In a subsequent Essay on animal spirits, he conceives them to be, if not the same with the nitro-aereal part of the atmosphere, yet to consist of this, so far as they are necessary to the production of muscular motion, which he attributes entirely as before to nitro-aereal particles, p. 24 and 40, of chap. 4, on the animal spirits.
I do not observe any thing else in Mayow’s book worth noting on the present occasion; or sufficiently connected with pneumatic Chemistry.
From the analysis thus given of[47] what Mayow has advanced, it appears, that he clearly comprehended the atmosphere to consist of a mixture of two parts, the one the efficient cause of life and of combustion, the other not of itself necessary to either.
[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part is equally necessary to the fœtus in utero as to the adult, and that the use of the lungs in the former case is superceded by the functions of the umbilical artery and placenta; by means of which, blood already impregnated with the vital air, is conveyed to the fœtus.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.