THE EVOLUTION OF THE BRAIN
By G. Elliott Smith
Professor of Anatomy in the University of London
In ancient times, before paper or good parchment was easy to obtain, writers used the leaves of old manuscripts again and again after attempting to erase the writing already inscribed on them. On examining one of these palimpsests, as they are called, the modern student may be able to read sufficient of its partly erased writing to decipher the story it told. The human body is a palimpsest, which has preserved in its every part the records of its inheritance, so that anyone who carefully studies its structure and compares it with the bodies of other living creatures can read the history of man written in imperishable symbols in its very texture. Seen in this light the structure of every bone and muscle, the arrangement of the blood vessels and nerves, the constitution of the organs of body, indeed, the nature of every tissue of the organism, proclaim the fact that, wonderfully as each and every part seems to have been designed to perform its particular function, it is really a readaptation of an organ or tissue that may originally have served a useful purpose very different from that which it serves now. Like the ancient palimpsests, the human body has been inscribed again and again with new devices that have only partly obscured the more ancient writings. Let us take two illustrations:
1. At a certain stage in the normal development of a
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