Sec. 26. And now when his Affection towards it was increas'd to the highest degree, both upon the account of its Beneficial Effects, and its Extraordinary Power; he began to think that the Substance which was departed from the Heart of his Mother the Roe, was, if not the very same with it, yet at least of a Nature very much like it. He was confirm'd in his Opinion, because he had observ'd in all Animals, that as long as they liv'd, they were constantly warm without any Intermission, and as constantly Cold after Death, Besides he found in himself, that there was a greater degree of Heat by much in his Breast, near that place where he had made the Incision in the _Roe_. This made him think that if he could dissect any Animal alive, and look into that Ventricle which he had found empty when he dissected his Dam the _Roe_, he might possibly find it full of that Substance which inhabited it, and so inform himself whether it were of the Substance with the Fire, and whether it had any Light or Heat in it or not. In order to this he took a Wild Beast and ty'd him down, so that he could not stir, and dissected him after the same manner he had dissected the _Roe_, till he came to the Heart; and Essaying the left Ventricle first, and opening it, he perceiv'd it was full of an Airy Vapour, which look'd like a little Mist or white Cloud, and putting in his Finger, he found it hotter than he could well endure it, and immediately the Creature Dyed. From whence he assuredly concluded, that it was that Moist Vapour which communicated Motion to that Animal, and that there was accordingly in every Animal of what kind soever, something like it upon the departure of which Death follow'd. Sec. 27. He had then a great desire to enquire into the other parts of Animals, to find out their Order and Situation, their Quantity and the manner of there Connexion one with another, and by what means of Communication they enjoy the Benefit of that Moist Vapour, so as to live by it. How that Vapour is continu'd the time it remains, from whence it has its Supplies, and by what Means its Heat is preserv'd. The way which he us'd in this Enquiry was the Dissection of all sorts of Animals, as well Living as Dead, neither did he leave off to make an accurate Enquiry into them, till at length he arrived to the highest degree of Knowledge in this kind which the most Learned Naturalists ever attain'd to.