Whether the air we breathe also causes some change in the mind

The second general cause of the changes that occur in the animal spirits is the air we breathe. For although it does not at first make impressions as noticeable as chyle, nevertheless in the long run it does what the juices of meat do in a short time.

This air enters from the branches of the trachea into those of the venous artery; from there it mixes and ferments with the rest of the blood in the heart; and according to its particular disposition and that of the blood, it produces very great changes in the animal spirits, and consequently in the faculty of imagination.

I know that there are some people who do not believe that air mixes with the blood in the lungs and in the heart, because they cannot discover with their eyes, in the branches of the trachea and in those of the venous artery, the passages through which this air communicates. But the action of the mind must not stop with that of the senses; it can penetrate what is impenetrable to them and attach itself to things that have no hold for them.

It is indubitable that some parts of the blood continually pass from the branches of the arterial vein into those of the trachea; the odor and humidity of the breath prove this sufficiently; and yet the passages of this communication are imperceptible. Why then could the subtle parts of the air not pass from the branches of the trachea into the venous artery, even though the passages of this communication are not visible? Finally, much more fluid is transpired through the imperceptible pores of the arteries and the skin than exits through the other passages of the body, and even the most solid metals have no pores so narrow that there are not still bodies in nature small enough to find free passage through them, since otherwise these pores would close.

The coarse and branched parts of the air cannot pass through the ordinary pores of bodies, and that even water, although quite coarse, can slip through paths where this air is obliged to stop. But we are not speaking here of the coarsest parts of the air; they seem quite useless for fermentation. We speak only of the smallest parts, stiff, sharp, and with very few branches to stop them, because they are apparently the most suitable for the fermentation of the blood.

I could however assure, based on the report of Silvius, that even the coarsest air passes from the trachea into the heart, since he himself assures that he saw it pass there through the skill of Mr. Swammerdam. For it is more reasonable to believe a man who says he has seen than a million others who speak idly. It is therefore certain that the most subtle parts of the air we breathe enter our heart; that they maintain there with the blood and the chyle the heat that gives life and movement to our body; and that, according to their different qualities, they bring great changes in the fermentation of the blood and in the animal spirits.

The truth of this is recognized every day by the various humors and the different characters of mind of people from different countries. The Gascons, for example, have much livelier imaginations than the Normans. Those of Rouen and Dieppe and the Picards all differ among themselves, and even more from the Lower Normans, although they are fairly close to one another. But if we consider men who live in more distant countries, we will encounter differences even more striking, such as between an Italian and a Fleming or a Dutchman. Finally, there are places renowned throughout time for the wisdom of their inhabitants, such as Thebes and Athens; and others for their stupidity, such as Thebes (in Egypt), Abdera, and some others.

Athenis tenue cœlum, ex quo acutiores etiam putantur Attici; crassum Thebis. (Cic., De fato.) — “The sky of Athens is thin, from which the Athenians are even thought to be sharper; that of Thebes is thick.”

Abderitanœ pectora plebis habes. (Mart.) — “You have the hearts of the Abderite crowd.”

Bœotum in crasso jurares aere natum. (Hor.) — “You would swear he was born of the thick air of Boeotia.”