In the 2nd half of the 16th century…

…the pair of bodys was reinforced further by adding whalebones (baleen, or cartilege from a whale’s mouth) to the front and the back.  The side lacing of the earlier period was changed to the more convenient center back or front opening.

When it became fashionable to open the gown in front, the “stomacher” was used to hide the front lacing.

(Photos:  Whale, baleen, and 1890’s corset bones made from baleen)