576 Professor C. Lloyd Morgan [Jan. 28, 



perience. My conception of " present," as I have elsewhere described 

 it, is that short but appreciable period of time, occupying only some 

 small fraction of a second, which is comprised in the fleeting moment 

 of consciousness. All anterior to this, if it were but a second ago, 

 I regard as past — past, that is to say, in origin, though still operative 

 in the limited field of the present moment. When we are reading a 

 paragraph and near its close, the net result of all that we have read 

 in the earlier sentences is present to influence the course of our 

 thought. But the very words — " all that we have read " — by which 

 we describe this familiar fact, imply that the guiding experience 

 originated in a manner which demands the use of the past tense. 

 Still I am none the less grateful to Mr. Stout for indicating what to 

 many may have seemed a serious omission in my interpretation. 

 Sufiice it to say that if we include under the phrase " present ex- 

 perience " the occurrences of five minutes or even of five seconds ago 

 (all of which I regard as past), I fully agree that present experience 

 (in this sense) exercises a most important guiding influence. 



We have distinguished four classes of messages afi'ecting con- 

 sciousness in the central office of the sensoriura : first, stimuli of the 

 special senses ; secondly, internal cravings ; thirdly, motor sensations 

 due to bodily activity ; and fourthly, emotional states. These are 

 combined in subtle synthesis during the growth of experience, and 

 are associated together in varied ways. Into the manner in which 

 experience grows we cannot enter here. It will be sufficient to 

 indicate very briefly the effects of this growth on the behaviour of 

 animals in the earlier stages of their life. This may be considered 

 from a narrower or from a broader standpoint. In the narrower view 

 we watch how, within the field of widening synthesis, particular 

 associations are formed. We see how, within experience, the taste 

 and appearance of certain caterpillars or grubs become so associated 

 that for the future the larva is left untouched. Or we see how that 

 terrible pounce of the cat becomes so associated with her appearance 

 as thenceforth to render her an object of dread to enlightened spar- 

 rows. But of the physiological mechanism of association we know 

 little. 



There is a familiar game in which a marble is rolled down an 

 inclined board at the bottom of which are numbered compartments. 

 The lower part of the board is beset with a series of vertical pins so 

 arranged that the marble, rebounding from one to another, pursues 

 a devious course before it reaches its destination. But if we tie 

 threads from pin to pin we may thus direct the course of the marble 

 along definite lines. Now the brain may be roughly likened to a 

 set of such pins, and the marble to an incoming nerve current. The 

 congenital structure is such that a number of hereditary threads con- 

 nect the pins in definite ways, and direct the discharge into appro- 

 priate channels. But a vast number of other threads are acquired 

 in the course of individual experience. These are the links of 

 association which direct the marble in new ways. Observation of 



