No. 585.

LONDON, SATURDAY, NOVEMBER 15, 1834. [1834-35.

PHYSIOLOGY.

LECTURES

ON THE

PHYSICAL CONDITIONS

OF THE

TISSUES OF THE HUMAN BODY

AS APPLIED TO THE EXPLANATION OF

VITAL PHENOMENA.

Delivered at the College of France in 1834,

BY F. MAGENDIE,Professor of Physiology and Medicine in the College.

LECTURE VII.

Four of tlte Quarantine Diseases certainlynot contagi us. The Fiftla most probaúlJ,not so.-Arguments against the Quarari-tine Laws.-The Transmission of Gasesthrough theA2zimat l’islmes.- Clwnges inthe Btoud effected in the Lungs.-Poison-ous Qualities of some Gases.-The ad-mission of Air into Veins. -Iode inwhich it produces Death, when fatal.-Experimental Injection of Air into theJugular irein of a Dog. -Error ofca.— TczM which will bear liijectionwith Implinity.THE diseases, Gentlemen, which are

contagious according to law are five, viz.lepra, typhusfever, yellow fever, the plague,and the cholera morbus. Here, you see,our legislature has passed over small-pox,although, without requiring a knowledgeof medicine, the slightest consideration offacts known to the whole world wouldhave demonstrated its contagious nature;but let this pass for the present; it is notthe only absurdity we shall find in thequarantine laws. Let us now examine Iin turn each of the diseases above enume-rated, and see how far the arrangements ofthe legislature agree BB ith the principlesof medicine. ’

Lepra is a very rare complaint, and we ’

cannot, therefore, enter into any exten-sive details with respect to it; I speak oflepra as it occurs in this climate, not ofthe disease so often observed in the colo-nies, to which the present remarks maynot apply. Lepra I say as seen in France,England, Germany, or other parts of Eu-rope, is not considered by medical men asa contagious complaint; if a case of leprahappen to fall under our care, we keepthe patient, as a kind of curiosity, in thehospital, for two or three years; we showhim to any one who visits the hospital;we touch the affected part without any ap-prehension of danger; we may get a pic-ture of him painted, and then dismiss thepatient, being fully convinced that he willnot transmit the disease to his neigh-bours. This is a fact which is familiar toevery physician who has had any length ofhospital practice. Lepra is not, therefore,a contagious disease, and should be erasedfrom the above catalogue.

Let us now turn to typhus fever, and seewhether it also merits to be enumeratedamong the five proscribed diseases. We emust examine the question closely, for itis difficult, and one of high practical im-portance. What are the circumstances,Gentlemen, under which this disease is

ordinarily developed ? A person goes intoa locality or habitation where the typhusfever already exists, and immediatelycatches the complaint; but is this conta-gion ? You may say so, if you like, in acertain sense, for he has respired the mias-matous exhalations of the patient, andcontracted the disease in this manner.But let us examine the case in a differentlight. Take this same patient from thehospital in which numbers of individuals,affected with the same malady are crowd-ed together, where the air is tainted withevery kind of unhealthy exhalation, andtransport him to some airy wholesomesituation. Is he there capable of communi-cating the disease ? No, Gentlemen, theso-called contagious nature of typhus islost by removal from one spot to another,and we never see the disease propagatedby persons affected individually.You are, therefore, entitled to say, that

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persons assembled together in great num- typhus fever. When a patient, affectedbers and in unwholesome situations, are with the worst form of yellow fever iscapable of communicating typhus fever carried away from home to a healthy situ-to others ; but experience proves that the ation, he does not propagate the diseasesame individuals when separated will not in the new locality, he carries no germ ofgive the disease. You may call typhus contagion with him ; and it is remarkablefever contagious, in the former case, if that the physicians of hospitals destinedyou wish, from the fact of its being for the reception of yellow-fever patientstransmissible in some form, but I should are not often attacked by it. In this cir-not apply the term " contagion" to this I cumstance it is less unfavourable thanmode of communication, because I re- the typhus fever. If you examine thegard those diseases alone as contagi- localities in which yellow fever is knownous, which may be transmitted from one to prevail most frequently, you will findindividual to another, at any time, inde- them favourable to the production of

