Fabricius ab Aquapendente, and after him, our Great Dr. Harvey, have assign'd divers Uses to this Cavity or Air Vesicle, the Extravagance of which have perhaps deterr'd others from enquiring so much into the Use, as the Importance of it requir'd. But though I can't agree to that Perspiration, Refrigeration, and Respiration, which they make it the Instrument of; yet perhaps the Air, that was inclos'd in that Cavity, may through the Augmentation of the Body of the Pullus, and its own Rarefaction (which is at last so great as to occupy half the Shell) break the Membrane, which separated it from the Pullus, and thereby give so much Respiration as to form the chirping Voice, which is often heard before the breaking of the Shell, and with it give an addition of Strength to enable it to break the Shell. But how it should respire sooner, is to me inconceivable.
There are many Problems of great seeming Difficulty, the Solutions of which flow naturally from what has been laid down here: But intending to prosecute this Subject farther, and to treat of the Impediments of Respiration, and the Consequences of Respiration obstructed or intermitted, I shall reserve them for that Opportunity, and content my self here to attempt the Harveyan Problem only, which has given abundance of Authors so much perplexity.
That incomparable Philosopher enquires, Why a Fœtus, taken out of the Uterus with the Membranes intire, shall live in Water some Hours without communication with the External Air; whereas if it be taken out and suffer'd once to breath, it can't afterwards survive a Moment without the benefit of Respiration.
Granting the Fact to be as he has deliver'd it, which yet is not so in all Cases, the main Difficulty is grounded on a Mistake, which from the stating of the Question I find this Great Man to have slipt into. For he thinks, that a Fœtus is sooner suffocated after having once breath'd, than if it had not breath'd at all, and that by breathing it had contracted something which render'd it more perishable. Idem tamen secundis exutus, (says he) si semel aerem intra Pulmones attraxerit, postea ne momentum quidem temporis absque eo durare possit, sed confestim moriatur. And presently after, Siquidem constat, fœtum, postquam eum semel hauserit, citius suffocari; quam cum ab illo prorsus accebatur. The Doctor observing a Fœtus to live longer without Respiration, and to dispence better with the want of Air while included in the Membranes intire, than it cou'd afterwards; infers thence, that the Air does in the first Act of Inspiration impress upon the Lungs some quality, which renders it ever after more indispensably necessary. But allowing his Observation, I must yet deny his Inference to be good: For deprive a Fœtus of means of respiring, and then take it out of the Membranes, and it shall be as soon suffocated, as if it had respired before. This proves, that this necessity of intercourse with the Air, by way of the Lungs, is not the Offspring, but the Parent of Respiration, and that, that Learned Man was drawn into a Fallacy of Non causa pro causa.
The Reason of this Necessity is the pressure of the External Air upon the Surface of the Body, from which it was defended by the Interposition of the Membranes, and the Humours contain'd, which are not so compressible as the Body of the Fœtus it self. So soon therefore as the Fœtus is excluded, and expos'd to the immediate contact of the ambient Atmosphere, the Vessels and all the Cavities of the Body must necessarily be so compress'd, that the Fluids can't have room for motion, and consequently the Fœtus could have no Life, if Nature had not contriv'd by the motion of the Thorax to remove and admit that pressure alternately, and thereby to impress a motion on the Fluids, which is the Spring of Life. But this motion of the Thorax being any way suppress'd, the equal pressure of the Atmosphere on all parts, occasions a total Cessation of motion, which is Death.
I shall prosecute this Subject no farther now, nor trouble the Reader with any Apology, for dissenting from those Great Men herein named; because, I hope, I have done it with Modesty, and all the Respect due to so great Authorities, and have assign'd nothing which is not Matter of Fact uncontroverted, or deduc'd from it by plain Mechanical Necessity.
Some Thoughts and Experiments concerning Vegetation. By John Woodward, M. D. of the College of Physicians, and R. S. and Professor of Physick in Gresham College.
THE Ancients generally intitled the Earth to the Production of the Animals, Vegetables, and other Bodies upon and about it; and that for that Reason 'twas, that they gave it so frequently the Epithets of Parent and Mother[1]. They were of opinion, that it furnished forth the Matter whereof those Bodies consist; and receiv'd it all back again at their Dissolution for the Composure of others. Even those who asserted four Elements, supposed that the Earth was the Matter that constituted those Bodies; and that Water and the rest, serv'd only for the Conveyance and Distribution of that Matter, in order to the forming and composition of them. 'Tis true, Thales, a Philosopher of the first Rank in those early Ages, has been thought to have Sentiments very different from these; but that without just Grounds, as I think I have sufficiently prov'd in another Paper, which I am ready to produce.
But though Antiquity thus gave its Vote for Terrestrial Matter, several of the Moderns, and some of very great Name too, both here and abroad, have gone quite counter, and given theirs in behalf of Water. The Dignity of the Persons that have espoused it, as well as their Numbers, renders this Doctrine very considerable, and well worth our enquiring into. The great Restorer of Philosophy in this last Age, my Lord Bacon, is of Opinion, That for Nourishment of Vegetables, the Water is almost all in all; and that the Earth doth but keep the Plant upright, and save it from over-heat, and over-cold[2]. Others there are who are still more express; and assert Water to be the only Principle or Ingredient of all Natural Things. They suppose that, I cannot tell by what Process of Nature, Water is transmuted into Stones, into Plants, and in brief, all other Substances whatever. Helmont,[3] particularly, and his Followers, are very positive in this; and offer some Experiments to render it credible. Nay, a very Extraordinary Person of our own Nation[4] tries those Experiments over again; and discovers a great Propensity to the same Thoughts and Opinion they had; declaring for this Transmutation of Water into Plants and other Bodies, though with great Modesty and Deference, which was his usual manner.