FUNCTIONS OF THE CEREBRUM. 525 



bral convolutions and proceeding to the muscles, yet a careful analysis 

 of the process fully bears out the idea already put forwards, that the 

 Will really operates through the Automatic apparatus, exciting parti- 

 cular groups of muscular actions, just as they would be called forth by 

 sensations directly excited by external objects. For it has been shown 

 that the Cranio-spinal Axis (consisting of the Sensory Ganglia, Me- 

 dulla Oblongata, and Spinal Cord) receives all the sensory nerves, 

 and gives origin to all the motor ; and that the fibres which pass between 

 the Cerebral convolutions and the Sensory Ganglia, probably serve to 

 bring these centres into mutual relation, and are not continuous with 

 those of any nerves, either sensory or motor. And we might expect, 

 therefore, that the addition of a Cerebrum to this automatic apparatus 

 would have the effect of supplying a new stimulus to movement, which, 

 whilst proceeding from mental operations, should still act through the 

 same mechanism as that already provided for the reflex and consensual 

 movements. Now when we attentively consider the nature of what we 

 are accustomed to call voluntary action, we perceive that the agency of 

 the Will is limited to the determination of the result ; and that it has 

 nothing to do with the selection and co-ordination of the individual 

 movements, by which that result is brought about. If it were other- 

 wise, we should be dependent upon our anatomical knowledge, for our 

 power of performing even the simplest movements of the body. Again, 

 there are very few cases in which we can single out any individual 

 muscle, and put it into action independently of others ; and the cases in 

 which we can do so, are those in which a single muscle is concerned in 

 producing the result, as in the elevation of the eyelid ; and we then 

 really single out the muscle by "willing" the result. Thus, then, how- 

 ever startling the position may at first appear, we have a right to affirm 

 that the Will cannot exert any direct or immediate power over the 

 muscles ; but that its determinations are carried into effect through an 

 intermediate mechanism, which, without any further guidance on our own 

 part, selects and combines the particular muscles whose contractions are 

 requisite to produce the desired movement. We have seen that the 

 Sensorial centres play (so to speak) upon the Cerebrum, sending to it 

 impressions of a kind fitted to call forth its peculiar activity as an instru- 

 ment of purely mental operations ; and in return, the Cerebrum appears 

 to play downwards upon the motor portion of the automatic apparatus, 

 sending to it volitional impulses which excite its motorial activity. And 

 thus we see that the very same action may be excited through an impres- 

 sion conveyed to the centres of the whole system through some one or 

 more nerves of the external senses, or through the fibres converging to 

 them from the cerebral convolutions, which have been not unaptly 

 called " the nerves of the internal senses ;" and may hence be automatic 

 in the first case, and voluntary in the second. For example, in the act 

 of Coughing, we have the very same combination and succession of 

 diverse but mutually-related actions, whether the operation be excited 

 by the presence of an irritating particle in the air-passages, or be per- 

 formed as the consequence of a voluntary effort. And a little attention 

 to his own consciousness will satisfy the reader, that as regards the 

 selection and co-ordination of the movements which are concerned, the 



