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AN 
 
 INAUGURAL DISSERTATION 
 
 ON 
 
 RESPIRATION. 
 
 SUBMITTED TO THE PUBLIC EXAMINATION OF THE 
 
 FACULTY OF PHYSIC 
 
 UNDER THE AUTHORITY OF THE TRUSTEES OF COLUMBIA COLLEGE, 
 IN THE STATE OF NEW-YORK, 
 
 ."he Right Rev. BENJAMIN MOORE, D.D. President; 
 
 FOR THE DEGREE OF 
 
 DOCTOR OF PHYSIC, 
 
 On the 12th Day of November, 1805. 
 
 BY THOMAS COCK, 
 
 CITIZEN OF THE STATE OF NEW-YORK, 
 
 Hear, O ye sons of time ! the powers of life 
 Arrest the elements, and stay their strife ; 
 From wandering atoms, ethers, airs, and gas, 
 By combination form the organic mass ! 
 And, — as they seize, digest, secrete, — dispense 
 The bliss of being to the vital ens. 
 
 Darwin, 
 
 NEW-YORK; 
 
 Ptfnwd by T. & J. SWORDS, Printers to the Faculty of phy»ic 
 of Columbia College, No. 160 Pearl-ttreet. 
 
 1805. 
 
71/ 
 /mr 
 
TO 
 
 VALENTINE SEAMAN, M. D. 
 
 Permit me to offer you, as a mark of esteem and respect, 
 
 the first fruits of that medical education which has 
 
 been conducted under your patronage. 
 
 The AUTHOR. 
 
to 
 WILLIAM HAMERSLEY, M.D. 
 
 Professor of the Theory and Practice of Physic in Columbia College, 
 
 THIS DISSERTATION 
 
 Is respectfully inscribed 
 
 By his obliged humble servant 
 
 The AUTHOR, 
 
INTRODUCTION. 
 
 WHEN we take a retrospective view of the 
 advancements that have been made in physiolo- 
 gical inquiries, we are fully impressed with the 
 advantages that have resulted from a correct 
 chemical examination of the materials operating 
 upon the animal body, together with a more ac- 
 curate investigation of its productions. Among 
 the agents acting upon the body, and entering 
 into it as an useful part, the aix of the atmosphere 
 demands the greatest attention ; and in this che- 
 mical inquiry has been productive of extensive 
 importance. 
 
 It is certain that the most important advant- 
 ages do result from a close attention to the dif- 
 ferent functions of the animal body in a state 
 of disease; therefore, in proportion as our 
 knowledge of these functions is more or less 
 correct in a state of health, so may the diseased 
 changes of the body be inferred, and their re* 
 
( i ) 
 
 moval understood. With an impression of this 
 nature I have been led to the investigation of 
 Respiration as the subject of an Inaugural Essay. 
 
 From the late experiments of some ingenious 
 chemists who have directed their attention par- 
 ticularly to this subject, many important facts 
 have been discovered. Among these experi- 
 menters may be reckoned Dr. Beddoes and 
 Mr. Davy; the latter of whom has exposed, 
 with great clearness, the fallacy of preceding 
 opinions, and has given more extensive expe- 
 riments upon the nature of different airs, with 
 their effects upon the body when respired. 
 These experiments have not only been made 
 upon himself, but upon others with the greatest 
 attention. 
 
 However clear and decisive the experiments 
 of Dr. Goodwin upon respiration may have 
 been considered, Mr. Davy has pointed out their 
 errors and imperfections, and has deduced from 
 his own discoveries a more correct explanation 
 of the phenomena of this function. 
 
 In the plan of this dissertation each particu- 
 lar division is briefly considered. In the first 
 place a short sketch is given of the parts con- 
 cerned in the performance of respiration. 
 
( 7 ) 
 
 2d. The importance of air in the support of 
 life, and its chemical properties are considered. 
 
 3d. The influence of different airs upon 
 blood out of the body, and the changes that 
 are effected upon this in its passage through the 
 lungs of animals during life. 
 
 4th. The application of these different phe- 
 nomena to the explanation of animal heat. 
 
 In the explanation of many subjects in phy- 
 siology great error has arisen from too general 
 conclusions by analogical reasoning, and this 
 by facts drawn from the operation of matter 
 upon inanimate substances. Hence the reason- 
 ing has been fallacious, as the laws of inanimate 
 matter are far different in their operations, sub- 
 ject to great variety from the actions of the ma- 
 chine itself, and changed by the influence of 
 mind upon matter, which is primarily operated 
 on by a variety of external as well as internal 
 causes. How far these objections are applica- 
 ble to the present opinions on the subject of 
 respiration, time will alone determine, as error 
 shall give way to truth, and the absurdity of 
 hypothesis be corrected by the power of just 
 experiments and correct reasoning* 
 
AN 
 
 INAUGURAL DISSERTATION 
 
 ON 
 
 RESPIRATION. 
 
 Jt5 Y Respiration is understood the taking in and 
 expelling air from the lungs. The importance of 
 this function has rendered it synonimous with life. 
 We are all sensible of the great inconvenience of 
 its being suspended only for a short time, or of 
 any imperfection in its performance, as takes 
 place in many diseases of the chest; such as 
 asthma, hydrothorax, &c. in which a free action 
 of the parts concerned cannot take place. 
 
