UNITED STATES OF AMERICA. * . . FOUNDED 1836 WASHINGTON, D. C. GPO 16—67244-1 VST DAT17 '.'<>■/" '//^/jy^///^ AN ESSAY PHILOSOPHY OP MEDICAL SCIENCE. " I TRUST THAT I HAVE GOT HOLD OF MY PITCHER BY THE RIGHT John Joachim Beccher. Whewell's History of the Inductive Sciences HANDLE." \ , vol. iii. p. 121. I BY ELISHA BARTLETT, M. D. PROFESSOR OF THE THEORY AND PRACTICE OF MEDICINE, IN THE UNIVERSITY OF MARYLAND. ' '? , ■' : ■■- \ ':■/*■ PHILADELPHIA LEA & BLANCHARD. 1844. w n Entered according to Act of Congress, in the year 1844, By Elisha Bartlett, in the Clerk's Office of the District Court of the District of Massachusetts. boston: printed by freeman and bolles, washington street. TO P. CH. A. LOUIS, PHYSICIAN TO THE HOTEL DIEU ; PRESIDENT OF THE SOCIETY OF MEDICAL OBSERVATION OF PARIS; AUTHOR OF RESEARCHES ON PHTHISIS, TYPHOID FEVER, PULMONARY EMPHYSEMA, ETC. ETC. Allow me, my dear sir, in this public manner, to return you my warmest thanks for the readiness and the kindness, with which you assented to my request, that I might be allowed the pleasure and the privilege of dedicating this essay to your- self: — and that it will be found not altogether unworthy of such distinction, I may venture to hope, for this reason, if for no other, that it endeavors to illustrate, to develop, and to vin- dicate those principles of medical philosophy, which lie at the foundation of your own various and invaluable researches,— researches, the institution and publication of which have con- stituted a new and great era in the history of medical science. With feelings of the highest regard, I am, very sincerely, your friend, E. Bartlett. September 1, 1844. PREFACE. I comply with the custom of writing a formal preface, only for the purpose of making one or two remarks, which may be more properly made here, than anywhere else, — referring particularly to the title and the subject of my book. ^ This title is not new ; but it is the only one at all suita- ble for the work to which it is applied, and I had no alternative but to adopt it.\ I wish to say fur- ther, that my essay has no resemblance, whatever, either in design or execution to the Essay on Medical Philosophy, published a few years ago, by M. Bouillaud ; and that it differs, not less widely, from all the formal treatises, that I have been able to obtain, upon the subjects with which it is concerned. The Elements of Medical Logic, by Sir Gilbert Blane, need no commendation from me ; they are admirable as far as they go, but they embrace only a small segment of the entire circle VI PREFACE. of medical philosophy. Dr. William Hillary pub- lished, in 1761, "An Inquiry into the means of improving Medical Knowledge, by examining all those methods, ivhich have hindered or increased its improvement, in all past ages; " a book which is strongly marked by many of the faults, which it is one of the principal objects of this essay to exhibit; mixed up, however, with much that is excellent and true. I regret, especially, not having been able to procure the two works with the following titles ; — " Traite de philosophic medi- cale, ou Exposition des verites generates et fonda- mentales de la medecine ; " by T. Auber; Paris, 1839; and "Novum Organum Medicorum ; — a new Medical Logic, or the art of thinking and right reasoning applied to practical medicine," etc. By Vicenzo Lanza, M. D. of Naples. The title is all that I have seen of the first; there is a short notice of an English translation of the second, by C. Stormont, M. D., in Vol. X. of the London Lancet, from which I am led to believe that its fundamental doctrines are sound and philosophi- cal. CONTENTS. PART I. PHILOSOPHY OF PHYSICAL SCIENCE. Primary Propositions, . . . 34 CHAPTER I. Object of Essay. All science consists exclusively in pheno- mena and their relationships, classified and arranged. Il- lustrations from gravitation. . . . 5__9 CHAPTER II. All physical science the result of observation. Inadequate ideas of this doctrine. Illustrations ; marble ; sources and means of our knowledge of this substance. One species, or kind, of knowledge, not deducible from another, inde- pendent of observation. Optics. All the properties of light ascertained exclusively by observation. Functions of mathematical calculations. Functions of a priori reason- ing. Newton. Fresnel. . . . 10 — 25 CHAPTER III. All true relationships invariable. Error of the common say- ing, that the exception proves the rule. Nature and con- stitution of laws, or principles, of science. They consist, exclusively, in constant phenomena and relationships, clas- vm CONTENTS. sified and arranged. Never in anything lying back of these phenomena and relationships. Gravitation. Chemical Science. The law of definite proportions. What it is. Other illustrations. Electricity. Light. . 26 — 32 CHAPTER IV. Most of our knowledge incomplete. Natural wish to render it perfect and absolute. Attempts and efforts to accom- plish this end give birth to hypotheses. Nature and con- stitution of hypotheses. Their true relation to science. All science independent of hypotheses. Constitution of matter. The atomic theory of chemical combinations. Optics. Corpuscular and undulatory hypotheses. New- ton's elastic ether. Uses and functions of theories. Their value overrated. Opinions of Newton and Davy. 32 — 52 CHAPTER V. Arrangement and classification of phenomena and relation- ships. Principles and grounds of this arrangement. Illus- trations. Marble. . . . 52—55. PART II. PHILOSOPHY OF MEDICAL SCIENCE. Primary Propositions, . . . 59? 60 CHAPTER I. Definitions. Anatomy; Topographical; General; Micros- copic ; Chemical; Comparative. Physiology. Pathology. Etiology. Therapeutics. . . . 61__67 CONTENTS. IX CHAPTER II. General prevalence of false notions. Medical science con- sists, exclusively, in the phenomena and relationships of life, classified and arranged. Anatomy. Physiology. Il- lustrations. Germination of seeds. Conditions of ger- mination. Phenomena of germination. Respiration; its phenomena. . . . . 67 — 74 CHAPTER III. Extent of erroneous notions. . . . 75 — 76 CHAPTER IV. Our knowledge of anatomy not dependent upon our know- ledge of other branches of medical science. Our know- ledge of one branch of anatomy does not include the know- ledge of any other branch. . . 77 — 78 CHAPTER V. Our knowledge of physiology not deducible from our know- ledge of anatomy. Qualifications. Final causes. Illus- trations. Brain. Stomach. . . 79 — 85 CHAPTER VI. Our knowledge of pathology not deducible from our know- ledge of physiology. Qualifications. Illustrations. In- flammation. Differences in the susceptibilities of different organs to this process. These differences not to be ac- counted for on physiological grounds. Gastritis. Other diseases. . . . . .85 —100 CHAPTER VII. Relations of pathology to its causes. Etiology. Our know- ledge of the causes of disease, the exclusive result of ob- B x CONTENTS. servation. Etiology not to be deduced from pathology. Illustrations. Age. Sex. Season. . 100—102 CHAPTER VIII. Relations of pathology to its modifiers. Therapeutics. Ra- tionalists. Empirics. Therapeutics not deducible from pathology. Inflammation. Periodical diseases. Cinchona and arsenic; Relations between them. Action of remedies on disease, not deducible from their action in health. Opium. Cinchona. Calomel. Action of remedies on the human body, not deducible from their action on those of other animals. .... 103 —120 CHAPTER IX. Diagnosis; its importance, and its relations to therapeutics. Illustrations. Pleurisy ; Typhoid Fever. 121 — 127 CHAPTER X. Diagnosis, twofold: — Nosological and Therapeutical. Ele- ments and means of nosological diagnosis. Diseases not to be required to be wholly unlike each other. Typhoidal fever, and congestion, common elements. Locality of dis- ease. Nature, or character, of disease. Combination and succession of certain phenomena. Symptoms. Relative value of these several elements. Tendencies of modern researches. Therapeutical diagnosis. . 127 —146 CHAPTER XI. The character and conditions of principles in medical science. These principles approximative, and not absolute. This approximative character fixed and determinate. Its degree of fluctuation confined within certain limits. Illustrations. Proportion of sexes at birth. Law of great numbers. Cal- culation of probabilities. Laws, or principles, of thera- peutics ; their complexity ; difficulty of ascertaining them. CONTENTS. XI Gavarret. Conditions of these laws. Facts must be com- parable. True value of therapeutical experience. Mis- taken notions. .... 147—179 CHAPTER XII. The nature and value of what are called Medical Doctrines. Universal prevalence of medical hypotheses. Their bad influences. Methodism. Cullen's Theory of fever. Ho- moeopathy : Statement of its principles. Standard by which they are to be tried. Evil effects of Medical Doctrines upon the minds of medical men, and upon the interests of medical science. Broussais : His History of Chronic Inflammations, and his Examination of Medical Doc- trines. Sydenham. How far interpretations may be al- lowed. ..... 180 — 224 CHAPTER XIII. American Medical Doctrines. Dr. Rush. Dr. Miller. Dr. John Esten Cooke. Dr. Gallup. Drs. Miner and Tully. Samuel Thompson. . . . 224 — 250 CHAPTER XIV. The principles and, conditions of nosological arrangements. These arrangements necessary. Classifications in botany. The artificial and natural methods. Are diseases legitimate objects of classification? Defects of nosological systems. Examples of natural groups, or families. Exanthemata. Fevers. Phlegmasiae. Cancer and tubercle. Neuroses. Definitions. .... 250—273 CHAPTER XV. Relations of Vital and Chemical Forces. . 273 — 282 CHAPTER XVI. Future prospects of medical science. Conclusion. Causes Xll CONTENTS. of the slow progress and imperfect state of medical sci- ence. Diagnosis must precede therapeutics. Reasons of this. Complexity of therapeutical relationships. Probable extent of our power over disease. French medical obser- vation. British medical observation. American medical observation. .... 282 — 310 PART FIRST. THE PHILOSOPHY OF PHYSICAL SCIENCE. 1 " Non excogitandum est quid natura faciat, sed inveniendum." Bacon. " The construction of the world, the magnitude and nature of the bodies contained in it, are not to be investigated by reasoning, which was done by the ancients, but to be apprehended by the senses, and collected from the things themselves.....They who before us have inquired concerning the construction of this world, and of the things which it contains, seem indeed to have prosecuted their examination with protracted vigils and great labor, but never to have looked at it. . . . For, as it were, attempting to rival God in wisdom, and venturing to seek for the principles and causes of the world by the light of their own reason, and thinking- they had found what they had only invented, they made an arbitrary world of their own. . . . We, then, not relying on ourselves, and of a duller intellect than they, propose to ourselves to turn our regards to the world itself and its parts." Bernar- dinus Telesius. Quoted by Whewell. Philosophy of the Inductive Sciences. Vol. II. p. 354. " Itaque hominum intellectui non plums addendae, sed plumbum potius et pondera ; ut cohibeant omnem saltum et volatum. Atque hoc adhuc factum non est; cum vero factum fuerit, melius de scientiis sperare licebit." Bacon, Nov. Org. Lib. 1, Aph. CIV. " Les hommes ne s' attachent aux faits qu' apres avoir epuise les hypothe- ses." Broussais. " Whatever is not deduced from the phenomena is to be termed hypothesis; and hypotheses, whether metaphysical or physical, or occult causes, or me- chanical, have no place in experimental philosophy." Sir Isaac Newton. " And if what I have said is but intelligible and true, and carries so much conviction with it, of its being so, that it may induce some others to pursue those methods of improving medicinal knowledge, which are herein recom- mended ; or if it contains anything that is either useful or new, which may contribute something to its improvement, or may be the means of exciting some other physicians to make any farther discoveries or imprcvements in the medical science, which may be useful to mankind, I shall not think my time and labor lost." William Hillary. PART FIRST. PHYSICAL SCIENCE. PRIMARY PROPOSITIONS. Proposition First. All physical science consists in ascer- tained facts, or phenomena, or events; with their relations to other facts, or phenomena, or events; the whole classified, and arranged. Proposition Second. These facts, phenomena, and events, with their relations, can be ascertained only in one way; and that is by observation, or experience. They cannot be de- duced or inferred, from any other facts, phenomena, events, or relationships, by any process of reasoning, independent of observation, or experience. Proposition Third. A law, or principle, of physical science consists in a rigorous, and absolute generalization of these facts, phenomena, events, and relationships; and in no- thing else. It is identical with the universality of a phenom- enon, or the invariableness of a relationship. Proposition Fourth. A hypothesis is an attempted expla- nation, or interpretation, of these ascertained phenomena, and relationships; and it is nothing else. It consists in an as- sumption, or a supposition, of certain other unascertained, and unknown phenomena, or relationships. It does not con- stitute an essential element of science. All science is abso- lutely independent of hypothesis. 4 PRIMARY PROPOSITIONS. Proposition Fifth. Theory is one of two things, accord- ing to the manner in which the word has been used. It is either a generalization of phenomena, and relationships, and in this case, identical with a law, or principle, of science ; or, it is an attempted explanation of phenomena, and relationships, through the intervention of other assumed, and unascertained, phenomena, and relationships, and, in this case, identical with hypothesis. Proposition Sixth. All classification, or arrangement, depends upon, and consists in, the identity, or similarity, amongst themselves, of certain groups of phenomena, or rela- tionships; and their dissimilarity to other groups of phe- nomena, or relationships. All classifications or arrangements are natural and perfect just in proportion to the number, the importance, and the degree of these similarities, and dissimilarities. PART FIRST. THE PHILOSOPHY OF PHYSICAL SCIENCE. CHAPTER I. PROPOSITION FIRST. ALL PHYSICAL SCIENCE CONSISTS IN ASCERTAINED FACTS, OR PHENOMENA, OR EVENTS J WITH THEIR RELATIONS TO OTHER FACTS, OR PHENOMENA, OR EVENTS ; THE WHOLE CLASSIFIED AND ARRANGED. Object of this essay. All science consists exclusively in phenomena, and their relationships, classified and arranged. Illustrations from gravi- tation. The sole object of this essay is an exposition of what I conceive to be the true principles of medi- cal philosophy ; and it will be mostly made up of this direct exposition. But, in order that I may be enabled to accomplish this object, successfully and satisfactorily, I have thought it necessary to state, in the first place, what I conceive to be the true, fundamental doctrines of the philosophy of all physical science. This I have done in the forego- ing first, second, third, fourth, and sixth primary propositions. These doctrines, with certain modi- 6 THE PHILOSOPHY OF PHYSICAL SCIENCE. fications, in one or two particulars, are identical with the true doctrines of the philosophy of medi- cal science. There is no essential difference be- tween the philosophy of physical, and that of phy- siological science. It happens, however, for rea- sons which it is not necessary here to give, that the former philosophy is susceptible of being ren- dered plainer, and more clearly intelligible, to most minds, than the latter. This circumstance induces me to make use of the illustrations, which may be derived from a brief exposition of the true principles of the philosophy of physical science, as an introduction to the more important and prin- cipal work before me, the statement and exposi- tion of the true principles of the philosophy of medical science. I do not think, that I can well and entirely accomplish the latter, without the aid of the former. At any rate, there are no other collateral sources, from which so important and so various assistance can be derived, as from these, which I have thus indicated; and for these rea- sons, I shall devote this, the first part of my essay, to this subjpct. The first proposition, that which stands at the head of this chapter,, does not require much illus- tration. Its truth is so manifest, as hardly to ad- mit of any doubt. It would seem almost impossi- ble, that there should be any difference of opinion in regard to its soundness, or any obscurity in its conception. I believe, nevertheless, it is true, that there has always been, and that there still is, in INTRODUCTORY REMARKS. 7 the minds of most men, and in those of philosophi- cal thinkers, a somewhat imperfect, or confused, apprehension of its doctrines. I do not think that its truth is seen and felt, as it should be, in the simplicity, the purity, and the absoluteness, which belong to it. The confusion, to which I allude, is this. There seems to be a common feeling, that the facts, phenomena, and events, with their rela- tionships, classified and arranged, constitute, not the entire science, to which they belong, but only the foundation of the science. There is a feeling, that these facts and relations arc to be used as ele- ments, out of which, the science is to be built up, or constructed, by what is called inductive reason- ing. The feeling implies, and the avowed doc- trine growing out of it often asserts, that the sci- ence is in this subsequent process of reasoning, and not in the facts, themselves, and their relationships. We are constantly told, that the facts are to be used as materials, to be sure ; that it is not safe to take for our materials anything but facts; that they constitute the basis of every science; but, after all this, the essential condition and constitu- ent of the science is often placed, more in the process of reasoning, as it is called, than in the facts and their relationships. Now, what I wish to insist upon is this ; that the science is in the facts and their relationships, classified and arranged, and in nothing else. The ascertained facts and their relationships, classified and arranged, consti- tute, in themselves, and alone, the science, and 8 THE PHILOSOPHY OF PHYSICAL SCIENCE. the whole science, to which they belong. The science, thus constituted, is, so far, complete. No process of inductive reasoning, or of any other reasoning, no act of the mind, can add anything to what has already been done. The only rea- soning, that has anything to do with the matter, consists, simply, in the act of arranging and classi- fying the phenomena, and their relationships, ac- cording to their differences, their resemblances, or their identity. Words are things ; and I cannot doubt, that much obscurity and confusion would be removed from our conceptions of the nature of the philosophy of science, if this long-abused term, inductive reasoning, could be suffered to disap- pear from the language of science and philosophy ; and if, for the indefinite and shadowy ideas, which it so often expresses, or attempts to express, could be substituted those, which are so clearly and ob- viously contained in this phraseology, — the classi- fication and arrangement of phenomena and their relationships. In seeking for illustrations of the true nature of the philosophy of physical science, we turn, almost instinctively, first, to the phenomena of gravitation. These phenomena are the results of one of the simplest of all known relationships,__ that of different portions of matter to each other, through space. This relationship is not mixed up with any others; it is not liable to be disturbed, or affected, by any others ; it is entirely independ- ant of all others. It has been very thoroughly ILLUSTRATIONS FROM GRAVITATION. 