Digital Libraries

HathiTrust Digital Library. Each full text item is linked to a standard library catalog record, thus providing good metadata and subject terms.  Thus a full text search of the whole database can be limited by title or Subject term.  The catalog can be searched separately.  Many post-1923 out-of-copyright books, especially government documents, are full text viewable. You can search within copyright books to see what page your search term is on. Sample searches in Advanced Full Text Search:

Full Text +All Fields all these words: Cancer hospital
AND
Subject any of these words: narratives OR diaries OR correspondence OR writings

I added the word hospital because Cancer is used in many non-medical contexts: a constellation, Tropic of Cancer, a genus of crabs, etc. Different medicine-related words may be added.

Similar searches can be done in the Internet Archive. Instructions for HathiTrust and Internet Archive