soon as the Organs by which it should be regulated are compleated, will in the Body of the Pullus be regular and circulatory .
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