9 and fully investigated ; and we have every reason to believe, that our knowledge of it is as absolute and complete, as human knowledge is capable of becoming. Now, the whole science of gravita- tion consists in its phenomena, classified and ar- ranged, and in nothing else. These phenomena, thus classified, constitute, not the foundation, and the materials, merely, on which, and out of which, by some recondite process of the intellectual powers, called inductive reasoning, the science is to be constructed ; they are, the science, in them- selves, icholly, and absolutely. When all the phe- nomena, depending upon this single relationship of matter, have been ascertained, and classified, the science of gravitation is complete ; it is finish- ed ; there is nothing more to be done. Nothing can be added to it by any subsequent process of reasoning, or act of the mind. And the same thing is true of all the departments of physical science ; but inasmuch as this subject will neces- sarily receive further incidental illustration, in other parts of my essay, it is not important that I should dwell upon it any longer, for the present. CHAPTER II. PROPOSITION SECOND. THE FACTS, PHENOMENA, AND EVENTS, WITH THEIR RELA- TIONSHIPS, CLASSIFIED AND ARRANGED, CONSTITUTING PHYSI- CAL SCIENCE, CAN BE ASCERTAINED IN ONLY ONE WAY; AND THAT IS BY OBSERVATION, OR EXPERIENCE. THEY CANNOT BE DEDUCED, OR INFERRED, FROM ANY OTHER FACTS, PHE- NOMENA, EVENTS, OR RELATIONSHIPS, BY ANY PROCESS OF REASONING, INDEPENDENT OF OBSERVATION OR EXPERIENCE. All physical science the result of observation. Inadequate ideas of this doctrine. Illustrations; marble ; sources and means of our knowledge of this substance. One species or kind of knowledge not deducible from another, independent of observation. Optics. All the properties of light ascertained exclusively by observation. Functions of mathematical calcu- lations. Functions of a -priori reasonings. Newton. Fresnel. Not only does all physical science consist, exclu- sively, in facts, phenomena, and events, with their relationships, classified and arranged ; but these phenomena and relationships can be ascertained and classified in only one way, by only one meth- od — that of observation. No single phenomenon, or property, or relationship of the objects of physi- cal science can be deduced, or inferred from any other phenomenon, or property, or relationship, unless the former is already contained in the latter. This independence of each separate class of phe- PHYSICAL SCIENCE THE RESULT OF OBSERVATION. J] nomena, and relationships, is entire and absolute. It is essential, to a clear comprehension of the philosophy of medical science, that this doctrine, thus stated, in its connexion with physical science, should be fully unfolded and distinctly seen ; and to do this, is the object of the present chapter. Ever since the time of Francis Bacon, the language of philosophy has been almost uniform upon this subject. The world has been constantly told, that all science, except that of a purely spe- culative, or metaphysical character, depends upon observation. This language has been eloquent and emphatic in its praises of the Baconian method of investigation ; and it has been filled with warnings against the danger of what it calls speculative reasoning, and premature conclusions. But, notwithstanding all this, it is true, I think, even in physical science, — it is true, I know, in physiological science, — that the common concep- tion of the doctrine of which I am speaking is inadequate and incomplete. The entire inde- pendence of each other, — so far as our knowledge of them is concerned, — of the several classes of phenomena and relationships, which go to make up physical science, is only partially and imper- fectly comprehended. The dependence of our knowledge of each and every class of phenomena and relationships, upon direct observation of the particular class itself, is more exclusive and abso- lute, than seems to be generally supposed. It is true of this doctrine, as it is of that contained in 12 THE PHILOSOPHY OF PHYSICAL SCIENCE. my first proposition, that ideas, and reasoning, and deduction are supposed to have much more to do with it, than is really the case. There is a common feeling, that such a connexion has been established between these different classes of phe- nomena and relationships, at least in many in- stances, as to enable us, one class having been already ascertained by direct observation, to infer, or deduce the existence of the others, by some act of the mind, independent of further and di- rect observation. This misconception, if such is its character, I wish now to expose and remove. For the purpose of illustration, let us take, in the first place, any one of the common forms of inorganic matter, as they exist about us. What is true of one of these forms, so far as my present object is concerned, is true of all the others ; and amongst these substances, there is no one better adapted, on the whole, to the end which I have in view, than that which is known by the name of marble. Our first and most readily acquired know- ledge of this substance has reference to the phe- nomena which it presents in its direct relation to our senses. These phenomena, in this relation, constitute what are called its manifest, sensible properties. They consist of its color, varying in its different varieties; its weight, or specific gra- vity ; its hardness; its brittleness; its mode of frac- ture ; its granular, or crystalline structure; its elasticity, and its susceptibility to polish. Our PHYSICAL SCIENCE THE RESULT OF OBSERVATION. 13 knowledge of each and all of these obvious, physi- cal properties is the result of direct observation of the particular, individual property itself; and the existence of no one amongst them could have been inferred, or deduced, by any conceivable process of reasoning, independent of observation or ex- perience, from the presence of any one, or more, of the others. Another element, in our knowledge of marble has reference to its intimate composition ; we are able to ascertain the number, the character, and the relative proportions of the simple, elementary substances, which are united to constitute it what it is. We find that it is composed of two substan- ces, carbonic acid, and lime, and that these sub- stances are united in definite and fixed proportions, ascertained by weight. We then find, on further examination, that the carbonic acid is, itself, com- posed of two substances, carbon, and oxygen, united in definite and fixed proportions; and, also, that the lime, like the acid, is composed of two substances, calcium and oxygen, united, also, in definite and fixed proportions. The oxygen, the carbon, and the calcium, are, in the present state of science and art, not susceptible of further division, or analysis. The union, in certain pro- portions, of these three elementary substances, constitutes the chemical composition of marble. Our knowledge of this composition is obtained through the agency of chemistry; and it is ex- clusively the result of what may be called chemical THE PHILOSOPHY OF PHYSICAL SCIENCE. observation. It could never have been acquired through any other means, or from any other sources. Certainly, there is nothing in the sensi- ble qualities of marble, which could have indicated, in the remotest degree, the character of its inti- mate composition ; and no acquaintance, however perfect, with the separate properties of the several elementary substances, themselves, of which it is composed, could have enabled us, by any process of reasoning, to infer or deduce the result of their combination, in the production of the marble itself. Our knowledge of marble is completed, when we have ascertained, in addition to the foregoing properties, its various relations. The most obvious of these relations is that of geographical locality, — the distribution of marble throughout the various regions of the earth. Another, somewhat analo- gous to this, refers to its position amongst the several layers, or strata of substances, which are more or less regularly aranged, one above another, to form the solid crust of the globe. This position, with the circumstances attending it, constitutes its geological relations. Still another important ele- ment in our knowledge of marble consists in its chemical relations. By the chemical relations of marble, I do not mean all the relations of its ulti- mate, elementary constituents; although it may, properly enough, be said, that our knowledge of marble is absolute and complete, other things being equal, in proportion to the extent and accu- PHYSICAL SCIENCE THE RESULT OF OBSERVATION. 15 racy of our knowledge of these relations. That is, the more extensive and complete our know- ledge of all the properties and relations of carbon, oxygen and calcium is; in a certain sense, at least, the more extensive and complete is our knowledge of marble itself. But, strictly speaking, the chemical relations of marble can hardly be said to be coextensive with the relations of its elementary constituents. Still, they are numerous and interesting. For instance, there are several substances, amongst the solid materials constituting the crust of the earth, which differ, more or less widely, in their manifest, sensible properties, and in some of their relations, from marble; which have, notwithstanding these differences, precisely the same chemical composition. One of these substances is lime-stone ; another is chalk ; and a third is marl. All these substances are, like mar- ble, carbonates of lime. Again, there are other substances, identical with the foregoing ones in their chemical composition, but differing widely from them in nearly all their other properties and relations. Amongst these it is sufficient for my present purpose to mention Iceland spar. This is a carbonate of lime, like marble, and like chalk; but it differs from these substances in its hardness; in its foliated fracture; in its structure, and, espe- cially in its singular relations to light and electri- city. In the language of optics, it is doubly refractive, which the others are not. Another relationship of marble, is that of its 16 THE PHILOSOPHY OF PHYSICAL SCIENCE. particles to each other, and to those of all other matter, through space. A piece of marble, when elevated to any distance, great or small, from the surface of the earth, and then left to itself, im- mediately falls to the surface ; and the velocity of its motion increases in a uniform ratio, which ratio has been accurately ascertained. Further- more, all other material substances are the subjects of the same phenomena: under the same circum- stances, they all fall, with the same uniform and increasing ratios of velocity, to the earth. In addition to this, these substances not only tend towards the earth, and that with a certain force, which can be measured, but they all tend towards each other, and this also, with a certain force, which can be measured. This universal fact, or phenomenon, is expressed by the term gravity, or gravitation, or the attraction of gravitation. The same piece of marble, when not falling, and when left to itself, will remain in the same position ; and this is also true of all other material substances. This property of matter is expressed by the term inertia. This quiescence, or rest, in the same position, can only be destroyed by the force, or pressure, of some other body, acting upon that at rest. The directions, the velocities, and so on, of these imparted changes of place, with their relations to the tendencies, which these same moving bodies have to approach each other, and all other material bodies, constitute the ele- ments of the science of motion. PHYSICAL SCIENCE THE RESULT OF OBSERVATION. 17 Such, then, are at least the principal relation- ships of marble. They are, as is the case with all other substances, numerous and interesting. But, here, again, as in the instance of its sensible qualities, and its chemical composition, there is no such connexion between them, as to enable us, independent of observation, to ascertain the existence of any one of them, from the presence of any other. Each distinct and peculiar relation- ship can be ascertained in one only way, by one only method, — that of observation of the relation- ship itself. The presence of any one relationship does not imply, or involve, the presence of any other. Our knowledge of the relations of marble to light could never have been derived, by any act of the pure reason, inductive, or otherwise, from our knowledge of its relations to electricity, or to heat, or to other bodies through space; and so on of all its relationships. No one of these is contained, or included, in any of the others, and is not, there- fore, susceptible of being deduced from them. And this doctrine is universal in its application; it is true of all the properties, all the phenomena, all the relationships, of all substances. I have already spoken of the independent character of our knowledge of the chemical constitution and relationships of marble. Our knowledge of the like constitution and relationships of all other sub- stances is equally independent; it is exclusively derived from observation of the constitution, and the relationships themselves. Is there anything in 3 18 THE PHILOSOPHY OF PHYSICAL SCIENCE. the sensible properties of water — is there anything in its dynamic relations — in its tendencies towards other bodies — in its inertia, or in its motions, which could, in any conceivable way, have led us to the knowledge, that it is composed of two simple sub- stances, so different from itself, and from each other, as oxygen, and hydrogen ? Is there any- thing in the other properties and relationships of these two substances, from which we could have inferred the production of water, by their combi- nation in certain proportions ? Most assuredly there is not. In the further development of this doctrine, let us look, for a moment, at the manifold and beau- tiful relationships of light. Not in all physical science — not in astronomy itself—have there been any more wonderful achievements of human genius, than in optics. Nowhere, have the inge- nious contrivances of art, and the nice applications of science, been productive of more marvellous and positive results, than here. But, in every instance, these results have been the fruit of simple obser- vation, generalized, to be sure, and applied, as in the case of the phenomena of gravitation, by the aid of mathematical calculation. All the various relations of light to other substances ; all its subtle and mysterious properties; its influence upon chemical combinations; the influence upon it of the intimate or molecular structure of bodies, through which it passes; the recondite affinities by which it is linked to heat, electricity, and gal- PHYSICAL SCIENCE THE RESULT OF OBSERVATION. 19 van ism, have, each and all, been ascertained, so far as they are ascertained, solely and wholly, by simple observation, thus generalized, and applied; and by observation of each separate property and relationship. Certainly, there is no conceivable process of inductive reasoning, by which, the mind of Sir Isaac Newton could have arrived at the knowledge of the heterogeneous and compound nature of light. It was with the prism, and his eyes, and not by any magic of his great intellect, that the web of its homogeneous rays was first un- woven and analyzed, and its composition ascer- tained. It was by means of the thermometer, and by this means alone, that Dr. Herschel determined the presence, in the solar spectrum, of heating rays, independent of the rays of light. The origi- nal discovery of what is called the polarization of light, the development of which has led to such extraordinary results, was quite accidental even. It was revealed to M. Malus, by a casual turn of the prism, through which, in 1808, he was gazing at a brilliant sunset, reflected from the windows of the Luxembourg palace, in Paris. It has been said, I know, by the highest living authority, that some of the more abstruse and subtle properties and relations of light have been ascertained, and demonstrated, by pure a priori reasoning. Sir John Herschel speaks of the in- vestigations and discoveries of Fresnel, in con- nexion with the effects produced upon rays of light, by doubly refracting substances, as of this 20 PHILOSOPHY OF PHYSICAL SCIENCE. character. These properties and these relations, thus supposed to have been ascertained, by means of pure reason, through the aid and instrumen- tality of mathematical calculations, of great length and complexity, are not sufficiently obvious and intelligible, to be used for my present purpose of popular illustration. But, it seems to me, that the functions of these mathematical processes have been mistaken, in the agency which has been thus assigned to them. It will be found, I believe, upon a close examination, and a strict analysis of these processes, and of the part which they play in optical science, that they are wholly incapable of being made the means of discovering any new property, or any new relationship of light. They are used for the purpose of illustra- ting, extending, and applying to new, but analo- gous, circumstances, certain phenomena and re- lations of light, already ascertained by observation. This is the province, it seems to me, and the only province ; these are the functions, and the only functions, of such calculations, in all the physical sciences. And although I am not capable of fully comprehending them, I have no wish to seem, even, to detract from their importance. I am fully aware, that this importance is paramount; and that it cannot be exaggerated. 