The Works, literary, moral and medical, of Thomas Percival ... To which are prefixed, Memoirs of his Life and Writings [by E. Percival] and a selection from his literary correspondence. A new edition

Front matter

" 7/y/(,/yy w THE WORKS or THOMAS PERC1VAL, M.D. IN FOUR VOLUMES. THE WORKS, LITERARY, MORAL, AND MEDICAL, or THOMAS PERCIVAL, M.D. F.R.S. AND A.S.— F.R. S. AND R.M.S. EDIN. LATE PRES. OF THE LIT. AND PHIL. SOC. AT MANCHESTER; MEMBER OF THE ROYAL SOCIETIES OF PARIS AND OF LYONS, OF THE MEDICAL SOCIETIES OF LONDON, AND OF AIX EN PROVENCE, OF THE AMERIC. ACAD. OF ARTS, &c. AND OF THE AMERIC. PHIL. SOC. AT PHILADELPHIA. TO WHICH AKE FREFIXED, MEMOIRS of his LIFE and WRITINGS, AND A SELECTION FROM HIS LITERARY CORRESPONDENCE. A NEW EDITION. VOL. III. PRINTED BY RICHARD CRUTTWELL, ST. JAMES's-STREET, BATH; FOR J. JOHNSON, ST. PAUL'S CHURCH-YARD, LONDON. 1807. THE CONTENTS

Part I. Page

Preface - xiu The Empiric, or Man of Experience - i The Dogmatic, or Rationalist - -26 Experiments and Observations on Astringents and Bitters - - - -36 On the Uses and Operation of Blisters - 119 An Inquiry into the Resemblance between Chyle and Milk - - - - 164 AExperiments and Observations on Water, 'particularly the hard Pump Water of Manchester 1 7 3 On the Disadvantages of inoculating Children in early Infancy - 230 On the Efficacy of external Applications in the Angina Maligna, or Ulcerous Sore Throat 248

Part II

Preface _ _ _ _ - 257 Observations and Experiments on the Columbo Root - - - - - 263 On the Preparation, Culture, and Use of the Orchis Root - - - - 285 Vol. I. b . Experiment. CONTENTS. X PAGE Experiments and Observations on the Waters of Buxton and Matlock - - 295 Observations on the Medicinal Uses of Fixed Air 307 On the Antiseptic and Sweetening Powers, and on the Varieties of Factitious Air - 321 On the Noxious Vapours of Charcoal - 329 On the Atrabilis -':-'-■- 342 On the Septic Quality of Sea Salt - - 344 On Coffee - - - - ~ 3Sl Seleft Histories of Diseases with Remarks. I. The History and Cure of a Difficulty in Deglutition, arising from a spasmodic Affection of the Œsophagus - - 364. II. Cafes of Dropsies - . - - 375 III. Cafe of a Palsy, from the Effluvia of Lead, cured by Eie ftricity - - 391 IV.

Cases of obstinate Colics, cured by the Use of Alum - - - -1-401 V. Cases in which the Warm Bath was successfully employed - . - - 407 VI. Miscellaneous Cafes and Observations - 419 Proposals for establishing more accurate and comprehensive Bills of Mortality in Manchester 428 Plan of Bills of Mortality by the Rev. Mr. Dade of York - - '-_._•- 436 Observations and Experiments on the Poison of 'Lead _____ 449 ESSAYS ESSAYS MEDICAL, PHILOSOPHICAL, AND EXPERIMENTAL. P A R T I. b fuerint* aliorum conamina, semper^ existimavi mihi vitalis aura ufum frusira datum fore, nisi et ipse, in hoc studio verfatus, fymbolum aliquod, utcunque exiguum, in commune medicina ararium contribuerem. Sydenham. T H E

Preface

. f ■ H E Author of the following '* Essays, presuming on the candour with which they have been received, commits to the fame indulgence, the present enlarged and im proved edition of them. The first and second Dissertations are the productions of his youth, and illustrate both the in-» sufficiency of theory, and the danger of trusting to experience alone in the practice of physic. The annals of medicine abound with instances of the fatal effects of empiricism, and hypothetical reasoning, founded on fictitious principles. But these examples, painful as they are to a feeling mind, impeach not the honour or

PREFACE.

