The Retentive Faculty

Nutrition occurs by an alteration or assimilation of that which nourishes to that which receives nourishment,299

Every part of the animal has a faculty which is assimilative and nutritive.

A sufficient supply of the matter which the part being nourished makes into nutriment for itself is ensured by virtue of another faculty which naturally attracts its proper juice [humour] that that juice is proper to each part which is adapted for assimilation, and that the faculty which attracts the juice is called, by reason of its activity, attractive or epispastic.300

Assimilation is preceded by adhesion.

This, again, by presentation,301 the latter stage being, as one might say, the end or goal of the activity corresponding to the attractive faculty.

For the actual bringing up of nutriment from the veins into each of the parts takes place through the activation of the attractive faculty,302 whilst to have been finally brought up and presented to the part is the actual end for which we desired such an activity; it is attracted in order that it may be presented.

After this, considerable time is needed for the nutrition of the animal; whilst a thing may be even rapidly attracted, on the other hand to become adherent, altered, and entirely assimilated to the part which is being nourished and to become a part of it, cannot take place suddenly, but requires a considerable amount of time.

But if the nutritive juice, so presented, does not remain in the part, but withdraws to another one, and keeps flowing away, and constantly changing and shifting its position, neither adhesion nor complete assimilation will take place in any of them.

Here too, then, the [animal’s] nature has need of some other faculty for ensuring a prolonged stay of the presented juice at the part, and this not a faculty which comes in from somewhere outside but one which is resident in the part which is to be nourished. This faculty, again, in view of its activity our predecessors were obliged to call retentive.

Thus our argument has clearly shown the necessity for the genesis of such a faculty, and whoever has an appreciation of logical sequence must be firmly persuaded from what we have said that, if it be laid down and proved by previous demonstration that Nature is artistic and solicitous for the animal’s welfare, it necessarily follows that she must also possess a faculty of this kind.

Chapter 2: The Retentive Faculty

In certain parts of the body, the retentive faculty is so obvious.

Its operation is sometime obvious, sometimes not.

It is most obvious in the largest and hollowest organs such as the stomach and 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; 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.

The stomach retains the food until it has quite digested it. The uterus retains the embryo until it brings it to completion.