1 am fully aware, that the science of optics owes very much of its perfection and beauty to the complex and difficult calculations of Newton, and Young, and Fresnel; and that the science of astronomy could PHYSICAL SCIENCE THE RESULT OF OBSERVATION. 21 hardly be said to exist, independent of similar calculations. But in both these instances, and in all others, it seems to me, that the functions of these calculations consist, solely and exclusively, in the development, the generalization, the ex- tension, and the application to new circumstances and conditions, of phenomena and relationships, previously ascertained by simple observation. The pure mathematics of Newton, La Grange, and La Place, constituted only an instrument, or ap- paratus, by whose subtle properties, and stupen- dous power, these philosophers were enabled to measure and estimate the force of gravity, in all conceivable conditions, and under all possible cir- cumstances of difficulty and complexity. With all its wonderful subtlety, with all its stupendous power, it could no more discover a new property, or relation, of an atom of matter, than it could create the worlds, whose motions it so accurately measures, and whose relations to each other, it estimates with such consummate precision, and such marvellous skill. It might seem quite im- possible, that the conclusions of Sir Isaac Newton, in regard to the dependence of the colors in the solar spectrum, upon different velocities in the motions of the assumed particles, constituting the several kinds of rays, should have been the result of mere observation. When, taking his researches for a foundation, it is alleged, on the undulatory hypothesis, that the red color of the spectrum is occasioned by the vibrations of an ethereal wave, 22 PHILOSOPHY OF PHYSICAL SCIENCE. the length of which wave is equal to the O'OOOO- 266th part of an inch, and the number of whose vibrations amounts to 458 millions of millions in a second, we may well be startled at the preten- sions, which profess to have estimated these num- bers, and to have measured these velocities. It is, nevertheless, strictly true, that these almost transcendental results, so far as they are establish- ed, have been established, not by any high and refined processes of pure a priori reasoning, but by simple observation, generalized and applied, through the agency of mathematical calculation, as an instrument and means. There is a certain sense in which many of the more subtle and recondite phenomena and rela- tions of light, like those of which I have just spo- ken, and some others, may be said to be ascer- tained by induction, or inference. But even in these cases, we shall find, on a careful examina- tion and analysis of our methods of investigation, that all our knowledge is the result of observation, and of observation alone. Thus it has been ascertained, that the intervention, under certain conditions, of very minute fibres or particles, be- tween the eye and a luminous body, causes the body to be surrounded with a ring of colors ; and that the width, or diameters of these rings in- crease with the size of the fibres, or particles, by the action of which they are produced. Dr. Young proposed an instrument, called an criome- ter, founded upon the ascertained relationship be- PHYSICAL SCIENCE THE RESULT OF OBSERVATION. 23 tween the size of the fibres, or particles, and that of their corresponding rings, round the luminous body, to be used for the purpose of ascertaining the size of these particles, themselves too minute for direct measurement, by ascertaining the width of their rings. Dr. Wollaston found, by measure- ment, the diameter of the seed of the lycoperdon boviste to be the 8500th part of an inch; and then by comparing with the rings, produced by this seed, those corresponding to other and much smaller particles of matter, he ascertained the size, or the diameters of these latter. There is no propriety in saying, that Dr. Wallaston dedu- ced, or inferred, by any process of pure reasoning, the length of these diameters. He merely made use of the rings, produced by the action of the particles on light, as an instrument, or scale of measurement, wherewith to determine the diame- ter of the particles themselves, so minute as to be inappreciable by any other means. He converted them into an eriometcr. By a beautiful application of the same instrument of observation, Sir David Brewster ascertained the diameters and shape of the extremely delicate fibres of which the crys- talline lens of the eye is composed. By a still more refined application of other known rela- tions, and properties of light, the arrangement of the grooved surfaces of mother of pearl, and the internal structure of various crystallized bodies, beyond the powers of the microscope, have, to a certain extent, at least, been ascertained. It is 24 PHILOSOPHY OF PHYSICAL SCIENCE. sufficiently obvious, I hope, that, in all these in- stances, we are indebted, for our knowledge, not to any intellectual process of induction or infer- ence, or a priori reasoning ; but to observation of each property and relationship, and to this alone. There is another seeming qualification of the doctrine, that I am endeavoring to illustrate, about which it may be necessary to say a few words. It has often been alleged, for instance, that Sir Isaac Newton inferred, by a process of a priori reason- ing, the combustibility of the diamond, before this combustibility had been demonstrated by observa- tion. But what did Newton really do in this case ? Manifestly this, and nothing more. A relationship had already been noticed between two certain pro- perties, or phenomena, — at least in many bodies, to wit, their refractive power, and their combusti- bility. Newton's reasoning, as it is called, con- sisted, simply, in the suggestion, or conjecture, that this relationship might be absolute and uni- versal ; and, if so, that the diamond would prove to be combustible. The only reasoning in the case consisted in the application to new circum- stances of an assumed relationship. It has been said of Fresnel, that he " proved, by a most pro- found mathematical inquiry, a priori,^ the existence of certain subtle properties of polarized light. But here, again, what did Fresnel really do ? He showed, by the agency of his mathematical calcu- lations, that certain relationships of light, assumed, or ascertained by observation, in certain condi- PHYSICAL SCIENCE THE RESULT OF OBSERVATION. 25 tions, must, if these relationships were true and genuine, exist, also, in all other identical condi- tions. He showed, that if certain modifications of light, wrought in its properties, by the action of Iceland spar, during its passage through this sub- stance, were dependent upon certain peculiarities in its crystalline structure, then the same modifica- tion must be produced in other substances, identi- cal in these peculiarities of structure with the Iceland spar. He applied, merely, and generalized, by means of his calculations, a phenomenon, or relationship, of light, already ascertained by direct observation. 4 CHAPTER III. PROPOSITION THIRD. A LAW, OR PRINCIPLE, OF PHYSICAL SCIENCE CONSISTS IN A RIGOROUS, AND ABSOLUTE GENERALIZATION OF THE FACTS, PHENOMENA, EVENTS, AND RELATIONSHIPS, BY THE SUM OF WHICH, SCIENCE IS CONSTITUTED; AND IN NOTHING ELSE. IT IS IDENTICAL WITH THE UNIVERSALITY OF A PHENOMENON, OR THE INVARIABLENESS OF A RELATIONSHIP. All true relationships invariable. Error of the common saying, that the exception proves the rule. Nature and constitution of laws, or principles of science. They consist exclusively in constant phenomena, and relation- ships, classified and arranged. Never in anything lying back of these phenomena and relationships. Gravitation. Chemical science. The law of definite proportions. What it is. Other illustrations. Electricity. Light. All genuine and legitimate relationships are invariable and constant. This, indeed, is only another mode of stating the doctrine of the ancient axiom, that like causes, under like circumstances, must be followed by like effects.1 An event, having once occurred, will always occur, under 1 Whether our belief in the truth of this doctrine depends, in any degree, upon experience, or wholly upon an innate and fundamental property of our mental conslitution, it in no way concerns my present purpose to inquire. It is sufficient for me, that this idea of cause, is, in the words of Professor Whew ell, "an indestructible conviction, belonging to man's speculative nature." THE NATURE OF LAWS, OR PRINCIPLES. 27 the same circumstances; a phenomenon, having been once observed, will always be observed, in a like state of things; a relationship, once ascer- tained, will never fail, under the same condition of the related substances, or phenomena. This, at any rate, must be true so long as the present constitution of the universe continues. If oxygen and hydrogen are united in certain proportions to constitute the drop of water, which holds in solu- tion the coloring matter of the ink, wherewith these words are written, so do they unite in the same proportions to make up the waters of the ocean and the rivers. The rays of light, now falling upon this page, have occupied precisely the same period of time, on their journey hither, from their great source and fountain, as was occupied by the first which visited the earth, when the sun was set in the firmament. Those which fell upon the seas, on the morning when the waters were first " gathered together unto one place," were changed from their direction at the same angle, that now marks their divergence. All exceptions, as they have been called, to this invariableness and uni- formity are apparent only, and not real. They are the result, only, of our imperfect knowledge. The old saying, so constantly and so blindly repeated, that the exception proves the rule, is as destitute of truth, as it is of meaning. Such an exception can prove only one thing, and that is, that the rule is not fully understood, or completely ascertained. The relations of many substances 28 THE PHILOSOPHY OF PHYSICAL SCIENCE. and agencies, in nature, to other substances and agencies, are so numerous, and so complex; they so cross, and intermingle with, and modify each other, as to render their analysis, with our imper- fect means of investigation, often difficult, and sometimes impossible. But even in these instan- ces of combination and complexity, we should find, if our means of investigation were adequate to their analysis, and separation from each other, that each single series of legitimate relationships is as absolute and constant, as that simplest and sublimest of all, which directs a falling apple to the earth, and guides the heavenly bodies, in their circuits through the celestial spaces. Without this constancy and uniformity, there could be no such thing as what we call a principle, or law of science; there could, indeed, be no such thing as science. " Order is heaven's first law ; " and the essential condition of all order rests in this funda- mental and absolute fact of the uniform constancy of phenomena, and the fixed invariableness of relationships, under the same circumstances.1 1 Professor Whewell says, that no law, or proposition, absolute and universal in its character, can be established by observation, or experience alone ; for the reason, that experience is limited, and not commensurate with the law or proposition to which it refers; that the laws, for instance, of gravitation, light, and so on, so far as they are established by observation alone, are known to be general only, and not universal; and that they acquiie the stamp and character of universality only by the light shed upon them by the fundamental ideas of the mind. But, certainly, the doctrine of the absolute invari- ableness of all true relationships, of the fixed uniformity of the ALL TRUE RELATIONSHIPS INVARIABLE. 29 My object, in this chapter, is to show, that all laws, or principles, of science consist, merely, in these constant and invariable phenomena and relationships. This is necessary, because there is a feeling, more or less common, that a law, or principle, of physical science is something more than a universal fact, or a uniform relationship ; and that it consists in some unknown power, or agency, lying back of the phenomena, or inter- posed between those which are related to each other ; of which power, or agency, the pheno- mena, themselves, are only the manifestation, and the result. To illustrate my meaning, let us first take what is called the law, or principle, of gravi- tation. This law consists in the generalization of a single ascertained phenomenon ; it is the expres- sion of a single, universal fact, to wit: that all substances, with the exception of the few, which are called imponderable, when left to themselves, and not restrained, or prevented, by any counter- acting, or opposing, forces, will approach each other; and this in a certain ratio of velocity, which is susceptible of admeasurement. The law consists simply in this generalization, and in no- thing else; the principle is the expression of this phenomena of nature, a doctrine universally and necessarily admitted, gives to the laws ascertained by observation the same degree of positiveness, as that which belongs to any conceivable laws whatever. I do not see how they are any more contingent, than those with which Professor Whewell contrasts them, and which he calls necessary laws or truths. Phil. lnd. Set. vol. i. p. 61. 30 THE PHILOSOPHY OF PHYSICAL SCIENCE. fact, and of nothing else. The universality of the fact, or the generalization of the phenomenon, constitutes the sole element of the law. One ex- pression is, literally and absolutely, equivalent to the other. No new element can be introduced into the law, by the super-addition of other ideas. The supposition of the existence, between the bodies, tending towards each other, of some invi- sible and inappreciable force, or power, or agency, in the form of an ether, or in any other suppos- able form, would, even if the reality of the force were demonstrated, in no way affect the truth of what I have said. The relationship might thus be rendered less direct, and simple, by this inter- vention of a new phenomenon, or series of phe- nomena ; but the law, or principle, itself, would still remain precisely what it now is — the ex- pression of a universal fact — and nothing else. The essence of Newton's immortal discovery con- sisted in seeing and demonstrating the absolute simplicity, universality, and invariableness of this great relationship ; and his dynamical system of the universe consists in its development and ap- plication. The same kind of illustration may be applied to any and to all of the laws, or principles, as they are called, of physical science, and with the same results. One of the fundamental principles of chemical science is this, — that different bodies combine with each other in definite proportions, ascertained by weight. The law is in this uni- THE CONSTITUTION OF LAWS, OR PRINCIPLES. 31 versal fact, and not in any other conditions, or circumstances, that may be supposed to attend it. The principle, or the law, and the expression of this simple fact, are precisely identical. No sin- gle idea enters into one, that does not equally enter into the other. It is a law of electrical science, that the two kinds of electricity, — the positive and the negative, as they are called, — are always evolved in equal quantities ; — that there cannot be an evolution of one, without an exactly corresponding, equivalent evolution of the other. It is a law of optical science, that light, in passing obliquely from a rarer into a denser medium, is turned, at a certain angle, depending upon the degree of difference in the density of the two media, towards a line perpendicular to the surface of the denser medium which it enters. In these, as in the foregoing, and in all other in- stances, the law, or the principle, is constituted, exclusively, by a rigorous and absolute generali- zation of the phenomena, or the relationships, which are its subjects. There is no other element than this, entering into the constitution of the law. The law is absolute, just in proportion to the universality of the phenomenon, or the inva- riableness of the relationship; and just so far as these are not rigorously and positively established, is the law partial and incomplete. Every separate and individual phenomenon, every separate and individual relationship, constitutes an element in a law or principle of science. There are just as 32 THE PHILOSOPHY OF PHYSICAL SCIENCE. many of these separate and independent laws, or principles, as there are distinct classes of pheno- mena, or relationships. CHAPTER IV. PROPOSITION FOURTH. A HYPOTHESIS IS AN ATTEMPTED EXPLANATION, OR INTER- PRETATION, OF THE ASCERTAINED PHENOMENA AND RELATION- SHIPS, CONSTITUTING SCIENCE ; AND IT IS NOTHING ELSE. IT CONSISTS IN AN ASSUMPTION, OR A SUPPOSITION, OF CERTAIN OTHER UNASCERTAINED AND UNKNOWN PHENOMENA, OR RE- LATIONSHIPS. IT DOES NOT CONSTITUTE AN ESSENTIAL ELE- MENT OF SCIENCE. ALL SCIENCE IS ABSOLUTELY INDEPENDENT OF HYPOTHESIS. Most of our knowledge is incomplete. Natural wish to render it perfect and absolute. Attempts and efforts to accomplish this end give birth to hypotheses. Nature and constitution of hypotheses. Their true rela- tion to science. All science independent of hypotheses. Constitution of matter. The atomic theory of chemical combinations. Optics. Cor- puscular and undulatory hypotheses. Newton's elastic ether. Uses and functions of theories. Their value overrated. Opinions of Newton and Davy. Our knowlege of nearly all the properties, phenomena, and relations, of the substances and agencies, which constitute the objects of physical science, is partial and imperfect. It is very rarely, if ever, absolute and complete. The senses, even THE NATURE OF HYPOTHESIS. 