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forcibly driven through, the pulmonary Vein into the left Ventri- cle of the Heart. And this, together with the general Com- preflion of the Body by the Weight of the Atmofphere, is that Power which caufes the Blood ro mount in the Veins, after the Force imprefs'd on it by the Heart, is fpent; and which forces the Heart itfelf, from its natural State of Contraction, to that of Dilatation. See Heart.
The reciprocal Dilatation and Contraction of the fuperficial Di- menlions ot the Body confequent on Refpirathn, are lo neceffary to animal Life, that there is no Animal how imperfect foever as to want it.
Though mod Kinds of Fillies and Infects want both Lungs and moveable Ribs, and confequently have no dilatable Thorax, yet that Want is made up to them by an analogous Mechanifm. Fillies, for Inflance, have Gills which do the Office ot Lungs, receiving and expelling alternately the Water, whereby the Blood Ved'els fuffer the fame Alteration of Dimenfions as they do in the Lungs of more perfect Animals. See Gills.
Infects having no Thorax, or feparate Cavity for the Heart and Lungs or Air-Vcflels, have the latter diftributed through the whole Trunk of their Bodies ; by which they communicate with the external Air through feveral Spiracles or Vent-Holes, to which are fattened lb many little Trache or Wind-Pipes, which fend their Branches to all the Mufcles and Vifcera, and feem to accompany the Blood- Veffels all over the Body, as they do in the Lungs only, of the more perfect Animals. — By this Difpofition. in every Infpiration, the whole Body of thefe little Animals is in- flated, and in every Expiration comprefs'd; confequently the Blood-Veffels muft fuffer a Viciflitude of Extention and Com- preflion.
The only Animal exempted from this neceffity of Breathing, is a Foetus : But this, while included in the Womb, feems to have little more than a vegetative Life, and ought fcarce to be reckoned among the Number of Animals: 'Tis rather a Graft on, or Branch of the Mother. See Foetus.
The Laws of Refpiration, are of the laft Importance to a right underftanding of the animal OEconomy; for which reafon a Computation of the Force of the referring Organs, and of the ftrefs and preflure of the Air upon the fame, will not be unac- ceptable. —] t may therefore be oblerved, that by blowing into a Bladder, a confiderable Weight will be raifed; by the mere Force of the Breath : For with a Bladder that is oblong, nearly of a cylin- drical Figure, and tied at both Ends, if a Pipe be fixed at one End, and a Weight at the other, and the Pipe fattened at fuch a Diftance from the Ground, as juft allows the Weight to reft up- on the Ground ; the Bladder by an eafy Infpiration will raife fe- ven Pound Weight, and by the greatelt Infpiration of a pretty ftrong Man, twenty eight Pound Weight.
Now, the Force by which the Air enters this Pipe, is that Force by which it is driven out of the Lungs ; if therefore the Force by which the Air enters the Pipe can be determined, we fhall
have the Force by which the Air is drove into the Trachea >
But the Preflure of Air upon the Bladder is equal to twice the Weight it can raife ; becaufe the upper Part of the Bladder be- ing fixed, it relifts the Force of the Air, juft as much as the Weight at the other End. And again, fince the Air prefTes eve- ry way equally, the whole PrelTure will be to that Part of it which preffes on the Orifice of the Pipe, as the whole Surface of the Bladder is to the Orifice of the Pipe ; that is, as the Sur- face of a Cylinder, whole Diameter, for inflance, is four Inches, and Axis feven, is to the Orifice of the Pipe.
Thus, if the Diameter of the Pipe be o. 28, and its Orifice o. 616; the Surface of the Cylinder will be 88. Therefore, as 88 : o. 616 : : 14. double the Seaft Weight raifed, to o. 098, which is almoft 2 Ounces,- and in raifing the greateft Weight it is near 7 Ounces.
Thefe therefore are the Forces by which the Air is drove through the Trachea, in an eafy and a ftrong Expiration.— Now if we confider the Lungs as a Bladder, and the Latynx as a Pipe ; the PrelTure upon the Orifice of the Trachea, when the Air is drove out, will be to the Preflure upon the Lungs, as the whole Surface of the Lungs to the Orifice of the Trachea.
Suppofe, e. gr. the Diameter of the Latynx to be 5 ; the Ori- fice of the Larynx will be o. 19. And fuppofe the two Lobes of the Lungs to be two Bladders, or Spheres, whofe Diameters are each fix Inches; their Surfaces are each 113 Inches, and the Preffure on the Larynx will be to the PrelTure upon the whole external Surface, as o. 19 to 226, which is as 1 Pound 1189; and therefore if the PrelTure upon the Larynx in an ordinary Breathing be two Ounces, the PrelTure upon the whole external Sutface of the Lungs will be 148 Pounds; and the utmoft Force, when the PrelTure upon the Larynx is feven Ounces, will be equal to 520 Pound.— But the Lungs are not like an emp- ty Bladder, where the Air preffes only upon theSurface; for they are full of Veficles, upon the Surface of each of which the Air prefTes as it would upon the Surface of an empty Bladder; and therefore to know the whole PrelTure of the Air, we muft deter- mine the internal Surfaces of the Lungs.
