• v;^.' ••'>•?, v '■■'>'■ ' si \it ' rt '■i!v'-r55r,iT*VA'.-" ^^ ■■*C ■^ •>l*W$'■•'*■■■■ .■■\,/-?..^-...i>-*V-'Af i': .■■/"." '■■ "■ "■-• y ■'i'"' KtStixifflaM-"^ UNITED STATES OF AMERICA WASHINGTON, D. C, GPO 16—67244-1 ►■re^v.v.-.^.'iv.^W?.*^.**!* A ft INAUGURAL DISSERTATION O K T HK PRODUCTION of ANIMAL HEAT: READ AMD DEFENDED AT A PUBLIC EXAMINATION, heid bt the MEDICAL PROFESSORS, before the Rev. JOSEPH WILL ARD, S.T. D. L.L.D. President, AMD THE GOVERNORS OF HARVARD COLLEGB, FOR 1HE DEGREE OF BACHELOR IN MEDICINE, July io, 1797. by LYMAN SPALD.ING. PRINTED at WALPOLB, Newhampshire, By DAVID CARLISLE, Jun. NATHAN SMITH, m. b. THIS DISSERTATION I s RESPECTFULLY INSCRIBED, BY HIS GRATEFUL PUPIL, The AUTHOR. ^°\^\5 A K INAUGURAL DISSERTATION, X HE heat of the human body, jn health, is generally about ninety fix degrees of Farenheit's thermometer. Yet fo ad- mirably is the economy of man adapted to the variations of heat, as not to be materially af- fected by it, excepting in its extremes. Man can dwell in all climates, free of dan- ger, from the intenfe cold of Siberia and Spitbergen, where mercury congeals fponta- neoufly in the thermometer, to the per- pendicular rays of Amazonia. Nay more, Dp&or Fordyce has by experiment prov- ed, that man can exift in a room, walled with bricks and gradually heated to the degree of boiling water, i. t. two hundred and twelve degrees; C « 3 degrees ; and all thefe variations of place and temperature 5 a difference of three hundred and thirty two degrees, or more, without de- ftroying life, producing difeafe, or altering the temperature of the common mafs of fluids, but a few degrees, from the ftandard ninety fix. It isfurprifing wherein confifts thecaufe of this equilibrium of animal heat, whether the fubjeft be expofed to the freezing Wafts of the pole or fcorching beams of the equinoctial fun. Animals therefore have a power of gen- erating heat, when placed under the poles; and a ftill more furprifing power of re- filling the introduction of heat or generating cold, when in a heated room. In the firft inftance the fluids are guarded from congelation, and in the fecond prevented from pafling into elaftic gafes; both of which principles are wanting in the vegetable king- dom. What t i 3 What havoc heat and frofl: make in the hufbandman's plantations! where a few hours midday fun or midnight frofl;, lays wade many months of labour; mars the beauty of the fields, and difappoints the expecting hufband- man. Of all the phenomena of the animal e- conomy, none is more flriking, none more worthy the attention of philofophers, than thofe, which accompany the function of ref- * piration. Little as we are acquainted with the objecl: of this Angular operation, we are fatisfied that it is effential to life, and that it cannot be fufpended for any length of time, without expofing the animal to im- mediate death or imminent danger. It is univerfally known that air is the agent or rath- er the fubjecl: of refpiration. But at the fame time there are fome kinds of air, which will not fupport life, in the higher order of ani- mals. There have been almoft as many theories, as writers, on animal heat. It is perhaps need- lefs C 8 3 lefs and unfeafonable for me to enter into an inve{ligation of them. Some have fuppofed it to be generated by the tendency of the fluids and folids to putrefaction; others attributed it to the attrition of the blood in circula- tion. We will obferve the different procefles, by which heat is known to be generated. Thefe may be confined to two ; which are, firft, Com- bination and Decompofition ; fecond, Friciion. We will take a curfory view of thefe, and fee which belt agrees with the phenomena of animal heat. First, of COMBINATION and DECOMPOSI- TION. THE theory of combuftion is now ex- plained on the abforption of the vital princi- ple from the air ; and fetting at liberty the a- zotic and carbonic principles, which arife in fmoke. That C 9 3 That the air is decompofed and robbed of fome of its conftituent parts,which it pofTeffed previous to its expofure to the burning body, and is combined with fome other matter^ which did not before appear in it, is evident from comparing atmofpheric air,previous to combuf- tion, with the fame afterwards ; the former■, of its common purity, M. d' Lavoifier founds by experiments, to confift of ,27 of oxygen, ,73 of azote, and ,01 of carbonic acid ;* the latter con- fifts of little or no oxygen at all, a fmall fhare of azote, but perhaps one half is carbonic ac- id. The union of concentrated acids with wa- ter, quick lime, pure alkalis, or metals, is pro- ductive of a ftrong heat; but the combina- tion of the nitric acid with certain oily fub- ftances is fo powerful this way as to caufe in- flammation. B Let * Thefe namoi were firft introduced by the French, in their new Nomenclature, inflead