33 when aided by all the means and appliances of science and art, reveal to us only a part, and pro- bably a small part, of the properties, phenomena, and relations, of the substances and agencies, which go to make up the material universe. Be- hind and beyond all these appreciable properties, phenomena, and relations, we feel that there must be others, with which these are connected, and upon which they depend. We feel that the posi- tion which we occupy, is at the confluence of numberless infinities, ourselves walled in, on every side, with impenetrable darkness, into which dark- ness, and from which, these infinities flow. The restless and inquisitive mind, from its very consti- tution insatiable, and ever unsatisfied with its ac- tual and absolute possessions, endeavors to ima- gine the phenomena, which it cannot demon- strate ; it struggles to overleap the boundary, whose inexorable circumference cages it in ; and, failing to do this, it fills the infinite and unknown regions, beyond and without it, with its own cre- ations. The fruits of these efforts, the results of these struggles, and of this constitution of the mind, are theories and hypotheses; or, in other words, interpretations and explanations, of appre- ciable and ascertained properties, phenomena, and relationships, through the medium of other un- known or imagined properties, phenomena, and relationships. It is the object of this chapter, to point out the true character of hypotheses, or the- 5 34 THE PHILOSOPHY OF PHYSICAL SCIENCE. ories, and to show the nature of their connexion with physical science. Amongst the earliest physical hypotheses, were those which had reference to the intimate and ul- timate constitution of matter. No region could be opened to the discursive and speculative dispo- sition of the human mind, so captivating and so boundless as this; and we accordingly find, that all philosophies, from the pure and subtilized idealism of Plato, even to the stern and triumph- ant generalizations of Newton, have allied them- selves, more or less closely, to some hypothesis of this character. They have thus endeavored to explain the appreciable composition and proper- ties of material substances, by supposing these substances to consist of certain ultimate atoms, which atoms they have endowed with definite qual- ities and attributes. In the same spirit, we still continue to say, that these atoms are solid, indivis- ible, impenetrable, and so on. We talk about their shape, their weight, their hardness, their number, and the spaces by which they are sepa- rated from each other. W7e fill up these spaces with electrical matter, or with some other ethereal fluid, of almost infinite subtlety; and then we go on to deduce many of the obvious properties of matter, from supposed relations between the par- ticles of this fluid amongst themselves, and from other supposed relations between this fluid and the atoms of matter. Now, what I wish particu- larly to insist upon is this, — that all these as- ALL SCIENCE INDEPENDENT OF HYPOTHESIS. S5 sumed phenomena and conditions are altogether matters of pure supposition. They enter, in no way, into legitimate science, so far as the proper- ties and relations of matter are concerned; they do not constitute one of its elements. Physical science is wholly and absolutely independent of them. The very existence of ultimate molecules, or atoms, with the qualities which we so confi- dently assign to them, is a matter of the purest conjecture; it is entirely a fiction of the mind. They may, or they may not, exist in nature. And I may remark, further, that this utter and ab- solute ignorance in which we are placed, of the ultimate constitution of matter, and of the rela- tions which may exist between its elementary con- stituents, ought at least to teach us caution in the construction of theories, or hypotheses, founded on an assumed condition of this constitution, and of these relations, and modesty in the promulgation and defence of such theories, or hypotheses. Art, with its manifold appliances, and science, with its marvellous insight, have opened to us so many of the mysteries of matter, that we are in danger of forgetting how infinite the distance may still be between what is known, and what is unknown. The smallest visible particle of marble appears, under the microscope, like a huge irregularly- shaped block ; and it may be, that the minutest atom, which is revealed to our straining sight, only by the most powerful microscope in the strong- est light, contains, still far within its appreciable 36 THE PHILOSOPHY OF PHYSICAL SCIENCE. form, the structure and arrangement upon which its properties depend. It may be, that infinitely beyond the boundaries of this microscopic vision, all those processes are carried on, and those rela- tions are established, which constitute the particle of matter what it is. Far, far beyond this visible boundary, and hidden within unapproachable re- cesses, actions may be going on, between the ulti- mate constituents of matter, not only utterly re- moved from our knowledge, but as truly beyond our powers of conception even, as eternity and space are beyond our powers of measurement, or estimate. Lest the tone of these remarks should seem exaggerated, I will quote the words of Pro- fessor Whewell upon this subject, with which I have become acquainted since my own were writ- ten. " But when we would assert this theory," he says, — of ultimate particles, — " not as a con- venient hypothesis for the expression or calcula- tion of the laws of nature, but as a philosophical truth, respecting the constitution of the universe, we find ourselves checked by difficulties of rea- soning, which we cannot overcome, as well as by conflicting phenomena, which we cannot re- concile." * Observation has shown, that when different bo- dies unite chemically, as we term it, so that a sub- stance differing in its properties and relations from those of its component or constituent ele- 1 Phil. Ind. Sci. vol. i. p. 414. THE NATURE OF HYPOTHESIS. 37 ments, is formed, they unite in certain fixed and determinate proportions. In order to account for this general fact, as a means of explaining and interpreting this law of combination, we resort to the assumed atomic constitution of matter, of which I have just been speaking; and we sup- pose, that a single atom of one substance, or ele- ment, can unite only with a single atom, or with two, or three atoms, and so on, of another sub- stance or element. Now, all this again is a mat- ter of pure supposition. The very existence, as I have already said, of the atoms themselves, with the properties that are ascribed to them, is wholly conjectural; and their union with each other, ac- cording to the Daltonian theory, is equally so. However plausible and beautiful this theory may now be considered, it is quite possible, that new and widely different explanations of the general fact, or law, of combination in definite propor- tions, may yet be suggested, displacing the other, and removing it entirely from the province of chemical science. Professor Whewell says, — " So far as the assumption of such atoms as we have spoken of, serves to express those laws of chemical composition which we have referred to, it is a clear and useful generalization. But if the atomic theory be put forward, as asserting that chemical elements are really composed of atoms, that is, of such particles no longer divisible, we can- not avoid remarking, that for such a conclusion, chemical research has not afforded, nor can afford, 38 THE PHILOSOPHY OF PHYSICAL SCIENCE. any satisfactory evidence whatever." At any rate it is true, that the science of chemistry is wholly independent of this, and of all other inter- pretations of its phenomena ; these interpretations do not constitute any of its essential or legitimate elements. There is, perhaps, no department of physical science, in which theory, or hypothesis, has played a more prominent part, than it has in optics. If the mind of Newton was unable to rest satisfied with the simple establishment of the laws of gra- vitation ; if he found it difficult to conceive, that the atoms and the masses of the universe should tend towards each other, without the intervening agency of some material bond of union, still more difficult was it for the same mind, to be satisfied and content with the discovery of the appreciable properties and phenomena of light. Many of these properties and phenomena appeal so strongly and directly to one of the most positive and accu- rate of our senses; they are of such wonderful and multiform variety and beauty, that by an in- stinctive and irresistible impulse of the mind, we refer them to other and more remote phenomena, with which we suppose them to be connected, and upon which we suppose them to depend. New- ton supposed, accordingly, that light consisted of very minute particles, of a peculiar imponderable matter, given off, principally, from the surfaces of all self-luminous bodies ; the various motions, com- binations, and relations of which particles, gave THE NATURE OF HYPOTHESIS —OPTICS. 39 rise to all the phenomena of light. The exist- ence of these particles could, in no way, be demonstrated ; their existence and properties were assumed, as the most convenient and plau- sible means of accounting for and explaining the appreciable properties and phenomena of light; and this assumption, with its development, consti- tuted what has been called the material, or cor- puscular theory of light. The progress of optical science, subsequent to the great discoveries of Newton, revealed the existence of properties and phenomena, which his hypothesis was inadequate satisfactorily to explain; and another theory, co- temporaneous in its origin, or nearly so, with that of Newton, is now, very generally at least, adopt- ed in its stead. This latter theory assumes the existence, in all space, between the masses and the atoms of matter, of a subtle and elastic ether, upon the vibratory motion of the particles of which, all the phenomena of light are supposed to depend; and this assumption constitutes what has been called the ethereal, or undulatory theory of light. I may remark here, that the latter is as much a corpuscular, or material theory, as that of Newton; both theories assuming the ex- istence of material particles, in the motion of which the phenomena of light are supposed to consist. Here, as in all the preceding illustrations, I wish • it to be seen, that the theory, or hypothesis, is merely a mode of explaining and interpreting, or rather 40 THE PHILOSOPHY OF PHYSICAL SCIENCE. of attempting to explain and interpret, certain ascertained phenomena and relations, by the as- sumption, or supposition, of the existence of un- ascertained and unknown phenomena. Certainly, the science of optics does not consist in either of the above theories. No single individual ever made so many and so brilliant discoveries in this science, as were made by Newton; and this may be alleged without obscuring one ray of the halos which may be said, almost literally, to surround the names of Malus, of Frauenhofer, of Fresnel, of Young, of Herschel, and of Brewster ; but the theory which Newton adopted, in order to explain the properties and phenomena which he discover- ed, is now almost universally rejected ; it is re- garded as insufficient, or erroneous. But these properties and phenomena, constituting, so far as they go, the science of optics, are altogether unaffected by the rejection of the hypothesis which assumed to explain them. The fate that has befallen the theory of Newton, may yet also befall that of Huyghens and Young. In the infi- nite future, which will ever stretch out before the advancing progress of science and art, properties and relations of all forms of matter, now unimagin- ed and undreamed of, may yet be discovered, by means and processes of investigation now wholly hidden, which shall utterly overthrow the present theory of light, beautiful and stable as it appears to be. Or if this does not happen, another result is likely to follow, which comes to THE NATURE OF HYPOTHESIS—OPTICS. 4] much the same thing; and this result, there can hardly be any presumption in saying, so far as the recent progress and the present state of science can enable us to conjecture, is the most probable of the two. The existence of the supposed ether, certain elements of its constitution and of its rela- tions, now only inferred, or deduced, from the phenomena of light, may yet be positively ascer- tained. In this case, the theory is no longer a theory ; the hypothesis no longer a hypothesis. Their character is destroyed. The phenomena are no longer assumed; and they take their place amongst the other known phenomena of the science, constituting now one of its permanent and legitimate elements. If there is still need of theory, or hypothesis, it must be placed one step further back, still beyond that wall of darkness, which has only receded, instead of having been destroyed. The new theory must consist in other assumed properties and relations, assumed for the purpose of explaining those, now ascer- tained and demonstrated, of the particles of ether. And so must it ever be. Now and always — in optics and in all other sciences — the science itself consists in ascertained phenomena and rela- tions ; hypothesis, or theory, in other assumed phenomena and relations, — assumed as conven- ient or plausible means of explaining, or account- ing for, these. There is one very common feeling in regard to these interpretations and explanations, which is, 6 42 THE PHILOSOPHY OF PHYSICAL SCIENCE. that they render the phenomena, to which they are applied, more intelligible — more easily com- prehended and understood, than they would oth- erwise be. It seems to me, that there is some fallacy in this feeling, or, at least, that its alleged value is exaggerated. We shall find, I think, on a close examination of the matter, that the diffi- culty to which I refer, is only changed in the place which it occupies, by these explanations; that it is neither removed, nor very materially diminished, by them. As this feeling, more than anything else, has given rise to the strong attach- ment to theories, which has always, and almost universally existed, and as a little reflection on its soundness may aid us in forming a correct esti- mate of the real value and importance of theo- ries, it may be well to say a few words here upon the subject. Sir Isaac Newton, it is well known, suggested that the phenomena of gravitation might possibly be explained and in some degree accounted for, by the presence and action, throughout all space, of a subtle and elastic ether. Professor Whewell remarks, also, that the presence of this pervading ether may remove a difficulty, which some persons find considerable, of imagining a body to exert force at a distance ;* and I know, that this diffi- culty is often felt, even by minds of much strength and acuteness. It would seem that Newton him- 1 Phil. Ind. Sci. vol. ii. p. 210. THE VALUE OF HYPOTHESIS. 43 self was driven to the supposition of his ether, not merely as a convenient means of explaining the phenomena of gravitation, but as a necessary condition of these phenomena. He found it im- poss'.ble to conceive of the existence of these phenomena, v.ithout the intervention of some material bond of connexion between the particles and masses of matter acting upon each other. In a letter to Dr. Bentley, he expresses himself in the following words: — "It is inconceivable that inanimate brute matter should, without the medi- ation of something else which is not material, operate upon, and affect other matter, without mutual contact, as it must do, if gravitation, in the sense of Epicurus, be essential and inherent in it. And this is one reason why I desired that you would not ascribe innate gravity to me. That gravity should be innate, inherent, and essential to matter, so that one body may act on another, through a vacuum, without the media- tion of anything else, by and through which their action and force may be conveyed from one to another, is to me so great an absurdity, that I believe no man who has, in philosophical matters, a competent faculty of thinking, can ever fall into it."] But I do not see how the existence of such an ether can render any more intelligible the fact of gravitation, than it now is, without the ether. The everlasting and unanswerable why ? 1 Stewart's Philosophy of the Human Mind. 44 THE PHILOSOPHY OF PHYSICAL SCIENCE. and how ? are not gotten rid of by this assump- tion, or by the discovery of a new phenomenon. We have only changed their position ; we have only carried them a step farther from us, or brought them, apparently, a step nearer to us. In the first instance, the question was this ; — how, or why, do all the solid particles of matter strive to approach each other, there being nothing but void space between them ? The question, in the second instance, becomes merely this ; — how, or why, does this rare, ethereal medium, impalpa- ble, imponderable, invisible, almost inappreciable by the most refined means of observation, draw together these solid particles ? How, and by what mysterious and incomprehensible agency, does it hold the ultimate elements of matter in their rela- tive positions, drag the avalanche from its rocky basis, call back the comet from its remote wan- derings, and retain the planets in their orbits ? I cannot see that one question is any easier of solu- tion than the other. I cannot see that there is anything especially difficult, or unphilosophical, in the supposition, that gravitation consists exclu- sively and entirely in the tendency of the solid particles of matter to approach each other. Why may not this tendency exist as well without any intervening agent as with one ? Furthermore, is it not true, that all our knowledge of the proper- ties of matter leads to the probable conclusion, that its ultimate elements do not absolutely touch each other; that each one is surrounded by an THE NATURE AND VALUE OF HYPOTHESIS. 