Urine and Bile

Book 1 showed that the kidneys have some faculty which attracts to them this quality existing in the urine.

But urine is carried through the kidneys into the bladder by 2 methods:

1. The blood into parts of the animal by another
2. The yellow bile separated out

For when once there has been demonstrated in any one organ, the drawing, or so-called epispastic168 faculty, there is then no difficulty in transferring it to the rest.

Nature did not give a power such as this to the kidneys without giving it also to the vessels which abstract the biliary fluid, nor did she give it to the latter without also giving it to each of the other parts.

Assuredly, if this is true, we must marvel that Erasistratus should make statements concerning the delivery of nutriment from the food-canal170 which are so false as to be detected even by Asclepiades.

Erasistratus asserts that if anything flows from the veins, one of two things must happen:

1. A completely empty space will result or
2. The contiguous quantum of fluid will run in and take the place of that which has been evacuated.

Asclepiades, however, has 3 effects:

1. There will be an entirely empty space, or
2. The contiguous portion will flow in, or
3. The vessel will contract.

This is because when reeds and tubes aresubmerged in water, and are emptied of the air then either a completely empty space will be left, or the contiguous portion will move onwards;

In the case of veins this no longer holds, since their coats can collapse and so fall in upon the interior cavity.

Erasistratus is so wrong!

He supposed that:

• the stomach can compress the veins
• the veins can contract the contents of the stomach and propel them forwards.172

No plethora would ever take place in the body, if delivery of nutriment resulted merely from the tendency of a vacuum to become refilled.

The principle of the refilling of a vacuum is a necessary addition if:

• the compression of the stomach becomes weaker the further it goes, and cannot reach to an indefinite distance
• some other mechanism makes the blood go in all directions

There will not, however, be a plethora in any of the parts coming after the liver, or, if there be, it will be in the region of the heart and lungs;

for the heart alone of the parts which come after the liver draws the nutriment into its right ventricle, thereafter sending it through the arterioid vein to the lungs (for Erasistratus himself will have it that, owing to the membranous excrescences, no other parts save the lungs receive nourishment from the heart).

Plethora comes about through the force of compression by the stomach to persist indefinitely.

This removes the need of the principle of the refilling of a vacuum, especially if we assume contraction of the veins in addition—as is, again, agreeable to Erasistratus himself.