To do this, fuppofe that -J Part of the Lungs is taken up with the Branches of the Trachea, that another third Part the Blood- VefTcls fill, and the remainder is Veficles, where we fup- pofe the chief PrelTure upon the Blood- Veflels to be made : Now,
both Lobes of the Lungs contain 226 folid Inches, of which one third, or 75 Inches, are full of Veficles.— Let the Diameter of each Veficle be T V Part of an Inch, the Surface of a Veficle will be .001256, and the Solidity 0000043, by which Sum if we divide 75 (the Space filled by the Veficles) the Quotient owes us 17441860 tor the Number of Veficles in both Lobes of the Lungs.— This Number multiplied by .001256, the Surface of a Veficle gives the Sum of the Surfaces of all the Veficles, to wit 21906.976 Inches. And therefore the Preflure upon the Larynx will be to the PrelTure upon the whole Surface of the Lungs, as o. 19 to 21906.976; and confequently, when in au ordinary Ex- piration the Preflure upon the Larynx is two Ounces, the Pref- fure on the whole internal Surfaces of the Lungs will be 14412 Pound Weight ; and the utmoft Force of the Air in Breathmo, when the Preflure upon the Larynx is fevcu Ounces, will be 50443 Pound Weight.
Though thefe feem to be prodigious Weights, yet it muft ftli be underftood, that the PrelTure upon each Pait of the Surface of the Lungs equal to the Orifice of the Larynx, is not greater than it is at the Larynx ; and that thefe vaft Weights arife from the vail Extent of the Surfaces of the Veficles upon which it was neceffary that the Blood fhould be fpread in the fmalleil ca- pillary Veflels, that each Globule of Blood might, as it were, im- mediately receive the whole Force and Energy of the Air, and by that be broke into fmailer Parts fit for Secretion and Circu- lation.
And hence we may learn the mechanical Reafon of the Struc- tute of the Lungs : For, being the whole Blood of the Body was to pafs through them in order to receive the Effect: of the Air, and that this could not be unlefs the Blood were diffufed in fmall capillary Veffels; it was neceffary that the Surfaces upon which they were to be fpread, fhould be proportioned to their Num- ber: Which is admirably well provided for by the wonderful Fabrick of the Lungs.
If the Graviry of the Air was always the fame, and if the Dia- meter of the Trachea, and the time of every Expiration were e- qual in all ; this Weight upon the Lungs would be always the fame. But fince we find by the Barometer, that there is three ^Inches difference between the greareft and the leaft Gravity of Ihe Air, which is a tenth Part of its greateft Gravity; there muft be likewife the Difference of a tenth Part of its Preffure upon the Lungs at one time and anothet : For the Momenta of all Bo- dies, moved with the fame Velocity, are as their Gravities. See Barometer.
This is a Difference which fuch as are afthmatic muft be ve- ry fenfible of; efpecially if we confider that they likewife breathe thicker, that is, every Expiration is performed in lefs time; if m half the time, and the fame Quantity of Air drawn be in, then the Weight of the Air upon the Lungs muft be 57648 Pounds, of which a tenth Part is 5764 Pounds : And confequently afthma- 52 Peo P le U P°" *e gteateft rife or fall of the Barometer, feel a dtfference ot the Air, equal to above one third of its Preffure in ordinary Breathing. See Asthma, Weather, 6c.
Again, if the Trachea be fmall, and its Aperture narrow, the Preflure of the Air increafes in the fame Proportion as if the times of Expiration were fhorter; and therefore a fhrill Voice is always reckoned amongft the prognoftick Signs of a Confump- tion, inafmuch as that proceeds from the narrownefs of the La- rynx or Trachea ; and confequently increafes the Preflure of the Air upon the Lungs, which upon evety Expiration beats the Vet fels fo thin, that at laft they break, and afpittingof Blood comes on apace. See Phthisis.
RESPITE, Respectus, in Law, &c. a Delay, Forbearance, or Prolongation of Time, granted any one for the Payment of a Debt, or the like.
Menage derives the Word Rejpite from trrnLatin, rejpeilus; as defpite from defpelhs.—Vu Cange will rather have it come from ref (irare, to Breathe; Re/pile being, in effect, a breathing-while, granted a Debtor, eye.
Letters of Respite, or Credit, are Inftruments antiendy granted by Sovereign Princes to honeit, but unfortunate Debtors, to fcreen them from their too rigorous Creditors.
Thefe ftill obtain in Frame.— They were firft introduced by Pope Urban II. in favour of the Croifes, i. e. of Perfons who went to the Holy War. See Croises.
S. Louis granted three Years Refite to all who made the Voyage ot the Holy Land with him.— In the Cuftomary of Normandj, Refpite i s a judicial Delay, or Demur, given to Pro- cedures.
Respite of Homage, is a forbearance of the Homage due from the Vaflal or Tenant holding bv Homage, or by Knight- Service to his Lord. See Homage, &c. °
Antiently thofe who held by thefe Tenures, paid a fmall Sum every fifth Year into the Exchequer, to be refpiled doing their Homage or Service.
By Stat. 12. Cur. II. this Rejpite of Homage is taken away, as a Charge arifing from Knight-Service; which is thereby likewife annull'd. See Tenure, &c.
RESPONDEAT Superior, a Law Phrafe.— Where the She- riffs are removeable, as in London, for Infufiiciency ; Refpond-at Superior, that is, the Mayor and Aldermen are to anfwer for them. See Sheriff, &c.
For
