Now the reason of this strange and peculiar noise, is deduced from the conformation of the wind-pipe, which in this bird is different from other volatiles. For at the upper extream it hath no fit Larinx, or throttle to qualify the sound, and at the other end, by two branches deriveth it self into the lungs. Which division consisteth only of Semicircular fibers, and such as attain but half way round the part; By which formation they are dilatable into larger capacities, and are able to contain a fuller proportion of air; which being with violence sent up the weazon, and finding no resistance by the Larinx, it issueth forth in a sound like that from caverns, and such as sometimes subterraneous eruptions, from hollow rocks afford. As _Aristotle_ observeth in a Problem, [SN: _Sect. 15._] and is observable in pitchers, bottles, and that instrument which _Aponensis_ upon that Problem describeth, wherewith in _Aristotles_ time Gardiners affrighted birds.
Whether the large perforations of the extremities of the weazon, in the _abdomen_, admitting large quantity of ayr within the cavity of its membrans, as it doth in Frogs; may not much assist this mugiency or boation, may also be considered. For such as have beheld them making this noise out of the water, observe a large distention in their bodies; and their ordinary note is but like that of a Raven.
5. That whelps are blind nine days and then begin to see, is the common opinion of all, and some will be apt enough to descend unto oaths upon it. But this I find not answerable unto experience, for upon a strict observation of many, I have scarce found any that see the ninth day, few before the twelfth, and the eyes of some not open before the fourteenth day. And this is agreeable unto the determination of _Aristotle_: who computeth the time of their anopsie or non-vision by that of their gestation. For some, saith he, do go with their young the sixt part of a year, two days over or under, that is, about sixty days or nine weeks; and the whelps of these see not till twelve days. Some go the fifth part of a year, that is, seventy-one days, and these, saith he, see not before the fourteenth day. Others do go the fourth part of the year, that is, three whole months, and these, saith he, are without sight no less then seventeen days. Wherein although the accounts be different, yet doth the least thereof exceed the term of nine days, which is so generally received. And this compute of _Aristotle_ doth generally overthrow the common cause alleadged for this effect, that is, a precipitation or over-hasty exclusion before the birth be perfect, according unto the vulgar Adage, _Festinans canis cæcos parit catulos_: for herein the whelps of longest gestation, are also the latest in vision. The manner hereof is this. At the first littering, their eyes are fastly closed, that is, by coalition or joining together of the eyelids, and so continue untill about the twelfth day; at which time they begin to separate, and may be easily divelled or parted asunder; they open at the inward Canthis or greater Angle of the eye, and so by degrees dilate themselves quite open. An effect very strange, and the cause of much obscurity, wherein as yet mens enquiries are blind, and satisfaction not easily acquirable. What ever it be, thus much may we observe, those animals are only excluded without sight, which are multiparous and multifidous, that is, which have many at a litter, and have also their feet divided into many portions. For the Swine, although multiparous, yet being bisulcous, and only cloven hoofed, is not excluded in this manner, but farrowed with open eyes, as other bisulcous animals.