Theou megaloio hekēti, Ad theses hasce de locorum affectorum cognitione generali

VI.
These kinds of sources are: First, from the uses and actions of the parts. Second, from the form of those things which are excreted, whether they be ex substantia partium from the substance of the parts, or ex contentis from the contained materials. Third, from the proper accidents. Fourth, from the position. Fifth, and finally, from the nature of the pain.

VII.
Knowledge of the use and actions of the parts is necessary for the present undertaking, not only in general but also in particular: so that we are imbued with true doctrine concerning the functions of individual parts. Wherefore, if, for example, we think like Asclepiades regarding the excretion of urine, we will not be able to judge the affections of these parts from this source.

VIII.
Just as arguments are supplied for recognizing affected parts from the sources already enumerated, so also a certain general observation concerning those things that pertain to recognizing the affections themselves depends on the same principles.

IX.
From the USES AND ACTIONS OF THE PARTS, very many and most certain signs are taken for recognizing affected locations: because a part and its function stand in relation to one another as cause and effect, and therefore, with one definitely known, the other is also known.