pendently of situation, atmospheric innu- animal exhalations in great quantity, suchence, or any of those circumstances which as the neighbourhood of marshes, burying-we know to favour the development of, grounds, &c., and places of this descriptionmiasmatous affections. Whenever pco- where masses of animal matter are col-ple are assembled together in large num- lected together and left to putrify. In

bers, · e may have a fever originated, Spain the yellow fever has never beenwhich is capable of being transmitted to prevalent without the concurrence of thosehealthy individuals. This is a fact which attending causes. You are riot to ima-we witness every day in hospitals, prisons, gine, as many are apt to do, that thisand other places of the same description, disease is confined to peculiar quarters ofbut we are far from regarding the disease the globe,-that it prevails only in Ame-so produced as contagious. rica, Spain, and a few other countries.

It is a practical remark, worthy of at- The disease, Gentlemen, may be excitedtention, Gentlemen, that some individuals at any time and in any place where theare much more apt to exhale injurious determining cause exists. I have seen invapours than others; thus, for example, France affections extremely similar to it;ill-nourished persons sometimes present indeed so like, that a physician who wasthis telldency in a very high degree. If a perfectly familiar with yellow fever, pro-man take nothing but bad indigestible nounced the affection identical with thatnutriment, or remain for any considerable malady. I remember particularly on onetime without taking any food at all, his occasion ten patients being brought toge-exhalations soon assume a deleterious ther to the Hotel Dieu labouring undercharacter. We have frequent occasion to fever of a severe form ; the season hadprove the truth of this observation in La been excessively hot, and the public at-Salpetriere, where a great number of pa- tention was much directed to the subjecttients labouring under mental alienation of yellow fever, which prevailed with vio-are received. These unfortunate indivi- lence at Barcelona in Spain. These pa-duals often refuse all food for a length tients presented adynamic symptoms in aof time, and then exhale the most fetid high degree, and several of them wereodours, capable, no doubt, under certain; affected with black vomit. We were all

circumstances, of generating disease. A naturally alarmed,- and a physician whosimilar effect is also produced by strong had just returned from Spain was calledmoral dispositions and passions. I re.. upon to examine the patients; he wasmember the case of an English lady in much embarrassed to decide whether theParis, who refused to take food for fifteen disease was yellow fever -or not. The

days, on account of some domestic afflic- symptoms, he said, were identical, but hetion, and at the end of that period she was unwilling to admit the existence ofexhaled an odour of the most disagreeable so frightful a complaint in the capital.and fetid character. Typhus fever is not, The patients, however, soon died, andthen, a contagious disease, and it is useless after death we found all the pathologicalto range it amongst those included in the phenomena presented by individuals cutsanatory code. off by yellow fever. I should remark to

Let us now turn to yelloiv fever, a com- you that they had been brought in fromplaint against which the utmost rigour of an unhealthy quarter of the town, andthe law has been exercised; yet it results that a change of weather, which.occurredfrom a multitude of observations made in in a few days, removed all traces of thethose places where yellow fever reigns disease, and restored us to a state ofmost frequently and to the greatest ex- tranquillity.tent, that it is simply an infectious disease. From the reasons just mentioned, weWith respect to its mode of propagation conclude with regard to yellow fever as inI may observe, that it resembles exactly typhus, that it is not contagious, and that

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the sanatory measures by which the law cholera ; these necessarily passed throughwould prevent the importation of the com- the hands of the garcon des salles, yet heplaint, are as useless as they are ridicu- is alive at this day to tell you that no dan-lous. ger of infection need be apprehended fromCholera is the next prohibited disease ; the dead body of a cholera patient. Inon the list, and, unfortunately, in one re- the whole history of the disease, in thespect it is one with which you are all too rapidity and eccentricity of its march,familiar; the opinions of medical men finally, in all the circumstances attendinghave been much divided as to the conta- its mode of propagation in this capital, Igious nature of this complaint, but they see no reason whatever for thinking thatwho support the affirmative question lean cholera is a contagious disease. In Ame-too much upon partial facts. We had a rica a most extensive experiment was