45 atmosphere, or space ? Mossotti and others have filled up these spaces with the assumed matter of electricity, or with the Newtonian ether; but this does not alter the essential constitution of matter, so far as this particular circumstance of the con- tact of its particles is concerned ; for this supposed ether, however rare and attenuated it may be, must, after all, be composed of elements, or particles, as truly as matter itself. It is, at least, as difficult for us to conceive of any other constitution for the ether, as for solid matter. It seems probable, then, that there is no such thing in nature as abso- lute contact; at any rate, there is nothing unphi- losophical in this conception of the ultimate ar- rangement of the elements of matter. Now if the supposed ultimate elements of common mat- ter, or those of the assumed ethereal medium, can act upon each other through absolutely void spaces of infinite minuteness, there is no reason why the same elements may not also act upon each other through void spaces of infinite extent. I cannot see that the tendency of all bodies to approach each other, constituting the principle of gravity, is at all more incomprehensible and mysterious, than any other ascertained relation of the particles or masses of matter; and if it were so, I do not see how the intervention of the supposed matter of electricity, or of the supposed ether of Newton, can in any way aid, either in removing or dimin- ishing the difficulty. I think that a similar study of the theories of 46 THE PHILOSOPHY OF PHYSICAL SCIENCE. light, electricity, chemical combination, and so on, would lead us to much the same conclusion. The theory, or hypothesis, in these, and in all analo- gous instances, might seem at first sight, to furnish material aid to the mind in its attempts to con- ceive and to comprehend the phenomena and relations to which the theory is applied. But we shall find, I think, that we get rid of one difficulty, so far as we do get rid of it, only by the substitu- tion of another, no less formidable, in its place. The expedient is just about as successful in the accomplishment of its professed object, as that of the Indian philosopher, who placed the world on the back of the turtle ; and it comes to much the same thing. The world would be well enough disposed of, if there were any stable resting place for the turtle to stand upon; and so our theories might indeed render more intelligible the subjects to which they refer, were not the theories, them- selves, quite as difficult to comprehend as the phenomena and relations, which they profess to interpret and explain. I shall conclude this chapter with a few remarks on the value and importance, in physical science, of theories, or hypotheses. Without qualifying, in any degree, the doctrine which I have been endeavoring to elucidate, that all science is inde- pendent of hypothesis, I am quite willing to admit, that hypothesis has often been of service to science, in suggesting, guiding and directing its researches. I am willing to go further than this, as has already THE NATURE AND VALUE OF HYPOTHESIS. 47 been intimated, and to admit, at least the possibility, in some instances, that the researches thus sug- gested and directed, may lead, ultimately, to the positive demonstration of the assumed phenomena, constituting the theory. I am willing to admit with Professor Whewell, (the speculative tenden- cies of whose mind are very evident in all his writings,) the great difficulty, perhaps the impossi- bility, in many cases, of forming any definite con- ception of phenomena, or of reasoning upon them, without resorting to some hypothetical machinery, for the purpose of expressing, or interpreting their nature and relations.1 But after all, I cannot avoid repeating the conviction, that an undue im- portance, and a false position, is still very generally assigned to these interpretations. The old and illegitimate usurpation of power, by the ideal philosophy, in the empire of science, is even yet only partially destroyed ; and the reign of ex- perience, with that divine right, and absolute dominion, which constitute her inalienable prero- gatives, has been only partially established. It is important to observe, farther, that the aids and uses, which may really be derived from hypotheses, will be in no way diminished, but increased rather, by assigning to them the subordinate character and station, which they ought always to occupy. If this is done, while their ability to advance the progress of science will not be in any degree 1 Phil. Ind. Sci. vol. ii. p. 268-9. 48 THE PHILOSOPHY OF PHYSICAL SCIENCE. lessened, their mischievous tendencies in obscuring its perceptions, and in leading it astray, will be neutralized. The influence of this particular element of false philosophy has been so disastrous in its effects on the progress of medical science, that 1 am especially anxious to exhibit it in its true light; and since the opinions which I have expressed may seem to be somewhat at variance with those which have been advocated by two most profound and elegant writers on the philosophy of science,— Sir John Herschel and Professor Whewell, — I will call to the support of the cause, which I have endeavored to vindicate, two other witnesses, cer- tainly of not inferior competency and authority. Sir Isaac Newton, as has already been stated, had his theory of light; and it is but reasonable to suppose, that whatever value it really possessed, must have been fully obvious to his own mind. At any rate, if we may judge from the nature and tendencies of the human mind, or from the history of science, he could not have been disposed, as its author, in any degree to undervalue its impor- tance. Now, it is beautiful to witness with what true appreciation Newton regarded this his own theory — as well as those of others — of the pro- perties and phenomena of light, which he had newly discovered; and with what lofty indif- ference, and disdain, almost, he cast it behind him. Amongst the intellectual elements, which contributed to his superiority, and which enabled THE VALUE OF HYPOTHESIS —NEWTON. 49 him to achieve a greatness and renown in the realms of science, now unrivalled and supreme, this rare quality was one of the earliest in its development, and most powerful in its operation. If he bowed at any time, or in any degree, his strong neck to the yoke of hypothesis, it was always with a perfect consciousness of his ability at will to shake it off, as the lion shakes the dew drop from his mane. It is well known, that his great discovery of the heterogeneous or compound nature of light was made in his early youth ; and in his modest, manly, unassuming letter to Mr. Oldenburg, announcing his discovery, he says, in connexion with the subject before us: — " But to determine more absolutely what light is, after what manner refracted, and by what modes or actions it produces in our own minds the phantasms of colors, is not so easy. And I shall not mingle con- jectures with certainties"l In the discussions which followed the announcement of Newton's discovery, he had frequent occasion to refer to this matter, — of the value and importance of hypothetical expla- nations ; — and I know, that in no other way can I do so much for the cause of sound philosophy, and for the gratification of its genuine lovers and disciples, as by quoting his golden words. In a reply to some rather captious animadversions of Father Pardies, he says : — " For the best and safest method of philosophizing seems to be, first 1 Phil. Trans. Anno, 1672. 7 / 50 THE PHILOSOPHY OF PHYSICAL SCIENCE. to inquire diligently into the properties of things, and establishing those properties by experiments, and then to proceed more slowly to hypotheses for the explanation of them. For hypotheses should be subservient only in explaining the properties oj things, but not assumed in determining them ; unless so far as they may furnish experiments. For if the possibility of hypotheses is to be the test of the truth and reality of things, I see not how certainty can be obtained in any science ; since numerous hypotheses may be devised, which shall seem to overcome new difficulties." And again he says : — " Give me leave, sir, to insinuate that 1 cannot think it effectual for determining truth, to examine the several ways by which phenomena may be ex- plained, unless where there can be a perfect enu- meration of all those ways."* Sir Humphrey Davy, during the early period of his scientific researches, yielding to the impulses of a vivid and fertile imagination, suffered his mind to run riot in the creation of hypotheses. But in the full maturity and development of his powers, when his mind had become disciplined by habits of positive investigation and rigorous analy- sis, he abjured altogether this spurious philosophy of his youth ; and no man ever saw more clearly and distinctly than he did the true character, and relations to science, of these hypothetical fancies. Amongst the many allusions to this subject, con- 1 Phil. Trans. Anno, 1672. THE VALUE OF HYPOTHESIS-SIR H. DAVY. 51 tained in his writings, it is sufficient for my present purpose to cite only the following : — " When I consider the variety of theories that may be formed on the slender foundation of one or two facts, I am convinced that it is the business of the true philosopher to avoid them altogether. It is more laborious to accumulate facts than to reason con- cerning them ; but one good experiment is of more value than the ingenuity of a brain like Newton's.1 ..." The theorizing habit in a sound mind can counteract only for a short time the love of seeing things in their real light; and the illusions of the imagination, in proportion as they often occur and are destroyed by facts, will become less vivid, and less capable of permanently misleading the mind." 2 . . . " Hypothesis should be considered merely as an intellectual in- strument of discovery, which at any time may be relinquished for a better instrument. It should never be spoken of as a truth ; its highest praise is verisimility; knowledge can only be acquired by the senses; nature has no archetype in the human imagination; her empire is given only to industry and action, guided and governed by expe- rience."3 . . . " I trust that our philosophers will attach no importance to hypotheses, except as leading to the research after facts, so as to be able to discard or adopt them at pleasure ; treating them rather as parts of the scaffolding of the 1 Life of Sir II. Davy. By Dr. Davy. Vol. i. p. 81, 82. 5 Ibid. p. 216. 3 Ibid. p. 12W. 52 THE PHILOSOPHY OF PHYSICAL SCIENCE. building of science, than as belonging either to its foundations, materials, or ornaments." x I am entirely content with the position and importance thus assigned to theories and hypotheses by New- ton and Davy. CHAPTER V. PROPOSITION SIXTH. ALL CLASSIFICATION, OR ARRANGEMENT, DEPENDS UPON, AND CONSISTS IN, THE IDENTITY, OR SIMILARITY, AMONGST THEMSELVES, OF CERTAIN GROUPS OF PHENOMENA, OR RELA- TIONSHIPS ; AND THEIR DISSIMILARITY TO OTHER GROUPS OF PHENOMENA, OR RELATIONSHIPS. ALL CLASSIFICATIONS, OR ARRANGEMENTS, ARE NATURAL AND PERFECT JUST IN PROPOR- TION TO THE NUMBER, THE IMPORTANCE, AND THE DEGREE OF THESE SIMILARITIES AND DISSIMILARITIES. Arrangement and classification of phenomena and relationships. Principles and grounds of this arrangement. Illustrations. Marble. I have said a good deal, in the course of this essay, about the classification and arrangement of phenomena and their relationships. I have said, again and again, not that science consists in phenomena and relationships, merely ; but in 1 Life of Sir H. Davy. By Dr. Davy. Vol. ii. p. 128. ARRANGEMENT AND CLASSIFICATION. 53 these phenomena and their relationships, classified and arranged. It is not enough to constitute science, that its materials should be discovered and ascertained ; they must be brought together; they must be compared with each other; they must be analyzed, divided into groups, or families, placed in their appropriate positions; — in short, they must be classified and arranged. Until this is done, the materials themselves, heterogeneous, and jumbled together in disorder and confusion, are comparatively worthless; they have neither value nor significance. It is, indeed, by this pro- cess of classification and arrangement, that science is constructed. The phenomena and their rela- tionships constitute the materials of the temple ; it is by their classification and arrangement, only, that the temple itself is built up. The principles which are to guide us in this process, and the conditions of the process itself are, I think, clearly and suc- cinctly stated in the proposition at the head of this chapter. I have endeavored, in some of the preceding pages of this essay, to illustrate some of its doc- trines by an examination of the nature and the sources of our knowledge of marble ; let us now endeavor to see by what process, and according to what rules, the elements of this knowledge, — the ascertained phenomena and relationships of mar- ble, — are so classified and arranged as to convert them into science. One of these relationships is that of its particles to each other and to those of 54 PHILOSOPHY OF PHYSICAL SCIENCE. all other material substances, through space. The property, constituting this relationship, is possessed by marble in common with all other material sub- stances. The relationship, so far as these sub- stances are concerned, is universal: in the posses- sion of this property all these substances are alike; they are absolutely identical with each other ; and by means of this identity they are constituted a class. They are called ponderable bodies: widely as they may differ in other respects, they all agree in this, that they are equally subject to the laws of gravitation. Now, there is another class of substances, or agencies, which do not possess this particular property ; they are not subject to the laws of gravitation ; this particular relationship does not touch them. Their freedom from this relationship, the absence of this single but funda- mental property, constitutes them a class, entirely unlike that to which marble belongs; — they are called imponderable bodies. The classification, in the instance before us, depends upon and grows out of the presence, or the absence, of this single property; but the property itself is so important and so fundamental, that the classification itself assumes the same character. In the second place, our knowledge of marble teaches us that it is a compound body — that it is formed by the intimate combination of several distinct substances. This property it possesses in common with all or nearly all other material sub- stances as they exist about us. They may differ ARRANGEMENT AND CLASSIFICATION. ■JO indefinitely in all other respects, but they agree in this, that they are formed by the union of other substances; and the possession of this common characteristic constitutes them a class; — they are called compound bodies. It is found further, that other bodies, or substances, at least in the actual state of our knowledge, are not formed by the union of distinct elements ; that they cannot be separated into other substances; they differ very widely amongst themselves in all other respects, but they are identical in this. Their entire and perfect similarity in this constitutes them a class; — they are called simple, or elementary bodies. Again, it is found, that marble consists of car- bonic acid in combination with another substance; and in this particular circumstance it resembles many other compounds; they constitute a class, and are called carbonates. It is unnecessary to carry this illustration any further. I am not writing a treatise on the phy- sical sciences; and I only wish to present, in as few words as possible, the principle on which all classification in these sciences must rest; and to show in what it consists. PART SECOND. THE PHILOSOPHY OE MEDICAL SCIENCE. i " Ars medica tota observationibus." Frederick Hoffman. " Hypotheses and imaginary suppositions never should be admitted either into philosophy, or the medical science." William Hillary. " From what we have said before, it appears, that all the knowledge that we have of the virtues, operations, and effects, which all plants, drugs, and all medicines that we yet know, have in and upon the human body, has been obtained by observation and experience; neither does the human mind seem capable of acquiring that knowledge by any other means." lb. " It is not from ingenious reasoning, or fine-spun theories, that we should estimate the value of a remedy, but from the effects actually produced by it in a majority of cases." Nathan Smith. " La medecine ne s'enrichit que par les faits." Broussais. " Calcul des resultats, seule maniere infaillible d'apprecier la valeur des methodes en medecine." Dupuytren, Mem. de VAcad. Roy. de Med. 1824. " It is only by computation, founded upon large averages, that truth can be ascertained, and hence the danger of founding a general practice on the experi- ence of a single case, or a few cases." Sir Gilbert Blane. " The materials of just pathology can be drawn only from large masses of observation assembled and arranged in the order of their subjects; nor can durable improvements in practice be established on less full and luminous evidence." Edward Percival. " Through medical statistics lies the most secure path into the philosophy of medicine." Henry Holland. "Sufficit si quid fit intelligamus, etsi quomodo quidque fiat ignoremus." Cicero. " It appears to me that the physician, who ascertains half a dozen of im- portant facts, performs a more valuable though a less splendid achievement, than he who invents a dazzling theory." Samuel Black. " Analogy, the fruitful parent of fallacious conclusions." William Wool- combe. " Analogy, that fertile source of error." Liebig. PART SECOND. MEDICAL SCIENCE. PRIMARY PROPOSITIONS. Proposition First. All medical science consists in ascer- tained facts, or phenomena, or events; with their relations to other facts, or phenomena, or events; the whole classified, and arranged. Proposition Second. Each separate class of facts, pheno- mena, and events, with their relationships, constituting, as far as they go, medical science, can be ascertained in only one way ; and that is by observation, or experience. They cannot be deduced, or inferred, from any other class of facts, pheno- mena, events, or relationships, by any process of induction, or reasoning, independent of observation. Proposition Third. An absolute law, or principle, of medical science consists in an absolute and rigorous generali- zation of some of the facts, phenomena, events, or relation- ships, by the sum of which the science is constituted. The actual, ascertainable laws, or principles, of medical science are, for the most part, not absolute but approximative. Proposition Fourth. Medical doctrines, as they are called, are, in most instances, hypothetical explanations, or interpre- tations, merely, of the ascertained phenomena, and their rela- tionships, of medical science. These explanations consist of certain other assumed and unascertained phenomena and 60 PRIMARY PROPOSITIONS. relationships. They do not constitute a legitimate element of medical science. All medical science is absolutely independ- ent of these explanations. Proposition Fifth. Diseases, like all other objects of natural history, are susceptible of classification and arrange- ment. This classification and arrangement will be natural and perfect just in proportion to the number, the importance, and the degree of the simiFarities and the dissimilarities between the diseases themselves. PART SECOND. THE PHILOSOPHY OF MEDICAL SCIENCE. CHAPTER I. Definitions. Anatomy ; Topographical; General; Microscopic ; Chemical; Comparative. Physiology. Pathology. Etiology. Therapeutics. Medical science, in the comprehensive meaning here attached to it, includes the whole science of organization, or life. This science is made up of many integral constituents ; it consists of a consid- erable number of distinct and separate classes of phenomena and relationships, constituting so many individual branches, or departments, of the entire science; and before proceeding to the prin- cipal subject of my essay, it is necessary, briefly and distinctly, to define these branches — to state what the phenomena and relations are, in which each and all of them consist. The first of these departments is that which re- lates to the material structure, or organization, of living beings. This department is called ana- tomy. Inasmuch as it involves a knowledge of all the conditions which combine to constitute the 62 THE PHILOSOPHY OF MEDICAL SCIENCE. structure and conformation of living bodies; and inasmuch as these conditions are many and di- verse, this primary division naturally separates it- self into several sub-divisions, founded upon this number and diversity of conditions, which unite to constitute the structure. The first of these sub-divisions relates to the manifest and sensible properties and relations of each separate individual part, or organ, of a liv- ing being. It involves a knowledge of the size, form, color, consistence, specific gravity, position, and arrangement, of each and all of these single parts, or organs. It is called special, or topo- graphical anatomy. Every separate individual, in the two great organic kingdoms — of animal and of vegetable life — has its own peculiar and cha- racteristic topographical anatomy, or conforma- tion ; constituting, so far as structure is con- cerned, its individual peculiarity. This may be called individual topographical anatomy. Each sex also, where the sexes are separate, both in the animal and the vegetable world, has its peculiar structure; and this peculiarity of structure con- stitutes the anatomy of the sexes. The obvious structure of the several parts and organs of living beings differs, more or less, during the successive periods of their growth and decay ; and these dif- ferences constitute the topographical anatomy of the several ages, or periods, of life. The second division of anatomy relates to the obvious structure and properties, not of the indi- DEFINITIONS — ANATOMY. 