68 STELLA BURNHAM VINCENT 



By associative memory a tinge of the affective tone of 



the consummatory reaction may suffuse the anticipatory. The 

 latter becomes indirectly a pleasure-pain reaction." ^^ 



Anatomical considerations as well as the experiments upon 

 the maze had seemed to show that the sense of sight was very 

 weak and imperfect in the rat.^° It may seem that the course 

 of this discussion would imply a reversal of this conclusion but 

 such an implication would be erroneous. The first statement 

 and previous work had shown wherein the sense was deficient, 

 these experiments together with those of others show in what 

 ways it is efficient. Sharp outlines, form, mintite details, etc., 

 no doubt are lacking in the casual experiences of a rat ; but some 

 degree of brightness, shadowy outlines, vague extent of surfaces 

 are also undoubtedly a part of that experience. The copper 

 plates, which it has been inferred entered as a visual factor into 

 the reactions of the normal rats, were bright polished inter- 

 lacing plates screwed upon the dead black surface of the floor 

 of the box. Directly above them, not quite three feet distant 

 was an electric light. These animals were used at night and if 

 brightness discrimination is possible at all it must surely have 

 been so here. 



It may be said in view of this discussion that vision, though 

 not the necessary sense to the accomplishing of this task, excites 

 activities, arouses impulses, permits the formation of associa- 

 tions which make success easier of attainment. It may also 

 be concluded with reason, and what is said here is only in the 

 light of this problem, that the loss of vision does not make the 

 tactile sense more keen but only more necessary and that vision, 

 even poor as it is in rats, is an inestimable boon in the life of 

 any animal. It is the sense which, because of its general exciting 

 and tonic effect, spurs it on; by extending the environment, 

 leads it out in new ways; guides it, however inaccurately, to 

 places where it would never go; and warns it of danger while 

 there is still time for escape. 



(c) The normal rats. — The behavior of these rats was so sim- 

 ilar to that of those used before that it is not necessary to go 

 into it here. A comparison of the records of the normal rats of 

 the two series shows that the numerical results are almost iden- 



^* Sherrington, C. S. : Integrative Action of the Nervous System, 1906, p. 326. 

 *' Vincent, S. B.: The Mammalian Eye, Jour. Animal Behavior, 1912, vol. 2, no. 4. 



