grey matter vs substantia grisea

grey matter

noun
  • A collection of cell bodies and (usually) dendritic connections, in contrast to white matter. 

  • Literal brains as a general substance. 

  • Brains; a person's ability to think. 

substantia grisea

How often have the words grey matter and substantia grisea occurred in a corpus of books? (source: Google Ngram Viewer )