63 vidual parts, or organs, which make up a living body, but of the organic elements, or tissues, as they are called, of which these single parts are composed. This is called general, or physiologi- cal, anatomy. It is found, by observation, that every separate part, or organ, is not simple and homogeneous, but complex and heterogeneous, in its anatomical composition; and general or phy- siological anatomy consists in a knowledge of all the sensible properties and relations of these sep- arate organic elements, or tissues, in whatever part or organ of the body they may be found. While topographical anatomy, for instance, informs us of the size, shape, arrangement, position, and relations of the heart, considered as a whole, general anatomy examines its organic composi- tion, and teaches us the properties of the several elements, or tissues, — the muscular, the serous, the cellular, and so on, — which unite to constitute it what it is. The third division of anatomy relates to the more hidden and delicate structure of organized bodies. With the aid of lenses, it pushes its inves- tigations far beyond the line which limits the unassisted senses, and strains its vision to detect the ultimate and final arrangement of the primor- dial organic elements. It traces the capillary vessels to their minutest anastomoses ; it unravels the smallest muscular bundles to their ultimate fibres ; it follows the gossamer thread of the nerve to its final termination ; it measures the diameter 64 THE PHILOSOPHY OF MEDICAL SCIENCE. of the blood-globule, and estimates the thickness of its colored envelope. It is called minute, or microscopic anatomy. The fourth division of this department relates to the chemical composition of the organs, tissues, and fluids of living bodies. All these organs, tissues, and fluids are made up of the elements of common matter; and this division teaches us what these elements are, and in what proportions they are combined. It may be called chemical anatomy. The structure of the human body, in its several sub-divisions, constitutes human anato- my ; that of vegetables, what may be called vege- table comparative anatomy ; and that of animals, below man, animal comparative anatomy. The second great department of the science of life is that, which relates to the actions or pro- cesses, which result from, or are connected with, the structure or organization of living beings. This department of the science is called physiology. Its sub-divisions, or branches, correspond very nearly to those of anatomy. So far as observation enables us to judge, every peculiarity and variety of structure is associated with a peculiarity and variety of action. Each organ, each apparatus of organs, each elementary tissue, plays its own part, performs its own specific duty, accomplishes its peculiar and individual office, in the living economy. The actions and processes, which take place in, and are effected by, each part, or organ, or tissue, constitute the physiology of this part, or PATHOLOGY- ETIOLOGY —THERAPEUTICS. 65 organ, or tissue. There is, therefore, a physiology of each organ, and of each elementary tissue ; there is a physiology of the sexes, and of each successive period of life ; there is a comparative vegetable physiology, a comparative animal phy- siology, and so on. Anatomy consists in the en- tire structure of organized bodies; physiology consists in the natural and regular actions and processes connected with this structure ; life is the aggregate sum of the two, — of the structure and its functions. The entire science of life, in its natural or normal condition, is contained in these phenomena, of structure and function, and in their various relations. The entire natural history of living beings, in all their infinite variety of form, structure, and function, — from the hyssop upon the wall, to the cedar of Lebanon, and from the microscopic animal monad, to man, — is contained in these phenomena and their relationships, classified and arranged. But inasmuch as the structure of living beings, and the actions and processes connected with this structure, are subject to various derangements, and departures from their natural and normal con- dition, we have a third fundamental department of the science of life, consisting in the phenomena, and their relations, of this altered structure, and of these disordered actions and processes. This department is called pathology. It is coextensive with the two preceding departments. Alterations of the structure, appreciable in any way by the 9 QQ THE PHILOSOPHY OF MEDICAL SCIENCE. senses, constitute what has been called morbid or pathological anatomy; derangements in the actions and processes, connected with the struc- ture, constitute what has been called, simply, pa- thology. The former may be more properly termed structural or organic pathology; and the latter, functional pathology. The entire science of pathology, or disease, consists in these phe- nomena and their relationships, classified and ar- ranged. These relationships are of a threefold character. The first are those which exist amongst the phenomena themselves; which rela- tions, with the phenomena, constitute, as has just been said, the department itself of pathology. The second are those which exist between these phenomena, on the one hand, and all those sub- stances, agencies and influences, of whatever sort or character, which occasion or give rise to the phenomena, — which precede, and stand to them, as causes. These relationships constitute the sub-division of pathology, which is called etiology, or the science of the causes of disease. The third class of relations are those which exist be- tween the phenomena of altered structure and disordered function, on the one hand, and all those substances, agencies and influences, on the other, the properties and operation of which are to arrest the progress of these phenomena, to re- strain them within such limits as are compatible with life, to shorten their duration, to modify them in one way and another, or to remove them alto- PRELIMINARY REMARKS. 67 gether, — thus restoring the structure and func- tions from a pathological to a physiological condi- tion — from disease to health. These relations constitute that sub-division of pathology which is called therapeutics. CHAPTER II. PROPOSITION FIRST. ALL MEDICAL SCIENCE CONSISTS IN ASCERTAINED FACTS, OR PHENOMENA, OR EVENTS ; WITH THEIR RELATIONS TO OTHER FACTS, OR PHENOMENA, OR EVENTS J THE WHOLE CLASSIFIED AND ARRANGED. General prevalence of false notions. Medical science consists exclusively in the phenomena, and relationships of life, classified and arranged. Anatomy. Physiology. Illustrations. Germination of seeds. Conditions of germi- nation. Phenomena of germination. Respiration ; its phenomena. If it is true, even in physical science, as I have endeavored to show, that the doctrine stated in my first proposition, is only partially and imper- fectly recognized, it is so to a much greater extent in regard to the same doctrine in its ap- plication to medical science; and the remarks already made upon this doctrine may be repeated with still less qualification, and with more emphatic significance, in connexion with my present subject. The fundamental and primary truth, that all medi- 68 THE PHILOSOPHY OF MEDICAL SCIENCE. cal science consists in the appreciable phenomena of life, with their relationships, classified and arranged, and in nothing else, has never been generally admitted and received. This science, to a vastly greater extent than any other, has always suffered, and still continues to suffer, from the general prevalence of a spurious philosophy, and from vicious or imperfect methods of investi- gation ; and one element in this false philosophy, leading to these mistaken methods, is to be found in the inadequate conception or half-belief of the doctrine above stated. Here, as in physical sci- ence, with very few exceptions, men, claiming to be disciples of the Baconian philosophy, eloquent in their praises of what they call inductive reason- ing, and full of earnest declamation against the dangers and the prevalence of false or premature generalizations, and of hypothetical speculation, have failed to see more than half the truth, and have, oftener than otherwise, fallen headlong into the errors which they were so ready to condemn. The feeling has been much more common in medical, than in physical science, that although facts and their relations might, indeed, and must constitute the foundation of the science, the sci- ence still consisted in something more than these facts and relations; — that upon these latter the science itself was to be somehow built up, by that magical and creative process of the mind, — that evil genius of medical science, — called, indeed, induction, but differing, when stripped of its dis- PRELIMINARY REMARKS. 69 guides, in no single function or attribute, from that speculation, the place of which it professed, with promises as loud and pompous, as they have proved to be barren and empty, to occupy. The feeling has been, and still is, — as much, almost, since the time of Bacon as before, — that the sci- ence is in the inductive or reasoning process, super- added to the facts and their relations, more than in these latter themselves. Here, at the commence- ment of this part of my essay, I wish to enter my protest against this doctrine, in all its forms and modifications. I wish to show, that the science of medicine consists in the phenomena of life, with their relationships, classified and arranged, — WHOLLY', ENTIRELY', ABSOLUTELY. I wish to show, that these elements constitute, — not the founda- tion upon which, nor the materials, merely, with which, the science is to be subsequently con- structed, by some recondite and logical process of the reason, — but that they are the science, and the whole science, already constructed, and so far completed; and that nothing can be superadded to them, by any act of the mind, which can in any way increase their value, or change their character. This doctrine, in its relation to anatomy, or the material structure of living bodies, needs but little, if any, illustration. It is so obviously true here, that there is hardly any room for misconception or doubt. Medical science, so far as anatomy is con- cerned, consists so manifestly in the physical phe- nomena connected with organization, and in no- 70 THE PHILOSOPHY OF MEDICAL SCIENCE. thing else, that there is no necessity for any formal discussion of the subject; and I will, therefore, pass at once to the consideration of the doctrine before us in its connexion with the other and more complicated branches of the science. It has already been stated, that the physiology of any living being consists in the sum or aggre- gate of its normal actions, and of their relation- ships. Now in order to see whether these actions and relations, classified and arranged, do, or do not, constitute the whole of the science, let us ex- amine some of the processes and series of pro- cesses, which are carried on in the organic struc- ture, both of vegetable and of animal life. Let us look first at the germination of a seed, and see what the actions and relations are in which it con- sists. We find, in the first place, that there are three indispensable or essential conditions, if either one of which be wanting, the changes or actions in the seed, the sum of which constitutes germination, will not take place. The first of these conditions is that of temperature, or the degree of heat, in the midst of which the seed is placed. The tempera- ture necessary to the process of germination varies somewhat with different kinds of seeds; but its range does not extend much below the freezing point, nor above 100° of Fahrenheit. Without these limits the susceptibility of the seed to take on, and to go through with, the processes consti- tuting germination, is not awakened into action, and it may be wholly destroyed. The second ILLUSTRATIONS —GERMINATION OF A SEED. 71 condition consists in the presence of water. If this latter substance is entirely wanting, the pro- cesses do not take place. The third condition consists in the presence of atmospheric air. If either of these conditions is wanting, the seed does not germinate; it remains quiescent, or its pecu- liar structure and susceptibilities are destroyed. When, however, the foregoing relations are estab- lished, the process of germination is set up and carried on, and this process consists in the follow- ing changes. Certain parts, or organs, of the seed, which are called its cotyledons, are increased in size ; and a part at least of this increase is occa- sioned by the reception of the surrounding water into the minute cells of their structure. This swelling of the cotyledons, ruptures their external investing membrane ; they separate somewhat from each other, and thus their original relative position is changed. The consistence of the cotyledons is also considerably diminished. Co- temporancous with these changes in the cotyle- dons, another part or organ of the seed, termed the plumula, is enlarged, and extends itself in an upward direction ; while still another, termed the radicle, is also enlarged, and extends itself in an opposite direction. Accompanying these obvious changes in the volume, the consistence, and the relative positions of the several organs, or anato- mical parts of the seed, there are others which have taken place in its chemical composition. The proportion of ultimate elements,—carbon, 72 THE PHILOSOPHY OF MEDICAL SCIENCE. oxygen, and hydrogen, — originally constituting this composition, is found to be altered, a portion of the carbon having disappeared from the seed, and united with a portion of the surrounding oxygen of the atmospheric air. The insipid and farinaceous substance of the cotyledons has be- come sweet and mucilaginous ; their albuminous and amylaceous parts having been converted into gum and sugar. These changes are accompanied by a considerable elevation in the temperature of the seed ; and all the processes are, furthermore, to a certain extent, influenced by the degree of light that is present. Such, very briefly stated, are the phenomena and relationships constituting the physiology of germination. When these phenomena and rela- tionships have been fully and positively ascertained, and classified, the science of physiology, so far as germination is concerned, is complete. These facts and relations are not to be used as materials, merely, wherewith the science is subsequently to be created by some process of reasoning. They are, already, the science, and the whole science. There may be difficulties, — many and great, — in arriving at a full and absolute knowledge of all the processes that have been spoken of; there may be difficulties in ascertaining positively all their relationships, — in referring each to its proper mechanical, chemical, or vital cause, or to various combinations of these several agencies; there may be much ingenious speculation about ILLUSTRATIONS — GERMINATION - RESPIRATION. 