Andreas Vesalius, De humani corporis fabrica libri septem, Basel: ex. off. J. Oporini, 1543, p. 258 [358], woodcut, leaf height 43 cm, N*.1.2(A).

The Fabrica included smaller and diagrammatic images that aided Vesalius’s explanation. Here, three kinds of directions of the fibres of the vein are illustrated: transverse (A), oblique (B and C), vertical (D) and an interweaving of all three types (E). The superior vena cava is shown below as having the interwoven type of fibre. Following Galen, Vesalius sought to provide explanations of why parts of the human body had the structures that they did. Thus the transverse fibres were suited to expulsion, the vertical to attraction, and the oblique to the retention of fluids.