40 ANTS AND SOME OTHER INSECTS. 



odor of violets, a sensation of hunger, or a stomach-ache, are in- 

 capable of recalling in me either simultaneous or subsequent odors 

 or feelings. 



These latter conditions call up in my consciousness much 

 more easily certain associated visual, tactile, or auditory images 

 (e. g., the visual image of a violet, a table set for a meal). As 

 ideas they are commonly to be represented in consciousness only 

 with considerable difficulty, and sometimes not at all, and they are 

 scarcely capable of association among themselves. We readily ob- 

 serve, moreover, that visual images furnish us mainly with space 

 recollections, auditory images with sequences in time, and tactile 

 images with both, but less perfectly. These are indubitable and 

 well-known facts. 



But when we seek for the wherefore of these phenomena, we 

 find the answer in the structure of the particular sense-organ and 

 in its manner of functioning. 



It is well known that the eye gives us a very accurate image 

 of the external world on our retina. Colors and forms are there 

 depicted in the most delicate detail, and both the convergence of 

 our two eyes and their movement and accommodation gives us be- 

 sides the dimensions of depth through stereoscopic vision. What- 

 ever may be still lacking or disturbing is supplied by instinctive 

 inferences acquired by practice, both in memory and direct per- 

 ception (like the lacunae of the visual field), or ignored (like the 

 turbidity of the corpus vitreum). But the basis of the visual im- 

 age is given in the coordinated tout ensemble of the retinal stimuli, 

 namely the retinal image. 1 Hence, since the retina furnishes us 

 with such spatial projections, and these in sharp details, or rela- 

 tions, definitely coordinated with one another, the sense of sight 

 gives us knowledge of space. For this reason, also, and solely on 

 this account, we find it so easy to supply through memory by asso- 



1 It is well known that in this matter the movements of the eyes, the move- 

 ments of the body and of external objects play an essential part, so that without 

 these the eye would fail to give us any knowledge of space. But I need not discuss 

 this further, since the antennae of ants are at least quite as moveable and their 

 olfactory sense is even more easily educated in unison with the tactile sense. 



