viscera vs vital organ

viscera

noun
  • Collectively, the internal organs of the body, especially those contained within the abdominal and thoracic cavities, such as the liver, heart, or stomach. 

  • The intestines. 

vital organ

noun
  • An organ of the body which performs a sufficiently important function that damage to the organ can cause death. 

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