of the old term-, vi- tal, impure, and fixed air. C >° ] Let us compare thefe phenomena with thofe of animal heat, and notice the agree- ment between them. It will be firft afked where are, and of what confift, the combina- tion and decompofition ? Will it be thought fufficient if I fay, in the lungs, during refpira- - tion, a part of the air is combined with the blood, and that in its turn fends off carbone* with the air expired. This procefs appears fimilar to combuftion, the fmoke of which is exa£tly fimilar to our breath expired ; the prefence of oxygen is nec- effary to the fupport of the one as well as the other, during both of which the calorict of the oxygen is feparated from the air; their refi- dues are totally unfit to fupport refpiration or combuflion, until they are again oxygenated. This, not being thoroughly underftood, has been treated as hypothetical.^ Therefore * This is the coaly principle, the bale of carbonic acid. + Matter of heat. J Cullcn'i Phyfiology. C » 3 Therefore, having found it impoflible to account for it on thefe principles, refort was had to FRICTION, WHICH we 6nd was the favourite theory of moft of the antients, as it has been that of the moderns. This theory was powerfully fupported by the celebrated Cullen, who faith that the caufe of animal heat is " the motion of the blood." Since friction has been generally at- tributed as the generating caufe of animal heat, we need not be furprifed at the many hypoth- efes advanced refpeding the manner in which, and the parts on which, it operated to produce it. I am difpofed to favour and fupport a the- ory, which attributes the production of animal heat to the combination and decompofition of air and blood, in their paffage through the lungs, during the a£t. of refpiration j by which the C »• 3 the caloric in the air is difengaged from its conftituents, and appears combined with the blood ; which may be deduced from this : the expired air having loft its caloric, which it poffeffed before infpiraticn ; and the blood having acquired an additional quantity of it, to what it had previous to its entering the lungs. In fupport of this, I fhall firft notice fome general fa&s refpeding the air's containing ca- loric. Then, that this caloric is difengaged from the air in its paffage through the lungs. Thirdly, that a decompofition of the blood takes place at the fame time. Fourthly, that there is a combination of fome fubftance with the air expired. And, laftly, that a certain matter is combined with the arterial blood in the lungs. Those truely ingenious philofophers, Doc- tors Black and Crawford, have proved, by a number of nice experiments, (which it would be difficult to give a juft idea of without en- gravings) that the caloric is contained in the oxygen; C »s 3 oxygen; and that expired air contains only one third part of the heat, which was contained in it previous to infpiration ; it follows that the former muft neceffarily have given off its ex- cefs of abfolute heat in the lungs. The comparative heat of florid arterial blood is, to that of venous, as eleven and an half to ten; the heat of that blood, which is re- turned from the lungs, is greater than it was previous to its entering them, from which it muft have received its fupply. We may conclude from hence, that, in the lungs,during the procefs of refpiration, a quan- tity of abfolute heat is feparated from the air, and combined with the blood. Dr. Crawford has inferred, from experi- ments, that, in the converfion of arterial blood into venous in the capillaries, the heat is difen- gaged from the arterial b!©od,and combines with the furrounding fubftances. So that venous blood muft have, by far, lefs fpecific heat, than whatappearedjuft before in the arterial; and, if that, C '4 ] that, on its arrival in the lungs, fhould be converted into arterial blood,without receiving any fupply of abfolute heat from the air, its fenfible heat would be fo diminifhed, as to fall from ninety fix degrees, to below the freezing point. In a warm medium, the fame animal decom- pofes Iefs air, in a given time, than in a cold one, alfo lefs heat is difengaged, the difference of colour in the arterial and venous blood is lefs ; and thefe in proportion to the tempera- ture of the circumambient air. A cubic inch of air, of the temperature of two hundred and twelve degrees,contains,by far,lefs oxygen,than when of a temperature one hundred and twen- ty degrees below o ; and in the docompofition of equal quantities of air, of fo different tem- peratures, an amazing excefs of heat will be in favour of the cold air. Hence inflammatory difeafes are moft prevalent in the cold feafons ; it is this, which, in animals, wards off the deftmftive effects of cold in the polar re- gions. On t >5 3 On the other hand, the quantity of caloric being very trifling, that is difengaged