striking example of this when cholera first made on this subject. I have already no-broke out in Paris; the leading physi- ticed to you how the inhabitants of Ame-cians of the capital were assembled, as rica are accustomed to desert those placesyou know, to pronounce a judgment on in which yellow fever breaks out, andthe nature of the disease; they were al- how they escape in this manner all dan-most unanimously of opinion that cholera ger of contracting the malady, dependingshould not be considered as contagious, as it docs on circumstances strictly localand agreed upon signing a document to -viz. on the development of animal ex-this effect, in order to quiet the public halations

in certain quarters. On themind ; but one of us, a physician of the appearance of cholera in America, the in"Hotel Diett, a man of excellent informa- , habitants naturally applied to it the prin-tion, and well known by his acquirements ciple which had been so successfully em-and talents, said, 11 I will sign this decla- ployed against yellow fever, and dispersedration, because I think it may have an themselves throughout the country, flying" useful influence in tranquillizing the from the towns and villages in which cho-apprehension which so generally pre- lera first broke out ; but they soon foundvails, but I do it perfectly against my this precaution to be unavailing, and atjudgment, as I am possessed of facts the same time exhibited certain proof, ofwhich establish the contagious nature the most extensive kind, of the non-con-of the disease in question." When tagious nature of this complaint, becausepressed to explain these facts, he cited in no single instance, we are told, was thethe case of a family in which the porter disease carried by healthy individuals fromhad been attacked, then the lady of the the spot where cholera prevailed, to otherhouse, and finally her husband, one im- localities in which it did not exist at the

mediately after the other, as if a similar time of their arrival; had cholera been aconcurrence of circumstances does not contagious disease, it is clear that ittake place every day during the preva- must have been simultaneously propa-lence of an epidemic disease. gated through all parts of America, by the

Such, Gentlemen, is an example of the manner in which the population dispersedreasoning on which the followers of con- itself from the infected towns.

tagion found their opinion ; but I have Of fltp. plague, Gentlemen, the last dis-watched the disease with the utmost care, ease prohibited by the sanatory code, weand never saw a phenomenon accompany cannot speak from experience, but we maycholera which might lead me to conclude at least examine and draw some conclu-it capable of being transmitted by conta- sions from its history. I would remark to

gion. Look at its history in our hospi- you, in the first place, that the l’laguetals; the physicians, surgeons, internes, commonly reigns in dirty countries, whereand sisters of charity, who were inces- cleanliness is not so much a fashion as insantly occupied about patients labouring the greater part of Europe, and where theunder cholera of the most severe descrip- inhabitants make it a custom to transmittion, were hardly ever attacked. Had it the same suit of clothes from genera-been typhus fever which prevailed to the tion to generation. It resembles typhussame extent, and with equal severity, we and yellow fever in the mode of pro-should have been all dead by this time. pagation, and in the way it first ori-There are some medical men, again, nates. Thus you will find that the plague

who say that cholera is only contagious generally breaks out after a very hot sea-after death; but this opinion is still less son, when the unfortunate people have-tenable than the former. Which of you been reduced by famine &c., and prevails.was ever apprehensive of catching the mostly in the neighbourhood of certaindisease, while making a post-mortem ex- unhealthy localities, where the air is

amination; or who ever saw cholera changed and corrupted by putrid animaltransmitted in this manner ? At the Hotel exhalations. But there is one fact, withDieu more than 2000 patients died of Asiatic respect to its transmission, which, if true,.

