Chapter IX: Section III (3)

Another mode of stimulating or exciting the whole system is, by putting into it a larger quantity of blood than it naturally contains. This is entirely similar to the breathing of _oxygen_; especially if arterial blood be used, which has already imbibed its spiritous part from the atmosphere. In the last century the transfusion of blood was proposed not only as a mode of curing diseases, but of restoring old people to youth; and Dr. McKenzie, in his Treatise on Health, quotes from the memoirs of the Academy of Sciences several instances of the blood of brute animals being infused into human veins, without any inconvenience. It seems, however, not only a bold but an unnatural attempt to use the blood of beasts for such a purpose; and, however lavish mankind may be of their blood upon certain occasions, it is to be feared that there are few who would be willing to spare any to relieve another from sickness; but indeed little can be said about the practice; as, on account of some bad consequences, or failures, it was forbidden by the king of France, and by the pope’s mandate in Italy, and has now fallen into disuse. In a paragraph at the end of Heister’s surgery (4to edition) it is asserted that the transfusion of blood was productive of madness. Dr. Darwin, however, in his Zoonomia, still proposes the transfusion of blood as a remedy, and even describes a convenient apparatus for performing the operation. In one part of his work he says, “Might not the transfusion of blood, suppose of four ounces daily, from a strong man, or other healthful animal, as a sheep or an ass, be used in the early state of nervous or putrid fevers?” In another place he mentions his having proposed it to a gentleman whose throat was entirely closed up by an incurable swelling, so that he could swallow nothing. This is a disease not very rare, and which always must be fatal; because the patients, though not affected by any sickness, die of hunger; and, to relieve them from this miserable situation, extraordinary attempts are not only allowable but laudable. The Doctor proposed to his patient, “to supply him daily with a few ounces of blood taken from an ass, or from the _human animal_, who is _still more patient and tractable_, in the following manner: To fix a silver pipe, about an inch long, to each extremity of a chicken’s gut, the part between the two silver ends to be measured by filling it with warm water; to put one end into the person hired for that purpose, so as to receive the blood returning from the extremity; and when the gut was quite full, and the blood running through the other silver end, to introduce that end into the vein of the patient, upwards towards the heart, so as to admit no air along with the blood. And, lastly, to support the gut and silver ends on a water plate filled with water of 98 degrees of heat; and, to measure how many ounces of blood were taken away, to compress the gut from the receiving pipe to the delivering pipe.” The gentleman desired a day to consider of this proposal, and then another; after which he totally refused it, saying that he was now too old to have much enjoyment of life, and that, being so far advanced in a journey which he must certainly accomplish sooner or later, he thought it better to proceed than return. The Doctor informs us that he died a few days afterwards, seemingly very easy, and careless about the matter. One experiment of this kind I have been witness to; not indeed on a human creature, but on a calf. This creature received into one of its jugular veins a considerable quantity of blood from the carotid artery of another, nearly of the same age (about a month, or little more.) It was impossible to say any thing about how much was transfused; only the bleeding was continued till the animal which lost the blood began to shew signs of faintness. The artery was then tied up, and the orifice in the jugular vein closed. The calf which had lost the blood appeared very languid and faint, but lived a few days in a drooping state; when it either died of itself, or was killed, as being supposed past recovery. The other, which had received the blood, appeared to be in every respect highly excited. It became playful, even in the room where the operation was performed, its eyes assumed a bright and shining appearance, and its appetite was greatly increased. Thus it continued for about a fortnight; appearing all the time to be in high health, and eating much more than usual; but at last died suddenly in the night. From these effects on healthy subjects, however, we cannot infer what would happen in such as are diseased; but it is plain that if the cure of diseases were to depend upon mere _excitation_, the means are in our power, without any local irritation, which always must take place in some degree by the use of ordinary medicines. This path is not absolutely untrodden: the pneumatic practitioners of the present day have tried oxygen in consumptions, and found it pernicious; and Dr. McKenzie informs us that the transfusion of blood was tried ineffectually in the same.

7. As all the medicines usually prescribed at present are only to be accounted partially stimulant, or as acting upon particular parts of the system, we see that some may promote one evacuation, and some another; while all produce some change in the organization, which may prove useful or detrimental, may increase the disease or cure it, or may produce another, according to the judicious or injudicious application. But for a knowledge of all this we must be indebted to experience: there is not a theory on earth that can lead us a single step.

Before we dismiss the consideration of medical theories, however, it will still be necessary to give some account of the new system as it hath branched out in various ways: for though the fundamental principle is now received by a great number of physicians, yet the superstructure is exceedingly different from what Dr. Brown himself erected and, indeed, from the very same principles we find conclusions made as directly opposite to one another as can be expressed in words. Drs. Yates and McLean, for instance, at Calcutta in the East Indies, have concluded that the plague “is a disease of a very high degree of exhaustion;” which Dr. Brown would have called debility. Dr. Rush at Philadelphia, proceeding also upon the Brunonian principles, determines it to be the most inflammatory of all diseases,[62] and which Dr. Brown would have called a disease of excitement. These two doctrines are, in every sense of the word, as distant from one another as east from west. Let us then consider both, if any consideration can avail us on the subject.

