STIMULI TO INVOLUNTARY MOVEMENT
Notion of Stimulus . An involuntary reaction in movement has already been analyzed into its three aspects or parts, i. e., stimulus, consciousness of reaction, and actual movement. Further, the second of these elements has been reduced to the third in cases where volition does not enter. Leaving the third for discussion in connection with voluntary movement, it remains to inquire into the nature of the various stimulations which issue in conscious but involuntary reaction.
By stimulus is meant the affective experience of any kind which tends to issue in conscious motor reaction. Looked at from the side of the nervous system it is the new element of tension, whence ever it comes, which disturbs the equilibrium outward. And from what we already know of the nervous system we readily see that such new elements of tension may come either from some condition of the nervous organism or from outside the system. Accordingly stimuli to the reactive consciousness may be distinguished as organic and extra-organic.
I. Extra-organic Stimuli to Movement: Reflexes . The various special kinds of stimulation, as light, sound, etc., have already been sufficiently discussed, as also have the external causes of the more obscure phases of sensibility.
All reflexes are stimulated from without, and they cover a wide range of phenomena. They occur in earliest child.____________________