from the warm air, inftead of increafing the heat of the arterial blood, it does not equal the cold pro- duced by the converfion of venous into arteri- al blood; and, inftead of increafing the heat, it generates cold. On this,'and evaporation, it is that man is capable of enduring an atmof- phere heated two hundred and twelve degrees, without fufpending the functions of life. The air is decompofed in its paffage through the lungs, and the caloric difengaged from it. Atmospheric air, or that which we refpire, is a heterogeneous fluid, compofed of oxygen, azote, and carbonic acid. The former main- tains life by refpiration, and fire by combuf- tion ; both the latter are totally unfit for either of thofe purpofes. Oxygen is alfo a compound,confilling of a principle of folidity and caloric, fire, or the matter of.heat. Caloric is moft abundant in oxygen; other airs, fuch as air expired, fmoke, Sec. C »« 3 Sec. contain but little if any at all; in any air that is nearly proportional to this power of fupporting life. An animal,placed in a vefTel containing air, as foon as it is nearly all changed by refpira- tion, fickens, is convulfed, and dies, if not re- moved. This happens inftantaneoufly in car- bonic acid, almoft as foon in azote, later in atmofpheric air, and lateft in oxygen, which fupports life about four times as long as atmof- pheric air, and is perhaps the much celebrat- ed pabulum viTiEof the antients. In the third place, we have to fhow that there is a decompofition of the blood, in the lungs, during refpiration. The venous blood, when brought to the lungs, is of a dark modena red, which is pro- duced by the prefence of a large quantity of hydrogene or azote, and abfence of oxygen. To prove this the following experiments were inflituted, two ligatures were made on the ju- gular vein of a living cat, one half of the blood contained C *r 3 contained between the ligatures was drawn ofF, the vein filled with hydrogene ; an hour after the blood, being drawn from the vein, v\ms flu- id, but had acquired a colour almoft as dark as ink. At, and for, the lame time, an equal quantity of blood was intercepted between two ligatures, on the crural vein of the fame# ani- mal. This blood, being drawn from the vein, was found in fome meafure coagulated, but mifcible with water; communicating, by far, lefs colour to it than the former. Hence it may be inferred ; that, when hydrogene or azote are in contact with the blood, they increafe its col- our and diminifh its tendency to coagulation. We will fhortly Mate how hydrogene and a- zote may be introduced into the circulating tnafs. Blood attracts hydrogene and azote, tvhich are feparated from animal fubftances, by heat and a tendency to putrefaction. The colour of the aTterial blood is a light icarlet; it undergoes the fame change in com- C pleting I *• 3 p'erin^ a circulation, as by exriofure to hydro- gene or azote. Therefore, we may conclude, that it is united wita thefe, in fome part of its routine, and perhaps in the capillaries, where they aie feparated by he.it and the putrefac- tive procefs. Thefe, united with the blood, account for the dark grumous colour of it in the vena portarum, where it has abforbed an unufual quantity from the femiputrefcent con- tents of the alimentary canal. The air, con- tained in the large interlines, is moftly hydro- gene. The greater the heat of the animal, and ten- dency to putrefaction, the more impure air will be difengaged, and the venous blood dark- ened proportionally. We have now to confider the combination of fonae fubftances with the air expired, which did not appear in it, when infpired; thefe are fixed air and carbone. An exoiration confifts of fixed air, hydro- gene, azote;aadrflftffeeae. The C >9 J Thi prefence of fixed air is proved by its precipitating lime wat^r, when agitated with it. The quantity of carbonic acid is greatly i.i- creafed by refpiration (-.vhere the oxygen com- bining with the cart-one, in the moporuon of feventy two to twenty ei~ ht, forms pure carbon- ic acid) inftead of bting one part in an Hun- dred, as in atmofpheric air, makes, periiaps, one tenth of tne wnole expiration. Fourcroy obferves, that carbonic acid is produced by refpiration, combuftioa of coals, and is exhaled from plants in the fhade ; is inftantaneoufly fatal to animals, and extin- guifhes flaming tapers. Azote arifesmofllyfrom putrefying animal matters; is very noxious to animals and flames. The prefence of thefe twogafes is the caufe of the great fatality obfervabie ir. tight bed chambers, where a pan of coals has been add- ed to ward off the cold, during a winter's night ; in prifon and cartel Clips hofpitals, jails, C *> ] jails, Sec. where numbers are crowded togeth- er, without proper ventilation. This is evident, from the fymptoms of thofe, who languifh, being the fame as are