Written about 100 CE, On Medicine (Ιατρικα) is partially preserved in a papyrus in the British Library (PBrLibr inv. 137 = P.Lit.Lond. 165). It is the most important surviving ancient Greek medical papyrus, a key source of information about the history of ancient Greek medical thought. 

"While only fragments survive of some portions of the text, the papyrus containing the work of Anonymus Londinensis is exceptionally well preserved, with 3.5 meters of the roll largely intact, containing almost 2,000 lines of text in 39 columns. It seems to be an unfinished draft (breaking off in mid-column) in the hand of the author, who compiled, digested, and manipulated various sources as he wrote, so that we may even observe the process of his thinking as he writes. The text consists of three parts: a series of definitions related to the affections of the body and soul (cols. 1-4), a doxographical part (cols. 4-20), and a physiological part (cols. 21-39)" (Wikipedia article on Anonymus Londonensis, accessed 06-02-2015).

It contains extracts from a lost collection of the opinions of earlier Greek physicians. It was found in 1891 and first described by Sir Frederick Kenyon in 1892, with the Greek text first edited and published by Hermann Diels. It was first translated into German by Heinrich Beckh and Franz Spät as Anonymus Londinensis. Auszüge eines unbekannten aus Aristoteles-Menons Handbuch der Medizin und aus Werken anderer älterer Aerzte. (Berlin, 1896). Digital facsimile of the 1893 edition from the Internet Archive at this link. Digital facsimile of the 1896 edition in German from Google Books at this link.

A catalogue of surviving manuscripts of texts and translations of classical Greek physicians. Republished in book form, 1905-08. Available online from the Corpus Medicorum Graecorum at this link.

Supplemented by:

Greek Manuscripts:

A. Touwaide, Byzantine medical manuscripts: toward a new catalogue, Byzantinische Zeitschrift 101, 2008, 199-208

A. Touwaide, Byzantine medical manuscripts.Towards a new catalogue, with a specimen for an annotated checklist of manuscripts based on an index of Diels' catalogue, Byzantion 79, 2009, 453-595

A. Touwaide. A census of Greek medical manuscripts: From Byzantium to the Renaissance. Abingdon, Oxford: Routledge, 2016. (No. 7518).

Latin Translations:

Campbell (No. 6509)

R. J. Durling, Corrigenda and addenda to Diels' Galenica. I. Codices vaticani, Traditio 23, 1967, 461-476.

R. J. Durling, Corrigenda and addenda to Diels' Galenica. II. Codices miscellanei, Traditio 37, 1981, 373-381.

S. Fortuna, A. Raia, Corrigenda and addenda to Diels' Galenica by Richard J. Durling. III. Manuscripts and editions, Traditio 61, 2006, 1-30.

R. J. Durling, A Guide to the Medical Manuscripts Mentioned in Kristeller's Iter Italicum I-II, Traditio 44, 1988, 485-536.

R. J. Durling, A Guide to the Medical Manuscripts Mentioned in Kristeller's Iter Italicum III, Traditio 41, 1985, 341-366.

R. J. Durling, A Guide to the Medical Manuscripts Mentioned in Kristeller's Iter Italicum IV, Traditio 46, 1991, 347-379.

R. J. Durling, A Guide to the Medical Manuscripts Mentioned in Kristeller's Iter Italicum V-VI, Traditio 48, 1993, 253-316.

Syriac Translations:

R. Degen, Ein Corpus Medicorum Syriacorum, Medizinhistorisches Journal 7, 1972, 114-122.

R. Degen, Galen im Syrischen: Eine Übersicht über die syrische Überlieferung der Werke Galens, in: Galen: problems and prospects. A collection of papers submitted at the 1979 Cambridge conference, edited by V. Nutton, London 1981, 131-166.

Arabic Translations: 

Campbell (No. 6509)

Sezgin (No. 6510.2)

Ullmann (No. 6510.01)