Concerning the Third, viz.

The Final Cause, or Use of Respiration.

[ 11] The most General opinion (to omit all o∣thers, as less considerable) is,* that the princi∣pal use of Respiration, is for the Refrigeration of the Heart. Which though very ancient and plausible, is rather meerly Conjectural, than Areopagitical or demonstrative. For (1) AS aer over-hot is injurious to the heart, so is aer over-cold: and as aer moderately cold is be∣neficial to the heart, when it is excessively hea∣ted; so is aer moderately hot, beneficial, when the heart is too much cooled. But, while the heart is in good temper, then the aer most agreeable to it, is neither hot, nor cold, but temperate. (2) It is inconsistent with the prudence of Nature, to make the natural heat of the heart so intense and excessive, as to re∣quire perpetual ventilation with cold aer: when it had been much easier for Her, to have kindled a more gentle fire there in at first, than to bring cold aer to the hearth with so much adoe, to keep it in moderation ever after. And, in case that-Fire should chance, at any time, to grow less, or languish (as it often doth, in ex∣treme cold aer, many men being frozen to death in Green-land, Russia, and other Northern Countries) what provision hath Nature made Page  139 for the reaccension or instauration of it? (3) If it be only the Cold of the aer, that is benefi∣cial to the heart; then, certainly, the Water, (which is much colder than the aer) would more conveniently satisfie that necessity in Fishes, which yet cannot live without aer. (4) In persons of cold and Leuco-phlegmatique constitutions, there would be no need at all of Respiration; especially in frosty weather, when the heart hath as much want of warmth, as of cold, and more too. We confess, indeed, that at such times, our Respiration is more slow and rare, and in the heat of Summer, more quick and frequent; as it is also in Fevers: but the reason hereof is, that in Summer, the blood being made hotter, is sooner subtiliated into spirits, and those spirits faster consumed and dissipated; and so requires more aer to pro∣mote the subtiliation and inflammability of its spiritual parts. So that it should seem, the Aer is required rather as an Excitement, than as an hindrance to the vital Flame. We say, for the Excitation, or Accension of the Flame of life, by subtiliating the blood, and making the inflammable parts thereof more conveni∣ent Fewell for the same vitall Flame, and for the matter of the spirits, which being diffused through the whole body, serve to conserve and vivifie all the parts; no otherwise than Bel∣lowes conduce to the accension of flame in wood.

For, as the Aer blown out of a Bellowes, [ 12] doth promote the accension of fire,* in wood, Page  140 or other combustible matter; not by reason of any Cold (for Contraries never generate each other) but by the subtility of its particles, and the vehemence of its motion, in respect where∣of it both dissipates the ashes, that hinder the ingress of the fire, and impells the particles of the fire into the pores of the wood; so as that they penetrating more deeply into the sub∣stance thereof, invade and kindle all the in∣flammable particles therein contained: so doth the Aer brought into the Lungs, and commix∣ing it self with the blood circulating through them, insinuate it self, by the Arteria Venosa, into the left ventricle of the heart; and there partly by its subtility, partly by its expansive motion, so conspire with the pulse of the heart, as to conduce to the rarefaction and subtiliati∣on of the more thin and inflammable parts of the blood, that so they may be made both com∣modious fewell for the Fire burning in the heart, and also fit matter of the vital spirits. All the difference is, there are no Ashes made in the heart, the Flame thereof being more pure, than focal-fire, and subsisting in a matter as fine and subtile, as spirits of wine. Nor are there any sooty exhalations; such as arise from oyle burned in a Lamp: but such a Flame is perpetually revived out of the blood in the heart, as is made by the purest spirits of wine set on fire.

[ 13] This Use of the Aer inspired, may be in some sort inferred from the very structure of the Lungs.* For, to what purpose doth both the Page  141 Vena arteriosa, and Arteria Venosa divide and disperse into so many branches and surcles, throughout the lobes of the Lungs; unless it be to convey the aer brought into them (out of the Bronchia, or pipes derived from the As∣pera arteria) together with the blood, into the left ventricle of the heart, there to excite the vital flame? For, certain it is, from the struct∣ure of these vessells, that the Aer doth not arrive at and enter the heart, pure and sincere (as it ought to do, in case it were to refrigerate the heart) but mixed with the blood returning out of the Lungs: which is the reason, why in the dissections of living creatures, no aer is to be found in the Arteria venosa, being, before it comes thither, throughly commixed or con∣fused with the blood. Nor can we force aer into the heart, through the Lungs of a dead body; because the motion of the blood is then ceased. And this we conceive to be the Prin∣cipal End, or Use of Inspiration.