. XIV or usefulness of the healing art ; and are chargeable only on the ignorance of a few of its professors, and on the credulity of mankind. The History of the Chris tian Church presents us with a picture still more shocking to humanity: But who disputes the influence of religion, to promote the peace, order, and happi ness of society, because superstition hath occasioned so much confusion, misery, and devastation ? It is seriously to be lamented that juster ideas are^not formed of the nature, extent, and objects of medicine in general ; and of the several branches, into which, as a practical science too comprehensive for any individual to profess, it is now divided. This would prevent the encouragement of illiterate pretenders ; would conciliate harmony, and excite a generous emulation amongst the different orders' of the faculty ; and by confining the exertions of each, within the sphere adapted to their genius and education, would powerfully promote the improvement of Physic, Surgery, and Pharmacy. No profeflion requires a more enlarged

PREFACE.

. XV enlarged and cultivated understanding, or comprehends a wider circle of knowledge than that of physic. And to the honour of the physicians of this age and country, it may with truth be asserted, that they are peculiarly distinguished as men of liberal education, and extensive learning. The third Essay consists of Experi ments and Observations on bitters and astringents in general, and on the Peruvian bark in particulars^. The utility fa) Of this Essay, which was first publilhed in 1767, large portions have been copied into several Cyclopædias, and Treatises on the Materia Medica, both foreign and domestic. The author has reason to believe that the practical and pharmaceutical doctrines it contains have been generally adopted. Two very ingenious writers, however, have lately controverted the results of some of the experiments which he has related.

He acknowledges with satisfaction the candour of these Gentlemen ; and thinks himself honoured by their approbation of his works. But the points in dispute, he must leave to the decision of others ; having noiu no leisure for such investigations. He is sensible that, in the course of his inquiries, he must have been liable to many sources of fallacy : But the fame observation, he presumes, is not more applicable to him than to others engaged in expeiimenta! researches. And he trusts the reader will perceive-

PREFACE.

. XVI utility of this method of inquiry is universally acknowledged j and nothing can tend more to the advancement of real science, than the steady pursuit of it. The improvements made in the art of medicine for this century past, are more than equal to those of a thousand preceding years. And these im provements may be justly ascribed to that taste for experiment, which hath of late so generally prevailed. But though much hath been done in this way of in vestigation, there are still numberless un trodden paths in physic which remain to be explored. And every person of tole rable abilities, who has patience, assiduity, and a sufficient minuteness of attention, may almost assure himself that perceive, in the following pages, that he has endea voured with cautious solicitude, to guard against the undue influence of preconceptions ; that he has faith fully related facts and appearances as they occurred, whether favourable or unfavourable to his opinions ; that his experiments are numerous, diversified, arrd frequently repeated in the pursuit of different truths ; and that they were made at a period when the Peru vian bark was easily obtained unadulterated, and of a good quality. March 7, 1788. his

PREFACE.

XVII his labours will be rewarded with success, and that he cannot fail of adding some new and useful discoveries to the common stock of medical knowledge. Multum egerunt qui ante nos fuerunt, fed non peregerunt ; multum adhuc rejlat opera, multumq; rejlabit, neque ulli nato post mille fecula prœcidetur occafo aliquid adhuc ad jiciendi(b). The author might have confirmed many of the observations contained in this Essay by a variety of experiments, which he has lately made on the Columbo Root; a medicine, which from its efficacy, deserves to be more generally known in practice. But his papers on that subject are laid before the Royal Society, and will probably be published in the next volume of Philosophical Transactions. The title of the fourth Essay fully explains the purport of it. An attempt to ascertain the use and operation of a remedy so well known as blisters, may at first view appear to be unnecessary.

But a more attentive examination will sb) Seneca. Vol. I. convince c xxiji P R; E FA C E. convince us of our mistake. The trite ness of the subject is the reason that it has been so much overlooked and neglected ; and though vesicatories are employed and recommended by almost every medical practitioner, yet few have attended to their real action, or to the general principles which ought to direct their application. The subject of the fifth Essay, the author confesses, is rather curious than useful ; of more importance to the in quisitive physiologist, than to the prac tical physician. But as all researches into the operations of nature merit our notice and regard, an inquiry into the resemblance between the chyle and milk hath certainly some claim to attention. And if it appear probable, as he presumes it will, that milk is the chyle unaffimilated, or at least very little changed, it may lead to some useful in ferences concerning the proper diet for nurses. The tracts on water, and on earlv inoculation, were published, separately, a few

PREFACE.