 Respiration is a function of a mixed kind, that 
 is, both voluntary and involuntary. We can 
 increase its frequency, and can take in a larger 
 quantity of air at will; but in this case the ope- 
 ration becomes fatiguing, the same as when any 
 motion is performed by voluntary muscles in 
 other parts of the body.* As an involuntary ac- 
 tion, it is rendered far more important to us, as 
 our existence is so immediately connected with 
 its regular performance and continuance; and 
 whenever we make it a voluntary action, its fre- 
 quency or force is always increased. 
 
 The principal parts concerned in respiration 
 are, the trachea, lungs, and diaphragm, to which 
 
 * In. the singular instance of Mr. John Hunter, his respiration was a 
 complete voluntary action for some time; he found it unnecessary to 
 respire except when he would speak. 
 
 B 
 
( io } 
 
 may be added, the intercostal and abdominal mus- 
 cles ; and when it becomes forced or laboured from 
 any cause, other muscles are called into action. 
 
 The trachea is a cartilaginous tube, extending 
 from the larynx to the bronchia, which are its 
 divisions, and whose more extreme ramifications 
 terminate in the air cells of the lungs. This tube 
 is lined throughout its whole extent with a deli- 
 cate membrane of extreme sensibility to all mat- 
 ters excepting air, and highly susceptible of in- 
 flammation. The lungs are organs of consider- 
 able size that completely fill up the two larger 
 cavities of the thorax; they possess little specific 
 gravity in animals that have breathed, being 
 made up of cells extremely numerous and minute, 
 upon which the branches of the pulmonary ar- 
 tery spread out : they always contain air in 
 greater or less quantity, according as they are 
 more or less distended or collapsed. The lungs 
 (contrary to the ancient opinion) are considered 
 as passive in the function of respiration; they 
 only fill up the increased cavity of the thorax, 
 which is produced by the actions of the inter- 
 costal muscles elevating the ribs; while the dia- 
 phragm encroaches upon the abdomen, which 
 it effects by bringing itself nearer to a plane; 
 and the lungs are enabled to fill up what would 
 otherwise be a vacuum by air rushing into them 
 through the trachea. These actions constitute 
 inspiration. The air is again expelled from the 
 lungs by the actions of the abdominal muscles 
 which are attached to the ribs, and are ex- 
 cited into action by their elevation and by the 
 
( 11 ) 
 
 protrusion of the abdominal viscera produced 
 by the descent of the diaphragm. The expul- 
 sion of the air is also assisted by the elasti- 
 city of the cartilages connected with the ribs; 
 by which power, after the intercostal muscles 
 cease to act, they restore themselves to their 
 former situation, which diminishes the cavity of 
 the chest and empty the lungs. Although these 
 combined actions produce respiration, yet it may 
 be performed with a less number, under certain 
 circumstances, as where the ribs are fractured, or 
 in inflammations of the pleura, where motion is 
 rendered painful: respiration takes place princi- 
 pally by the actions of the diaphragm, in which it 
 is an essential part. The use of thus taking in 
 and discharging air from the lungs was little un- 
 derstood until the time of Dr. Priestley, although 
 many hints had been thrown out by his predeces- 
 sors of its probable effects. It was with this, as 
 with many other important discoveries, that when 
 its nature was understood, the discovery itself 
 explained the mysterious opinions found in the 
 writings of former ages, which before were en- 
 tirely inexplicable. Something of this is apparent 
 in the observations of Dr. Beddoes upon the 
 writings of Mayow, where he says, " he not 
 only understood the composition of the atmos- 
 phere, but was also aware of the increased weight 
 of metallic bodies, and that certain bases are 
 rendered acid by combination with vital air. He 
 also asserted, that the air was diminished in res- 
 piration, and that a certain portion was conveyed 
 to the blood. If this be an accurate analysis of 
 
( 12 ) 
 
 his writings, he appears to have understood 
 almost the whole doctrine of respiration and 
 combustion as determined by modern chemists. 
 The mysterious manner in which the opinions of 
 Mayow are expressed, has given rise to a differ- 
 ence of opinion as respects the merit which he 
 deserves as a discoverer of the nature of the at- 
 mosphere. The celebrated experiments of Hook 
 (who was the predecessor of Mayow) before the 
 Royal Society, appear to contain some knowledge 
 of the uses of air in respiration. He laid open 
 the thorax of a dog, and kept the animal alive for 
 some time by blowing air into his lungs. These 
 experiments and facts could not have come within 
 the knowledge of Dr. Hunter, or he considered 
 them as not having in any degree developed the 
 nature of this function, as we should infer from 
 his introductory lecture published in 1784, where 
 he says, " respiration we cannot explain, we only 
 know that it is in fact essential and necessary to 
 life. Notwithstanding this, when we see all the 
 other parts of the body and their functions so 
 well accounted for, we need not doubt that res-^ 
 piration is so likewise. And if ever we should 
 be happy enough to find out clearly the object of 
 this function, we shall doubtless as clearly see that 
 this organ is as wisely adapted for an important 
 office, as we now see the purpose and importance 
 of the heart and vascular system; which till the 
 circulation of the blood was discovered was to- 
 tally concealed from us." This has since been 
 realized by the discoveries of Priestley, Scheele, 
 d Lavoisier^ in modern chemistry, which have 
 
{ 13 ) 
 
 thrown great light not only upon this, but upon 
 many other functions of the human body. fc The 
 establishment of this truth alone is almost suffi- 
 cient to subvert the old and to erect a new„system 
 of physiology. And if no other benefit than this 
 had arisen from all the brilliant discoveries which 
 chemistry offers to the world, it would have suf- 
 ficed to rescue that science from neglect, and to 
 assign it an elevated rank among the objects of 
 human knowledge. " Perhaps one of the most 
 mysterious operations of the human body yet re- 
 mains to be explained by it, namely, secretion. 
 
