In surgery his writings are important and interesting, but they do not bear the same character of caution as the treatises on medicine; for instance, in the essay _On Injuries of the Head_, he advocates the operation "of trephining" more strongly and in wider classes of cases than would be warranted by the experience of later times. The _Hippocratic Collection_ consists of eighty-seven treatises, of which a part only can be accepted as genuine. The collection has been submitted to the closest criticism in ancient and modern times by a large number of commentators (for full list of the early commentators, see Adams's _Genuine Works of Hippocrates_, Sydenham Society, i. 27, 28). The treatises have been classified according to (1) the direct evidence of ancient writers, (2) peculiarities of style and method, and (3) the presence of anachronisms and of opinions opposed to the general Hippocratic teaching--greatest weight being attached to the opinions of Erotian and Galen. The general estimate of commentators is thus stated by Adams: "The peculiar style and method of Hippocrates are held to be conciseness of expression, great condensation of matter, and disposition to regard all professional subjects in a practical point of view, to eschew subtle hypotheses and modes of treatment based on vague abstractions." The treatises have been grouped in the four following sections: (1) genuine; (2) those consisting of notes taken by students and collected after the death of Hippocrates; (3) essays by disciples; (4) those utterly spurious. Littre accepts the following thirteen as absolutely genuine: (1) _On Ancient Medicine_ ([Greek: Peri archaies ietrikes]); (2) _The Prognostics_ ([Greek: Prognostikon]); (3) _The Aphorisms_ ([Greek: Aphorismoi]); (4) _The Epidemics_, i. and iii. ([Greek: Epidemion a' kai g']); (5) _On Regimen in Acute Diseases_ ([Greek: Peri diaites oxeon]); (6) _On Airs, Waters, and Places_ ([Greek: Peri aeron, hydaton, kai topon]); (7) _On the Articulations_ ([Greek: Peri arthron]); (8) _On Fractures_ ([Greek: Peri agmon]); (9) _The Instruments of Reduction_ ([Greek: Mochlikos]); (10) _The Physician's Establishment, or Surgery_ ([Greek: Kat' ietreion]); (11) _On Injuries of the Head_ ([Greek: Peri ton en kephale tromaton]); (12) _The Oath_ ([Greek: Horkos]); (13) _The Law_ ([Greek: Nomos]). Of these Adams accepts as certainly genuine the 2nd, 6th, 5th, 3rd (7 books), 4th, 7th, 8th, 9th and 12th, and as "pretty confidently acknowledged as genuine, although the evidence in their favour is not so strong," the 1st, 10th and 13th, and, in addition, (14) _On Ulcers_ ([Greek: Peri helkon]); (15) _On Fistulae_ ([Greek: Peri syringon]); (16) _On Hemorrhoids_ ([Greek: Peri haimorrhoidon]); (17) _On the Sacred Disease_ ([Greek: Peri hieres nousou]). According to the sceptical and somewhat subjective criticism of Ermerins, the whole collection is to