breastbone vs rib cage

breastbone

noun
  • The central narrow bone in the front of the chest, connecting the collarbone and the top ribs. 

rib cage

noun
  • A part of the skeleton within the thoracic area consisting of ribs, sternum and thoracic vertebrae. 

  • The enclosed area created by and within the ribs. 

How often have the words breastbone and rib cage occurred in a corpus of books? (source: Google Ngram Viewer )