Pneuma and Vapor

Only a very little nutrient matter gets from the stomach into the arteries.

This is because these first become filled with lighter matter.

There are 2 kinds of attraction that refills a vacuum:

1. Air Pressure
2. Magnetism

The heart and the arteries are hollow organs capable of diastole.

They always attract the lighter matter first.

Their nourishment is actually into their coats.

Of the blood, then, which is taken into their cavities when they dilate, that part which is most proper to them and most able to afford nourishment is attracted by their actual coats.

The following is proof that something is taken over from the veins into the arteries.

Kill an animal by cutting a number of its large arteries.

The veins will become empty along with the arteries.

This could never occur if there were not anastomoses between them.

Similarly, also, in the heart itself, the thinnest portion of the blood is drawn from the right ventricle into the left, owing to there being perforations in the septum between them: these can be seen for a great part [of their length]; they are like a kind of fossae [pits] with wide mouths, and they get constantly narrower; it is not possible, however, actually to observe their extreme terminations, owing both to the smallness of these and to the fact that when the animal is dead all the parts are chilled and shrunken.396

The principle is that nothing is done by Nature in vain. This manifests in the following ways:

1. The anastomoses between the ventricles of the heart

These could not be at random and by chance that there occurred fossae ending thus in narrow terminations.

2. The orifice of the right ventricle that gets blood in is much larger than the one that lets blood go out.

This suggests that not all the blood which the vena cava gives to the heart is driven away again from the heart to the lungs.*

And even if a certain amount is so expended, still the vein leading to the lungs is not to such a slight extent smaller than that inserted into the heart as to make it likely that the blood is used as nutriment for the heart: the disparity is much too great for such an explanation. It is, therefore, clear that something is taken over into the left ventricle.402

Moreover, of the two vessels connected with it, that which brings pneuma into it from the lungs403 is much smaller than the great outgrowing artery404 from which the arteries all over the body originate;

This suggests that it not merely gets pneuma from the lungs, but that it also gets blood from the right ventricle through the anastomoses mentioned.

The treatise “On the Use of Parts” shows that:

• some parts of the body is nourished by pure, thin, and vaporous blood
• other parts are nourished by thick, turbid blood
• Nature has overlooked nothing in this.

There are 2 kinds of attraction:

1. Some bodies exert attraction along wide channels during diastole.

This is by the principle by which a vacuum becomes refilled.

This can attract even from a distance.*

2. Other bodies exert it by their appropriateness of quality

This can attract only in short-range.

The very longest tube let down into water can easily draw up the liquid into the mouth.

But if you go away from the lodestone, or corn from the jar, no further attraction can take place.

This can be observed most clearly in garden conduits.

These have a moisture distributed into every part lying close by.

• But it cannot reach those lying further off.

Therefore one has to arrange the flow of water into all parts of the garden by cutting a number of small channels leading from the large one.

The intervening spaces between these small channels have a size that best allows these spaces to satisfy their needs by drawing from the liquid which flows to them from every side.

So also is it in the bodies of animals.

Numerous conduits distributed through the various limbs bring them pure blood, much like the garden water-supply.

The intervals between these conduits have been wonderfully arranged by Nature from the outset so that the intervening parts will:

• be plentifully provided for when absorbing blood
• never be deluged by superfluous fluid running in at unsuitable times.

Erasistratus supposes his simple nerve vessel to be continuous throughout the body.

Its superficial parts first use of the nutriment that they get in contact with.

The parts coming next draw their share from these by their contiguity.

The deepers parts then draw from these.

This does not stop until the quality of the nutrient substance has been distributed among all parts of the corpuscle in question.

For such parts as need the humour which is destined to nourish them to be altered still further.

Nature has provided a kind of storehouse, either in the form of:

• a central cavity or
• separate caverns

Thus the flesh of the viscera and of the muscles is nourished from the blood directly, this having undergone merely a slight alteration.

The bones, however, in order to be nourished, require very great change, and what blood is to flesh marrow is to bone;

The small bones do not have central cavities. This marrow is distributed in their caverns, whereas in the larger bones which do contain central cavities the marrow is all concentrated in these.

For, as was pointed out in the first book,408 things having a similar substance can easily change into one another.

But it is impossible for those which are very different to be assimilated to one another without intermediate stages.

Such a one in respect to cartilage is the myxoid substance which surrounds it, and in respect to ligaments, membranes, and nerves the viscous liquid dispersed inside them.

for each of these consists of numerous fibres, which are homogeneous409—in fact, actual sensible elements;

In the intervals between these fibres is dispersed the humour most suited for nutrition; this they have drawn from the blood in the veins, choosing the most appropriate possible, and now they are assimilating it step by step and changing it into their own substance.

All these considerations agree with one another.

For, from what has been said, anyone can readily discover in what way all the particular [vital activities] come about. For instance, we could in this way ascertain why it is that in the case of many people who are partaking freely of wine, the fluid which they have drunk is rapidly absorbed410 through the body and almost the whole of it is passed by the kidneys within a very short time.

For here, too, the rapidity with which the fluid is absorbed depends on appropriateness of quality, on the thinness of the fluid, on the width of the vessels and their mouths, and on the efficiency of the attractive faculty.

The parts situated near the alimentary canal, by virtue of their appropriateness of quality, draw in the imbibed food for their own purposes, then the parts next to them in their turn snatch it away, then those next again take it from these, until it reaches the vena cava, whence finally the kidneys attract that part of it which is proper to them.

This is why wine is taken up more rapidly than water due to its appropriateness of quality.

• Clear white wine is absorbed more rapidly due to its thinness.
• Black turbid wine is retarded on the way because of its thickness.

These facts, also, will afford abundant proof of what has already been said about the arteries;

Everywhere, such blood as is both specifically appropriate and at the same time thin in consistency answers more readily to their traction than does blood which is not so; this is why the arteries which, in their diastole, absorb vapour, pneuma, and thin blood attract either none at all or very little of the juices contained in the stomach and intestines.