38 STELLA BURNHAM VINCENT 



tance by the fatigue produced in achieving it, in terms of time, 

 or the units taken to cover it, i.e. steps. But all these prove 

 more or less inexact. The precise point to be attained has to 

 be marked by some visual or tactual object. 



Second, it may be that if such problems are learned in sections 

 and largely through kinaesthetic factors, that too great an 

 interval of time must not elapse between the sections in order 

 for them to be synthesized into a whole. That is, in this case 

 the sluggishness of the animal may have prevented any entire 

 organizat on of the series. 



Third, and this is probably an important factor, the distur- 

 bances of equilibrium brought about by loss of both sight and 

 vibrissae render the acquiring of any such cooordination by 

 these animals almost impossible. 



Figs, 15, 16, 17, 18 and Plates II and III, show characteristic 

 positions of the animals in some of these experiments. The normal 

 rat keeps to the middle of the path as a rule. The blind rats 

 follow edges with vibrissae and use feet and toes much over the 

 edges. The picture of the blind rat without vibrissae shows the 

 way they use noses also The rat whose nerve is cut stands with 

 feet far apart for balance and head up — a characteristic pose. 



H. Summary of Labyrinth Experiments with Conclusions 



Experiment I showed that so far as concerns mazes, this one 

 w^as entirely comparable w4th others of its kind and the results 

 with normal animals were typical results. In Experiment II, 

 and all the other labyrinth experiments, the same maze was 

 used with no sides to the runways. A very different type of 

 behavior was revealed ; but the results showed, as had been sus- 

 pected, that although entirely open it was still a maze to the 

 rats and the difficulties were not lessened. The next. Experi- 

 ment III, with rats with no vibrissae was made under greater 

 difficulties. There was increase in errors, decrease in speed, 

 slightly lengthened learning period and a great number of slips 

 and falls with much incoordination in the whole behavior. 

 When Experiments IV and V were reached where the vibrissae are 

 cut on one side it was found that a condition was produced 

 which was actually helpful in this problem. The animals fol- 

 lowed the edges of the paths with their vibrissae and being forced 

 to keep to one side learned the maze in less time than any other 