ob- fervable, when introduced into carbonic acid, or azote, as mentioned above, they firft ap- pear flupified, foon agitated ; refpiration be- comes laborious and hurried; from this, the fymptoms of diftrefs faft increafe, till fubfuitus tendinum and convulfions clofe the fcene with death. The fame caufe we give for the production of endemic difeafes in compact towns, during the hot feafons of the year, when the putre- factive procefs feizes all inanimate animal fubftances and many vegetulles, difeflgaging therefrom the noxious azote, which remains ftagnant for want of a current of air to dif- peiie it. LASTLY, We have to fj-.ck of caloric, which is com- bined with the si:teri-l bleed in the lungs. This C « 3 This is feparated from the air in refpira- tion, and changes the colour of the venous, to a light fcarlet, and greatly incrcafes the abfolute heat of the arterial blood. To prove thi*,the experiment above relat- ed may be introduced, with this diiference ; introduce oxygen into th..: vein :a lieu of hy- drogene. The blocfd when dra./n w:il oe of a moft beautiful fcarlet. Alfo.expoic a glals of venousbloodto the ~£tion of oxygen,the i-mie effect will be produced ; or fpi inkle ic.vith a neutral fait, as muriate of foci , nitrate of pot- £{h,&c. which, on decompofiticn, are known to fend forth a large portion of oxygen, and we fhall fee the furface changing rapidly to a li^hc fcarlet. . When two or more bodies are united by the attraction of competition or glandular at- traction, their terrperature fuiTjrs a change. The cxygenjs combined with the blood in the lungs by this attraction of com polk: on, nd there eliminates a part of its heat j but when it airivei at the capillaries, which are £&uJ;y glands, [ «« 3 glands, a new attraction of compofition, with a glandular attraction, eliminate the remain- der, which was the greateft part of the caloric. The heat of the arterial blood is,to the ven- » ous, as eleven and an half to ten ; this is fuffi- ciently eftablifhed by direct experiments';, From the preceding obfervations, may be drawn the following inferences : animal heat, and heat fent forth by combuftion, depend on the fame caufe. Animals, who refpire little or no air, are always cold ; fuch are fifhes, toads, lizards, infects, ferpents, &c. whofe arterial blood is defiitute of that florid rednefs. RESPIRATION, THEREFORE, appears to be but combuf- tion in a lefs degree, in v.hich atmofpheiic air is decompofed in its paffage through the lungs, is robbed of its vital principle, caloric of the oxygen, which is combined with the blood, and with it diflufed through every and the mi- nuteft part of the f> fkm, fpre luing its geniul warmth L *3 J warmth and animating every fibr? ; till, in tha capillary veffels, it is ex~hifwt.d i>jl ay Uogene and azote, where the blood parts v.tii its fear- let hue for a da.k modena red; furcharged with thefe new properties, it returns to the lungs,-where they are difpofed of and a new routine commences. In this manner then, is animal heat gene- rated ; and all parts of the body receive con- ftant fupplies from this great fountain of heat, the lungs.* Man does not receive his natural warmth from the temperature of the furrounding at- mofphere. * The author, fince reading his Diflertation, hai found Iot-: obTervations in Dr. Darwin's Zoonomia, which corrofpond fo nearly with his own opinion and obfervations, that he was almoft per funded to introduce them to elucidate this work ; bu: to abridge is a delicate tafk. However, he hepes thofe, who are not fully per- fuaded of the truth of this theory, will con:'u>: that juft- ly celebrated work ; particularly Sc£l:on XXIII. 4. Scftion XXXVIII. and Clais II. 1. 1. 2. C *4 3 mofphere. Why fhould wc expe& his body to be of the temperature of Spitbergen or Am- azonia, as he may chance to inhabit one or the other place ? We find the principles of animal heat innate with him, and never diminishing lor increafing beyond bounds ; although the fur- rounding at-no'phere fhould vary three hun- dred and thirty tv.-o degrees, or more. Such is the wonderful economy of nature. It may be afked, if combuflion and refpira- tion be fimilar procefTes, why does not light and! flame appear from the one as well as the oth- er ? The anfwer is plain, the procefs of res- piration is like combuftion, but accompli fh- ed in a much more gradual manner ; the rapid- ity of the former ill fuits the flow progrefs of the latter. However, the phenomena of the two bear the fame affinity to eech ether, as the phenomena of the fudden and general, the mod- erate and partial combination of nitric acid with oil. The former buiils into fume, Chew- ing Iip;hr, beat and all the phenomena of com- buflion ; but the I.Ut.v is more moderate, like refill alien, C *5 3 refpiration, not being accompanied with any figns of light or flame, but all the