Despite embryologic teachings, that old notion that man is an entity who undergoes development alone, still controls pathology and physiology. The human being, however, is a compound animal in whom organs have their own nervous system and their own life under control of the cerebrospinal system. The child is not an undeveloped man, but man is an imperfectly developed child. The embryo has to contend with retrogressive as well as progressive factors, and the same is true of man after birth. Vertebrate embryos are of common type at their origin and assume successively many common forms before definitely differentiating. The higher vertebrates contain in essence the organs and possibilities of all lower vertebrates. The human organism is therefore a balance. While the balance is maintained the organs work in unity, though there is a constant struggle for existence between them. During embryonic existence this struggle is more intense and diversified
KIERNAN JG. PERIODS OF STRESS AND THEIR DENTAL MARKS.. JAMA. 1901;XXXVII(2):94–97. doi:10.1001/jama.1901.62470280018002d
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