Cantor, Geoffrey. "Presidential Address: Charles Singer and the Early Years of the British Society for the History of Science." The British Journal for the History of Science, vol. 30, no. 1, 1997, pp. 5-23, JSTOR, http://www.jstor.org.kras1.lib.keio.ac.jp/stable/4027896.
Singer, Charles. "The Herbal in Antiquity and Its Transmission to Later Ages." The Journal of Hellenic Studies, vol. 47, 1927, pp. 1-52, JSTOR, doi:10.2307/625251.
"herbals are quite devoid of any rational basis. author makes a direct attack on diseases, without any nonsense about theories. the herbal is thus to be distinguished from the scientific botanical treatise by the fact that its aims are exclusively "practical" -- a vague and foolish word with which, men have sought to conceal from themselves and from others their destitution of anything in the nature of general ideas."
"a herbal is primarily a descriptive drug-list or, as we now call it, a pharamacopoeia."