Galen then proceeds—under the heading “necessary to read before the The Method of Healing”—to take a new starting-point, in physical theory. Study of the fundamental elements of the cosmos and biological world, discussed in Elements according to Hippocrates (Hipp. Elem.), should be followed by their study in the specifically animal, and human, context, in Mixtures (Temp.)—a major and very influential work of Galenic theory. From this point there is again a dual pathway: the third book of Temp., with its discussion of the nature of change brought about by drugs, may lead into specialist pharmacological study; alternatively, the latter may be bypassed in favour of a series of works on health and disease in the human body, which in turn lead into works on clinical practice, and on diagnostic and prognostic procedures.