[62] See above, p. 102.

By the ancients it was supposed that diseases were occasioned by something either bred in the body or received into it, and that the power of nature produced, during the course of the disease, a certain change in this matter, called _coction_, or _concoction_; which, if we please, we may express by the English word _cooking_. The matter of the disease, called also _morbific_ matter, thus _cooked_, was in a state proper for expulsion, and was therefore thrown out by sweat, vomit, stool, &c. or it might be expelled artificially, which could not have been attempted with safety before. Modern systems deny the existence of morbific matter, and resolve all into an affection of the nerves, according to Dr. Cullen by certain sedative causes, but according to Dr. Brown by an accumulation in some cases, and an exhaustion in others, of the excitability or excitement of the body. The Science of Life commences with stating what they suppose to be an improvement of the Brunonian principles, and from which the following account of the origin of diseases is extracted. “Upon the different states of _excitability_ depend all the phenomena of health and disease. There are three states of the excitability. 1. The state of accumulation; when a portion of the usual stimuli is withheld.... When a portion of the usual stimuli is withheld, the excitability accumulates, and the body becomes susceptible of impression in the direct ratio of the subduction. This state constitutes diseases of accumulation, or of direct debility. 2. The middle state; when the excitability is such that the application of the accustomed degree of exciting powers produces _tone_ or _health_. 3. The state of exhaustion. When the application of stimuli has been greater than that which produces healthy action, the excitability is exhausted, and the body becomes less susceptible of impression in the direct ratio of the excess. This state constitutes diseases of exhaustion, or of indirect debility. The states of accumulation and exhaustion of the excitability, in their different degrees, constitute all the diseases to which living bodies are subject.”

Here the chime runs on the word _excitability_, which is not defined. If we call this property _life_, then we are only informed, that, as life is more or less vigorous, the body enjoys a greater or smaller degree of health; which we know without any medical instructor. If, instead of the accumulation and exhaustion of excitability, we take the original doctrine of excitement and debility laid down by Dr. Brown himself, we are nothing better. The whole theory is lost for want of the definition of a single word. As long as _excitability_ remains an unknown property, we can explain nothing by it. We may indeed vary our terms. We may call it _nervous influence_ with Dr. Cullen, or _sensorial power_ with Dr. Darwin; but we shall still be as much in the dark as ever; and all that can be made out of our theories, when our language is _decyphered_, must be, that sometimes people are well, and sometimes they are sick!

Dr. Rush, in his Treatise on the Proximate Cause of Fever, adopts in part Dr. Brown’s system pretty nearly as the author himself laid it down. “Fevers of all kinds (says he) are preceded by general debility. This debility is of two kinds, viz. direct and indirect. The former depends upon an abstraction of usual and natural stimuli; the latter upon an increase of natural, or upon the action of preternatural, stimuli upon the body.... Debility is always succeeded by increased excitability, or a greater aptitude to be acted upon by stimuli.... The diminution or abstraction of one stimulus is always followed by the increased action of others.” Here it is evident we are as much in want of definitions as ever. We know neither what _excitability_ is, nor what _debility_ is, and yet they are both held out as the _causes_, and _proximate_ or _immediate_ causes, too, of symptoms produced by things quite obvious to our senses. Thus cold and heat, with which we are daily conversant, are only called the _predisposing_ causes of fever; while _debility_ and _excitement_, words to which we have no meaning, are said to be the _proximate_ cause. It would certainly be better to throw away such words altogether, and say that cold, heat, &c. cause fevers, without troubling ourselves farther about the matter.

