Oxygen

"Drebbel conceiv’d, that 'tis not the whole body of the Air, but a certain Quintessence (as Chymists speake) or spirituous part of it, that makes it fit for respiration, which being spent, the remaining grosser body, or carcase to cherish the vitall flame residing in the heart: So that (for ought I could gather) besides the Mechanicall contrivance of his vessell he had a Chymicall liquor, which he accounted the chiefe Secret of his submarine Navigation. For when from time to time he perceiv’d, that the finer and purer part of the Air was consum'd, or over clogg’d by the respiration, and steames of those that went in his ship, he would, by unstopping a vessell full of this liquor, speedily restore to the troubled Air such a proportion of Vitall parts, as would make it againe, for a good while, fit for Respiration, whether by dissipating, or precipitating the grosser Exhalations, or by some other intelligible way, I must not now stay to examine; Contenting my selfe to add, that having had the opportunity to do some service to those of his Relations, that were most Intimate with him, and having made it my business to learne what this strange Liquor might be, they constantly affirm'd that Drebell would never disclose the Liquor unto any, nor so much as tell the matter whereof he made it, to above one Person, who himselfe assur'd me that it was. ...I have been sometimes inclin'd to favourable thoughts of their opinion, who would have the Aire necessary to ventilate, and cherish the vitall flame, which they do suppose to be continually burning in the heart. For we see, that in our Engine the flame of a Lamp will last almost as little after the Exsuction of the Air, as the life of an Animall ..."

"If... too much blood is supplied to the brain, congestion of the vessels takes place, and irregularity in its action is at once produced; if too little, the brain (and, therefore, the nervous system) becomes first irritable and then lethargic. The quality of the blood supplied is also of great importance. As it courses through the body it has two principal functions to perform — to supply oxygen and to provide nutrition to the different organs of the body; and if it be unable adequately to fulfill either of these functions, a certain disorganization will follow. If the supply of oxygen to the brain be deficient, it becomes overcharged with carbon dioxide, and heaviness and lethargy very shortly supervene. A common example of this is the feeling of dullness and sleepiness which frequently overtakes one in a crowded and ill-ventilated room; owing to the exhaustion of the oxygen in the room by the continued respiration of so large a number of people, the brain does not receive its due modicum, and therefore is unable to do its work properly."

"You are (we hope!) consuming oxygen as you read."