THE PHYSIOLOGY OF THE BRAIN. 625 



movements the cortical area connected through the pyram- 

 idal tract with the muscles concerned is the place from 

 which efferent impulses start throwing into action lower 

 centres which more immediately co-ordinate the muscles: 

 these lower centres in mid brain, cerebellum, medulla or cord 

 may of course be thrown into reflex action by afferent im- 

 pulses having no connection with the cortex, and to the eye 

 the resulting movement would be exactly the same as a 

 willed one. In another person, and still more in a dog or 

 monkey, we must often be in doubt whether an action is or 

 is not intentional; and as already pointed out, many move- 

 ments of our own which were at one time even painfully in- 

 tentional become quite unconscious after* practice and are 

 carried out by lower centres. It is also to be borne in mind 

 that the cortical area from which the efferent processes of a 

 willed movement make their start is in connection by as- 

 sociational and other commissural fibres with many other 

 regions of the cortex, and with fibres from the optic thalamus 

 which may bring nerve impulses exciting it, and it is also in 

 connection with the whole gray cortical network, so that the 

 brain antecedents or excitants leading to a given movement, 

 either alone or in combination with others, may be very 

 different, and may be associated or not with concomitant 

 sensations or emotions. 



Take such a movement as clenching the fist. On a corpse 

 this might be brought about by pulling on the flexor tendons 

 of the digits, but in an imperfect way; or, again in a very 

 imperfect manner by stimulation of the motor nerves of the 

 flexor muscles in the arm of a living person. If, however, we 

 knew exactly the proper sensory fibres in spinal nerve-roots 

 to stimulate and could thus act on the centre co-ordinating 

 the proper muscles, there is no doubt we could bring about 

 reflexly, and apart from all consciousness, a quite normal 

 clenching movement. Next suppose a person struggling for 

 breath : as his extraordinary muscles of respiration come into 

 play his fists are clenched; here impulses from the medulla 

 oblongata travel down the cord and throw the " clenching " 

 spinal centre into activity along with many other muscles, 

 and co-ordinating them all so as to give as good a pull as pos- 

 sible to ail muscles which can help an inspiration. In a 

 higher but still not volitional stage, more groups of muscles 

 are concerned, and centres of co-ordination in the pons and 



