chorion vs thorax

chorion

noun
  • The outer case of an insect egg. 

  • The outer membrane of seeds of plants. 

  • The protective and nutritive membrane in higher vertebrates that attaches the fetus to the uterus. 

thorax

noun
  • The middle of three distinct divisions in an insect, crustacean or arachnid body to which the legs are attached. 

  • The region of the mammalian body between the neck and abdomen as well as the cavity containing the heart and lungs. 

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