 The importance of respiration to animal life 
 consists in a frequent change of air. When ani- 
 mals are deprived of this, they soon cease to exist, 
 as when confined under the receiver of an air- 
 pump, where life is terminated by convulsions 
 as the air becomes vitiated. Life becomes pain* 
 ful and imperfect where the same air is breathed 
 by a number of persons, as in large assemblies; 
 or produces great destruction, as was particularly 
 exemplified in the distressing instance of Mr. 
 Holwell and his companions in the black hole 
 at Calcutta; where, in consequence of a consi- 
 derable number of persons being crowded toge- 
 ther in a place illy ventilated, great mortality 
 ensued; and among those who survived the 
 most serious form of disease was produced. 
 The instance related by Dr. Trotter, of the fatal 
 effects arising from a large number of Africans 
 being closely crowded together on board of 
 the slave ships, also strongly illustrates this fact, 
 lie savs, " I have often observed the slaves draw- 
 
( 14 ) 
 
 ing their breath, with all the laborious and anxi- 
 ous efforts for life which are observed in expir- 
 ing animals subjected to foul air, or under the 
 receiver of an air-pump." In instances similar to 
 these, though not under circumstances so afflict- 
 ing, the great Lavoisier instituted experiments 
 to ascertain the changes effected upon the purity 
 of the air. This was done at the principal theatre 
 in the city of Paris during the play, and after 
 the conclusion, in which the house was much 
 crowded. He here found, as the purity of the 
 air was diminished, the effect upon the audience 
 was very perceptible in producing great languor 
 and inattention. Similar changes resulted from 
 experiments made upon the air of the closed 
 wards in the principal hospital of France. In 
 order to understand more particularly the nature 
 of these changes, it will be necessary to trace 
 those experiments which have been made upon 
 the chemical properties of our atmosphere as 
 connected with animal life. 
 
 After the mechanical effects of the atmosphere 
 had been investigated by philosophers, chemists 
 were led to examine more particularly into its 
 nature. cc It had been considered by them here- 
 tofore as an homogeneous fluid, and little notice 
 was taken of it in their operations; for when 
 their materials vanished in air, they considered 
 the experiment at an end, and stopped at that 
 part when only their analysis became interest- 
 ing. "* Several phenomena had been observed* 
 
 * Bell's Anatomy, vol. ii. 
 
( 15 ) 
 
 which led to a more particular examination of its 
 nature, such as the increased weight of metallic 
 bodies, which, when burned in atmospheric air, 
 became altered in their properties from a mild 
 substance to a caustic drug; — the support given 
 to animal life and flame was limited according to 
 the quantity of air and the formation of acids by 
 combustion. For an explanation of these phe- 
 nomena, we are greatly indebted to the investi- 
 gations of the celebrated Priestley. He, from ex- 
 tensive experiments upon aerial fluids, was led 
 to a particular examination of the atmosphere, 
 and proved by accurate analysis, that it was made 
 up of two separate airs, to which he gave names 
 expressive of their different natures. The larger 
 and impurer part he called phlogisticated air; the 
 second or smaller portion, which possessed di- 
 rectly opposite effects, he denominated dephlo- 
 gisticated, or an air deprived of phlogiston. 
 
 Scheele was led to the same conclusion by 
 a different course of experiments, in which he 
 was engaged at nearly the same time, but ap- 
 plied different names to the result of his inqui- 
 ries. He called the phlogisticated air of Priest- 
 ley foul air; to the dephlogisticated he gave the 
 name of empyreal air, or an air pure in the ex- 
 treme. Lavoisier, extensively engaged in expe- 
 riments upon almost all substances, and without 
 a knowledge of what had been done by the 
 other discoverers, was led to an investigation of 
 the same subject, and drew the same conclu- 
 sions from them, but applied also different names, 
 as more particularly expressive of their different 
 
( 16 ) 
 
 effects and properties. The phlogisticated air 
 he called azotic gas> from its noxious effects 
 upon animal life and combustion ; to the de- 
 phlogisticated he gave the name of oxygen gas* 
 These two airs he found, from accurate experi- 
 ments, to exist in the proportion of seventy-three 
 parts of azote to twenty-seven of oxygen in the 
 hundred of all uncontaminated atmospheric air. 
 Later chemists have added another gas as a con- 
 stituent part, which, however, forms only a small 
 proportion; but its strong tendency to combine 
 with various substances whenever it is generated 
 in any considerable quantity, is the probable cause 
 of its not being reckoned a constituent part by 
 some chemists. This air is called carbonic acid 
 gas, from its having carbon as its base, and 
 from the uniform disposition which that sub- 
 stance possesses to combine with oxygen. It 
 exists in the state of an acid, possessing greater 
 specific gravity than either of the other gasses, 
 and for that reason is supposed to be found only 
 near the surface of the earth. f 
 
