EVOLUTION AND SIGNIFICANCE OF CEREBRAL CORTEX 309 



so inwrought into the course of the process that it cannot be dissociated. 

 Each step is an integral part of a unitary adaptive process to serve a definite 

 biological end, and the animal's motor acts are not satisfying to him unless 

 they follow this predetermined sequence, though he himself may have no 

 clear idea of the aim. 



These reactions are typical organic circuits. The cycle in some of the 

 instincts of the deferred type comprises the whole life of the individual. 

 In other cases the cycle is annual (as in bird migrations, etc.), diurnal, or 

 linked up with definite physiological rhythms (e. g., the nidification of birds 

 as described by F. H. Herrick, see p. 61). In still other cases there is no 

 apparent simple rhythm. But always the process is not a simple sequence 

 of distinct elements, but rather a series of reactions, each of which is shaped 

 by the interactions of external stimuli and a preformed or innate structure 

 which has been adapted by biological factors to modify the response to the 

 stimuli in accordance with a purpose, which from the standpoint of an out- 

 side observer is teleological, i. e., adapted to conserve the welfare of the 

 species. 



Every intelligently directed response to external stimulation involves a 

 large measure of highly complex unconscious cerebration of this type; 

 and it is possible to describe with considerable precision the mechanisms of 

 the subcortical activities involved in many of those organic circuits which 

 are commonly regarded as typically cortical. 



Much of that which goes in psychological literature under such contra- 

 dictory terms as unconscious mind or subconscious mind is, in reality, the 

 subcortical elaboration of types of action system which ordinarily do not 

 involve the cortex at all, but which upon occasion may be linked up with 

 cortical associational processes and then come into consciousness in such a 

 form as to suggest to introspection that they are all of a. piece with the 

 conscious process with which they are related. In fact, within the cortex 

 itself there are doubtless many routine activities which do not ordinarily 

 come into consciousness, particularly of the sort known as acquired autom- 

 atisms or lapsed intelligence; and these, though of quite different origin 

 from the innate instinctive systems, cannot easily be distinguished from 

 them in the form in which they are experienced in the adult. 



In the organic circuit as defined by Dewey the process is considered as a 

 whole, so that the response is conceived as logically implicit in the stimulus. 

 The motor reaction, he says, is not merely to the stimulus; it is into the 

 stimulus. "It occurs to change the sound, to get rid of it. What we 

 have is a circuit, not an arc, or broken segment of a circle. This circuit is 

 more truly termed organic than reflex, because the motor response deter- 

 mines the stimulus just as truly as sensory stimulus determines movement." 

 This notion, which is difficult for the practical scientific mind to understand, 

 is considerably clarified by some neurological considerations. 



From the standpoint of the cerebral cortex considered as an essential 

 part of the mechanism of higher conscious acts, every afferent stimulus, as 

 we have seen, is to some extent affected by its passage through various sub- 

 cortical correlation centers (i. e., it carries a quale of central origin). But 

 this same afferent impulse in its passage through the spinal cord and brain 

 stem may, before reaching the cortex, discharge collateral impulses into the 

 lower centers of reflex coordination, from which incipient (or even actually 

 consummated) motor responses are discharged previous to the cortical reac- 

 tion. These motor discharges may, through the "back stroke" action, in 

 turn exert an influence upon the slower cortical reaction. Thus the lower 



