Note p — BOOK IV.

The Sea-Calf hath the Foramen Ovale, by which means it is enabled to stay long under the Water, as the Paris. Anatomists. Of which see in Book VI. Chap. 5. Note (c).

But the fore-commended Mr. Cheselden thinks the Foramen Ovale is neither open in amphibious Creatures, nor any adult Land-Animals. When I first (saith he) applied my self to the Dissection of Human Bodies, I had no distrust of the frequent Accounts of the Foramen Ovale being open in Adults: but I find since, that I mistook the Ostium Venarum Coronariarum for the Foramen. The like I suppose Authors have done, who assert that it is always open in amphibious Animals: for we have made diligent Enquiry into those Animals, and never found it open. Neither would that (as they imagine) serve these Creatures to live under Water, as the Fœtus doth in Utero, unless the Ductus Arteriosus was open also.

This Opinion of Mr. Cheselden hath this to render it probable, that the Ostium Venarum Coronariarum is so near the Foramen Ovale, that without due regard, it may be easily mistaken for it. Such therefore as have Opportunity of examining this Part in amphibious Animals, or any other Subject, ought to seek for the Ostium, whenever they suspect they have met with the Foramen.