It remains now to take into consideration the pneumatic theories, founded upon the discoveries made by Dr. Black, Dr. Priestley, Lavoisier, and others, concerning various kinds of aerial fluids, or _gases_,[63] as they are also called. Some of these, particularly that afterwards called fixed air, were discovered by Van Helmont. Considerable advances were made by a German chemist, named _Mayow_, in the last century; but his book had fallen into such oblivion that his name was scarce ever mentioned, until his discoveries were repeated, and still greater advances made by others. Dr. Hales obtained air from a great many different substances, but was unable to ascertain any thing concerning its nature. Dr. Black of Edinburgh laid the foundation of pneumatic chemistry, by discovering that a certain species of air is capable of being absorbed by earths of different kinds, and that many very heavy substances owe at least one half of their weight to this condensed air. The discovery was accidental. Wishing to obtain a very pure and white lime, he had recourse to the fine white earth called _magnesia alba_. Some of this he distilled with a heat sufficient to make the vessel red hot. Only a very small quantity of water came over, but the magnesia had lost almost two thirds of its weight. This immense loss was found to arise from an emission of air during the operation; and by other experiments it was likewise found that the air might be transferred from one portion of magnesia to another from which it had been previously expelled; that the existence of this species of air in certain bodies was the cause of that fermentation which takes place when any acid is poured upon them, as vinegar upon chalk or potash. Hence if any of these substances be deprived of its air, it will not any longer ferment in this manner. It must not be forgot, however, that when air thus unites itself with any terrestrial substance it no longer has its former properties. It is reduced exceedingly in bulk, and in proportion to this reduction only the body is increased in weight; and therefore though we say that the _air_ is absorbed, we must still remember that only _one part_ of it is so, and that by far the least considerable in bulk. A violent fire will always expel the air again, and restore it to its former bulk; and again the condensation or absorption of the air is always attended with the production of heat. This last property was not much attended to by Dr. Black, but others have observed it; and the late Dr. Charles Webster of Edinburgh published a theory in which he maintained that condensation was in _all_ cases the cause of of heat. But, however true it may be that condensation of any kind is followed or accompanied by heat, it is evidently necessary to know the cause of the _condensation_ also, otherwise we make no advance in solid theory.

[63] _Gas_ is a German word, or derived from one, signifying
_spirit_. The word _ghost_ comes from the same original.

The aerial fluid, discovered by Dr. Black, was one of those most commonly met with. He called it _fixed air_, from its property of adhering or fixing itself to different bodies. It was found to be the same with that which had been discovered by Van Helmont, and by him named _gas sylvestre_ (spirit of wood)[64] or the fume of charcoal; it was found to be the same with the steam of fermenting liquor, and with that very frequent and dangerous vapour, met with in coal mines, called in Scotland the _choke-damp_. Like other discoveries, this was quickly pushed beyond its proper bounds, and applied to the solution of phenomena which it could not solve. Dr. MBride, particularly, supposed it to be the bond of union between the particles of matter, or in other words the principle of cohesion itself. It was also supposed to be the substance of those scorching winds, called _samiel_, met with in Asia and Africa, and which sometimes prove fatal to travellers. The pernicious vapours called _mofetes_, which sometimes issue from the old lavas of Vesuvius in Italy, were likewise supposed to be the same;[65] but of this, particularly with regard to the samiel, there seems to be no sufficient evidence.

[64] This must be understood only of its general properties and
effects; for, though the fume of charcoal possesses many of the
apparent properties of pure fixed air, it contains also a very
considerable quantity of another kind of gas.

[65] Many fabulous stories have been related concerning the samiel.
Even so late a traveller as Mr. Ives has adopted some of those
exaggerated accounts which have been discredited by those who have
long resided in the countries where this wind is commonly met with.
It is not peculiar to the deserts of Arabia, but is met with in all
hot countries which are destitute of water. In the African deserts
therefore it is common; and Mr. Bruce describes it by the name of
_simoom_. It was preceded by whirlwinds of a very extraordinary
kind. “In that vast expanse of desert (says he) from W. and to N. W.
of us, we saw a number of prodigious pillars of sand at different
distances, at times moving with great celerity, at others walking on
with a majestic slowness. At intervals we thought they were coming
in a very few minutes to overwhelm us; and small quantities of sand
did actually more than once reach us. Again they would retreat so as
to be almost out of sight; their tops reaching to the very clouds.*
There the tops often separated from the bodies; and these, once
disjoined, dispersed in the air, and did not appear more. Sometimes
they were broken near the middle, as if struck with a large cannon
shot. About noon they began to advance with considerable swiftness
upon us, the wind being very strong at north. Eleven of them ranged
along side of us at about the distance of three miles. The largest
of them appeared to me at that distance to be about ten feet
diameter.... It was in vain to think of flying; the swiftest horse or
the fasted sailing ship could be of no use to carry us out of this
danger; and the full persuasion of this rivetted me as if to the spot
where I stood.” At another time he saw them in much greater number,
but of smaller size. They began immediately after sunrise, like a
thick wood, and almost darkened the sun. His rays darting through
them gave them the appearance of pillars of fire. They now approached
to the distance of two miles from our travellers. At another time
they appeared beautifully spangled with stars. in Darwin’s Botanic
Garden we find a reason assigned for the appearance of these
whirlwinds; viz. the impulse of the wind on a long ledge of broken
rocks which bound the desert. By these the currents of air which
struck their sides were bent and were thus like eddies in a stream of
water which falls against oblique obstacles. In the same work we have
the following poetical description of them:

* _N. B._ In these sandy deserts, where it never rains,
there are no clouds.