 Hydrogen gas, so called from its being the 
 base of water, is formed from numerous sources, 
 and often exists in the air we breathe; from its 
 
 * Oxygen gas is thus denominated from its base being necessary in 
 the formation of all acids. 
 
 f Sassnre found it at the top of mount Blanc, the highest point of 
 the old continent ; a point covered with eternal snow, and not exposed 
 tc the influence of vegetables or animals. Lime-water, diluted with its 
 own weight of distilled water, formed a pellicle on its surface after an 
 hour and three quarters exposure to the air on the top of that mountain ; 
 and slips of paper acquired the property cf effervescing with acid after 
 being exposed for half an hour in the same place. Thompson's Che- 
 mistry, vol. iii. p. 284. 
 
( n ) 
 
 possessing less specific gravity than the other airs* 
 it occupies the higher regions of the atmosphere. 
 
 Oxygen exists in the state of gas by being com- 
 bined with caloric, or the matter of heat which 
 is separated in the combustion of inflammable 
 bodies,* while its base enters into combination 
 with the combustible substance forming (if the 
 union be complete) an acid, as with sulphur; 
 but if imperfect or partial, a calx or oxyd. All 
 bodies, when burned in this gas, are rapidly con- 
 sumed, and give out a bright flame that is pain- 
 ful to the sight. Azotic gas is also united with 
 caloric; it is lighter than common air, enters 
 largely into animal bodies as a constituent part, 
 and being chemically united with oxygen, forms 
 nitric acid. The necessity of these airs, or some 
 one of them in particular, in respiration, is an 
 obvious fact, and is best ascertained from experi- 
 ments made upon animals when breathed in an 
 -uncombined state. 
 
 If an animal be confined in azotic air, its life 
 is suddenly destroyed, and the effect is almost as 
 sudden from hydrogen gas. This, however, ap- 
 pears to be contradicted from the experiments of 
 Scheele : he found he could breathe it for some 
 time without much difficulty. The same ex- 
 periment was also made by Pilatre de Rosier, 
 and nearly with fatal consequences upon his first 
 respiring it ; but afterwards he was enabled to 
 continue the experiment without much inconve- 
 
 * This is denied by Mr. Davy from some experiments of his. See 
 JScddoes' Observations. 
 
( is ) 
 
 nience for some time. This experiment was re- 
 peated by Fontana: he ascertained that the abi- 
 lity to breathe this gas arose from the common 
 air contained in his lungs when he began to 
 breathe. Mr. Davy was unable to breathe hy- 
 drogen, but with the greatest difficulty, after a 
 complete voluntary exhaustion of his lungs. It 
 produced an uneasy feeling in his chest, momen- 
 tary loss of muscular power, and sometimes a 
 transient giddiness. The probability therefore is, 
 that this air is respirable only till the common 
 air contained in the lungs becomes vitiated, for 
 they always contain it in considerable quantities. 
 Forty cubic inches of air is the quantity usually 
 taken in at each inspiration ; by a forced expira- 
 tion much more can be expelled: hence the 
 lungs are supposed to contain, at their utmost 
 fulness, not less than two hundred and twenty 
 cubic inches of air, and it is not in our power 
 to empty them completely. 
 
 The fatality of carbonic acid gas to animal life 
 is proved from numerous instances; as that of 
 holding animals over the tubs of fermenting beer, 
 where we know this gas is generated, or over 
 springs from which it is thrown off. The instances 
 of people going into wine cellars that have been 
 long shut up, by which they are instantly suf- 
 focated, and the experiments made at the cele- 
 brated Grotto del Cani in Italy, to satisfy the idle 
 curiosity of travellers, are sufficient evidences of 
 its fatal properties. 
 
 These gasses then being evidently proved noxi- 
 ous to animal life, oxygen is that part alone that 
 
( 19 ) 
 
 remains which appears essential and necessary; 
 this, in an increased or diminished quantity, ren- 
 ders a certain portion of atmospheric air respira- 
 ble for a longer or shorter time, the life of the 
 animal always being proportioned to the quan- 
 tity of oxygen. And in these particulars the 
 same facts are true as respects combustion : as the 
 quantity of oxygen, in a limited proportion of 
 air, is diminished, the flame begins to decay, and 
 is, at length, entirely extinguished: on exami- 
 nation this air is found to be entirely consumed, 
 while, in some instances, other substances are 
 generated. It is from a similarity of results in 
 the experiments upon animal life and combus- 
 tion, that this process has been concluded to be 
 the same, which, however, is contradicted from 
 some known facts hereafter to be enumerated. 
 
