No attempt at an exhaustive analysis of the writers between Hippocrates and Galen will be made here. Only a few will be considered; the aim is merely to illustrate the divergent opinions that were prevalent.

Whether or not Celsus was himself a physician, and whether his work is his own or a translation of a lost Greek original, it is of the greatest value in reconstructing medical opinion between the Hippocratic writers and Galen. In addition to many incidental references he devotes a chapter to venesection, which opens with the significant remark: ‘It is not new to let blood by cutting a vein; but that there is hardly any disease in which blood is not let, is new.’ This is, in effect, Galen's indication from the severity of the disease, regardless of its nature; his primary indication for bloodletting is the presence, or indeed only the expectation, of any severe disease whatsoever. According to Celsus this was in his time – some two centuries before Galen, unless he is reproducing an earlier work – a new concept. It cannot be Hippocratic, since Celsus describes Hippocrates as ‘the most ancient author’. As we have seen, the idea appears in the Corpus only in the Appendix to Regimen in Acute Diseases, which most scholars think spurious, although Galen says that this particular statement is good Hippocratic doctrine; this does not apply, however, to everything else in the treatise. It has already been shown that the Hippocratic writers used venesection far less extensively than Galen did, though Galen would like us to think otherwise; Celsus confirms this opinion.