73 these processes and relationships ; but, after all, the physiology of germination will be found to consist, solely and exclusively, in these ascertained processes and relations. No act of the mind can add anything to what has already been done. These phenomena and relationships are not to be concerted into the science of physiology, by any inductive process ; — they are the science ; — the science consists of these and of nothing else. The several obvious acts and changes consti- tuting the function of respiration, in the higher classes of animals, are very well ascertained. By a strictly mechanical process, the atmospheric air is introduced into the lungs, and after a short continuance there, again driven out. The ex- pelled air is found, on examination, to have parted with a portion of its oxygen, during its presence in the lungs, and to have acquired an undue pro- portion or quantity of carbonic acid. On farther examination it is found, that the carbon in the acid, or the acid already formed, has been derived from the venous blood; and that the oxygen, which has disappeared from the respired air, has been either absorbed by the blood, or united with the carbon to form the acid. Cotemporaneous with these changes, the venous blood has been altered in its color, and in some other of its prop- erties, by which it has been converted into what is called arterial blood. And here, as in the germination of a seed, the whole science of physi- ology, so far as respiration is concerned, consists 10 74 THE PHILOSOPHY OF MEDICAL SCIENCE. in the phenomena and their relationships. When the phenomena and relationships, constituting this function, have been ascertained and classified, throughout the entire range of living beings, the physiology of respiration is completed. No rea- soning upon these phenomena, no speculations about them, can give them any new character, or make them any more legitimate elements of sci- ence than they already are. And a similar study of each and of all the functions of living beings will lead us to the same results. But my purpose here is only to establish and illustrate a doctrine, not to teach physiology ; and such a study would be an unnecessary waste of labor and time. This doctrine is just as true in its application to pathology, etiology, and therapeutics, as to physi- ology. In each of these fundamental branches of medical science, the science consists in the phenomena and relationships, with which the particular branch is concerned, classified and ar- ranged, and not in any superadded reasonings or inductions of our own. But inasmuch as the doctrine has already been somewhat fully de- veloped, and as it will receive other incidental illustrations in the further prosecution of my sub- ject, I will say no more of it here. CHAPTER III. PROPOSITION SECOND. EACH SEPARATE CLASS OF FACTS, PHENOMENA, AND EVENTS, WITH THEIR RELATIONSHIPS, CONSTITUTING, AS FAR AS THEY GO, MEDICAL SCIENCE, CAN BE ASCERTAINED IN ONLY ONE WAY ; AND THAT IS BY OBSERVATION, OR EXPERIENCE. THEY CANNOT BE DEDUCED, OR INFERRED, FROM ANY OTHER CLASS OF FACTS, PHENOMENA, EVENTS, OR RELATIONSHIPS, BY ANY PROCESS OF INDUCTION OR REASONING, INDEPENDENT OF OBSERVATION. Extent of erroneous notions. The development of the doctrine, enunciated in the above proposition, will constitute a very pro- minent portion of my essay. We are approach- ing, 1 think, one of the strong holds of error in the philosophy of medical science, and a good part of my remarks thus far have been preliminary, only, to the inquisition which we are now prepared to institute into the nature and extent of this error. I have already said, that even in physical science, the doctrine, that each separate class of pheno- mena and relationships can be ascertained only by direct observation of these phenomena and rela- tionships, themselves; and that a knowledge of one class cannot be deduced or inferred from the knowledge of any other class, by any process of 76 THE PHILOSOPHY" OF MEDICAL SCIENCE. the pure reason, is only partially admitted. But it is in medical science, especially, that this great and fundamental principle has been most gene- rally and extensively disregarded. The feeling has been almost universal, and it still continues so, that the several classes of phenomena and relation- ships, constituting the science, are somehow so allied to each other, that a knowledge of one class may be, to a greater or less extent, deduced from a knowledge of the other classes. The prevalent idea is, that this connexion between the different branches of medical science is of such a character, that a knowledge of one branch may lead, by some deductive process, as it is called, to a knowledge of other branches. We are constantly told, for instance, that physiology is founded upon anat- omy ; that pathology is founded upon physiology ; that therapeutics is to be deduced from pathology, and so on. This assumed connexion between these and between other branches of medical sci- ence ; this alleged dependence of a knowledge of one series or class of phenomena and relationships upon a knowledge of another class, or series, con- stitutes the principal ingredient in the error to which I have alluded, and which I wish to expose and remove ; and the opposite doctrine of the en- tire dependence of all our knowledge of each series of phenomena and relationships upon direct observation of each particular series, is that which I wish to vindicate, and set up in its place. CHAPTER IV. Our knowledge of anatomy not dependent upon our knowledge of other branches of medical science. Our knowledge o/one branch of anatomy does not include the knowledge of any other branch. That our knowledge of the structure and com- position of all living bodies is the exclusive result of observation is so plain and obvious a truth as to stand in need of no illustration ; and we find, accordingly, that the influence of a false philoso- phy, and a vicious method of investigation has been less felt in this than in any other department of the science of life. I shall, therefore, have but little to say in this chapter. I wish to remark, however, that our knowledge of each sub-division of this special department is wholly independent of our knowledge of other sub-divisions. One kind of structure, or composition, is not to be deduced from another. Our acquaintance with each sub-division is the exclusive result of our examination of that particular sub-division. Topo- graphical anatomy is to be learned only by direct study of the form, the volume, the color, the con- sistence, the position, and so on, of the several individual parts or organs. Physiological or gen- eral anatomy, in its turn, is to be learned only by studying the properties of the several elementary 78 THE PHILOSOPHY OF MEDICAL SCIENCE. tissues which go to make up the organs; it cannot be deduced, or inferred, from the former. A knowledge of the anatomy of any one sex does not involve a knowledge of the anatomy of its corresponding, opposite sex. The intimate and minute structure of the several organs and tissues can never be inferred from their obvious physical qualities. For our knowledge of this we must rely wholly upon minute and microscopic exami- nation. And the same thing is true of thechemi- cal composition of the organs and tissues. This can in no way be inferred, or deduced, by any process of reasoning, from their other properties. No knowledge, however accurate, of the con- formation of the brain, or the liver; no knowledge, however accurate, of the shape and arrangement of the ultimate anatomical elements of the two organs, could ever have furnished us with the remotest intimation of the chemical constitution of one or the other. The knowledge of this latter is to be obtained by direct observation, through the aid of chemistry, and in no other way. So, also, of vegetable anatomy in all its sub-divisions. Each of these latter is independent of the corresponding sub-divisions of animal anatomy; and each, also, is independent of the others, in its own depart- ment. Each must be learned by the direct study of its own characteristic phenomena : — no one can be inferred from either or from all of the others. CHAPTER V. Our knowledge of physiology not deducible from our knowledge of anatomy. Qualifications. Final causes. Illustrations. Brain. Stomach. My object, in the present chapter, is to show, that the actions of the organs and tissues which constitute living bodies can be ascertained only by direct observation of the actions themselves; — that they cannot be inferred from the structure of the organs and tissues; or, in other words, that physiology cannot be deduced from anatomy. Before proceeding, however, to do this, it is necessary to make one qualification, or explana- tion. This qualification grows out of, and depends upon, the great principle of the adaptation of means to ends. But this principle, as we call it, can hardly be regarded as an exception to the doctrine which I wish to set forth. It consists simply in the fact, always observed, when our means of observation are adequate, that through- out the universe, means are invariably and per- fectly adapted to ends; and the qualification to which I allude consists merely in the application of this universal fact to the subject before us.1 1 This is the doctrine of final causes, — a doctrine, which, notwith- standing the objections of Geoffroy Saint-Hilaire, and some others, 80 THE PHILOSOPHY OF MEDICAL SCIENCE. Thus, when we examine the structure and con- formation of the skull, we might justly and safely come to the conclusion, that it is intended to con- tain some organ or substance, which requires to be protected from the mechanical action of exter- nal bodies. In conformity to this great law of adaptation, running through all nature, and ascer- tained by observation, we might say, that the structure of the skull presupposes this as one of its functions. In conformity again to this law, and having ascertained by experience the action and offices of a valvular apparatus; from an accu- rate knowledge of the internal structure, and mechanical arrangement, of the heart, and its connexions with the venous and arterial tubes, we might justly and safely come to the conclusion, that its office, — so far as this structure and ar- rangement, and these connexions, are concern- ed, — is to receive from one set of tubes, and to it seems to me utterly impossible not to see, written legibly and boldly, throughout all organized nature, — so legibly and so boldly, that he who runs may read. The theological relations of this doc- trine I in no way allude to on the present occasion. They have no bearing whatever on the question before us. The strength and soundness of the great argument of Paley and others, drawn from this universal fact of adaptation and apparent design, in favor of the existence and agency of an intelligent designer, has nothing to do with the fact itself. Whatever may be thought of the former, it seems impossible that the latter can be denied. The existence of 5 what are called final causes, in physiology, or the fact itself of the | adaptation of the organs to their uses, is an observed fact, just as I obvious and positive as any other fact or phenomenon, whatever, in nature. PHYSIOLOGY NOT DEDUCIBLE FROM ANATOMY. 81 transmit to the other set, some kind of a circula- ting fluid. So, we might infer, in the same way, that the stomach, the gall bladder, the urinary bladder, the uterus, and so on, are intended to act as reservoirs ; and that the several canals, leading to and from these reservoirs, as well as the other canals in the body, are intended for the passage or transmission of some kind or kinds of substances. From our knowledge of the properties and rela- tions of light, and in accordance with the same principle of adaptation, we might conclude, that the transparent cornea is intended for the trans- mission of light, and that the crystalline lens has for its function the refraction of this same trans- mitted light, and the consequent formation of the images of visible objects upon the nervous expan- sion at the bottom of the eye. An examination of the structure of a bony articulation might fairly lead to the conclusion, that its surfaces are in- tended to move upon each other. But in these, and in all analogous cases, we can go no further. Our inferences, or deduc- tions, as we call them, are very limited in extent; and they consist only in the particular application of the law oi' final causes, or the general fact of the observed relation of means to ends. The conformation of the skull gives us no intimation of the character, the properties, or the uses of the substance contained within it. The arrangement of the heart, and its dependencies, throws no light upon the nature or the offices of the fluid which n 82 THE PHILOSOPHY OF MEDICAL SCIENCE. they are designed to circulate. This fluid, for aught that the anatomical arrangement of the or- gans teaches us to the contrary, might be water, or milk, or air, as well as blood. The same thing is true of the other canals, and of the several reservoirs of the body. Their structure points out only their general, and not their particular and positive uses. No one could ever have in- ferred, from any a priori reasoning, that the gall bladder was intended as a receptacle for bile, or the urinary bladder as a reservoir for the urine. It is a matter of very little importance, what organs, or what functions, of a living body are se- lected, for the purpose of illustrating the doctrine of this chapter; any and all of these organs and functions will answer this purpose. No know- ledge, however complete, of the structure and composition of a seed, could ever have shed any light upon the vital actions which it is capable of manifesting; no acquaintance, however perfect, with the anatomical and chemical elements of its plumula and radicle, could ever have furnished the remotest intimation of the tendency in one to stretch upwards, to form the stem, and in the other, to reach downwards, to form the root of the new plant. Is there anything in the obvious phy- sical properties of the glands of the human body — is there anything in their chemical composi- tion, or in their minute, molecular arrangement, — from which even the obscurest and most shadowy glimpse could have been obtained, of the several PHYSIOLOGY NOT DEDUCIBLE FROM ANATOMY. 83 offices which they are destined to perform ? Could the scalpel of the dissector, or the lenses of the optician, or the retort of the analyst, or all com- bined, have ever revealed to us the power of the liver to secrete bile, of the kidneys to secrete urine, of the mammary glands to secrete milk ? Let us suppose that our anatomical knowledge of the brain had reached its ultimate limit of accu- racy and perfection — that its complicated and delicate meshes of tubes and fibres had all been unravelled — that its intricate connexions and de- pendencies had all been ascertained — that no element or condition of its material organization had escaped us; — would all this knowlege have furnished us with any information as to the part which it plays, and the offices which it performs, in the living economy ? Has human reason any power sufficiently subtle and acute, to have ex- torted from this structure the secrets of its vital capacities ? Has she any wand of so potent ma- gic, as to have opened the mysteries wrapped up in the organization of the brain ? Could she have detected, even in the ultimate recesses of this organization, if she could have penetrated thither, the latent power of the will — the yet unawakened capacity of sensation — the slumber- ing, but manifold and stupendous energies of emotion and thought ? Were not some of the noblest functions of the brain, indeed, actually at- tributed by the a priori physiologists of former times to other and remote portions of the body ? 84 THE PHILOSOPHY OF MEDICAL SCIENCE. Is there, in short, any conceivable process of in- duction, by which the physiology of the brain could have been derived from its anatomy ? Cer- tainly, there can be but one answer to these ques- tions. It may possibly be said by some, that this illus- tration is not a fair one, on account of the very peculiar functions of the brain, partaking, as they do, of what is regarded as immaterial or spiritual, in its nature. I cannot see that there is any dif- ference, in regard to the subject before us, be- tween the brain and its functions, and any other organ or apparatus of the body, and its functions. What is true of one, will be found, I think, with the qualifications already made, to be true of all. Let us look, for a moment, at some one of the or- gans and functions, of a purely material charac- ter. How is it with the structure of the stomach, and its functions ? Could the latter have been deduced, by any act of the reason, independent of observation, from the former, any more readily than the functions of the brain could have been deduced from the structure of that organ ? Is there anything in the anatomical character — to- pographical, microscopic, or chemical — of the mucous membrane of the stomach, that includes, or presupposes, in any way, its peculiar vital pro- perties ? For aught that mere anatomy teaches to the contrary, the function of digestion might just as well have been carried on by any other portion of the mucous membrane, as by that of PATHOLOGY NOT DEDUCIBLE FROM PHYSIOLOGY. 85 the stomach. In short, here, as everywhere else, each separate class of phenomena and relation- ships can be ascertained in only one way, and that is, by direct observation of the phenomena and relationships themselves. For our knowledge of { the offices and uses of every tissue, of every or- \ gan, of every apparatus, in the body, we must de- pend exclusively upon observation of these parti- cular offices and uses, themselves; in no case can we derive this knowledge from any other sources. CHAPTER VI. Our knowledge of pathology not deducible from our knowledge of physiology. Qualifications. Illustrations. Inflammation. Differences in the suscepti- bilities of different organs to this process. These differences not to be ac- counted for on physiological grounds. Gastritis. Other diseases. In the preceding chapter, I have endeavored to exhibit the independent nature of our knowledge of physiology. I propose, in the present, to treat, in the same manner, of pathology. I wish to show, in the first place, that our knowledge of the morbid processes and susceptibilities of the seve- ral organs and tissues of the body cannot be in- ferred or deduced from our knowledge of their healthy processes.^Pathology is not founded upon physiology. The latter is not the basis of the for- 86 THE PHILOSOPHY OF MEDICAL SCIENCE. \ mer. The one does not flow from the other. Our J knowledge of the one does not presuppose our know- J ledge of the other. These assertions are so di- rectly opposed to the common doctrine upon this subject, that it becomes necessary to show their truth and soundness, by a somewhat full develop- ment and illustration. It will not do, here, to say with Rousseau, " Ma fo net ion est de dire la verity, metis non pas de la faire croirc." * On the con- trary, my function is, not only to speak the truth, but also, and especially, to make this truth felt and believed. I wish not only to announce sound and true doctrines, but also, and especially, to show that these doctrines are sound and true. In the discussion of this subject, I leave wholly out of consideration the question of the dependence of our knowledge of pathology upon our know- ledge of anatomy. If the healthy actions, and the natural uses of a part, or organ, or apparatus, cannot be inferred from its anatomical composi- tion, much more evident is it, that the same thing is true of its diseased actions. The doctrine, thus stated, and which I now pro- ceed to illustrate, is subject to certain apparent qualifications, which ought, in the first place, to be pointed out. I have already said, that every simple and direct relationship, is constant and in- variable. Supposing now the physiological ac- tions and relationships of the body to be fully as- 1 My function is to speak the truth, but not to make it believed. PATHOLOGY NOT DEDUCIBLE FROM PHYSIOLOGY. 