other phe- nomena of the former, as heat, Sec. Never- thelefs the two proceffes are identically the fame, only differing in degree. Perhaps thefe obfervations have been couched in too chemical terms, to be ftrict- ly adapted to the animal economy, which is not to be compared to a chemift's labora- tory ; but the procefs is fo fimilar to a chem- ical DOUBLE ELECTIVE ATTRACTION, that, without this order, the definition could not have been perfect. The foetus, egg, and feed, receive their vivifying heat from the parent animal or earth ; but as foon as the animal is ufhered into perfect exiftence, we find it capable of generating this principle, independent of its parent, but the vegetable, ever (o perfectly formed, is dependent on its parent earth for exiftence. D HlRACHTUS C *s ] Heraclitus maintained that fire was the vivifying principle of all bodies, both animal and vegetable. The ingenious Dr. -.Brown has added that their exiftence, growth and maturation depend on fomething, which acts from without, and this a " ftimulus." Living animals and vegetables have, be- fides the common properties of matter, a pe- culiar fomething, which diflinguifhes them from dead ones ; in thefe we fee all the folids and fluids too : what then is lacking ? A gen- tle ofcillation, or motion of the fluids, a cir- cumgiration of the liquors, which is produced and continued through life by a certain fome- thinj, abforbed from the air. Our ingenious profeffor, in a " Difcourfe on the Principles of Vitality," obferves, "it is a portion of that fubtle electric fluid, which fills the immenfe fpace of the whole univerfe, pervades all bodies, and actuates every particle of matter. By it the phenomena of magnet- ifm, fire, and light are produced ; and on it the C *7 ] the various and aftonifhing phenomena of vegetation and animation depend." The arterial blood, having received the ca- loric, from the lungs, is directly dillributed to every part of the body, and in every part is changed into venous blood, in the operation of which, it difengages the matter of heat, and abforbs a proportional quantity of hydrogens and azote, which are plentifully fupplied from fermenting and putrefying matters ; the greater the quantity of hydrogene and azote, yield- ed in any one place, the greater will be the quantity of heat exchanged for it in that place : inftance fermentation in the flomach, called heart burn, what an increafe of heat in that re- gion. Also, PUTRID FEVERS, IN which, tp the accelerated velocity of the blood add, that the folids and fluids are tend- ing to putrefaction; hence an unufual quantity of hydrogene and azote will be yielded, and an C ** ] an unufual quantity of heat will be exchanged for them at the converfion of arterial into ve- nous blood. To thefe caufes it is probably owing that the heat of the human body is greateft in thefe fevers. Local inflammation is accompanied with rednefs, tumour, and unufual heat, with in- creafed circulation, and at length with a flag- nation of ferous fluid, which is effufed in- to the adjoining cellular fubftance, the putre- factive procefs, commencing, the heat in the part is then greateft. In the flate of health, the motion of the blood through the different parts of the fyflem, and the hydrogene and azote with which the blood is fupplied in thefe parts, is adjufted fo exactly to each other that the exchange is e- qual through every part of the fyflem. But if by any excefs the balance be de- flroyed, as by increafed circulation, or by a tendency to putrefaction, it is evident that a greater quantity of heat will be extricated in that [ '9 3 that part, in a given time; this heat will ftimu- late the veffels into more frequent and forcible contractions,by which the velocity of the blood, and confequent extrication of heat will be ftill farther increafed. On this principle we may probably account for the partial heats, which are produced by topical inflammations, and thofe, which arife in hectic and nervous com- plaints. So the fire increafes in that place where the air is gently agitated by the bel- lows. Dr. Crawford obferves that the doctrine which refults from his experiments on animal heat, will probably lead to an explanation of the ufes of the fpleen and lymphatic glands. May not the fpleen, fays he, be intended partly to apply a proper degree of heat to the left fide of the flomach, and partly to fupply the liver with azotic blood ? As a quantity of fire is extricated, during the converfion of arte- rial into venous blood, in the capillaries, if blood, which is changed in the fpleen, had paff- ed to the liver, as arterial blood, and had been changed [ 3» ] changed into venous in that organ, it feems ev- ident there would have been a redundancy of heat in the right hypochondriac region, and a deficiency of it in the left. a, I Nt«L.Hi»t wz no nil t«i J^lb