CLASSIFICATION OF MUSCLES. 829 



direct influence upon them, only affecting them indirectly by its power of 

 determining these states. But over those Muscles, also administering to the 

 organic functions, and doing so in obedience to impulses purely automatic, 

 which are called into action by the Cranio-Spiual nerves, the Will, as we 

 have seen, exerts some power; and such, therefore, cannot be properly 

 regarded as involuntary, since the Will can influence their state; whilst 

 they are far from being truly voluntary, since the Will cannot control their 

 tendency to automatic action beyond a certain limited amount ( 294). On 

 the other hand, every one of the Muscles usually styled voluntary, because 

 ordinarily called into action by the Will, is liable to be thrown into action 

 involuntarily; either by an Excito-motor stimulus, as in tetanic convulsions, 

 or by Consensual action, as in tickling, or Emotionally, as in laughter or rage, 

 or simply Ideatioually, as in somnambulism and analogous states. Hence 

 although there are certain groups of muscles which are more frequently 

 acted on by the Will than by any other impulse, and certain others which 

 are more frequently played on by the Emotions, and so on, it becomes 

 obvious that every muscle called into contraction by the Crauio-Spiual 

 nervous system, is capable of receiving its stimulus to movement from any 

 of these sources; the nerve force transmitted along the motor fibres, being 

 issued either from the Spinal Cord, from the Sensory Ganglia, or from the 

 Cerebrum, as the case may be, but being in its nature and effects the same 

 in every instance. 



679. The grouping or combination of muscular actions, which takes place 

 in almost every movement of one part of the body upon another, must be 

 attributed, not to any peculiar sympathy among the Muscles themselves, but 

 to the mode in which they are acted on by the Nervous Centres. This is 

 most obviously the case with regard to those of the primarily automatic 

 class ; but it can scarcely be doubtful as to those of the secondarily automatic 

 kind ( 510), such as walking, which, though at first directed by the Will, 

 comes by habit to be performed under conditions essentially the same with 

 the preceding; and when it is borne in mind that even in voluntary move- 

 ments the Will cannot single out any one muscle from the group with which 

 it usually co operates, so as to throw this into separate contraction, but is 

 limited to determining the result ( 540), it seems pretty obvious that even 

 here the grouping is effected by the endowments of those Automatic centres 

 from which all the motor impulses immediately proceed to the muscles, and 

 not by Cerebral agency. In fact, the whole process by which we acquire 

 the power of adapting our muscular actions to the performance of some new 

 kind of movement, as in the case of an infant learning to walk, a child 

 learning to write, an artisan learning some occupation which requires nice 

 manipulation, a musical performer learning a new instrument, and so on, 

 is found, when attentively studied, to indicate that the Will is far from hav- 

 ing that direct and immediate control over the contractions of the Muscles, 

 which it is commonly reputed to possess; and that the operation really 

 consists in the gradual establishment of a new grouping of the separate ac- 

 tions, in virtue of which, the stimulus of a Volitional determination, acting 

 under the guidance of the muscular sensations ( 536), henceforth calls into 

 contraction the group of muscles whose agency is competent to carry that 

 determination into effect. For, however amenable any set of muscles (as 

 those of the arm and hand) may have become to the direction of the Will, 

 in any operations which they have been previously accustomed to perform, 

 it is only after considerable practice that they can be trained to any method 

 of combined action which is entirely new to them ; and 'even if we attempt 

 to bring our anatomical knowledge into use for such a purpose, by mentally 

 fixing upon certain muscles whose action we wish to intensify and to associ- 



