_OF_ _SERPENTS_ ---------------------------------------------------------------- PART I. ---------------------------------------------------------------- SECTION I. I begin with the Division of Serpents, which I distribute into _Terrestrial_, that live upon Land only; _Aquatick_, that live in Water; and _Amphibious_, that inhabit both Elements. Under these I comprehend all the Relatives to the venomous Tribe. But how can Land-Serpents live in Water? I answer, their Bodies are equally formed for both Places. Among Animals, some breathe by _Lungs_, and others by _Gills_, as all sanguineous Fish, (excepting the _Whale_.) By _Gills_, I mean those membranous cartilaginous Parts on both sides the Head, whereby they hear and respire: What we call _Gills_ in Fish, are properly their _Lungs_. Respiration (which is an involuntary Motion of the Breast, whereby Air is alternately taken in and thrown out) is as necessary to Fish as to Land-Animals: In Water, is a great Quantity of Air inclosed, and it is that Air they respire, and by their _Gills_ they separate the Air from the Water, and present it to the _Blood_, after the same manner as ’tis presented to the Lungs of Land-Animals. The _Gills_ of Fish have an alternate Motion of Dilatation and Compression; when they _dilate_ their _Gills_, the Water is taken in; when they _contract_ them, ’tis expelled again. Thus the Water is carried in by the Mouth, and carried off again (stript of its Air) by the _Gills_, which perform the Office of Lungs. Their sucking Water is Breathing, and their Food as little of Water, perhaps, as other Creatures use. _SERPENTS_ will swim in all Liquids; this appears in the Experiment made by a _learned Italian_, who put a Serpent into a large Glass-Vessel of Wine, where it lived swimming about six Hours: and when it was by force immersed and kept under that Liquid, it lived only about an Hour and a half. He put another in common Water, where it lived three Days; but when it was kept under Water, it lived only about twelve Hours[2]. Footnote 2: _Fr. Redi Exper. circa res nat._ p. 170. Some Serpents are reptitious, creep on the Belly, and some have Feet; the Form of their Legs is peculiar and different in divers Species, whence the slow Motion of some, and wonderful Agility and Swiftness in others: Their Feet are some cloven (as it were) into Hoofs, others divided into Claws, with Variety of different Nails to answer the several Purposes of Life; among them are _Flying Serpents_: for which purpose, they are furnished with Wings to buoy themselves up in the fluid Air, whereby they keep their Bodies on a due Balance in their Motion.