40 'Journal of Comparative Neurology and Psychology. 



culty with this corner as with any of the others. He ran into the 

 wall quite hard the first trial, touched it lightly on the second 

 trial and hesitated there the third trial. On the second day, he 

 ran into the wall twice and made the turn correctly thereafter. It 

 may be supposed that this difference between the conduct of the 

 blind rat and that of the normal rats indicates that the latter 

 effected this turn with the aid of visual data. This assumption 

 is hardly legitimate, inasmuch as the normal animals failed to use 

 vision effectively at the other three corners. Neither can one 

 assume that the turn at IV presented visual distinctions not pos- 

 sessed by the other corners, because, if such visual differences 

 exist, they are too minute for the human eye to detect, and, in case 

 the rat possesses a visual acuity superior to that of human beings, 

 it ought to be able to detect a solid wall sufficiently well to refrain 

 from running headlong into it time after time. Again, one may 

 suppose that the normal rats were accustomed to see the opening 

 B before reaching the turn at //, and made the correct adjust- 

 ment in response to this visual cue. On this basis, the normal 

 animals should have had no trouble at the turn V because the 

 opening H bears the same relation to the turn V as does B to the 

 turn //. However, this assumption may be supported by the 

 fact that the cul-de-sac H has been open during the previous 

 experiment, while B has been open only some eight days. One 

 may argue that the normal rats had neglected the opening i/ as a 

 visual cue in the course of the long series of trials which was given 

 them in the learning maze from the first, while the recent opening 

 o{ B had attracted their "visual attention" and they had learned 

 to utilize it as a visual cue. Such a conception is possible, but 

 the argument is based upon a rather precarious foundation. If 

 the rats can see the opening B so as to react to it, it seems that 

 they ought to be able to see the opening into any alley at the turn 

 and utilize it as a visual cue, inasmuch as there is no reason why 

 they should neglect this cue throughout the course of the long 

 series of tests. When the fact was noticed that the normal ani- 

 mals turned the corner // correctly, it was suggested that the 

 shortened alley leading up to //, which is five feet long, possessed 

 the same kinaesthetic characteristics as some alley in the lengthened 

 maze. As a matter of fact, the alley leading from the box O, four 

 and one-half feet long, is very similar to alley //. Hence it could 

 be argued that, since the alleys possess the same motor peculiari- 