 It is presumable, from the facts and expe- 
 riments that have been detailed, that the air 
 answers some important purpose in the animal 
 body; and from its coming nearly in contact with 
 the blood while it circulates through the lungs, 
 separated only by a delicate membrane, it may be 
 inferred, that this becomes the medium through 
 which the necessary changes are answered. Some 
 sensible effect may therefore be rendered evident 
 upon this fluid, as so frequent a change becomes 
 necessary for the support of life. These effects 
 may be judged of by exposing blood to the in- 
 fluence of each gas out of the body, from which 
 we may probably infer the importance of the 
 oxygenous portion. 
 
 1st. If we expose a quantity of venous blood, 
 
( 20 ) 
 
 which is of a dark colour, to a certain quan- 
 tity of atmospheric air, it becomes of a bright 
 colour, and the air is diminished in quantity. 
 This change of colour is effected not only by an 
 immediate contact of air with the blood, but the 
 same effect is produced through the thick coats 
 of a bladder, which fact was first noticed by Dr. 
 Priestley. 
 
 2d. If venous blood be exposed to oxygen gas 
 alone, the change in colour is the same, but the 
 diminution not so sensible; and in this experi- 
 ment, agreeable to Girtanner, a quantity of hy- 
 drogen and carbon are given out, which form 
 water and carbonic acid. 
 
 3d. Venous blood exposed to azotic gas un- 
 dergoes no change in its colour, neither is the 
 gas diminished in quantity; but if arterial blood 
 be exposed to its influence, it becomes of the 
 colour of venous blood, and after being exposed 
 for a short time, the air contained in the bottle 
 in which the experiment was made, was found 
 capable of supporting animal life and combustion .* 
 
 4th. Venous blood exposed to carbonic acid 
 gas becomes of a brownish-red colour, and the 
 gas is slightly diminished in quantity. 
 
 5th. Venous blood exposed to hydrogen gas 
 renders the colour darker, but its action upon 
 arterial blood is to render it suddenly of a dark 
 colour. 
 
 These experiments, with others that have been 
 made, show that the principal apparent change 
 
 • Venous blood possesses the power of decomposing the oxyd of azote, 
 which heightens its colour. 
 
( 21 ) 
 
 wrought upon the blood is in the colour; and that 
 by the absorption of oxygen it is also capable of 
 giving off this air when exposed to other matters 
 which have a stronger attraction for it, as is also 
 proved by the experiments mentioned above. 
 
 If these changes are effected upon blood out 
 of the body by the influence of air, it becomes 
 necessary to ascertain whether the same effect is 
 produced upon the mass of venous blood while 
 passing through the lungs of animals during life ; 
 for a confirmation of which, we must refer to the 
 experiments of Hook, Goodwyn, and Hunter. 
 They took a dog, opened the chest, removed the 
 pericardium, and kept the animal alive by an ar- 
 tificial respiration. Here it was found that the 
 blood carried to the lungs by the pulmonary artery 
 was of a dark purple hue, answering in all its 
 appearances to that of venous blood in other parts 
 of the body, while that returned to the heart by 
 the pulmonary veins became of a bright Vermil- 
 lion colour: if they ceased to throw in air this 
 change did not take place ; the blood returned by 
 the veins was as dark as that brought by the 
 artery; a diminution of the pulsations of the heart 
 and arteries took place, and finally ceased. These 
 were all renewed upon air being again thrown 
 into the lungs; and life was in this way suspended 
 and renewed at pleasure. 
 
 From the similarity of change effected upon the 
 blood both in and out of the body, and from the 
 immediate connection that exists between it and 
 its vital actions, we may justly conclude that oxy- 
 gen is that part of our atmosphere which, when 
 
( £2 ) 
 
 combined with the blood, gives the vital spring, 
 as it is immediately applied to the most irritable 
 muscular organ of the human body, and which 
 from its earliest formation is highly susceptible 
 of every stimulating impression, and capable of 
 maintaining its irritability longer than any other. 
 This principle of the heart is more accumulated 
 upon the internal surface than in any other part.* 
 If the air of expiration be examined, it will 
 be found to differ materially in its properties from 
 that of inspiration. The oxygen, and a small por- 
 tion of the azote, have disappeared ; a quantity of 
 carbonic acid, and water in the state of vapour, 
 has been generated. In respect to the quantity 
 of air that disappears during each inspiration, the 
 experiments of different chemists vary : Lavoisier 
 and Dr. Menzies made it one-twentieth of the 
 air inspired, while others have made the quan- 
 tity greater or less, according to the perfection 
 of the apparatus with which the experiments 
 have been made, and the accuracy of observation, 
 These chemists confined the diminution only to 
 the oxygenous portion of the atmosphere, while 
 the later experiments of Mr. Davy have confirmed 
 the supposition of Dr. Priestley, that a certain 
 portion of azote as well as oxygen was absorbed 
 by the venous blood. He found by repeated ex- 
 periments, the average quantity of air that disap- 
 pears to be 1.4 of a cubic inch, of which 0.2 are 
 
 * It is a position that has been considerably contended for, whether 
 the heart derived its principle of irritability from the oxygen of the air ; 
 whether it was a principle derived from another source, or resident within 
 itself. The former position has been strongly contended for by Girtan* 
 p.ex and other pneumatic physiologists. 
 
