Tao Hongjing was a great scholar who devoted much of his efforts to studying herbs. His principal contribution to Chinese medicine was his recovery and rearrangement of the first formal herbal the Sheng Neng Pen-T'sao Ching [Shen Nong Bencao Jing; ca. 100 A.D.]. He collected the fragmentary records, arranged them together, and then doubled the number of herb entries (by adding another 365 herbs that were in use at the time. In addition, he divided the herbs into three classes: upper {which would promote longevity if taken a long time), middle (which could be used for treating diseases and promoting health), and lower (those which ought to be used for a short time to cure a disease or symptom). He also classified herbs according to basic sources, listing seven (e.g., herbs, animals, stones, vegetables, etc.).