“Now o’er their heads the whizzing whirlwinds breathe,
And the live desert pants and heaves beneath;
Ting’d by the crimson sun, vast columns rise
Of eddying sands, and war amid the skies,
In red arcades the billowy plains surround,
And whirling turrets stalk along the ground.”

Whether the simoom is always preceded by these whirlwinds we know
not; but Mr. Bruce mentions an extreme redness of the air, pointed
out by his attendant Idris, as the sure presage. His advice was, that
all of them, upon the approach of the pernicious blast, should fall
upon their faces, with their mouths on the earth, and hold their
breath as long as possible, so that they might not inhale the deadly
vapour. They soon had occasion to follow this advice; for next day
Idris called out to them to fall upon their faces, for the simoom
was coming. “I saw (says Mr. Bruce) from the S. E. a haze coming, in
colour like the purple part of the rainbow, but not so compressed
or thick. It did not occupy twenty yards in breadth, and was about
twelve feet high from the ground. It was a kind of blush upon the
air, and it moved very rapidly; for I could scarce turn to fall upon
the ground, with my face to the northward, when I felt the heat of
its current plainly upon my face. We all lay flat on the ground, as
if dead, till Idris told us it was blown over. The meteor, or purple
haze, which I saw, was indeed passed; but the light air that still
blew was of heat sufficient to threaten suffocation. For my part, I
felt distinctly in my breast that I had imbibed a part of it; nor
was I free of an asthmatic sensation till I had been some months
in Italy, at the baths of Poretta, near two years afterwards.” It
continued to blow for some time, and in such a manner as entirely to
exhaust them, though scarcely sufficient to raise a leaf from the
ground.

The account given by Mr. Ives is, that it blows over the desert (of
Syria) in the months of July and August, from the northwest quarter,
and sometimes continues with all its violence to the very gates of
Bagdad but never affects any body within its walls. Some years it
does not blow at all and in others it comes six, eight, or ten times,
but seldom continues more than a few minutes at a time. It often
passes with the apparent quickness of lightning. The sign of its
approach is a thick haze, which appears like a cloud of dust rising
out of the horizon, on which they throw themselves with their faces
on the ground, as already mentioned. Camels are said, instinctively,
to bury their noses in the sand. As for the stories of its dissolving
the cohesion of the body in such a manner that a leg or an arm may
be pulled away from those who are killed by it, or that their bodies
are reduced to a gelatinous substance, we cannot by any means give
credit to them. From its extreme quickness, and luminous appearance,
it would seem to be an electrical phenomenon immediately preceding
those vehement hot winds which all travellers agree in likening to
the vapour issuing from a large oven when the bread is newly taken
out. Its electrical nature will be more probable from the account
given by Mr. Ives, that the Arabians say it always leaves behind it a
very sulphureous smell. These particulars do not at all accord with
the supposition of its consisting of fixed air. I have indeed been
assured by a gentleman long in the service of the English East India
Company, that the samiel cannot pass over a river. Hence probably it
has been supposed to be a blast of fixed air, because this species
of gas is readily absorbed by water; but we know that the same thing
would also take place with any quantity of electric matter; for water
takes up this also much more completely than it does fixed air.

The _mofetes_ are invisible, and kill in an instant. They rise from
old volcanic lavas, and, as it were, creep on the ground, and enter
into houses, so that they are very dangerous; but, though they may
probably consist of fixed air, we have not as yet any direct proof
of it. It is not indeed easy to imagine why any lava should suddenly
emit a great quantity of fixed air, and then as suddenly cease; nor
in what manner the air thus emitted should continue unmixed with
the atmosphere; for fixed air will very readily mix in this manner,
insomuch that a large quantity of it being let loose in a room has
been found to vanish entirely in less than half an hour. Sir William
Hamilton mentions a mofete having got into the palace of the king of
Naples.

The industry of other experimenters did not long leave theorists without abundance of materials upon which they might exercise their talents. It is impossible in this place to assign to each his proper rank in the way of discovery, or indeed to mention their names. Dr. Priestley has distinguished himself far above the rest. He not only repeated and improved Dr. Black’s experiments on _fixed air_, but likewise found out a number of other kinds; particularly that from animal substances in a state of putrefaction, which is so pernicious to living creatures, insects excepted; for these last will thrive amazingly in air that would prove certain death to a man. He also discovered that this kind of air, and some others, were absorbed by vegetables, and thence inferred the use of vegetables in purifying the atmosphere. He even analysed the atmosphere itself, and found that it consisted of two different kinds of fluids, one of which he called _dephlogisticated_, the other _phlogisticated_ air. The former was found to support animal life for a time, the latter to destroy it instantly. Their effects upon fire were the same; the former exciting the most vehement heat and bright flame, the latter extinguishing a fire at once.

