This paper argues that the Alexandrian physicians Erasistratus of Iulis and Herophilus of Chalcedon adopted an Aristotelian analysis of the composition of organic bodies into three levels, namely elements, uniform and non-uniform parts. They asserted that it was not the task of the doctor to analyse the body at the level of elements, that the uniform parts, being perceptible, should be taken to be most basic in the context of medicine and that the inquiry into the elements be left to (...) philosophers. The paper explores the possible motivations behind this restriction, and considers more generally its connections to the Peripatetic background. (shrink)