. XIX a sew years ago j and as no copies of the former impressions now remain, they are reprinted and annexed to this volume of Essays. The Observations on the efficacy of External Applications in the ulcerous sore throat were written in the summer of 1770, a period when that disease was epidemical in the town and neighbourhood of Manchester. The Measles also prevailed very generally at the fame time ; but though these disorders have been often observed to associate together, and may seem to bear some analogy to each other, from the efflorescence on the skin, and inflammation of the eyes, with which they are both accompanied, no instance then occurred to the author of their union. MANCHESTER, JANUARY I, I77*. ESSAY E S S A T I. THE EMPIRIC O R MAN of EXPERIENCE, BEING ARGUMENTS AGAINST THE USE OF THEORY AND REASONING IN PHYSIC, fa) Sujficit si quid fiat intelligamus, etiamfi quomodo quidque fat ignoremus.

C I C E R O. IN this polished age, when every art is advancing towards perfection, and every science enlarging its boundaries, it is a melancholy consideration that medicine should alone be left behind, in the general career of improvement. The fa) This and the following dissertation contain a dis cussion of the arguments for and against the use of theory and reasoning in medicine. They are not intended as an explanation of the tenets of those two ancient and celebrated sects of physicians, the Empirics and Ration alists, of which Celfus hath given us so elegant an ac- Vol. I. B count; The mists of ignorance and error are now vanish ing before the lights of genuine philosophy ; and knowledge, practical and speculative, extends its influence even to the meanest mechanic. But the Hippocratic art, amidst this rapid and almost uni versal revolution, is at least stationary,' if it move not in a retrograde course.

And what is singular in its fate, the fame causes which have promoted the advancement of the sister sciences, have, by a wrong direction, checked the growth, and retarded the progress of one, which is fairly worth the seven. Pope. The industry of its professors, by an injudicious application, hath served only to darken and perplex it. Instead of patiendy treading in the sure steps of experience, they have followed the false clue of count ; but to point out opinions which now prevail in the world, and which naturally arise from the different lights, in which the fame subject is viewed by different minds. The author hath endeavoured to suppose himself first of the one party, and then of the other ; in order more fully to enter into the sentiments of each, and by that means to do justice to both fides of the question.

In this kind of writing it is not easy to avoid declamation ; and he hopes to be excused, if he has indulged some de gree of that enthusiasm, with which two antagonists may be supposed to be actuated, when pleading against each other, in support of a favourite cause. THEORY ; theory ; and whilst, with infinite pains and labour, they endeavour to penetrate into the recesses of physic, they have lost themselves in the labyrinths of error. Unhappily for the healing art, their mistakes have coincided with die common pro pensities of mankind, who are more inclined to search aster hidden and undiscoverable causes, than to attend to the obvious phænomena of nature. Blinded with their own fictions, these wanton theorists conceal their ignorance from themselves and the world, by unmeaning terms and pompous phrases.

" Omnia enim stolidi magis admirantur amantque " Inversis qua sub verbis latitantia cernunt." Lucretius. But descending from the flights of declamation,^ let us point out the folly, detect the fallacy, and trace the dangerous consequences of theory and reasoning in medicine. Whoever searches into the annals of physic, cannot fail of being astonished at the almost infinite variety of systems and hypotheses, which at different times have been obtruded on the world. The amazing fertility of the imagination is there displayed in its full extent ; and perhaps so ample an exhibition of the powers of human invention might gratify the vanity of man, if the agreeable effect were not more than counterbalanced by the B 2 humbling humbling view of so much absurdity, contradiction, and falsehood. The idlest opinions have had their abettors, the most groundless fictions have been swallowed with credulity.

A list of all the follies which, at different periods, have been established as articles of faith in medicine, would form the severest satire on the healing art. Who can withhold his laughter when he reads of expelling, attracting, and concocting faculties ; of energies, sympathies, an tipathies, idiosyncrasies, and occult causes ; of the body being nothing but salt, sulphur, and mercury ; of man being a microcosm, and uniting in his frame the motion of the stars, the nature of the earth, of water, air, all vegetables and minerals, the constellations, and the four winds. Yet ridiculous as these several tenets may appear, they have given rife to sects, have been espoused with warmth, and defended with acrimony. But the excentric genius of the theorists hath not been confined within the limits of physiology, and the laws of the animal œconomy: the hidden causes of diseases, the elements or first principles of me dicines, and their secret mode of action on the body, have afforded another no less extensive field for the exercise of their creative imaginations.

