Literary Notices. 53 '^ 



point, in others heated to 75° C. In no case did it disturb the rats. Changing 

 the direction of air currents sent through the maze with an electric fan was 

 also without effect. Tests of the rat's sense of taste indicated that it is 

 not delicate enough to be a factor in maze reactions. Very suggestive are the 

 experiments where the rat was put down not at the beginning of the maze but at 

 some point along its course, the results showing that sometimes immediately, 

 sometimes after a certain amount of movement, the rat would get the proper 

 orientation, even if put down with the wrong one, and traverse the remainder of 

 the path without error. The most remarkable results are those obtained when 

 the maze was rotated through an angle of 90°. Both blind and normal rats were 

 decidedly confused by this proceeding, although not a single turn required of them 

 was in any way altered thereby. Dr. Watson suggests the possibility " either that 

 static sensations have a role or else that the rat has some non-human modality of 

 sensation which, whatever it may be, is thrown out of gear temporarily by altering 

 the customary relations to the cardinal points of the compass." When the maze 

 was rotated through 180°, however, blind rats were not disturbed, and there still 

 seems some possibility that further experiments will furnish an explanation involv- 

 ing retinal factors. 



Such are the facts resulting from this careful and painstaking investigation. 

 A few considerations in the way of criticism may be briefly appended. The first 

 of these concerns the value of the method. Without sympathizing with any accu- 

 sations of cruelty, which Dr Watson's account of the condition of the animals 

 after operation shows to have been imfounded, one has still a certain prejudice 

 against turning a normal animal into an abnormal one, even though the abnormality 

 may seem to be restrained within desired limits. This prejudice might be over- 

 come if the conditions could be altered in no other way. But that such is the fact 

 remains to be proved. The role of vision in learning and traversing the maze 

 cannot, Dr. Watson maintains, be investigated by experiments in darkness 

 because adaptation to darkness may be much more rapid and complete in rats 

 than in human beings. Surely this is merely a question of securing a sufficiently 

 dark room. There is no such thing as adaptation to darkness; there is only adapta- 

 tion to faint light; and it ought not to be insurmountably difficult to assure one- 

 self of a degree of darkness in which even the rat cannot make visual discrimina- 

 tions. Similarly with the tactile and olfactory senses; the experimental conditions 

 can be varied so as to exclude them without operating on the animal. 



Again, a certain caution must be observed in making inferences from any 

 experiments thus far designed to study the conditions that influence learning a 

 labyrinth. In the first place, it must be recognized, as Dr. Watson does recognize, 

 that experiments on an animal that has previously learned the labyrinth prove 

 nothing. You do not show, when you show that an animal having learned a 

 maze perfectly is not disturbed by the removal of (say) visual landmarks in its 

 path, that it took no account of the landmarks during the learning process. After 

 it has acquired the habit perfectly, it has become an automaton, and the stimuli 

 originally used as clues have become unnecessary to it. Yet, although Dr. Watson 

 realizes the force of this consideration, he neglects it in his experiments on the 

 temperature sense. The rats that ignored the hot or cold metal plate were 

 practiced rats. Secondly, even if you show that an animal can learn the maze as 

 well in the absence of a given set of stimuli as in their presence, you have not 



