The psychic development of young animals and its physical (somatic) correlation with specific reference to the brain / by Wesley Mills.
- T. Wesley Mills
- Date:
- 1896
Licence: Public Domain Mark
Credit: The psychic development of young animals and its physical (somatic) correlation with specific reference to the brain / by Wesley Mills. Source: Wellcome Collection.
Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.
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![Appointed out in my ]):i|)er on the functional development of the cerebral cortex, the latter is absolutely inexcitahle 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 inexcitahle at birth there seems to he no other view i>o.ssihle of these movements than that they are reflex 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. Nevertheless the animal at this period is ])rogres.sing, for the improve- ment of these reflexes implies the more perfect organization of a neuro- muscular mechanism whicli is probably availed of later in all voluntary movements. In adult life our own movements arc often carried out witli a ]>crfec- 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. Blit even so early as the twelfth to the fifteenth day new move- ments are possible. The eyes 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 eaix 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 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. 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 nineteenth day was probably a reflex, much simpler than such as results later. At this stage puppies often bark in their slee]>, 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 Uieir 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 movemeuts, so that by tins tune, and probably before, there are undoubted voluntary movements, t'orrespond- ing with this advance, I have found before the twentieth day very distinct cortical localization for the limbs, head and face. Later than this imjirovernent in I'efloxes is noticeab.e, but still moie the rapid development of older and the introduction of new voluntary movements, involving more and more complex co-ordinations, and from the iisychic aspect the manifest possession of the power to use the machinery of the nervous system and muscles in a way that implies the existence of a growing intelligence and will ; and the careful ob-servation](https://iiif.wellcomecollection.org/image/b22471650_0006.jp2/full/800%2C/0/default.jpg)