The bare recital of their fictions, would sufficiently demonstrate their absurdity. But to enumerate them would be an almost endless task. Erasistra tus defines disease to be a translation of blood from the the veins to die arteries ; whereas Galen asserts that, as health consists in the equilibrium between dryness and moisture, heat and cold, sickness must depend upon the subversion of that equilibrium. One sect adopts plethora as the cause of all diseases ; another denies the possibility of its existence in the body. Sylvius exults in the discovery that an acid is the sole morbid principle ; his antagonists ascribe that honour to their alkali. Salt, sulphur, acrimonies, caustics, volatiles, ferments, &c. &c. have each, at different times and by different syste matics, been received as the undoubted principia morborum.

No less absurd are the fictions of the theorists, concerning the elements and qualities of medicines, and their operation on the body. The fame drug is represented as hot in one degree and cold in another, or as dry in one proportion and moist in another. Certain remedies are whimsi cally assigned to particular parts of the body, on which they are supposed to exert their effects by a peculiar predilection. Hence the classes of pec torals, stomachics, hepatics, cephalics, cordials, &c. One medicine attracts and eliminates the bile, another the pituita, and a third the atra bills or melancholy. Some preparations irradiate the ani mal spirits, others darken and obscure them. But enough of these idle conceits, the offspring of theory, and the disgrace of physic ! B 3 Perhaps Perhaps it may be objected, that though many vain and groundless hypotheses have been ad vanced, there are two which will bear the test of ridicule, and which have had the suffrages of the wisest and most learned men in their favour.

Let us briefly examine their pretensions to credibility. i. George Ernest Stahl, a German physician, of a subtil and metaphysical genius, supposes two opposite principles or propensities in the hu man frame ; one constandy and uniformly tending to corruption and decay, the other to life and health. The former is founded on the elementary composition of the body, the latter depends on the power and energy of the mind. By means of the nerves, the influence of the mind is extended to every part of the system, and if their action be impeded, disease is the unavoidable consequence. A superabundance and spissitude of the blood is therefore the proximate cause of sickness, as the energy of the mind is diereby diminished, and its action on the body obstructed. Hence to lessen the quantity, and break down the lentor of the blood, the soul exerts all its powers and excites hemorrhages, sweats, diarrhœas, fevers, and the like.

Dr. Porterfield and Dr. Nichols have carried this theory still further. The latter, in his prælection de anima medica, affirms without reserve, that the soul at first forms the body, and afterwards governs governs it ; that she regulates and conducts all its vital and natural motions; circulates the fluids and distributes them to the different parts of the system, with such velocity and in such proportion as she judges right; and that whenever the body is disordered, she excites those conflicts and commotions, which are best adapted to restore it to health and soundness. Such are the principles of the Stahlians. — Let the unprejudiced judge whether they need a serious refutation. Could a mariner plan and construct a ship, launch it into the wide ocean, govern it in storms, direct it from shoals and rocks, and steer it safe into the destined harbour, without being conscious of the skill he exerts, and the labour he employs ?

The analogy is obvious ; and it would be equally absurd to suppose that the mind could form the body, regulate all its motions, superin tend its health, rescue it from disease, and be per petually occupied in planning and executing the wisest designs, without the least knowledge or con sciousness of the power and energy she every moment exerts. But the first proposition of the Stahlians con futes itself. For if the body and mind, with equal force, be constantly and uniformly tending differ ent ways, no change can possibly ensue ; agree- B 4 ably ably to the well known axiom in physics, that action and reaction are equal, and destroy each other's effect. Not to insist however on this error in philosophy, thedoctrine of the Stahlians in confininoall diseases to lentor and plethora is false and absurd.

