liberties, those originally in Greek, as a kind of bonus for his sons. For instance, the “Letter from Celsus”, addressed to a Callistus, deals with the physician's ethical duty in relation to the Hippocratic Oath. Thirty-six chapters on treatments, consisting mainly of recipes both pharmacological and magical, and arranged by convention anatomically a capite ad calcem (“from head to toe,” in the equivalent English expression) as were Marcellus's sources Scribonius Largus and the Medicina Plinii. The treatment chapters run to 255 pages in Niedermann's edition. Meyer lists 262 different plant names in Marcellus; allowing for synonyms, of which there are many, the number of plants mentioned would be around 131. About 25 of the botanicals most frequently prescribed are “exotica”’ such as galbanum, sagapenum, and ginger; these may have been available in Gaul as imports, but only to elite consumers. Other ingredients likely to have been rare for Marcellus’s intended audience include cinnamon, cloves, candied tragacanth, Alexandrian niter, and African snails, perhaps the Giant African land snail, which are prescribed live for pulping into a mélange. Availability is possibly a lesser criterion of selection for Marcellus than completeness and variety of interest. And last, the Carmen de speciebus (“Song of Species”), a 78-line Latin hexameter poem on pharmacology, which Marcellus contrasts to his prose assemblage of prescriptions by asserting his originality in writing it. Significance as medical writer Marcellus was a transitional figure between ancient and medieval materia medica. Although the contents of the recipes — their names, uses, and methods of treatment — derive from the medical texts of ancient Greece and Rome, the book also points forward to doctrines and approaches characteristic of medieval medicine. Marcellus is seldom cited directly, but his influence, though perhaps not wide or pervasive, can be traced in several medieval medical texts. A major change in the approach to writing about botanical pharmacology is signalled in the De Medicamentis. As texts associated with Mediterranean medicine traveled west and north with the expanding borders of the Roman empire, the plants required by drug recipes were no longer familiar, and the descriptions or illustrations provided by earlier herbals failed to correspond to indigenous flora. Marcellus's practice of offering synonyms is one attempt to bridge this gap. He often provides a string of correspondences: the Greek plant name polygonos is first glossed as sanguinaria in Latin (1.2), then as "what we [in Gaul?] call rubia" (1.44);