The fame of Dr. Priestley’s discoveries quickly reached the continent of Europe; the French chemists repeated his experiments with improvements, as they thought; and indeed certainly made many curious discoveries. Lavoisier was particularly remarkable for his numerous and accurate experiments; but, by his changing entirely the language of former chemists, and substituting a set of new terms of his own invention, he certainly entailed the greatest curse upon the science it ever met with. It belongs not to this treatise to give an account of his system farther than to say, that, from the immense proportion of condensed aerial matter found in most terrestrial substances, he and his followers were led to conclude, that different species of air constitute almost the _whole_ of the terraqueous globe. Water particularly they have absolutely and most positively determined to be a composition of two airs condensed, viz. the dephlogisticated and inflammable, which they call _oxygen_ and _hydrogen_. However, this doctrine is still opposed by Dr. Priestley and some others.

In the midst of so much theory, and so many new and surprising discoveries, it would have been wonderful indeed if the science of medicine had kept free from innovation. It did not: the new chemistry, with all its formidable apparatus of hard words, was introduced, and thus the study of the science, already very difficult, was rendered still more so. In passing this censure upon the modern _nomenclature_, as it is called, I am sensible that I must rank with the minority; nevertheless, I have the satisfaction of finding that I am not altogether singular. Dr. Ferriar, in the preface to his second volume, complains, “that, with every attempt towards the formation of a system, new applications of words are introduced, which, though desirable in the art of poetry, are very inconvenient in pathological books, especially when this is done to give an air of novelty to old theories and observations. For, between the ancient language, which practitioners cannot entirely reject, and the new dialect, which they cannot wholly adopt, the style of medical books is reduced to a kind of jargon, that the author himself may possibly understand, but which his readers find it very difficult to unriddle. Hence results a neglect of medical literature, and hence the pernicious habit of regarding as new whatever has not appeared in the publications of the last half century.” To the same or a similar purpose, in the preface to his first volume, he cites Quintilian. [66]“Some have such a multitude of vain words, that, while they are afraid of speaking like other people, by a kind of affected elegance, they confound every thing they have to say with their immense loquacity.”

[66] Est etiam in quibusdam turba inanium verborum, qui dum communem
loquendi morem reformidant, ducti specie nitoris, circumeunt omnia,
copiosa loquacitate, quæ dicere volunt.

The pneumatic system naturally arose from a consideration of the composition of the atmosphere we breathe. Finding this fluid to be composed of two others, the one of which would preserve life for some time at least, and the other instantly destroy it, it became natural to think that diseases might be produced by any considerable variation in the proportion of these ingredients. An instrument was soon invented by which any considerable variation in this respect might be discovered; but upon trial this was found to be of very little use. Dr. Priestley himself tried, by means of this instrument, some very offensive air which had been brought from a manufactory, and could find no remarkable difference between it and that which was accounted pure. Still, however, it was evident that by increasing very much the proportion of one of the ingredients, some considerable alteration might be produced, which could not but be perceptible in the human body; and this led to the application of aerial chemistry to disorders of the lungs. The mixture chosen for this purpose was pure dephlogisticated (_oxygen_) with inflammable air (_hydrogen_;) and, though this has not been known to effect a radical cure, it certainly has given relief in many cases. In fevers also the application of fixed air (carbonic acid) hath been found advantageous; but with regard to oxygen and some others we have not yet a decided instance of their good effects in any case. Dr. Beddoes indeed is of opinion that it would be of service in the sea-scurvy; but in this (whether his conjecture be right or wrong) the theory is certainly erroneous, as shall presently be evinced.

In considering the pneumatic system it is evident that modern chemists have fallen into the same error with their predecessors, viz. of supposing that every thing which by the force of fire or otherwise they could produce, from any substance, previously existed in it. Hence, as from a piece of bone for instance, a chemist can produce water, salt, oil and earth, it was supposed that these four were the principles or elements of the bone. But this was false reasoning; for if these were really the chemical principles, they ought to have been able to produce some kind of bony substance by mixing them together after they had been distilled. But no such thing could be done; and though we should add to the mixture the whole quantity of air emitted during the distillation, and which escaped the notice of ancient chemists, our success would be no better. In like manner, because in certain circumstances oxygen is obtained from the flesh of animals, it has been concluded that it necessarily exists as an ingredient in their bodies while living; and that, if this kind of air happens to predominate, the animal will be affected in one way, or if hydrogen prevail, in another. But though we have already quoted Dr. Girtanner with approbation as having obtained oxygen gas from fresh meat, yet this does not by any means prove to us that it exists in flesh as one of its component parts. Even in the Doctor’s experiment it was necessary to expose the flesh to the atmosphere in order to procure the gas by distillation; which undoubtedly must excite a strong suspicion that the air in question comes from the atmosphere itself; and, if this is the case, it is not reasonable to suppose that a disease could be cured by any addition of oxygen to the solid parts; because, though sound flesh may have an inclination to absorb this kind of air, we do not know whether it would have such a property of absorption in a diseased state. Indeed in the scurvy, which Dr. Beddoes chooses as an example, experiment seems to determine in favour of _fixed air_ rather than any other. But let us hear Dr. Girtanner himself, who has at large discussed this subject in two memoirs; one upon the laws of irritability, and another on the principle of irritatibility.

