THE PSYCHIC DEVELOPMENT OF YOUNG ANIMALS 157 



element of will as well as a fine example of neuro- 

 muscular co-ordination. 



The study of the development of such acts as 

 scratching, and that next to be referred to, are very 

 suggestive and instructive to the physiologist and 

 psychologist. I call special attention to this reflex 

 and its psychic effects referred to in the diary on 

 the 17th day, and, in the case of the Bedlington 

 terriers, on the 30th day. 



WAGGING OF THE TAIL. The tail movements of 

 the dog are so expressive that the history of their 

 development, and the analysis of their meaning at 

 the various stages of the evolution of his life, are 

 of more than ordinary interest. They are to him 

 what words are to mankind. 



It is notable that I have been unable to be positive 

 as to the existence of any tail movements during the 

 period when the eyes are unopened, and this alone is 

 significant of the relatively low state of development 

 at this period. The reader is referred to the records 

 of the 13th, 17th, 21st, 23rd, 28th, 31st, 35th, and 

 42nd days especially for notes that bear on this 

 subject. 



These movements, positions, etc., of the tail have 

 been to me signs of great significance, but I will leave 

 the reader to draw his own conclusions. Certain it is, 

 they are characteristic of certain stages of development, 

 but if I were to go into full detail in reference to all 

 they have suggested, this paper would become of in- 

 ordinate length. It throws not a little light on this 

 subject to remember that a centre for tail movements 

 has been demonstrated in the cerebral cortex of the 

 dog. 



SOCIABILITY. Of all animals known to us the dog 

 is the most sociable. This he early indicates by his 

 tail, the expression of his face, his attitudes, locomotive 



