[47] At the time this was written neither Dr. Bostock’s treatise on respiration or the books therein quoted p. 200 had arrived here. Nor have I had an opportunity of consulting the references there made to Prof. Robinson, Dr. Thompson, Dr. Yeates, or Fourcroy’s account of Mayow. That the vital part of the air, was also a constituent part of nitre, the effects of both being in essential particulars the same.[48] That the vital part of the atmosphere entering the blood through the vessels in the lungs, is conveyed to the left ventricle of the heart, and becomes the stimulus to the contractions of that muscle, and is equally essential to the whole system of muscular contraction. [48] Mr. Ray wrote “A dissertation (in 1696) about respiration,” in which he supposes the air to pass from the bronchia and lungs into the substance of the blood, and there (pabuli instar) it foments and maintains the vital flame which he supposes to be in the sulphureous parts of the blood, as the air foments the common flame of a candle, and that the nitre has nothing to do with it. See Durham’s collection of Ray’s letters. That the vital part of the atmosphere thus combined with the blood becomes also the source of animal heat. That this vital part is equally necessary to the fœtus in utero as to the adult, and that the use of the lungs in the former case is superceded by the functions of the umbilical artery and placenta; by means of which, blood already impregnated with the vital air, is conveyed to the fœtus. That the respiration of fishes, is dependant on the particles of air mixed with watery element they inhabited. That heat, flame, and combustion, depend on two universal principles, and the gentleness or violence of their mutual conflict: the one being a principle of inflammability universally diffused in combustible bodies, and the other the vital or igneous part of the atmosphere. These propositions evidently touch upon the most brilliant of the pneumatic discoveries of the authors already quoted; and not a little extraordinary it is, that they should have remained so long unknown, unnoticed, and not understood. The sulphur of Mayow is decidedly the Phlogiston of Stahl; the fire air of the former is the fire air of Scheele, the dephlogisticated air of Priestley, and the Oxygen of Lavoisier. The combination of oxygen with the blood by means of respiration, first discovered as was thought by Lavoisier, is clearly stated by Mayow; who has also forestalled the elaborate theories of Crawford on animal heat, of Goodwyn, on muscular stimulus, and of Beddoes on the succedaneum for respiration in the fœtus.