In these memoirs we find the Brunonian doctrine set forth with such silence in regard to Dr. Brown himself, that some have not scrupled to charge Dr. Girtanner with literary _theft_; but this is a matter which belongs not to us to consider: the theory may be very good, whether stolen or not. He changes the word _excitability_, used by Dr. Brown, for _irritability_; but hath the misfortune of not being able to tell us what he means by it. He goes on, however, to distinguish the three states of _tone_ or health, _accumulation_, and _exhaustion_, as other Brunonians do. Health, he says, in a fibre “consists in a certain quantity of the irritable principle necessary for its preservation. To maintain this state, the action of the stimulus must be strong enough to carry off from the fibre the surplus of this irritable principle which the lungs and the circulation of the fluids are continually supplying. For this a certain equilibrium is necessary between the stimuli applied and the irritability of the fibre, in fine that the sum of all the stimuli acting upon it may be always nearly equal; powerful enough to carry off from the fibre the excess of its irritability, and not so strong as to carry off more than this excess.... When the sum of the stimuli acting upon the fibre is not great enough to carry off all its excess of irritability, the irritable principle accumulates in the fibre, and then it is found in that state which I call the _state of accumulation_; the irritable principle accumulates in the fibre, its irritability is augmented, and the stimuli produce much stronger contractions than when the fibre only retains its tone.... When the sum of the stimuli acting upon the fibre is too great, the fibre is deprived not only of the excess of its irritability, but also of some portion of the irritable principle necessary for the tone of the fibre; or, more properly speaking, the fibre loses more irritability than it receives, and, of course, in a short time finds itself in a state of _exhaustion_; and this exhaustion will be either _temporary_, or _irreparable_.”

Here it is evident that we have nothing but Dr. Brown’s system, without the least explanation to render it more intelligible. A definition is still wanting. This invisible and incomprehensible property of _irritability_ ruins our whole fabric; nor can the deficiency be supplied by human art or skill: of consequence we must abandon this part of the system entirely, and come to something more cognizable by our senses. It is impossible, however, to pass over in silence the amazing inattention of the author, in imagining that on such unintelligible principles he could explain other phenomena. “In the state of _temporary exhaustion_ (says he) the fibre loses its tone, and fails for want of irritability. The application of a stimulus while it is in this state will not make it contract. Provided the stimulus be not very strong, it will produce no effect at all, but in a short time the irritable principle will accumulate afresh in the fibre, and then it will again contract. It is only by little and little that the fibre recovers its irritability. This truth, I dare venture to say, is as new as it is striking. It unfolds a vast number of phenomena hitherto inexplicable.” Here we have nothing but the pompous declaration of a fact already well known; viz. that not only a _fibre_, but the whole body, may be in a state of temporary insensibility, and yet recover either of itself or by the use of external means. How many people have fallen into a _syncope_, and yet recovered! How many limbs have become paralytic, and in time recovered their sense and motion! Yet this is all that we are informed of with so much parade and assumption of novelty. We know that when a person is in a faint he is insensible to ordinary stimuli, though very strong ones will rouse him; but what can we infer from this? Nothing; only we see it is so. Does it avail us any thing to be told that during the time of fainting the _irritability_ is exhausted, and “in a short time the irritable principle will accumulate afresh;” in which case the patient will no doubt recover, unless he happens to be dead, which is the true meaning of an _irreparable exhaustion_ of the irritability.

In speaking of the principle of irritability he expresses himself in the following manner. “I think that the oxygen is absorbed by the blood, and that the venous blood is oxygenated in the lungs during respiration. The most celebrated naturalists and chemists are of a different opinion: they think that the oxygen does not combine with the venous blood. According to them, this last loses carbon and hydrogen, and recovers the bright colour natural to it, without absorbing any thing from the atmosphere.... After having a long time attended the phenomena of respiration, and made many experiments upon this subject, I think it may be concluded that one part of the oxygen of the vital air combines with the venous blood, of which it changes the black colour, and makes it vermilion;[67] the second part of the oxygen unites with the carbon contained in the carbonic-hydrogen gas, which exhales from the venous blood, and forms carbonic acid air; a third part unites with the carbon of the mucus, contained in great quantities in the lungs, and which is continually decomposing; this part also forms carbonic acid air; a fourth part of the oxygen combines with the hydrogen of the blood to form water.”

