Let us once more, then, recall the actual purpose for which Nature has constructed all these parts. Its name, as previously stated, is nutrition, and the definition corresponding to the name is: an assimilation of that which nourishes to that which receives nourishment. And in order that this may come about, we must assume a preliminary process of adhesion, and for that, again, one of presentation. For whenever the juice which is destined to nourish any of the parts of the animal is emitted from the vessels, it is in the first place dispersed all through this part, next it is presented, and next it adheres, and becomes completely assimilated.

The so-called white [leprosy] shows the difference between assimilation and adhesion, in the same way that the kind of dropsy which some people call anasarca clearly distinguishes presentation from adhesion. For, of course, the genesis of such a dropsy does not come about as do some of the conditions of atrophy and wasting, from an insufficient supply of moisture; the flesh is obviously moist enough — in fact it is thoroughly saturated — and each of the solid parts of the body is in a similar condition. While, however, the nutriment conveyed to the part does undergo presentation, it is still too watery, and is not properly transformed into a juice, nor has it acquired that viscous and agglutinative quality which results from the operation of innate heat; therefore, adhesion cannot come about, since, owing to this abundance of thin, crude liquid, the pabulum runs off and easily slips away from the............