Let us begin our exposition, then, by first dealing systematically for a while with certain definite parts of the body, in reference to which we may accurately test and enquire what sort of thing the retentive faculty is. Now, could one begin the enquiry in any better way than with the largest and hollowest organs? Personally I do not think one could. It is to be expected that in these, owing to their size, the activities will show quite clearly, whereas with respect to the small organs, even if they possess a strong faculty of this kind, its activation will not at once be recognisable to sense. Now those parts of the animal which are especially hollow and large are the stomach and the organ which is called the womb or uterus.[306] What prevents us, then, from taking up these first and considering their activities, conducting the enquiry on our own persons in regard to those activities which are obvious without dissection, and, in the case of those which are more obscure, dissecting animals which are near to man;[307] not that even animals unlike him will not show, in a general way, the faculty in question, but because in this manner we may find out at once what is common to all and what is peculiar to ourselves, and so may become more resourceful in the diagnosis and treatment of disease. Now it is impossible to speak of both organs at once, so we shall deal with each in turn, beginning with the one which is capable of demonstrating the retentive faculty most plainly. For the stomach retains the food until it has quite digested it, and the uterus retains the embryo until it brings it to completion, but the time taken for the completion of the embryo is many times more than that for the digestion of food. II All' hêmeis ou toutô monô tô genei tês apodeixeôs eithismenoi chrêsthai, prostithentes d' autô kai tas ek tôn enargôs phainomenôn anankazousas te kai biazomenas pisteis epi tas toiautas kai nyn aphixometha kai deixomen epi men tinôn moriôn tou sômatos houtôs enargê tên kathektikên dynamin, hôs autais tais aisthêsesi || 146 diagignôskesthai tên energeian autês, epi de tinôn hêtton men enargôs tais aisthêsesi, logô de kantautha phôrathênai dynamenên. Arxômeth' oun tês didaskalias ap' autou tou teôs prôton methodô tini procheirisasthai mori' atta tou sômatos, eph' hôn akribôs esti basanisai te kai zêtêsai tên kathektikên dynamin hopoia pot' estin. Ar' oun ameinon an tis heterôthen ê apo tôn megistôn te kai koilotatôn organôn hyparxaito tês zêtêseôs? emoi men oun ouk an dokei beltion. enargeis goun eikos epi toutôn phanênai tas energeias dia to megethos; hôs ta ge smikra tach' an, ei kai sphodran echei tên toiautên dynamin, all' ouk aisthêsei g' hetoimên diagignôskesthai tên energeian autês.