[67] Here Dr. Beddoes, from whose publication this account of
Girtanner’s memoir is taken, has the following note: “Dr. Goodwyn
had proved this before. Could Dr. Girtanner be ignorant of his
experiments?” In justice to myself, however, I must observe that this
very doctrine had been published in the Encyclopædia Britannica long
before either Dr. Goodwyn or Dr. Girtanner had made any experiments
on the subject. It may still be seen under the article BLOOD, and
reasons are there given for supposing that only one part of the
oxygen, viz, the elastic part, can be absorbed.

On this theory I shall only observe, that though I lay claim to the former part, I allow the Doctor all the latter part to himself; particularly where he speaks of the _formation_ of water to be exhaled during respiration. The air in question consists of two parts, like _fixed air_ already mentioned. One of these is capable of being attracted, condensed, or united with certain substances; the other vanishes, leaving no other traces of its having ever existed, but heat, greater or less according to circumstances. When the air is taken into the blood, one part of it undoubtedly combines with something thrown out by the lungs, and forms _fixed air_, of which our breath contains a considerable quantity. We know certainly that the condensable part of fixed air is formed out of the condensable part of the oxygen, with certain additions. As therefore great part of this condensable oxygen is thrown out in fixed air at every expiration, it is natural to suppose that all of it is so: at least we cannot know the contrary without a series of very difficult and tedious experiments, which have never been made by Dr. Girtanner or any body else. But if the whole of this condensable part be thrown out, none can enter the blood by the breath; and consequently whatever true oxygen may afterwards be expelled from that fluid, must be a factitious substance, formed either during the artificial process, used for distilling it, or by a natural process In the body itself. It is not therefore at all probable that the oxygen which flesh emits in distillation can be derived from the air by respiration.

Another and more probable source is the food and drink we take; all of which are more or less impregnated with air of different kinds, particularly fixed air. This, we know, very readily condenses, and certainly will do so when taken into the body. In this state it not only may, but certainly will, pass into the blood, and through all the different parts of the body, until, having accomplished its purpose, whatever that may be, it is thrown out by insensible perspiration, as has been already explained.

The conclusions drawn by Dr. Girtanner from his experiments are, 1. That the change of colour which the blood undergoes during the circulation is not owing to its combination with hydrogen air[68]. 2. The deep colour of the blood in the veins is owing to the _carbon_ it contains. 3. That the vermilion colour of the arterial blood proceeds from the oxygen with which the blood is conjoined during its passage through the lungs. 4. That respiration is a process exactly analogous to the combustion and oxydation of metals; that these phenomena are the same, and to be explained in the same manner. 5. That, during circulation, the blood loses its oxygen, and charges itself with _carbonic hydrogen_ air, by means of a double affinity. 6. That, during the distribution of the oxygen through the system, the heat which was united with this oxygen escapes; hence the animal heat. 7. That the great capacity of arterial blood for heat is owing to the oxygen with which it is united in the lungs.

[68] Here it is necessary to observe, for the sake of accuracy and
perspicuity, that, in the new chemistry, the terms of which are
now very generally adopted, the words _oxygen_ and _hydrogen_ when
mentioned by themselves are not understood to signify any kind of
air, but what I have called the condensable part of the air. If
the word _air_ is added, then the whole substance of the fluid is
understood. But though this is the strict orthodox language of the
new chemistry, it is impossible to say whether every one who adopts
the terms be sufficiently careful in this respect. Indeed this is
one out of many inconveniences that might be pointed out which
have arisen from this nomenclature; for thus the mere omission of
a monosyllable, which may happen in numberless instances, totally
perverts the meaning of the author, and may of course subject him
to unmerited censure. Besides, it is not to be known, unless the
author tells us so, that he designs to observe this strictness, and
of consequence we must in multitudes of cases be uncertain of the
meaning of what we read. Thus, in the present instance, when Dr.
Girtanner speaks of _oxygen_, we know not certainly whether he means
the air in substance, or only one of its component parts. Probably
he means the condensable or solid part. If he does so, there must be
a very material difference between his theory and that laid down in
the Encyclopædia, and which is supported throughout this treatise. In
the latter it is maintained that the condensable part is thrown out
by the breath, being previously converted into fixed air, while the
elastic part enters the vital fluid, communicating to it not only the
red colour, but heat, and the principles of life and sensation, as
will be more fully explained in the sequel.

