SENSORY MECHANISMS INTRODUCTION 



367 



moment. Clearly we attend to stimuli which are un- 

 expected or are intense in themselves or likely to 

 give rise to a chain of activity by reason of past 

 association, but the afiferent nerxous discharges must 

 be studied at all levels before we can say where and 

 why some fail and some reach through to conscious- 

 ness. Fortunately the investigation of the reticular 



formation has given a new impetus to the studv of 

 attention. With modern techniques the afferent signals 

 can be traced in their passage through the intact 

 brain and we can e.xpect that soon there will be fresh 

 data bearing on this penultimate problem of the 

 sense organs. The ultimate problem of their effect on 

 the mind is scarcely one for the physiologist to settle. 



