THE CONSCIOUS ASPECT 103 
factors, we may perhaps, at any rate, go so far as to give pro- 
visional acceptance to the view that in instinct these wants 
and felt needs enter into the conscious situation in a manner 
and to a degree that are so far distinctive—which seems to be 
the position adopted by Professor Wundt. 
There is, however, a further relation between the external 
stimulus and these internal factors which is presumably of no 
little importance. The stimulus intensifies the want, or may 
in some cases call it into existence. Just as a whiff from the 
kitchen may lead us to realize that we need the satisfaction 
that will erelong be presented at table, so may the sight of 
his mate in the spring evoke in the breast of the yearling 
sparrow a need, having its source in morphological and 
physiological changes, that spurs him on to the courtship that 
shall lead to its due satisfaction. Popular attention has, 
indeed, been so naturally drawn to the internal needs or wants 
with which we are now dealing, as to give them an almost 
exclusive monopoly of the term “ instinct,” which thus often 
comes to be regarded asa connecting link between the stimulus 
and the act. The sight of a mouse, for example, is said to call 
forth the instinct of the cat, which is satisfied by her pouncing 
upon it. And so it comes about that, while the biologist 
fixes upon the instinctive act as the essential feature, the 
psychologist is apt to regard the impulse * which prompts to 
action as the more central and characteristic element. We are 
here endeavouring to combine both these points of view. 
To come to closer quarters with the relationship which 
holds good between the external and internal elements, it 
appears that, when the stimulus evokes or intensifies the want 
or need, this is probably effected by efferent waves which call 
the organs or parts into tonic action, of which the animal 
becomes conscious through the afferent messages which come 
in from them to the sensory centres ; in much the same way 
as the whiff from the kitchen takes effect on the salivary and 
other glands, and throws the organs of digestion into a felt 
preparedness for the fulfilment of their functions. But it 
* On the nature of impulse, see infra, p. 235. 