On these propositions, which constitute in a great measure the fundamental principles of the doctrine of _oxygenation_ of the human body, we may remark,

1. Nobody can reasonably suppose that hydrogen air is the cause of the dark colour of the blood in the veins, because there is no source from which it can be derived; and, besides, it is certain that no kind of air can exist in its elastic state in the blood, without destroying the life of the animal. Some experiments proving this are given by Dr. Girtanner himself. It is true that an aerial vapour, of the nature of _fixed air_, exhales from the body by insensible perspiration; but there can be no doubt that this receives its elasticity only at the surface of the body, and is expelled the moment it is formed. It has indeed been proved, by undeniable experiment, that no air of any kind exists in the larger veins; because a portion of a vein, included between two ligatures, being cut out, and put under the receiver of an air-pump, does not swell in the least when the air is exhausted, which yet must be the case, did the smallest quantity of elastic air exist in it.[69]

[69] _Hydrogen_ air is the same with that by Dr. Priestley called
_inflammable_ air. He also discovered the true composition of it.
Having included a few grains of charcoal in the receiver of an
air-pump, and exhausted the air, he heated it in vacuo by means of
a large burning glass. The charcoal was entirely volatilized and
converted into this kind of air. He found, however, that without some
small portion of moisture this volatilization did not take place.

2. When the Doctor asserts that the dark colour of the venous blood is owing to the carbon it contains, he is in the first place chargeable with the error of former chemists, who supposed that every thing which could be extracted from any substance by fire, existed previously in it, in that very form in which it is extracted by the fire; and in the second place he speaks entirely at random, without even a shadow of proof. Nay, he himself tells us, that he has repeated two of Dr. Priestley’s experiments, which in the clearest manner demonstrate, that neither the addition nor the abstraction of carbon, or any thing else, give this dark colour to the venous blood. “A small glass tube (says he) filled with arterial blood, of a bright vermilion, was sealed hermetically,[70] and exposed to the light. The blood changed its colour by degrees, and in six days became black as venous blood. The same experiment was repeated, with this difference only, that the tube was exposed to heat, and not to the light. The blood became black in a shorter time.” In these experiments it is plain, that if the blood contained oxygen at first, it did so at the last; the same with regard to carbon. How came it then to pass, that without either evaporation of the former, or addition of the latter, the change should be produced? If the oxygen imbibed by the blood in the lungs was sufficient to produce the red colour, why did it not preserve it? The case here is precisely similar to what happens with the calx of silver. When that metal is dissolved in aqua fortis, and again reduced to a solid form, it appears as a white powder, and will preserve its colour if carefully kept from the light; but if a vial be filled with it, and exposed to the sun, that side on which the light falls will in a short time become black, and this though the vial has been ever so carefully sealed.[71] Formerly, chemists had a method of accounting for this appearance, as well as that of the venous blood, by what they called the _evolution of phlogiston_: but now that the very existence of phlogiston is denied, we are deprived of this resource. But, whatever words we may use, it is plain that in neither case have we any ideas affixed to them which can make the matter at all more intelligible than it was before. But with regard to the blood, we are at a considerable loss to understand what the natural colour of it is; and indeed the question can only be determined by examining the blood of a fœtus which has never breathed. If the arterial blood of such a fœtus be of a dark colour, resembling that in the veins of a grown person, we must look upon this to be _natural_ to it, and we may as well inquire why a rose is red, or an iris blue, as why the blood is of a dark, and not of a bright red. But, if we find this dark red change to a bright scarlet in the arteries, as soon as the child has breathed, we have as much reason to conclude that the air occasions this superior redness, as that an acid is the cause of a red colour in the syrup of violets, or an alkali of a green colour in the same. Experiments are yet wanting to determine this matter. Mr. Hunter has observed that “in such fœtuses as convert animal matter into nourishment, they most probably have it (the colour of the blood) influenced by the air, such as the chick in the egg, although not by means of the lungs of the chick, we find the blood, in the veins of their temporary lungs, of a florid colour, while it is dark in the arteries.”--The probability therefore is, that the blood is naturally dark; by the elastic principle of the oxygen that it is rendered brighter; and that, this elastic principle being expended in the course of circulation, the fluid reassumes its original colour.

[70] A glass tube is sealed hermetically, by heating the open end or
ends, till they become soft, and then closing them with a pair of
pincers.

[71] Thus letters, or other characters, may be curiously marked upon
the calx within the vial, by cutting them out in paper, and then
pasting them on the side to be exposed to the light. We may have them
in this manner either dark upon a white ground, or white upon a dark
ground.

3. Though enough has already been said to evince that the superior redness of the arterial blood is derived from oxygen gas, we shall still quote two instances from Mr. Hunter’s Treatise on the Blood, which set this forth in the clearest manner; and these instances are the more remarkable, because they demonstrate the phenomena not of the _dead_, but of the _living_ body. 1. A gentleman in an apoplexy, who seemed to breathe with great difficulty, was bled in the temporal artery. The blood flowed very slowly, and for a long time. It was as dark as venous blood. He was relieved by the operation; but, on opening the same orifice in two hours, the blood flowed of the usual florid colour. 2. A lady in an apoplexy was treated in the same manner, and Mr. Hunter observed, that when she breathed freely, the blood from the temporal artery assumed a bright red colour; but when her breathing was become difficult, or when she seemed scarce to breathe at all, it resumed its dark colour, and this several times during the operation.