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is very extraordinary. Writers upon the employed to examine the cotton never

plague say, that if you simply approach an contract the plague, nor has the diseaseindividual labouring under the disease, been ever introduced into France, not-

you incur no danger of contracting it; withstanding the imperfect precautionarythat it resembles in this respect syphilis measures employed in our sea-port towns.or the itch; but if you touch the affected In fact, all the precautions about mer-person, or his clothes, you are sure to get chandise are equally ridiculous, and servethe complaint next day. only to cramp our commerce and injureThis is a circumstance which requires individuals, without insuring the publicto be well, extremely well, established health in the slightest degree. Look,before we can believe it, for it is contrary again, at the sanatory cordons, how in-to all we know of the history of diseases, efficacious they are. I remember it was aand of the phenomena attending imbi- common practice for individuals to passbition. It would follow from this fact, the cordon by which we were separatedthat the poisonous germ of the plague from Spain, when the yellow fever pre-

passes readily through the epidermis, and vailed in that country, merely for the sakeis transmitted with difficulty through the of having to say, " I passed the cordon."membranous tissue of the lungs, a pheno- From the facts which I have stated tomenon, I say, directly contrary to our expe- you, Gentlemen, I cannot see how we canrience of all other diseases. This and many affirm the plague to be a very contagiousother facts which I have not now time to disease; and if contagious at all, it isdraw your attention to, lead me to conclude eminently less so than small-pox. This isthat we require further knowledge and ex- a fact upon which all physicians mustperience of the plague before we can give concur. Again, it is a complaint whichany decided opinion as to its contagious is not transmissible by the respiration ;nature, for a great part of the history of this circumstance is agreed upon by allthe diseases contained in modern works is writers on the plague, and if it be true, istaken from writers of the middle ages and aphenomenon of a highly curious nature.the sanatory laws regarding the intro- Finally, to draw some conclusion from theduction of the plague are founded upon preceding observations, I think that the

principles which were established several plague may perhaps be communicablecenturies ago. This circumstance alone from one individual to another in theis sufficient to prove how much they re- place where it exists, but that we have noquire revision, and nothing can be more ground whatever to imagine that it maybeabsurd or ridiculous than the precautions transported to a distant country in clothes,adopted by our forefathers, several of cotton, or other articles of merchandise.which exist in full force to the present day. As far as we have hitherto gone, Gen-I need only give you an example of what tlemen, the phenomena of imbibitionI saw in some seaport towns in the south, have been applied to various facts of greatand of the manner in which the quaran- interest, and particularly to the theory oftine officers decide whether the cotton contagion, a subject which has been dis-imported from Turkey and Egypt con- puted with so much acrimony, and in atains the plague or not. A man is great measure has divided the medical pub-employed to thrust his hand into each lic. The question, as you must see, frombale of cotton, and take out a handful. what has been said, is closely connected withThis is their only test. They say, if the the permeability of membranes to vapours,cotton be infected, the man will exhibit and many circumstances attending the

symptoms of the plague within ten or propagation of disease are explained in atwenty days; after the expiration of which satisfactory manner by reference to thistime, if the health of the individual re- property of the animal tissue.main sound, the cotton is released from The whole question of contagion, then,quarantine, and passed into the interior. requires revision, and when life and pro-Now I ask you, Gentlemen, can any- perty are so extensively interested as they

thing be more nonsensical than this pre- are under the sanatory laws, we shall notcaution, or less efficacious, even if we grant be content with rules made in old times,the principle upon which it is founded to and by ignorant men who were guided bybe just? How can the man tell whether prejudice rather than any just or esta-

he touches exactly the portion of cotton blished principles. If you take the troublecontaining the germ of the plague ? Or is of examining the quarantine laws, youthe contagious matter expanded through cannot fail to conclude with. me that theythe whole mass? Granting the existence are irrational, and that the measures of pre-of contagion, is it not probably confined caution therein enforced, under the mostto a few points of the bale, which escape severe and sanguinary penalties, are trulyexamination ? However these matters ridiculous. Again, when you investigatemay be, one thing is certain, viz., the men the nature of diseases, perhaps twenty in

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number, regarded by the old law as con- mospheric air has been perfectly explainedtagiom, you will not find a single one by chemists, we are able to understandwhich really merits ’this character. We the reason why the respiration of this gashave applied ourselves in a brief way to is essentially necessary to the life of anthe examination of the five contagious animal. When a quantity of venous blood,diseases comprehended in the sanatory a substance alterable by atmospheric air,code, as it now exists, and showed by a is drawn from the vein of an animal, itreference to well-known facts, that not comes out of a dark purple colour, andone is certainly contagious, while small- presents several peculiarities which I needpox has been totally neglected. Perhaps not enumerate to you, the change ofwe may be accused of presumption in colour being sufficient for our presentgiving too decided an opinion on the na- purpose. This dark purple blood mustture of the plague, of which we have no become of a scarlet colour in the arteries.