As for that of Exspiration, it seems to be no [ 14] other but the explosion of the same aer former∣ly received;* together with the Halitus, or va∣pours of the blood, that steam from it, while it is circulating through the Lungs. For, as to that Antique opinion, of the discharging of Fullginous Exhalations issuing from the heart; to the reasons by us formerly alleaged to dis∣credit the Generation of them, we shall sub∣joyn two or three convincing ones, to disprove their Exclusion through the Lungs. (1) The motion of the blood out of the Lungs, by the Page  142 Arteria Venosa, into the left ventricle of the Heart, being continual and strong; doth ma∣nifestly forbid any thing to come from the Heart, into the Lungs that way: and (2) the situation of the Valves in the same Arteria Venosa, doth as much. (3) That the Aer pas∣sing to the Heart, and the (supposed) Fuligi∣nous exhalations issuing from the Heart, should be carried through one and the same vessel, by contrary motions; is insolent to Na∣ture, and incompetent to the oeconomy of the body.

[ 15] And here we aske leave to propose a Pro∣blem. Certain it is,* that the Foetus, while in the Mother's womb, doth receive nourish∣ment (not by the Umbilical Vessels, for in them nothing is contained, but Blood, which is not the Aliment of the parts; and the Umbilical Vein serveth onely to the Circulation of the blood, by bringing back to the heart, what the two Umbilical Arteries carried from it into the Placenta Uterina: but) by the Mouth, sucking in that milky liquor, wherein he swimmes: which Hippocrates long since, and Dr. Harvey of late, have undeniably proved. Now, this being so, doth it not seem necessary, that the Foetus should also have the use of Respira∣tion? For, since all Suction is by Impul•ion (as we have elsewhere at large demonstrated) being caused only by the pressure of the thing sucked, by the Aer impelled in round (as we lately expressed, in the cause of the influx of the aer into the Lungs, in Inspiration) certain∣ly, Page  143 without the help of aer, the Foetus cannot possibly suck in his nourishment. To this Reason (and we think it a weighty one) may be added, (1) the Authority of the Divine old Man,* who in most expresse termes saith, 〈 in non-Latin alphabet 〉 [viz. Foetibus] 〈 in non-Latin alphabet 〉, Puer ab •lto respirat, & ore & nari∣bus. (2) that Chickens breathe in their shells (through which the aer hath a more difficult passage, than through the secundines) and Fi∣shes in the water. And as the Chicken pipes within the shell not yet broken; so hath it been observed and recorded by sundry learned and authentical Writers, that Infants have been heard to cry in their Mothers wombs: which were impossible, unlesse they enjoyed the be∣nefit of Respiration.

(3) The posture of the Child in the womb seems to assert the same. For, as there is an ample space betwixt the coats of the Secun∣dines, and the Child, to the end that a suffici∣ent magazine of milk for his sustenance, might be stored up, and conserved therein; so is not that whole space filled up with that Liquor, but in the upper part there remains so much space unpossessed by any thing but Aer, as is sufficient for so gentle a Respiration, as the Infant hath need of: just as in the blunter end of an Egge, we perceive a certain empty space after the Hen hath sate upon it. And lest the Chorion should at any time be corrugated or shrieveled up together, and so streighten or compresse either the Liquor, or the Infant; Page  144 Nature hath affixed the same to the Placentae Uterina, to the end, that adhering to the bot∣tome or upper part of the womb, it might hang fast, as an Apple hangs by its stem, or as our Globes of Glass are hung up by strings to the Seeling of a room. So that the Chorion thus adhaering to the Placenta Vterina, which is fast∣ned to the bottome of the womb, and the Am∣nios in like manner adhering to the Ch•rion, in the same upper part; and the lower part of each membrane being depressed by the weight of the Infant, and of the Humors contained in them: it thence comes to pass, that this Natu∣ral Machine both of the Child, and Membranes (though at first it were perfectly round, as the yolk of an Egge) is afterward made of an o∣val figure. For, though the Foetus, sitting in∣curved or bowed forward, as much as possible doth keep himself in a round figure, because of taking up the lesse room (for he sits with his leggs crossed, his heels drawn up to his but∣tocks, his elbowes resting on his knees, one hand held up close to his ear, the other to his cheek, for the more firme and easie sustenta∣tion of his head) yet, in that situation he hath need of a Mansion of an Oval Figure, that swimming in liquor, he might keep his head above water, and at his pleasure take in his nourishment by his mouth, and also inspire the temperate aer surrounding his head, in the void space of the Secundines; according to the opinion of Hippocrates newly recited. (4) Nor is the ingress of Aer into the womb impossi∣ble. Page  145 For, albeit the mouth of the womb, in pregnant women, be shut up, so as to exclude ones finger, or (as others will have it) a small probe: yet is it not so sealed or luted up, as to exclude the Aer; as may be inferred from hence, that many Femals have superfoe•ations, and more women (especially in this our moist Iland) are troubled with the Fluor albus, all the time of their Gravidation; neither of which could be, unless the Cervix Uteri were pervious: For, if there may be an ingress for the seed of the male after a former Conception; and as free an egress for the matter of the Fluor albus, all the time of the gestation of the Foetus▪ then, doubtless, Hâc etiam penetret per cuncta meabilis Aer. These Reasons duely perpen∣ded, though it seems a Paradox, yet is it no light and vain Conjecture, that the Foetus doth respire in the womb, at least gently and placidly, and in proportion to the pulsation of his heart; which being calmly and softly moved (as are the hearts of Dormice and o∣ther Animals, that sleep all the winter) hath but a small necessity of Aer. However, re∣flecting upon the singular fabrique of the ves∣sels in the heart of an Infant unborn, which all Anatomists conceive made by the provi∣dence of Nature, only in defect of Respira∣tion; as we proposed it a Problem, so we leave [ 16] it to the consideration of wiser heads.

