Hapant' oun allêlois homologei tauta kai tê gastri kai tais hysterais kai tais kystesin einai tinas emphytous dynameis kathektikas men tôn oikeiôn poiotêtôn, || 158 apokritikas de tôn allotriôn. hoti men gar helkei tên cholên eis heautên hê epi tô hêpati kystis, emprosthen dedeiktai, hoti de kai apokrinei kath' hekastên hêmeran eis tên gastera, kai tout' enargôs phainetai. kai mên ei diedecheto tên helktikên dynamin hê ekkritikê kai mê mesê tis amphoin ên hê kathektikê, dia pantos echrên anatemnomenôn tôn zôôn ison plêthos cholês heuriskesthai kata tên kystin; ou mên heurisketai ge. pote men gar plêrestatê, pote de kenotatê, pote de tas en tô metaxy diaphoras echousa theôreitai, kathaper kai hê hetera kystis hê to ouron hypodechomenê. tautês men ge kai pro tês anatomês aisthanometha, prin aniathênai tô plêthei baryntheisan ê tê drimytêti dêchtheisan, athroizousês eti to ouron, hôs ousês tinos kantautha dynameôs kathektikês. Houtô de kai hê gastêr hypo drimytêtos pollakis dêchtheisa prôiaiteron tou deontos apepton eti tên trophên apotribetai. authis d' an pote tô plêthei baryntheisa ê kai kat' amphô synelthonta kakôs diatetheisa diarrhoiais healô. kai men ge kai hoi emetoi, tô plêthei baryntheisês || autês ê tên poiotêta 159 tôn en autê sitiôn te kai perittômatôn mê pherousês, analogon ti tais diarrhoiais pathêma tês anô gastros estin. hotan men gar en tois katô meresin autês hê toiautê genêtai diathesis, errhômenôn tôn kata ton stomachon, eis diarrhoias eteleutêsen, hotan d' en tois kata to stoma, tôn allôn eurôstountôn, eis emetous. VI This may often be clearly observed in those who are disinclined for food; when obliged to eat, they have not the strength to swallow, and, even if they force themselves to do so, they cannot retain the food, but at once vomit it up. And those especially who have a dislike to some particular kind of food, sometimes take it under compulsion, and then promptly bring it up; or, if they force themselves to keep it down, they are nauseated and feel their stomach turned up, and endeavouring to relieve itself of its discomfort. Thus, as was said at the beginning, all the observed facts testify that there must exist in almost all parts of the animal a certain inclination towards, or, so to speak; an appetite for their own special quality, and an aversion to, or, as it were, a hatred[324] of the foreign quality. And it is natural that when they feel an inclination they should attract, and that when they feel aversion they should expel. From these facts, then, again, both the attractive and the propulsive faculties have been demonstrated to exist in everything.[325]