personal experience; let us, therefore, This change we know to be necessary forqualify the above phrase, and say, that the support of life in man and the higherfour at least of these diseases are not con- animals. The existence of every beingtagious; and if the plague be communicable who breathes depends on this pheno-in this manner, it differs from all other menon.maladies of a similar kind, as it is not Where, then, does this alteration so in-transmissible by the respiration. It is dispensable for life take place ? It is ef-an affecting circumstance, Gentlemen, to fected, as you all know, in an organ pe-see the commercial relations of a great culiarly formed for the purpose. Examinenation depending on such errors, espe- the intimate structure of the lung, andcially when the government have ample you will find an extensive membrane dis-means of obtaining every information on posed in a manner most favourable for thethe subject, and purging the sanatory code reception of atmospheric air ; you will seeof the absurdities by which it is now the last branches of the bronchial tubes,disfigured. Had we followed up this so arranged as to present an immensequestion to a greater extent, it were easy surface to the action of that fluid, whileto point out a multitude of anomalies the minute ramifications of the pulmonaryequally ridiculous. What, for example, artery spread out on all sides, and covercan be more revolting to common sense the surface of the membrane. One of thethan the attempt at impeding or arrest- functions most essential to man becomesing the passage of miasmatous vapours by thus founded on this physical condition,a military cordon ? Yet the whole line of that atmospheric air is placed in contactthe Pyrenees is from time to time guarded with a membrane, and parses through itby soldiers employed on this useless and to the parietes of the pulmonary artery.absurd duty. The transmission of mias- As soon as this transmission of the gas ismatous exhalations can never be arrested effected, the vital change takes place, andby the bayonet. To prevent their pas- the fluid assumes the scarlet colour of

sage we should have recourse to the arterial blood. I have put some venousmeans adopted in chemical or physical blood into this vial, containing atrno-

laboratories, for the destruction of inju- spheric air, and the upper part of the fluidrious vapours, and these can never he has become, as you see, of a bright scarletapplied to miasmata, on a scale sufficiently colour. This bladder also contains a

extensive to be useful. quantity of blood, drawn from a vein, andWe shall now pass to another part of although the colour is not as red as that in

our subject, which completes what we the glass, it has been changed sufficientlyhave to say on the permeability of mem- to prove that even this thick membrane isbranes, viz., the phenomena accompany- permeable, and permits the action of theing the transmission of gases through the air to take place through it.animal tissues. It is scarcely necessary to The permeability of membranes to bodiesremark, that gases and vapours are ex- in a state of gas is a question whichtremely analogous, being composed of wants further investigation, for the ex-particles arranged in a very similar man- periments of modern chemists teach usner ; hence it is not extraordinary if they very little. Thus, for example, we want toproduce similar effects on the animal know whether there are different degreeseconomy. of permeability, and whether this property,The permeability of membranes to gas like imbibition and absorption, is modi-

is one of the first and most important con- fied by the temperature of the gas, byditions of animal life, for no animal can its composition, &c. It is extremely pro-exist for any length of time, unless the bable that such modifications take place,air by which he is surrounded have a free but in the present state of our knowledgepassage through the membranous tissue we cannot affirm it to be the fact, becauseof the lungs, !5ince the composition of at- we have no precise experiments oii the

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subject. The property seems to belong,, brane of the lungs:, giving rise to fatal ac-univcrsally to all gaseous bodies. Indeed cidents, from its volume, &c. No suchI am not acquainted with one which is not ; thing ; the gas enters the system in thecapable of being transmitted through a! most gradual manner; molecule after mole-membrane. If you enclose any gas in a cule is transmitted through the membranebladder, its chemical properties are soon ’ in a state of almost infinite subdivision,altered by the passage of atmospheric air, and the effects resulting to the economythrough the membrane. If you fill a ; depend on the chemical properties of thebladder with hydrogen, the air enters gas, like those produced by various reme-equally, and converts it into a detonating dies in a solid form.gas. i But should the gas enter the circulation

