12 STELLA BURNHAM VINCENT 



experimental situations. A very great difficulty arises when 

 an attempt is made to separate the function of the tactual from 

 that of the kinaesthetic or organic. The tactual impulses alone, 

 or in the complex, are the stimuli to the digging movements in 

 Problem I, and in part to the movements of pressing down the 

 plane in Problem II. In the Problem III, certain familiar tactual 

 impressions are evidently the stimuli to the discovery of the 

 latch after the rat has arrived at the locality of the door. Con- 

 tact seems to be the cue to movements which result in the rais- 

 ing of the latch, during both the learning process and the period 

 in which the movements are habitual."* 



She also experimented with the rats in some jumping tests 

 and from her notes these extracts are taken: — " Up to a certain 

 distance the rat was able to step across wHth little difficulty, 

 and the contact of the snout or vibrissae with Platform II seemed 

 to be the essential stimulus in the majority of cases."' 



" This (blind) rat would not allow his fore feet to leave the 

 platform unless his vibrissae reported contact with some object. 

 When the platform was beyond the reach of his vibrissae the 

 experimenter touched their tips with a pencil, whereupon he put 

 out his fore feet to step over." '" 



" She used her vibrissae to locate the platform."" (Another 

 blind rat.) 



Her conclusions are given on page 99. " Touch as a partially 

 controlling factor does, however, enter into the early adjust- 

 ments of the bl nd animals, since they will more readily form 

 the habit of jumping if the snout or vibrissae are stimulated by 

 the platform to which the animal has to jump. This latter 

 statement applies in some degree at least even to animals pos- 

 sessing vision. Once the habit is formed, however the initial 

 tactual impulses can be dispensed with." 



" In regard to the function of the kinaesthetic impulses in the 

 case of the blind animals it seems safe to affirm that they soon 

 come to usurp whatever functions tactual impulses from the 

 snout and vibrissae exert in the learning process." (Jumping.) '^ 



We will postpone a discussion of these conclusions until it 



* Richardson, Florence: A Study of Sensory Control in the Rat. Psychol. Rev. 

 Mon. Sup. 1910, vol. 12, p. 68. 

 » Ibid p. 73. 

 '« Ibid p. 80. 

 " Ibid p. 81. 

 '2 Ibid p. 99. 



