The paradoxical text 'On the Heart'. II.

'(V Tfj aIae T0n tI Kpoias'-Aristotle* ERASISTRATUS AND THE VALVES Erasistratus described all four valves, 'On the Heart' describes only two. Is 'On the Heart' using the discovery which Galen emphatically attributes to Erasistratus, and to no-one else, but using it only in part? This question prompts a further one: what was the real nature of Erasistratus' discovery? References to Erasistratus on the valves are scattered throughout the corpus of Galen's works, and Galen, it is salutary to remember, was not writing history but defining his own views and defending them against rival views. Polemic is ofthe essence of Galen's mode of exposition, and in this he was a true Greek. We may at times suspect his accuracy, and in any case the removal, intact and undistorted, of a particular doctrine from among the complicated tissues of Galenic controversy is an operation which requires some care. Thus the locus classicus on Erasistratus' discovery of the valves occurs in de Placitis 6.6 (V, 549K), and the context of this passage is Galen's development and defence of his own view that not the heart, as Aristotle and Erasistratus said, but the liver is the ARCHE or starting point ofthe veins. The context is further complicated by the fact that Galen opposes his own view not only to that of Aristotle and Erasistratus but to that of certain followers of Erasistratus who appear to have 'developed' Erasistratus' views on the function of the liver in line with Aristotelian doctrine. This view, according to Galen, assumes a flow of material from the right heart down the vena cava. But this, he says, contradicts the celebrated discovery of their own master Erasistratus, for the tricuspid valve on (as both Erasistratus and Galen regarded it) the vena cava prevents any backward flow of material from the right heart into the vena cava. Thus from Galen's point of view it is the atrio-ventricular valves which are important, and more particularly the right atrio-ventricular valve; and it is the function of these that he stresses. In view of the passage cited earlier, where Galen seems to say that it was these, atrio-ventricular, valves that Herophilus described 'carelessly', and Erasistratus 'precisely', we might be disposed to argue that it was these valves which it was Erasistratus' peculiar glory to have discovered, rather than the semilunar valves. In another passage too Galen seems to stress the atrio-ventricular valves (Nat. Fac. 2, 1, II, 77K): 'not even Erasistratus wishes any other part [sc. than the lung] to be nourished from the heart, because of the implantation of the membranes (DIA TEN TON HUMENON EPIPHUSIN, i.e. the tricuspid valve which prevents any backward flow into the vena cava).' Such a possibility," should not be immediately rejected: it may be a means of discerning the true arrangement of the historical facts, if any confirmatory evidence can