( 23 ) 
 
 azote and 1.2 oxygen. This, allowing twenty-six 
 respirations per minute, which is about the ave- 
 rage number, amounts, in twenty-four hours, to 
 rather more than thirty-eight ounces of air, or 
 precisely 4.68 of azote, and 33.54 of oxygen* 
 
 That carbonic acid gas exists in the air of ex- 
 piration, is proved from the simple experiment 
 of breathing through lime-water, which renders 
 it turbid by the new combination that is formed: 
 the carbonic acid unites with the lime that is sus- 
 pended in the water, and forms a carbonate of 
 lime that is insoluble. 
 
 That water is also continually passing off from 
 the lungs in the state of vapour, is rendered evi- 
 dent to every one that breathes in a cold atmos- 
 phere, or upon the surface of a polished body, 
 by the condensation that takes place. Whe- 
 ther these substances are formed in the lungs by 
 the combination of the oxygen with the hydro- 
 carbon that is thrown off from the blood, or, 
 whether they are formed during its circulation 
 through the body, remains a question not satis- 
 factorily determined from experiments. As far 
 however as experiments have been directed to 
 the particular investigation of this subject, their 
 results favour the latter opinion. From a collec- 
 tion of these facts, it follows to investigate how 
 far they may tend toward an explanation of the 
 phenomena of animal heat. 
 
 It is a singular property which animals possess 
 of supporting a standard degree of temperature 
 
 * Thompson's Chemistry. 
 
{ 24 ) 
 
 in every vicissitude of climate.* Thus we find 
 that the degree of temperature is the same in the 
 coldest regions of the earth where man can exist, 
 and where even mercury may become solid, as 
 well as in the higher ranges of temperature up to 
 that of boiling water, as was proved from the 
 experiment of Dr. Fordyce and others. In this 
 extreme degree of heat, they found the body sup- 
 ported its standard degree of temperature, that of 
 98 deg. And it is even said, that man, by habit, 
 may become able to bear a much greater extreme. 
 In the different classes of animals, there is a 
 considerable variety in the heat of their bodies. 
 This variety is dependant upon the perfection of 
 their respiratory organs, and their capability to 
 take in a large proportion of air. As for exam- 
 ple, in birds, where, from the particular struc- 
 ture of their lungs, the blood is exposed to the 
 extensive influence of air, their temperature ex- 
 ceeds an hundred degrees of Fahrenheit's ther- 
 mometer. 
 
 In the lower classes of animals, or what are 
 called the cold-blooded, their heat exceeds very 
 little the medium in which they live. In these 
 animals, the process of respiration is slow, and 
 the quantity of air that is absorbed is small. 
 They retain their irritability longer than the more 
 perfect animals, and suffer less from any injury 
 which they receive. Their power of generating 
 heat is not sufficient to prevent them from be- 
 
 * This power, from experiments, appears to extend also to vegetables 
 a very considerable decree. Their standard temperature does not 
 :ceed 56 deg. 
 
{ 25 ) 
 
 coming torpid during the severities of" winter, but 
 are soon renovated from the warmth of spring. 
 
 The standard heat of animal bodies is regu- 
 lated not only by the nature of the air taken in, 
 but by a function of its own, the cutaneous per- 
 spiration: for, in the extremes of cold, we not 
 only take in a larger proportion of vital air, by a 
 condensation from a diminished temperature, 
 f but the perspiration is in less quantity, and a 
 portion of heat is retained. When respiration 
 becomes quickened from any cause, the heat of 
 the body is increased, and continues so until a 
 proportional increase of perspiration subducts 
 the superabundant heat from the system. As it 
 is an established law, that in proportion as aque- 
 ous fluids are converted into insensible vapour, 
 caloric, or the matter of heat is absorbed. 
 These facts are particularly exemplified in walk- 
 ing more rapidly than usual, or in any other 
 species of exercise which calls a number of 
 muscles into considerable and continual action; 
 and in fever, where the perspiration becomes ob- 
 structed; while the actions of the heart and ves- 
 sels are increased, and the respiration propor- 
 tionably quickened, the heat will be more con- 
 tinued, and is diminished only by a free dis- 
 charge of perspirable matter. In high degrees of 
 temperature, the air we breathe is much rari- 
 fied, and a much less quantity of vital gas res- 
 pired in an equal volume of air; while, at the 
 same time, the cutaneous perspiration is much 
 more increased, and its vicarious discharge, that 
 by the kidneys, diminished. We are hence en- 
 
( 26 ) 
 
 abled to live under every vicissitude of climate 
 and season. The different opinions which have 
 been offered to explain this property of animal 
 bodies, admit of considerable diversity, even af- 
 ter the importance and influence of air was un- 
 derstood from experiments. Dr. Priestley made 
 respiration to consist in an elimination of a noxi- 
 ous principle from the blood, which is thrown 
 off from that brought to the lungs by the pul- 
 monary artery, for which the air of inspiration 
 has a stronger affinity than the blood, and when 
 separated renders it of a bright colour. This prin- 
 ciple is denominated phlogiston. It was this 
 theory that was adopted and improved upon by 
 Crawford and Elliot, by means of which they at- 
 tempted the explanation of the different pheno- 
 mena of animal heat ; saying that in proportion 
 as the blood parted with phlogiston its capacity 
 for containing fire became increased, which it 
 absorbed from the air, and distributed to every 
 part of the body. The exceptions to this doc- 
 trine are obvious ; for the explanation is entirely 
 dependant upon an assumed principle, of whose 
 evidence we have no certainty, and, of course, 
 are incapable to judge of its properties. The 
 theory of Lavoisier is similar to that of Priestley, 
 differing only in terms. His opinion was, that 
 the quantity of oxygen was diminished by its 
 combining with hydrogen and carbon, to form 
 water and carbonic acid gas; at the same time a 
 portion of caloric was given to the blood. This 
 theory is incorrect, inasmuch as it asserts the 
 combination of hydrogen and carbon at a lower 
 