Finally, all the facts connected with the suddenly, and in greater quantity, it givesfunction of respiration show that animal rise to other phenomena of a nature quitemembranes are very permeable to gases. distinct and different. We have often oc-The effects produced by the introduction of casion to witness these results in the prac-gaseous bodies into the system are various. tice of surgery, especially when we areSome gases destroy life in a rapid manner; compelled to operate on large tumours,this is easily proved upon animals, and situate about the lower part of the neck.holds good for the human subject; for, I ; During the tedious dissection to whichrepeat, there is no difference betwen man these tumours sometimes give rise, theand the higher animals in this respect, jugular, or some other large vein, may beThus, if you place a warm-blooded ani- ! wounded, and a quantity of atmosphericmal in a jar containing sulphuretted hy- ! air be introduced into the current of thedrogen, the poisonous gas soon enters the circulation, in greater or less quantity.economy, and it dies. This is a very Under these circumstances, accidents of acommon experiment, and most of you peculiar nature are produced; and if thehave no doubt seen it, but I shall perform air have been introduced suddenly, theit now for the benefit of those who may not. respiration and circulation become greatlyI now place this little animal, a guinea- embarrassed, and the individual soon dies,pig, in a jar, containing a quantity of sul- or is reduced to a state of considerablephuretted hydrogen gas, and you see how danger. BICHAT sustained the opinion,instantaneously the poisonous effect is that a single bubble of air introduced intoproduced; in fact, the animal has scarcely a vein, was sufficient to destroy life; but theremained more than a second in the jar, assertion is by no means strictly true; a

and he is now quite dead. The fatal result very small quantity of air passed slowlyis to be attributed to the entrance of the into a vein, mixes with the blood, traversesgas into the circulation, because if the the lungs, and is exhaled with the pulmo-animal were opened, we should find evident nary transpiration, without causing anytraces of sulphuretted hydrogen in the remarkable accident; but when the quan-bloodvessels. tity is increased, especially in a suddenA similar result is produced when the manner, the air mixes with the blood con-

human body is exposed to the action of tained in the heart, and forms witir it adeleterious gases; thus workmen are fre- foamy kind of liquid, which does not passquently destroyed by entering incautiously readily through the capillary system ofinto privies and other places in which the pulmonary artery. In consequence ofnoxious vapours are generated; the sul- this obstacle to the passage of the bloodphuretted hydrogen, or carbonic acid gas, through the lungs, the respiration and

abounding in those unwholesome localities, circulation become excessively troubled,finds a ready passage through the mem- and the animal soon dies in a state ofbrane of the lungs, and the individual is asphyxia,-not from any pernicious actionpoisoned in that manner. of the air on the nervous system. I re-

There are some gases, again, capable of member once to have introduced at leastproducing death rapidly, although they thirty quarts of air into the circulation ofare not poisonous ; thus azote will destroy a horse, at the veterinary school of Alfort,an. animal by asphyxia, by suddenly inter- without killing the animal ; but perhapsrupting the respiration. On this account this extraordinary tolerance, if I may sogases have been divided, with respect to call it, may in part be attributed to thetheir action on the human system, into circumstance, that in old horses the struc-respirable, non-respirable, and poisonous; ture of the lungs, the circulation throughand I would remark of the latter class, them, and their sensibility, are very muchthat they kill by their chemical qualities modified. In former times, the patientalone; you are not to suppose, when an was supposed to die from the pain occa-individual has been destroyed by a poi- sioned by the introduction of air into thesonotis gas, that a large quantity has been bloodvessels during the course of an ope-suddenly introduced through the mem- ration, but this idea is totally groundless.

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and we are now perfectly sure that the: give rise to apprehension and anxiety,fatal results arise simply from the sudden ; but experience has convinced me of theentrance of the air. - ! contrary.

