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An extremely rare and early Syrian instrument to measure the amount of blood let by the surgeon. A similar one appears in an Egyptian manuscript of 1354 but no such apparatus was known in the West. The instrument consists of a shallow bronze bowl with a pipe outlet at the bottom. This sits on a rectangular base with moulded sides which contains 2 empty chambers. Rising from the bowl are 4 hollow columns (2 seen in section) supporting a hollow podium upon which are seated the figures of 2 physicians. The figure on the left holds a pen, that on the right a tablet inscribed with numbers. As the blood drains from the bowl into the empty chamber at right, it raises a float hanging on the end of a brass rod in the hollow column (right). The upper end of the rod, beaten flat, is actually the scribe's tablet, and as the rod rises, a reed in the scribe's hand indicates the corresponding amount of blood.

Arabic manuscript, 1315: Washington DC, Freer Gallery, MS 30.76. Al Jazari, Book of knowledge of ingenious mechanical contrivances. Source: Loren MacKinney. Medical illustrations in Medieval manuscripts. Wellcome Historical Medical Library, London 1965.