I know ‘tis objected by the Epicureans,¹ that the Parts of Animals were first made, and their Uses afterwards found out by mens Sagacity. But this is a Sophistical Objection. For, first, as to many of the Inner parts, as, the Heart, Liver, Spleen, Kidneys, &c, They perform their Functious without so much as Our Knowledge of their Structure, or perhaps their Situation; so far are they from being applyed to such Uses by Our Sagacity. And as for the Limbs and other Parts, which we can Move at pleasure; ‘tis true, that they cannot be actually Imployed to the respective Uses, till they be actually Form’d; but That hinders not but that in their Formation they were therefore so Formed, that they may be in due time fit for such Uses. And therefore we see, that the Chick is furnished with compleat Eyes, and with Wings and Feathers, before he be Hatch’d; tho’ whilst he is yet inclos’d in the Egg, he can not make use of them to See or Flye. And why was it, do the Epicureans think, that Nature provided a whole Set of Temporary Parts for Pregnant Females, and Animals in the Womb, which, when they are come into a freer state, partly fall away of themselves, and partly turn to a Ligament, fitted no longer for the former, but for a more seasonable Use? And ‘tis to be noted, that the Production of these Umbilical Vessels, and the Placenta or Analogous Body in the Womb to which they are fasten’d, is of no Necessity nor Use to the Female before Conception; and thereby those Temporary Parts appear to have bin Design’d by Nature, not so much for the Personal Preservation of the Female as for the Propagation of the Species: Which Destination not coming to be accomplished, till a Woman, for instance, has attain’d to a competent Age, appears to have been preordain’d by the Author of Mankind for the Continuation of It.

And tho’ it be true, that the Sagacity of men may have found out some Uses of some Parts of their Bodys, that cannot be made appear to have been Primarily Intended by the Author of Nature; yet That is no good Argument, that those Uses were not Intended, which either are made Within us, or do, as it were obtrude themselves Upon Us. And as for other Uses, the Prescience and Goodness of God are such, that it ought not to appear incredible, That He that gave man both the Limbs of his Body, and the Rational Endowments of his Mind, and that has made many Parts, as the Eyes and the Ears, Double, that One may supply the want of the Other; Did both Foresee what Uses men might, according to their Sagacitys and Emergencies, make of these Parts, and so Contrive the Parts that they should be applicable to such Uses. Suppose, a Wise man should send his Son to Travel, and among other things give him a Pocket-Dyal with a Magnetic Needle; and this Traveller having lost his way in some wild Plain, or being at Sea in a Vessel, whose Compass was broken or spoyl’d by a Storm, or some other Mischance: If, I say, in this case tho’ the Traveller Ordinarily Imployed his Dyal only to find the Hour of the Day, He shall now Imploy it to Guide his Course, or Steer the Vessel, by the help of the Needles pointing Northward; tho’ this would be an Effect of His own Sagacity, yet his Father being a Wise and Experienced Man, may reasona bly enough be suppos’d to have Foreseen, that his Son might have need of knowing the Northern and Southern Points of the Horizon. And accordingly may have given him a Dial furnish’d with a Magnetic Needle, rather than an Ordinary Gnomonic Dial. And so a Man that has taught another to Paint Landskips, when he gives him a Pencil and a Pallet furnish’d with Colours, to draw a Particular Prospect, is not to be suppos’d to have Design’d, that he should not Imploy them to any other purpose, if Urgent Circumstances made it requisite for him to do so.

Having insisted longer than I intended upon the former part of my Proposition, I now proceed to the latter; namely, That in some cases we may from the known Ends of Nature, as well as from the Structure of the Parts, ground Probable Conjectures, both Affirmative and Negative, about the particular Offices of the Parts. Which I could not seasonably doe before, because the Arguments, that were founded on the Uses of the Parts of Animals, suppose, not only that those Parts were destinated to Particular Uses knowable by Us, but that the several Parts of the Body were Contrived as Wisely and Commodiously as Men are able to Devise, in order to the Ends of Nature; which is always to be understood to have. United in her Designs, the Uses of the Parts, and the Welfare of the Whole.

And indeed if we consider, how admirable a Fitness there is in the Parts of the Human Body, for instance, to those Particular Ends we can discover them to have been Predesign’d for; it seems allowable to Conjecture, that such a Part was not Primarily Design’d to such an Use, because it is, on the account of its Structure or otherwise, less Fitted for it, than the constant Wisdom of Nature seems to require; especially if there be any Other Parts, by which That Office may be more commodiously perform’d. And on the other side, it may be a Probable Ground, tho’ not altogether so Probable as the former, to Conclude that such a Part was Destinated to such an Use, if the Use it self appear to be necessary, and the Part better fitted for it than any Other is.

Thus, tho’ Anatomical and Optical Writers, as well as the Schools, did for many ages unanimously conclude, the Crystalline Humor to be the Principal Seat of Vision; yet the industrious Scheiner, in his useful Tract intituled Oculus, does Justly enough reject that receiv’d Opinion, by shewing, that it Suits not with the Skill and Providence of Nature, to make that Part the Seat (or chief Organ) of Vision, for which it wants divers requisite Qualifications, especially most of these being to be found in the Retina. And I remember that when I asked our famous Harvey, in the only Discourse I had with him, (which was but a while be fore he dyed) What were the things that induc’d him to think of a Circulation of the Blood? He answer’d me, that when he took notice that the Valves in the Veins of so many several Parts of the Body, were so Plac’d that they gave free passage to the Blood Towards the Heart, but oppos’d the passage of the Venal Blood the Contrary way: He was invited to imagine, that so Provident a Cause as Nature had not so Plac’d so many Valves without Design: and no Design seem’d more probable, than That, since the Blood could not well, because of the interposing Valves, be Sent by the Veins to the Limbs; it should be Sent through the Arteries, and Return through the Veins, whose Valves did not oppose its course that way.

Thus, whereas former Anatomists and Physicians generally believed the Nutrition of the Parts by the Venal Blood, the more Recent Writers are wont to teach, that the Parts are nourish’d by the Blood in its passage through the Arteries. Not that they Think, the Blood that runs through the Veins altogether unfit to Irrigate the Parts with that Vital Liquor; but that they Judge the Veins to be less fit than the Arteries, into which the Blood comes immediately from the left Ventricle of the Heart, Agitated and Spirituous, and with a brisk Impulse, which forces out the Particles of the Blood, at those Pores of the Arteries that they find Congruous to their Shape and Size, and which answer to the several Parts that are to be nourished by Corpuscles so Qualified. ‘Twere not Difficult, if ‘twere Necessary, to accumulate Instances to the same purposes with those already mentioned; there being nothing more frequent in the Books of Anatomists, and those that treat of the Physiological and Pathological parts of Physick, than to draw Arguments, as well Affirmative as Negative, about the Use of the Parts of the Body, from their Fitness or Unfitness, or their greater or lesser Fitness, to attain such Ends as are suppos’d to have been Design’d by Nature. And indeed these Argumentations occur so frequently, that I think there is less need of my Increasing them, than of my Proceeding to give you a Caution about them, which I shall do in the following Proposition.

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Footnotes

1. Illud in his rebus vitium vehementer inesto Effugere, illorumque errorem premeditemur, Lumina qui faciunt Oculorum clara creata Prospicere ut possimus, Lucret. de Nat. l. iv. Nihil ideo quoniam natum est in Corpore ut uti possemus, sed quod natum est, id procreat Vsum. Ibid. ↩