I shall now proceed, Gentlemen, to prove Vt-heiiever, then, you are compelled byby experiment some of the opinions just the circumstances of the case to inject theadvanced ; we shall, for example, intro- veins of the human subject, you need notduce a quantity of air slowly into the cir- be anxious if a little air should be intro-culation of an animal, and see whether the duced with the fluid, provided always thispernicious effects, so generally dreaded be not done in too rapid a manner, for thefrom an accident of this kind, will result; gas will be exhaled by the lungs in a shortif I mistake not, the operation will be at- time without producing any unpleasanttended with little or no inconvenience. or dangerous consequences. You have aYou may choose indifferently an artery or proaf of this in the experiment which hasa vein for the purpose, and I would have, just been performed. I have introducedyou remark that some veins permit the one or two small syringefuls of air intointroduction of a vast quantity of air;: the jugular vein of this dog, without giv-thus, if you choose a vein which traverses ing rise to any accident, because the ope-a parenchymatous substance before it dis- ration was performed in a very gradualcharges its blood into the heart, as, for in- manner. Let us now change the experi-stance, one of the mesenteric veins, you ment, and see what will be the result whenmay introduce, without danger, an exces- a quantity of air is suddenly pushed intosive quantity. The reason of this depends a vein. I proceed, as you see, to injecton the peculiar course of the circulation. the same quantity as before, but I do itThe mesenteric veins, as you know, dis- much more rapidly; however, it seems tocharge the fluid contained in them into produce no remarkable effect.the vena portse, and the air is thus divided Let us try a second syringe ; the dog isin such a manner, and is mixed so intimately not yet affected by the quantity of air,with the blood during its passage through although it has been passed in very ra-the liver, that it does not present an in- pidly; the air is manifestly mixed withsurmountable obstacle to the subsequent the blood in the heart, for I can hear thepassage of the vital fluid through the bullse distinctly by placing my ear to thelungs. But if we choose a branch of the parietes of the chest. Perhaps a thirdvena cava, and introduce suddenly a cer- syringe may have more effect. No, thetain quantity of air, accidents of a very I animal’s respiration still remains perfect-severe character will soon be developed, as ly calm, and the pulse is natural; youyou shall now witness. therefore see it requires much more than

This is the same dog into whose circu- one bullae of air to destroy an animal, forlation we introduced the other day some the contents of three syringes have al-putyid animal matter, in order to demon- ready been injected into the veins of thisstrate the pernicious effects of -a putrid dog, without giving rise to any accident

fluid injected by the veins; but the matter, whatever. The fact is we have not intro-as I remarked at the time of making the duced a sufficient quantity. The air col-

experiment, was not sufficiently decoiii- lected in the right ventricle must be inposed, and acted in a way much less ener- sufficient mass to form a kind of foam withgetically than it otherwise would; the dog the blood, and as soon as this takes place,has now nearly recovered, although he is the blood is unfit to pass through the ca-thin, and will serve to-day to exhibit the pillary vessels of the lungs ; the respira-phenomena occasioned by the introduction tion is at first impeded, then arrested, andof gas into the system. I now proceed the animal dies. In the present instanceslowly to pass some air into the jugular we must introduce a much larger quan-vein, which has been exposed for the pur- tity of air, if we wish to produce any visi-pose. It is not the first time, Gentlemen, ble effect. Here is a very large syringe,that I have injected the venous system of as you see, capable of containing a largean animal, or even of the human subject. quantity of air; we have filled it withSeveral years ago I injected the veins of oxygen, and shall inject the contents ra-patients afflicted with hydrophobia, for I pidly into the jugular vein. This haswas desirous of trying whether the injec- now been done, and within two seconds ation of water in large quantities by the manifest effect has been produced. Lookveins could modify the poison or not. I at the animal, he has the air of sufferingrepeated this operation on many occa- a good deal; his respiration has becomesions, and frequently saw large bubbles of dinicult and considerably accelerated, butair pass in with the water, but no unplea- yet he sustains the injection of even thissant accident was the result. Now, if we extensive quantity of air, and the circula-were to believe BICHAT, the smallest bub- tion still goes on in the arteries of theble passing into the circulation should limbs.

