily refrained from breathing for a few seconds, the inspiratory impulse so 

 rapidly increases in strength with the continuance of the suspension, that it 

 at last overcomes the most powerful effort we can make for the repression of 

 the movements to which it prompts ( 300, note). Now in this and similar 

 cases it would seem as if the Will interfered to prevent that direct trans- 

 verse passage of the stimulus from the afferent to the efferent nerves through 



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