The dropsy, scurvy, cacochymia, jaundice, putrid fevers, and many of the nervous class of ailments, are accompanied for the most part with a thin and colliquated state of the fluids. Nor is there more truth in the assertion, that every distemper is an effort of the mind to relieve the body. The slightest laceration of a tendon has been succeeded by the locked jaw, convulsions, and death. An indolent glandular tumour terminates not unfrequently in a cancer, A neglect to evacuate the bladder in due time hath occasioned a suppression of urine; and the palsy has been the consequence of a profuse he morrhage. Are these then the wise conflicts of the soul, to rescue her suffering partner from im pending evil ! And must we view in the same light the angina maligna, the tuffs convulfiva, the spas modic colic, the tetanus, catalepsis, worms, rickets, &c. &c. No one but a theorist, blinded with the mists of his own brain, would answer in the affir mative. 2.

The important discovery os the circulation of the blood, in the beginning of the last century, by by the ever memorable Dr. Harvey, gave rise to the introduction of mechanics into medicine. And as that system of philosophy was founded on the general laws of nature, it was obvious to infer its application to the human body; which was supposed to differ only from the universe of things, in the wonderful variety and complication of its machineiy. Bellini, Borelli, Pitcairn, Keil and Boerhaave are the great supporters of this theory. According to the description of the latter, the body is chiefly composed of a conic, elastic, inflected canal, divided into similar lesser ones proceeding from the fame trunk, which being at last collected into a retiform contexture, mutually open into each other, and send off two orders of vessels, lymphatics and veins, the one terminating in different cavities of the body, the other in the heart.

These tubes are destined for the conveyance of the animal fluids; in the circulation of which lise consists, and on whose free and undisturbed motion health depends. Obftruftion therefore is the proximate cause of most diseases. And as it is produced either by a constriction of the vessels, or by a lentor in the blood, these are considered as the remote causes. However plausible this theory may appear to be at first sight, it will be found, on a stricter ,examination, to be fallacious and defective. The mathematician mathematician, who calculates the projectile force of the heart, the velocity of the blood in the arteries, and the various secretions of the glands, from the known laws of fluids in motion, and the nature of tubes of different shapes and sizes, must unavoidably be exposed to a thousand mistakes.

The vessels of the body are too numerous and minute to admit of an accurate mensuration; and they are perhaps every moment undergoing changes, from the diversified action of that vital power which animates our wonderful system. Hence arises the contrariety in the computations of philosophers on this subject. Borelli reckons the resistance which the heart overcomes, in propelling the blood through the arteries and veins, to be equal to 180,000 pounds weight: Dr. Hales makes it amount to no more than 51 pounds; and Keil, though he computes the fluids of the human body to be five times more in quantity than Borelli supposes, hath reduced the sum to a single pound. One asserts that the pressure of air, overcome in ordinary respiration, is equiva lent to the weight of 14000 pounds ; a second proves it to be equal only to a 100 pounds; and a third makes it so inconsiderable, as to be almost below comparison ; whilst all the three appeal to mathematical demonstration.

A similar diversity appears in the conclusions of the mathematicians, concerning the quantity of bile separated by the liver. liver. To determine this point, Borelli first mea sures the diameter of the duftus communis chckdo chus, which he finds to be the 225th part of the diameter of the vena cava, ]x_\ before it enters the right auricle of the heart. Hence he infers that if 7680 pounds of blood (supposing the whole mass to be twenty pounds, and to circulate sixteen times every hour) passes through the vena cava in twenty-four hours, the 225th part of this quantity, i. e. thirty-four pounds of bile must, in the fame space of time, be transmitted through the hepatic ducts : a conclusion altogether repugnant to fact and experience. And it will appear to be -much more so, if we admit, with the latter ma thematicians, that the vessels of the human body contain at a medium thirty pounds of blood ; for then the quantity of bile, according to Borelli's method of reasoning, must amount to eighty-five pounds in one day.

But in this, as in the former instance, Keil widely differs from Borelli, and with greater probability concludes that two drachms of bile and no more, are hourly separated from the liver. In these calculations no attention is paid to the peculiar nature of the animal fluids. Water and wine, a poisonous and wholesome liquid, are governed by the same hydraulic laws, but their effects when circulating in the body would certainly be very different. We know, from experience, that the velocity of the pulse is influenced influenced by the state of the blood. Even the accession of new chyle, after each meal, quickens the action of the heart and arteries. The human body therefore is not to be considered as a mere machine; and that theory which is built on this foundation is evidently fallacious, sb) But the mechanic hypothesis is also inadequate and defective ; for the animal frame is incident to numberless diseases which have no dependence on obstruction.