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When the introduced air does not give Although the animal is not yet com.rise to fatal accidents, and the animal re- pletely dead, though he is far beyondcovers, as he would in the present in- experiencing any suffering, we maystance, if left to himself, the gas becomes proceed to examine the chest. In open-dissolved in the mass of the blood, and is ing it I have unfortunately touchedexhaled by the pulmonary membrane, the vena cava, and you see how thewhich gives a ready passage to suhstances blood spouts from it in jets at eachfrom the circulation, as it readily admits pulsation of the heart; this arises fromthem from the external world into the the elastic pressure of the air contained ininterior of the system. The accidents the right ventricle. After experiments ofarising from the introduction of air into this kind, you generally find the heartthe blood vessels may be combated by sonorous to percussion, and the arteriesphysical means, and we shall now try often contain some air, but in most caseswhether we can extract the air from the you find the air in the heart only, becauseveins of the dog by means of this little it is not sufficiently subdivided, when in-

glass tube. I will introduce a hollow sound troduced suddenly, to traverse the lungs,as far as the right auricle, and probably and mix with the fluid in the arterialsave the animal’s life. The pipe, as you system. Here is the heart of the animalsee, has been passed in through the supe- considerably enlarged, as you see, andrior cava as far as the heart, and the blood distended, but not so much as it wouldflows from time to time through the glass have appeared had we not relieved thetube attached to it, but I see no trace of distention by accidentally opening theair escaping by the tube. In the mean vena cava near the heart. In openingtime the air is producing its accustomed the chest, however, the organ contains aeffects; the animal’s respiration is exces- great deal of air, which also fills the coro-sively troubled, and the mucous mem- nary vessels ; but we do not find any tracebrane lining the interior of the mouth of air in the bloodvessels of the lungs orbegins to assume a white appearance, other parts of the body.showing that blood no longer arrives in It results from what we have said,the capillary vessels, and I cannot f<el any Gentlemen, that gaseous bodies follow thepulsation in the arteries of the lower ex- same rules which govern the transmissiontremities. of solids and liquids from the exterior toWe shall now try whether the skin the interior of the human frame; they

possesses the power of absorbing gases in traverse our membranous tissues with thethe same way as it takes up liquids or same facility, and often produce effects ofsblid substances; and for this purpose I a very remarkable natut e. Some are ad-shall repeat an experiment before you vantageously, nay, highly, necessary, towhich I have already tried during a the support and continuance of our exist-former lecture. I place, as you see, this ence, as, for example, oxygen gas; otherslittle bird, a sparrow, into a glass bottle, do not produce any direct results on theleaving the head and neck outside, but economy, although they may, in one reoat the same time taking care that no in- spect, be pernicious, like the non-respira.terval exists by which the air may escape, ble gases; and there are others, finally,and I inject into the bottle a quantity of whose introduction is almost instantane-

poisonous gas. It will no doubt require ously followed by death, as you have seensome time before the gas can penetrate in the case of the guinea-pig compelledthe skin nnd produce its effects on the to respire sulphuretted hydrogen gas.system. We shall, therefore, in the mean These different effects arise fom the che- _time, proceed to inject another syringe ot mical properties of the different gasesair into the veins of the dog, and watch mixing with the circulating fluid in infi-the effect produced by the introduction of nitely small quantities, for if you intro-this fresh quantity. The respiration, duce the gaseous body in a mass, in thewhich had become very slow and labo- form of gas, if I may so say, it forms with

rious, has been again accelerated by the the blood a fluid incapable of traversinglast air thrown in, and the dog breathes the small vessels of the lungs, which be-only in a convulstve manner. We have come obliterated in this manner, andnow passed a second syringe of air, and death is consequently the result.the respiration is, as you see, completely arrested ; in a few minutes the animal will Dr. WARREN, in the American Cyc. ofbe dea I, and we shall have an opportunity Prac. Med., relates two cases in which airof examining the physical condition of the obtained admission into veins during ope-heart, and observing what change has ration. The instant effects were mostbeen wrought in the central organ of the serious. One patient (a man) was savedcirculatory system, by the presence of air by bleeding. The other (a female) died -in a large quantity. in about twenty minutes. -