Here also we may opportunely touch upon the Motion of the Brain,* which consisting (as that of the Lungs) of a Diastole and Systole, Page  146 many have referred to the Inspiration and Ex∣spiration of Aer; as if the Brain were dilated for the admission of Aer, and contracted again for the exclusion of it. Whereas, indeed, this Motion doth not belong (1) to the substance of the Brain; for, that being very soft, tender, and delicate, seems uncapable of any such dilatati∣on and compression. Nor (2) to the Membranes investing the braine; because, as Riolan ob∣served in the head of a Sheep, the diastole and systole of the brain hath been continued long, after part of the skull and Membrans also were cut off. But only to the Arteries, (1) because the Motion of the brain is exactly coincident and concordant with that of the Arteries, as may be discerned by the touch, in the heads of Infants new born, and in large wounds of the skull. (2) Because the chief Pulsation is in the upper part of the Dura Mater, which is conspersed with store of Arteries ascending from the Plexus Arteriosus Mirabilis, and disse∣minating themselves upon it. (3) Because Wa∣leus observed, that in some persons, who fell into extrem agonies, and swooning fits, upon great fractures of the skull, the motion of the brain ceased, and was begun again, as their Pulses recovered. (4) Of what Use should the inspired Aer be to the Brain? For Refrigeration, It cannot be; the temper of the brain being such, as seems to require rather Ca•efaction. And, as for the Generation of Animal spirits; Dr. Harvey hath upon good reasons made it doubtfull, whether there be any such or not: Page  147 and if there be, certainly they consist only of the purest and most subtile parts of the blood, and not of Aer, by the admistion of which they must needs become more crass and unfit for those noble uses,* to which they are consigned. And, therefore, Riolan said well; Nec spiritibus permiscetur Aer in Cerebro, quia debent esse sub∣tilissim•; alioquin permixtione aeris cr•ssiores eva∣derent, nec tam celeriter in universum eorpus ex∣currerent per nervos.

Nor must we here omit to touch upon the [ 17] Secundary Uses of Respiration,* which are Ma∣nifold. For, it serveth (1) to the creation of the Voice (whether Articulate, as in Man; or In∣articulate, as in Bruits) the Lungs exploding the inspired aer, through the Aspera Arteria, with such impetuosity and swiftness, as that its frequent and strong Elisions in the head of the Larynx, the throat and other parts of the mouth, cause it to yeeld a found. (2) to the Distribution of the Chyle both out of the stomach and guts, through the venae Lacteae, into the grand Receptacle, and out of that Receptacle into the ductus Chyliferi: the middle part of the Diaphragme, in Inspiration, depressing the stomach and guts; and its two long carneous productions lying so immediately under the Receptacle, as that they cannot be distended, but they must at the same time also distend it, and so express the Chyle out of it. (3) to the Exclusion of the Excrements both of the Guts and Bladder; the depression of the Diaphragme to∣gether with the compression of the Abdomen, Page  148 streightning and urging those parts. (4) to Smelling; the odours being brought into the Nostrills together with the inspired Aer. (5) to Coughing, Sternutation, Exscreation, and Emunction of the Nose; while the breath is driven forth with violence and suddainly. And (6) to assist the whole body in any strong and vehe∣ment motion; while, either the Inspiration be∣ing made gentle and small, and the breath kept in, the Muscles of the Abdomen and other parts are consequently stretched; and so we are the better enabled to lift up things of great weight, or to repell things making resistence by force of impulsion or otherwise: or, after a great inspiration, a vehement and suddain ex∣•piration succeeds, and then the Muscles are extended together with the like force, so as the Armes and Legs are strengthned either in giving a blow, or leaping, or other the like efforts, to which main force is required. And thus much of Respiration.