THE PSYCHIC DEVELOPMENT OF YOUNG ANIMALS 149 



subject of pain on the first day, even in the first hour. 

 This has been made good in part by brief extracts 

 from a diary kept of a litter of Bedlington terriers, 

 previously introduced. Such experiments are necessary, 

 as the discomfort one witnesses in young puppies might 

 be due in certain cases to internal and not to skin 

 sensations. 



TACTILE SENSIBILITY. Very striking, indeed, are the 

 effects on a puppy of any age up to two months (and 

 noticeable even in mature dogs) of stroking, smoothing 

 movements with the hand. In some very young 

 animals, as birds, I find a similar effect, due to placing 

 the hand on them or over them. In this case the 

 effect is largely due to the heat of the hand ; in young 

 puppies the gentle tactile stimulus is the principal, but 

 not the sole cause of the quieting effect. In this way 

 a puppy may, when very young, soon be put to sleep, 

 i.e. the activity of the nervous centres is inhibited by 

 tactile sensations, so that the frequent lickings of the 

 dam not only cleanse but soothe the puppies. There 

 is, after the eyes are opened, a very rapid increase in 

 the acuteness of tactile sensibility, well shown in the 

 readiness with which a slight touch on the lips will 

 induce motor response, especially well seen in sucking 

 movements, etc. 



TEMPERATURE SENSE. Experiments in this subject 

 were, unfortunately, not made in the early days. How- 

 ever, I tested a kitten, five days old, with an iron 

 warmed and also with ice, getting decisive results of 

 a positive kind. I think that it is likely that the 

 temperature sense is well marked from the first, though 

 the squirming, cries, etc., of young animals are not of 

 themselves conclusive as to this. 



THE MUSCULAR SENSE. On this subject a few words 

 will suffice. Considering how numerous and perfect 

 are the co-ordinated muscular movements of compara- 