The morbi fibra debilis et laxa are not, even by Boerhaave himself, ascribed to this cause. The dropsy, scurvy, putrid fevers, small pox, measles, and lues venerea are inexplicable on mechanical principles. The hydrophobia seems to be entirely a nervous affection, and cannot with the least propriety be supposed to arise from ob struction. No inflammation is observable on dissection in the fauces or gullet; nor is there any palsy in the muscles subservient to deglutition. A numerous class of diseases depend upon that sym pathetic connexion, which subsists between different fb) In the Philosophical Transactions there is a table, in which the several purgatives and emetics, commonly in use, are enumerated and adjusted by mathematical rules to all ages, sexes, and constitutions. The doses of the me dicines are as the squares of the constitutions.

And in the Edinburgh Medical Essays there is a formal attempt to correct the errors of this table. ' parts parts of the body. When the stomach is out of order, languor, debility, watchfulness, the night mare, and sometimes a cephalaa, vertigo, or hemi crania are the consequences. A rough bone stimulating the nerves of the great toe, hath pro duced epileptic fits. And it is well known that children, from the irritation of the gums in denti tion, are liable to vomiting, purging, fever, and convulsions. These few instances are sufficient to shew that the body is unhappily subject to many disorders, besides those which proceed from ob struction. And perhaps the conclusion may be carried still further, when we consider that in the operation for the aneurism a large artery is tied up, and the circulation of the blood for some time almost totally suppressed in the part, without any material injury to health.

Morgagni relates that Valfalva affixed two ligatures to the carotids of a dog, who lived above twenty days after the ope ration, and might have continued longer, if he had not been killed for the purpose of dissection. Is it then to be supposed that the obstruction of a few capillaries, which are united together by an infinite number of anastomosing branches, can be pro ductive of such fatal consequences, whilst the course of the blood is stopped in large vessels with impunity ? Equally false and absurd is the mecha nical hypothesis, concerning the operation of me dicines, which is supposed to depend upon the size, figure, figure, and gravity of their constituent particles, Thus chalybeates, for example, are recommended in obstructions of the catamenia, on account of the momentum which they communicate to the blood.

And on the fame principles, mercury is said to break down the texture, and produce a colliquation of the animal fluids. But both these explanations, however elegant in theory, are false in fact. From the experiments of the late Dr. Wright' sc) it is evident that steel never enters the lacteals, and that it exerts its effects solely on the stomach and bowels. And it is surely beyond the bounds of credibility to suppose, that a few grains of corrosive sublimate, which are light enough to be suspended and dissolved in brandy, are capable, by their extraordinary weight, of dissolving the crassamentum of the blood. But it is die genius of theory to dignify trifles, and to ascribe the most wonderful effects to the most insignificant causes. Happy however had it been for the world, if the medical systems, which have been obtruded on it, were only chargeable with inutility, absurdity, or falsehood.

But alas ! they have milled the un derstanding, perverted the judgment, and given rise to the most dangerous and fatal errors in practice. A short view of the history of physic sc) Phil. Trans, vol. L. part IJ. p. 595. will will convince us of this melancholy truth. The divine Hippocrates knew how to distinguish be tween theory and experience ; and he suffered not his doctrines of fire and water, his elements With their powers, nature with its inclinations, aversions, attractions, repulsions, and ratiocinations, to influ ence his treatment of diseases. But the conduct of his successors was widely different. Erasistratus reasoning on false and precarious principles, and neglecting experience, the sole test of utility, proscribes the use of venæsection and purgatives, and condemns them as remedies equally infamous and dangerous.

Asclepiades, from whom the modern sect of mechanics have borrowed many of their doctrines, supposing that health depends on the just propor tion between the pores of the body and certain corpuscles, which they are destined to receive and transmit, and that it is impaired whenever these cor puscles are obstructed in their passage, orders exer cise on horseback in the most ardent fevers. He advances it as a maxim, that one fever is to be cured by raising another ; and that the strength of the patient is to be exhausted by watching, and the endurance of thirst. And his practice was strictly and severely conformable to his principles ; for he would not allow the sick to cool their mouths with a drop of water, during the two first days of the the disorder. But he indulged his phrenitic patients in the use of wine, even to intoxication.