Observations on Young Mammals. 113 



after the eyes are opened. It seems to be but slowly 

 developed in the dog and cat, and is never so marked as 

 with man. For some days after the eyes are open, the 

 time being longer for the dog than the cat, Dr. Mills found 

 it difficult to get evidence of anything like distinct sight, 

 and, in the dog especially, sight seems at this stage quite 

 subordinate to smell. In the rabbit, too, on the sixteenth 

 day, Dr. Mills can say no more than " I think they begin 

 to distinguish objects by sight." In these cases experience 

 seems to play an important part in the development of 

 anything like distinct vision. 



The rabbit, like the kitten and the dog, appears to be 

 deaf at birth; but one moved its head and ears on the 

 tenth day (twelfth in the case of the Himalayan rabbit) 

 when a dog-whistle was sounded. The kitten showed 

 signs of hearing on the eighth day ; but it was not till 

 the seventeenth day, or thereabouts, that puppies 

 responded in a definite way to sounds; the responsive 

 ear-movements in the two animals being somewhat 

 different. The hearing soon becomes delicate and 

 accurate as to direction. In such observations it is, of 

 course, necessary to remember that it is only by the 

 answering movements that one can obtain any evidence 

 of sensation. It may be that there are sensations, but 

 that answering movements are not yet developed in re- 

 sponse to them ; on the other hand, what we interpret as 

 a felt sensation may be at first only a physiological 

 stimulus. 



Much has been written on the instinct or reflex of 

 sucking. There is no doubt that the lip and mouth- 

 movements for sucking may be initiated in a just-born 

 infant or young mammal by inserting any suitable object 

 into the mouth. Prof. Preyer found that with young 

 guinea-pigs, only eight to sixteen hours old, and separated 



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