digestive system vs liver

digestive system

noun
  • A system of organs for the purpose of digesting food. 

liver

noun
  • This organ, as taken from animals used as food. 

  • Someone who lives (usually in a specified way). 

  • A dark brown colour, tinted with red and gray, like the colour of liver. 

  • A large organ in the body that stores and metabolizes nutrients, destroys toxins and produces bile. It is responsible for thousands of biochemical reactions. 

adj
  • Of the colour of liver (dark brown, tinted with red and gray). 

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