THE PSYCHIC DEVELOPMENT OF YOUNG ANIMALS 269 



which they are reflex, or according to the facility with 

 which higher centres use lower ones, and thus economise 

 psychic energy. 



But even so early as the 12th to the 15th day 

 new movements are possible. The eyes have opened, 

 the ears also, and both eyes and ears move, rather 

 reflexly at first beyond doubt, but very soon the puppy 

 moves both eyes and ears voluntarily at times, and 

 still later he fixes the eyes, which is clearly a voluntary 

 act. 



It is obvious that there is now an approach to walk- 

 ing (instead of crawling). There are tail movements 

 by the 17th day, and the scratching reflex is excitable. 

 The tail movements are, at this period, almost certainly 

 reflex. Voluntary movements of the tail do not seem 

 to be possible till a good deal later, which corresponds 

 with the well-established fact that the cortical centre 

 for tail movements is not developed till comparatively 

 late. 



The barking of the 19th day was probably a reflex, 

 much simpler than such as results later. At this stage, 

 puppies often bark in their sleep, not a common occur- 

 rence with mature dogs, though it does take place in 

 dreaming. By the 23rd day, the puppies stand with 

 the paws on the edges of the boards constituting the 

 walls of their pen. This act may be reflex at times, 

 possibly, but on other occasions it is clearly voluntary, 

 and, as they try to get out, we are left in no doubt that 

 they are capable of willed movements, so that by this 

 time, and probably before, there are undoubted volun- 

 tary movements. Corresponding with this advance, 

 I have found before the 20th day very distinct cortical 

 localisation for the limbs, head, and face. 



Later than this, improvement in reflexes is noticeable, 

 but still more the rapid development of older and the 



