EXPLANATION OF OBSERVATIONS 177 



of this sort has been known concerning the dog for some 

 time. His ability to single out an object upon which his" 

 master had intently fixed his gaze, was made the basis of 

 a special form of training, called " eye-training," ^'^ nearly 

 one hundred yf^^'s ago. The dog was taught to focus 

 constantly upoti his master's eyes and then upon com- 

 mand to select the object which he, the master, had been 

 fixating. Such a dog has been described by the natural- 

 ists A. and K. Mtiller.°^ But the master of the dog, unlike 

 Mr. von Osten, would not permit anyone else to work 

 with the animal, and the two brothers, recognizing the 

 trick, were justified in adding that " the whole afifair 

 aimed at deceiving the public, and the dog's reputation 

 was but a means of making money ". The success of 

 such exhibitions appeared furthermore, to depend upon 

 the close proximity of the trainer and the dog, whereas 

 the direction of the head (and even of the body) could 

 very probably be perceived at greater distances also. 

 At least we learn from a reputable source that in the 

 hunt, dogs can perceive from the mere posture of their 

 master, what direction he intends to take.'* 



But a still more curious fact is this, that dogs, too, learn 

 — evidently spontaneously — to react to the minimal in- 

 voluntary expressive movements of their master. The 

 first example mentioned in the literature on the subject 

 is that of an English bull-dog called Kepler, belonging 

 to the English astrophysicist. Sir William Huggins.^' 

 We are told that this dog seemingly could solve the most 

 difficult problems, such as extracting square roots and 

 the like. The numbers were indicated by barking, — 

 thus one bark was for one, two barks for two, etc. Every 

 correct solution was rewarded with a piece of cake. 

 Huggins states explicitly that he gave no signals volun- 



