20 ROYAL SOCIETY OF CANADA 



As pointed out in m}' paper on the functional development of the 

 cerebral cortex, the latter is absolutely inexcitable at birth and for a good 

 many days after, indeed not till about the period of the opening of the 

 eyes, and as I find the white matter also inexcitable at birth there seems 

 to be no other view possible of these movements than that they are retlex 

 and that when the brain is called into action parts lower than the cortex 

 or even the underlying medulla in the youngest puppies must function. 



î^evertheless the animal at this period is pi'Ogi'essing, for the improve- 

 ment of these reflexes implies the more perfect organization of a neuro- 

 muscular mechanism which is probably availed of later in all voluntary 

 movements. 



In adult life our own movements are often carried out with a perfec- 

 tion in proportion to the degree in 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 twelfth to the fifteenth day new move- 

 ments are possible. The ej'es have opened, the ears also, and both eyes- 

 and ears move, rather reflexly at fii*st 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 appi'oach to walking (instead of 

 crawling). There are tail movements by the seventeenth day, and the 

 scratching reflex is excitable. The tail movements are at this period 

 almost certainly reflex. Yoluntary 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 develo2)ed 

 till comparatively late. 



The barking of the nineteenth day was probably a reflex, mucli 

 simpler than such as results later. At this stage puppies often bark in 

 their sleep, not a common occurrence with mature dogs, though it does 

 take place in dreaming. By the twenty-third 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 tr}^ 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 voluntary movements. Correspond- 

 ing with this advance, I have found before the twentieth day very 

 distinct cortical localization for the limbs, head and face. 



Later than this improvement in reflexes is noticeable, but still more 

 the rapid development of older and the introduction of new voluntary 

 movements, involving more and more complex co-ordinations, and from 

 the psychic aspect the manifest possession of the power to use the 

 machinery of the nervous system a)id muscles in a way that implies the 

 existence of a growing intelligence and will ; and the careful observation 