( 27 ) 
 
 temperature than is evident from experiments 
 out of the body, where the decomposition does 
 not take place in any instance without the 
 production of flame. Lavoisier, however, did 
 not prove this theory from experiments; it was 
 the subject in which he was engaged when 
 cut off by the tyrannical hand of Robespierre, 
 The theory of Le Grange differs somewhat 
 from that of Lavoisier. He has asserted that a 
 portion of oxygen is taken up by the blood in the 
 lungs, and at the same instant a quantity of wa- 
 ter and carbonic acid are given out. This, how- 
 ever, makes the lungs still the fire-place of the 
 system, and besides allows only the oxygenous 
 portion of the atmosphere to be absorbed, which 
 is contradicted by the experiments of Mr. Davy, 
 as mentioned above, whose theory appears liable 
 to the least objections. He considers the blood, 
 while passing through the lungs, to absorb air in 
 an undecomposed state, which it carries through 
 the bloodvessels. In the course of the circulation 
 this air is gradually decomposed, the oxygen 
 of the azote entering into new combinations, 
 while a portion of azote and carbonic acid are 
 evolved. On returning to the lungs, the blood 
 receives a fresh supply of air, and, at the same 
 time, discharges the azotic gas, carbonic acid 
 gas, and watery vapour formed during the cir- 
 culation. 
 
 From the experiments of Mr. Davy, respecting 
 a diminution of a portion of the azotic part of 
 the atmosphere, some new reasoning upon the 
 process of respiration may be introduced: for, be- 
 
( 28 ) 
 
 fore these experiments, the writers upon this sul> 
 ject confined themselves to an investigation of 
 those substances in the blood that should account 
 for the strong affinity that existed between it 
 and oxygen. Accordingly iron, whose presence 
 is universally proved to exist in all animals that 
 possess red blood, was considered, from its rea- 
 diness to combine with oxygen, as best calcu- 
 lated to explain the change produced. cc But 
 as the temperature at which this oxydation takes 
 place is not sufficiently great to account for that 
 instantaneous change which the blood under- 
 goes in the lungs, or when exposed to the influ- 
 ence of oxygen out of the body, it is therefore 
 necessary to call in some other of the component 
 part of the blood ; and as phosphorus is always 
 found in the blood of animals, and its attraction 
 for oxygen is very strong, and that at a low tem- 
 perature, it explains more satisfactorily the ef- 
 fect produced."* If these then are the substan- 
 ces with which the oxygen combines, to what is 
 the azote united ? We are told by Mr. Davy, that 
 the blood becomes completely animalized in the 
 lungs. If this be the fact, it may be explained 
 why so small a portion of the azote disappears, for 
 the discharge of chyle into the subclavian vein is 
 slow and gradual, and this absorption must be in 
 that proportion ; and as azote is a constituent 
 part in all animal bodies, whether their food be 
 taken from the animal or vegetable kingdom, 
 its appearance upon their decomposition, in conn 
 
 * Youle on Respiration. 
 
( 29 ) 
 
 giderable quantities, and its production as the 
 result of chemical experiments, are facts that 
 lead us to conclude, that azote enters into com- 
 bination with the animal fibre, as derived from 
 the air through the lungs,* These discoveries 
 show that what is fatal to animal life in an un- 
 combined state, is necessary to it when combined, 
 and demonstrates the economy of nature in the 
 regular preservation and support of life. 
 
 Oxygen gas, when breathed in a pure state, 
 gives new vigour to animal life, quickens the cir- 
 culation, increases the heat of the system, pro- 
 motes digestion, and is said to produce the most 
 pleasurable sensations. The sense of heat in these 
 instances has been said to begin in the lungs as a 
 centre, and to be diffused from thence more gene- 
 rally over the body. These experiments were 
 however closely connected with the establishment 
 of a favourite hypothesis, and the sensations were 
 felt more evidently by the authors than by disinter- 
 ested persons. That oxygen is however a power- 
 ful stimulus is an acknowledged fact, and like all 
 other powerful stimuli, when continued for some 
 time, destroys the animal machine. Azote may 
 therefore answer a further purpose in the animal 
 economy, that of properly tempering the air, be- 
 
 *From some late experiments that have been made by Dr. J. Ley- 
 merie, of France, he has found that ammonia is one of the essential 
 parts in the formation of red blood. Now, as the component parts of 
 this substance are azote and hydrogen, we are again shown the neces- 
 sity of a supply of the former material in order to answer the essential 
 properties of an animal fluid. He has succeeded in converting milk into 
 blood by the addition of pure ammonia in certain adjusted proportions, 
 within a given time. A more full account of his experiments will pro- 
 bably soon be given to the public. 
 
( so ) 
 
 sides allowing of a more extensive exposure of 
 blood in the lungs, to the influence of that quan- 
 tity of oxygen that is necessary to the support of 
 life, by inflating them with a gas whose stimulant 
 properties are not so powerful, but whose presence 
 is at the same time equally necessary. This po- 
 sition, therefore, appears consistent, inasmuch as it 
 explains many of the phenomena connected with 
 animal life. 
 
 The following conclusions may then be drawn 
 from the facts and experiments detailed : 1 st. That 
 respiration is of use, by imparting oxygen to the 
 system through the medium of the blood circu- 
 lated in the lungs, for the principal purpose of 
 giving heat to the body by the new combinations 
 that are formed. Of this we are convinced di- 
 rectly from experiments. Mr. Davy took blood 
 from the carotid artery of a calf, enclosed it in a 
 phial, to which was affixed a pneumatic appara- 
 tus; it was then exposed in a sand bath to a tem- 
 perature of 96 deg. gradually increased to 108 deg. 
 The blood now began to coagulate, some glo- 
 bules of gas were emitted; the temperature of 
 the bath was raised, and the blood became of a 
 dark colour. On examining the nature of the 
 air disengaged, it was found to be oxygen, with 
 a small quantity of carbonic acid.* We are also 
 convinced that oxygen is absorbed by the blood 
 from its presence p many of the secretions and 
 excretions formed from this fluid; as in the urine, 
 where it is discovered passing ofT as excrementi- 
 
 * Beddoes' Observations. 
 
( 31 ) 
 
 tious in the form of an acid. In the bones it has 
 entered into union with calcareous matter when 
 combined with phosphorus. In the fat of ani- 
 mals a particular acid is also discoverable. The 
 formation of acids in these different secretions 
 depend upon the presence of oxygen, as it is an 
 acknowledged principle in chemistry, without it 
 no acid can be formed. If oxygen then be main- 
 tained in its gaseous state by means of caloric, 
 its decomposition and new union must have set 
 it free. It is therefore probable that oxygen is 
 decomposed in the extreme vessels ; for, as far as 
 we have yet become acquainted with secretion 
 from the ultimate structure of glands, the pro- 
 cess appears to be effected in the extreme arteries. 
 And further, while a partial action of the minute 
 ramifications of arteries become excited, as in 
 local inflammation, a preternatural heat is accu- 
 mulated without an increase of respiration: but 
 this effect cannot be produced to any considera- 
 ble extent without an increase of arterial action, 
 which produces a disease of the whole body. This 
 fact is more particularly exemplified where the 
 principal arterial trunk of a limb is tied up, and the 
 circulation is to be carried on by the small anas- 
 tamosing branches. Here at first the limb is cold, 
 until the blood begins to find its way by the mi- 
 nute vessels which are excited into great action, 
 the heat becomes preternaturally accumulated, 
 and continues so until some of the branches are 
 sufficiently dilated to transmit the former quan- 
 tity of blood. 
 
 2d+ The union which has taken place between 
 
( 32 ) 
 
 the chyle and azote, as a constituent part, and 
 which has now become of the nature of blood* 
 in all respects fit to answer its purposes in the 
 body, of forming new secretions, generating new 
 parts, and effecting every property which is ne- 
 cessary in the maintenance of the animal body. 
 
 It is a fact admitted by physiologists, in which 
 they have been aided by the experiments of the 
 chemist, that the coagulable lymph is that por- 
 tion of the blood approaching the nearest to the 
 nature of the animal fibre; and from this property 
 the inference is consistent, that it is more parti- 
 cularly calculated to answer every purpose of nu- 
 trition to the body, the wastes of the machine 
 are continually going on, and it is necessary 
 that they should be as continually repaired. From 
 these different changes, is it not probable that 
 the animal heat is in some degree assisted in 
 its regular maintenance ? It must also be admit- 
 ted, that as azotic gas enters into union with 
 the coagulable lymph to render it of the nature 
 of the animal fibre, it also parts with its caloric 
 in the same manner as the oxygen. And it is 
 an established law, that as gaseous substances 
 assume the solid form, their caloric is set free; 
 this heat being disengaged from its base, which 
 has formed a union, assists itself also in answer- 
 ing a useful purpose. 
 
 Animal heat may therefore not be dependant 
 upon the respiration of oxygen alone, but upon the 
 absorption of azote also, which two gasses are so 
 changed by means of vascular action, that their 
 bases enter into union with the body to answer 
 
( S3 ) 
 
 useful purposes in the animal economy. And it 
 is by means of these changes that the regular main- 
 tenance of animal heat is kept up, subject to 
 irregularities from increased respiration and di- 
 minished perspiration, as in fevers and active exer- 
 cise ; regulated also in colder climates by the 
 volume of air being more condensed and perspi- 
 ration lessened. These facts may be consider- 
 ed fully evident, yet the chemical changes that 
 occur in the animal body are so obscure, that it 
 will require a number of well conducted expe- 
 riments before every objection can be answered 
 that may be urged against the opinions advanced, 
 which the genius for improvement appears to be 
 rapidly investigating. 
 
 THE END 
 
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