87 certained, we may safely conclude, independent of positive experience, that a change in these rela- tionships will be followed by a change in the ac- tions themselves, and in the results of these ac- tions. Thus, after physiology has taught us, as far as it can teach us, the action of the oxygen of the atmosphere upon the blood, we may safely and positively conclude, prior to all experience, and independent of it, that if this action is inter- rupted, all the subsequent physiological processes with which it is connected will be also, and neces- sarily, more or less disturbed; and the same thing is true, of all physiological actions and relation- ships. Again, inasmuch as the integrity of the mecha- nical contrivances and apparatuses of the body is necessary to the perfect performance of their offices, and inasmuch as these contrivances and apparatuses are manifestly liable to injury, from external and obvious mechanical causes, it follows that, as in the former case, we may, so far as these mechanical relationships are concerned, infer the effects and consequences of such injuries, inde- pendent of absolute experience. Independent of any knowledge derived from observation of the fact itself, we might be quite certain, that an in- jury, or the destruction, of the aortic valves, would be followed by more or less disturbance of the function of circulation; and that the fracture of the femur would impede or destroy the act of lo- comotion, so far as this bone is concerned in the 88 THE PHILOSOPHY OF MEDICAL SCIENCE. performance of this function. So, from the con- formation of the skull — from the manifest design for the protection of its contents from mechanical injury, which this conformation exhibits — we might, independent of any other or further know- ledge derived from experience, very safely and confidently conclude, that such mechanical injury of its contained organ, or organs, would be fol- lowed by serious disturbance of the functions of the latter. But even here, we could go no fur- ther ; how this disturbance would manifest itself, and in what it would consist, it would be utterly impossible for us to say, or to conjecture. Our knowledge of the functions of the brain would not enable us to predict, independent of actual experience, what particular manifestation of these functions would be injured or destroyed by any particular form of mechanical injury. No pro- cess of deduction, or of a priori reasoning, could lead us to the knowledge, that one species of in- jury would produce coma, another convulsions, and so on. In accordance with the same law of the inva- riableness of relationships, having ascertained, by observation, the forms and modes of diseased ac- tion, to which a certain part or tissue of the body is subject, we might infer, with a reasonable de- gree of certainty, that other parts or tissues, re- sembling the former in composition and in func- tion, would be subject to similar forms and modes of diseased action. But, inasmuch as the re- PATHOLOGY MOT DEDUCIBLE FROM PHYSIOLOGY. 89 semblance in these cases is almost always one of a greater or less similarity, and not one of abso- lute identity, our priori conclusions must be pro- bable, only; not positive. The differences of structure and function, between analogous parts or tissues, though apparently slight, may still be sufficient to give rise to very great differences in the character and the importance of the lesions to which they are subject. Thus, notwithstanding the close similarity of structure and function, be- tween the mucous membrane lining the trachea, and that lining the smaller bronchial ramifica- tions, we find that the two are subject to import- ant differences of morbid action, when they are attacked with acute inflammation ; the former throwing out fibrine upon its surface, in the form of a membrane ; the latter secreting only mucus. So, in acute inflammation of the serous covering of the lungs, and of the abdominal viscera; not- withstanding the near resemblance in the struc- ture and functions of these two membranes, and notwithstanding the almost exact similarity in their appreciable pathology, the former is attended with a small degree of danger, the serum being absorbed, and adhesion taking place between the corresponding surfaces of the membrane ; while the latter, at any rate after serum and fibrine have been thrown out, is almost invariably followed by a fatal termination. Again, physiology having taught us the con- nexion between certain organs of the body, and 12 90 THE PHILOSOPHY OF MEDICAL SCIENCE. their dependencies and influences upon each other, we might properly enough conclude, that a similar connexion and dependence would show itself in their morbid actions and susceptibilities. Having ascertained, for instance, the existence of this con- nexion, and of these dependencies, between the several organs, in the female, constituting that ex- tensive and complicated apparatus, for the continu- ance of the species, we might reasonably suppose, that a morbid condition of one portion of this apparatus would not be without influence upon the other portions. But, here, as in some of the cases already spoken of, our a priori conclusions could only be more or less probable; they could have nothing whatever of a certain and positive character. Actual observation would, in many instances, destroy instead of confirming them. Finally, so intimate, and complicated, and mani- fold, are the physiological relationships of the living economy; so closely is each part connected with the rest; so readily and powerfully do these parts act and react upon each other; so complete, in many instances, is the union and the coopera- tion of the mechanical, the chemical, and the vital processes, that, independent of actual experience, we might safely conclude, that an injury inflicted upon one part of the body might often affect, more or less seriously, many other parts ; and that a dis- turbance, or suspension, of any one of the three great processes might, in many cases at any rate, disturb, or suspend, the other two. Having ascer- PATHOLOGY NOT DEDUCIBLE FROM PHYSIOLOGY. 91 tained, by observation, the complicated physiology of the circulation and of respiration ; having ascertained the existence of various mechanical, chemical, and vital actions, and their necessary cooperation in order to produce a certain result, consisting in the circulation, the oxygenation, and the decarbonization of the blood; it would follow, as a matter of course, and independent of positive experience, that a disturbance, or suspen- sion, of one of these associated actions, should disturb, or suspend, the others. Inasmuch as the integrity of the mechanical contrivances for the repeated exposure of the blood to the influence of the atmospheric oxygen is necessary, to secure this exposure, and inasmuch as this exposure is ne- cessary, in order that the oxygenation, and decar- bonization of the blood should be effected; and inasmuch as this change in the blood is essential in order to prepare it for answering its purposes in the vital processes of the body, it follows, ne- cessarily, that any disturbance, or imperfection, in the first, mechanical process, will be followed by corresponding disturbances and imperfections in the subsequent and associated chemical and vital processes. In the same way, also, having ascer- tained that certain substances are eliminated from the body by the physiological actions of the liver, and the kidneys, we might justly come to the con- clusion, without waiting for the positive teachings of experience, that the retention of these substan- ces within the system would be followed by un- 92 THE PHILOSOPHY OF MEDICAL SCIENCE. favorable results. But, even in these cases, we could go no further. Although we might safely enough predict, that the non-oxygenation of the blood, and the failure of the liver, and the kidneys, to eliminate and to remove from the system their appropriate excrementitious and effete secretions, would be followed by unfriendly and probably fatal consequences, we could not predict by what sub- sequent processes these effects would be produced, nor in what mode they would manifest themselves. With the qualifications and exceptions, thus stated, I do not see how it is possible, that the pathology of the living economy can be deduced, or inferred, from its physiology; and before pro- ceeding to the chief object of this chapter, I wish to call the attention of the reader to the very limited extent, and the unimportant character, of these qualifications and exceptions. They are more nominal than real. When closely examined and analyzed, they reduce themselves within very insignificant dimensions. Swelled to their utmost possible importance, they hardly amount to any- thing more than the truisms, that if a part of the body, manifestly intended for the accomplishment of a certain purpose, is injured or defective, then that purpose will in some degree fail of being accomplished; and that, where certain associated and mutually dependent processes are necessary to the production of certain results, a disturbance, or failure, of one of the processes will be followed by a disturbance, or failure, of the others, and by PATHOLOGY NOT DEDUCIBLE FROM PHYSIOLOGY. 93 the imperfection, or failure, of the results them- selves. If the doctrine which has been announced is sound and true, and to the extent which is thus asserted, then the entire domain of pathology, vast and various as it is, ought to furnish instances and exemplifications of its soundness and its truth. And such, I think, is the case. There is hardly a morbid process, in any organ or tissue of the body, that would not serve my purpose, as an instance and an exemplification of the truth which I wish to exhibit. It will be sufficient, however, to cite a few only of these, for this purpose. Let us look first at that pathological process, or series of processes, which is designated by the term inflammation. There is no morbid process, or con- dition, more common than this; there is none more important; there is none which has been more carefully and thoroughly studied; there is none which is better understood. The apprecia- ble elements of which it is composed; its forms and modifications in different organs and tissues; its causes; its tendencies ; its terminations; its results, have been very accurately and closely investigated. Now, I ask, if any attainable know- ledge of the healthy action of the parts, in which this process is seated, could, of itself, have led us to a knowledge of that diseased action of the same parts, constituting inflammation ? Is there anything, susceptible of being ascertained, in the natural functions of these parts, in the properties, 94 THE PHILOSOPHY OF MEDICAL SCIENCE. the susceptibilities, the actions of the minute arte- ries, the minute veins, of the capillary vessels, of the nervous filaments involved in this morbid pro- cess, which could have presupposed their liability to this process? Could any knowledge of the former have led, by any course or method of rea- soning, independent of observation, to a know- ledge, or a prediction, of the latter ? Could a knowledge of one have been deduced from a knowledge of the other ? Most clearly and in- disputably not. There is nothing, whatever, in the physiological condition and relations of the parts concerned in inflammation, which could have shadowed forth, or indicated, in the dimmest possi- ble degree, their liability to this condition. By what conceivable process of reasoning — by what imaginable steps of logical deduction — could a knowledge of the former have led us to a know- ledge of the latter ? Do the natural, the unfelt, the unnoticed actions of these minute vessels and nervous filaments presuppose, in any way, their liability to those numerous and complex pro- cesses— the contractions and the distentions of the vessels — the increased, the diminished, the irregular velocity of the blood — the pain, the heat, the secretions — which enter as elements into this morbid condition ? Certainly not. What physiological properties of these minute vessels could have informed us of their power, under any circumstances, to separate the fibrine from the other proximate constituents of the blood, or to PATHOLOGY NOT DEDUCIBLE FROM PHYSIOLOGY. 95 secrete pus ? Certainly none. So far, then, as the phenomena themselves of inflammation are concerned, I do not see how it is possible, that they should be inferred or deduced from the phy- siological phenomena of the parts with which they are concerned, or in which they are seated ; and 1 think, that an examination of all the other cir- cumstances connected with this morbid condition will serve to elucidate and to strengthen this result. Let us take one of these circumstances, — that of the different degree of liability, in the different organs and tissues of the body, to be affected by this morbid process. This difference is very great. Certain parts and organs are very liable to inflam- mation ; other parts and organs are very little lia- ble to inflammation. Now, is there anything in the physiology of these several parts and organs, — in their natural and healthy offices and functions, — from which, by any a priori reasoning, these different degrees of liability could have been ascertained ? Why are the lungs so frequently, and why is the spleen so rarely, the seat of this pathological pro- cess ? Why is acute inflammation of the pia mater, and the pleura, so common, and acute inflammation of the peritoneum, so uncommon an affection ? It will not do to say, that these different degrees of liability to this disease can be accounted for by any obvious or appreciable differences in the structure and functions of the organs or tissues, in which it is seated. These differences between the peritoneum and the pleura, for instance, are 96 THE PHILOSOPHY OF MEDICAL SCIENCE. not sufficiently striking to account for the result. Neither will it do to say, as has often been said, that the degree of this liability is in proportion to the importance and functional activity of the different organs and tissues. I do not know that this importance and activity are any greater in the case of the pleura, than in that of the peri- toneum ; — I do not know that they are any greater in the case of the lungs, than in that of the kidneys. Let us test the value of this pre- tended explanation, by a reference to the mucous membrane of the stomach. It would be difficult, I think, to find any part of the body, in which, from mere a priori reasoning, we should be jus- tified in looking for acute inflammation more fre- quently, than in this. In what part is there greater activity of function ? In what part are more important processes carried on ? In what part is there a quicker or more delicate susceptibility to impressions ? What part is more intimately connected with the other important acts and organs of the body ? Is it not the great centre of the organic sympathies ? What part is more constantly exposed to the action of irritating sub- stances ? And yet, notwithstanding all these ap- parent, and a priori causes of acute inflammation, very few tissues, or organs, of the system are so rarely affected by this morbid process as the mucous membrane of the stomach. Certainly, nothing can show more clearly the utter futility of the attempt to explain the fact of which I am speak- PATHOLOGY NOT DEDUCIBLE FROM PHYSIOLOGY. 79 ing, by referring it to differences in the importance and activity of the functions of the different or- gans, than this striking exemption of the gastric mucous tissue from attacks of acute inflammation. I will very briefly allude to one other circum- stance, connected with inflammation, which will serve still further to illustrate the doctrine, which I am advocating. 1 mean the different forms, under which this morbid condition shows itself, not only in dissimilar organs and tissues, but in the same organ, or tissue, at different times, and under different circumstances: Sometimes the march of inflammation is rapid; sometimes it is slow. Sometimes, and under certain circumstances, the irresistible tendency of this process is to extend and multiply itself throughout the same, or even throughout widely different, and dissimilar organs and tissues of the body. At other times, and under other circumstances, no such tendency exhibits itself. Now, if it is obvious, as I think it is, that this pathological process, even in its simplest form, and on the supposition, that it never showed itself in any other form than this, could not have been inferred, by any mode of reasoning, from the physiological actions of the parts in which it oc- curs ; still more evident is it, that the various and diverse forms of this process, of which I have spoken, could never have been so inferred ; and an examination of all the more obscure and com- plicated phenomena of pathology will lead to the same conclusion. Why are organic alterations 13 98 THE PHILOSOPHY OF MEDICAL SCIENCE. of the aortic valves so much more frequent, — in the proportion of nearly twenty to one, — than similar alterations of the valves of the pulmonary artery ? What is there in the functions and offi- ces of any portion of the body, from which the ex- istence, the properties, and the tendencies of tubercle could have been predicted, or deduced ? On what physiological grounds could the predilec- tion of this morbid deposition for the lungs have been anticipated ? Why is this deposition almost invariably commenced in the upper portion of these organs ? Why is the inferior portion of the lungs more frequently the seat of acute inflamma- tion, than the superior portion ? What knowledge of physiological relationships could ever have in- dicated the existence of those associated morbid actions and conditions, which are found in the ex- anthematous fevers? What means had physi- ology by which it could have predicted the con- nexion between the cutaneous efflorescence, and the inflammation of the fauces, in scarlatina ; or that, between another form of cutaneous inflamma- tion, and an inflammation of the mucous mem- brane of the air passages, in measles; or that, be- tween congestion of the spleen, inflammation of the aggregated follicles of the small intestine, and a peculiar cutaneous eruption, in typhoid fever ? What knowledge of the physiological composition, properties and relations of the blood could have in- formed us, that in all simple, acute inflammations, the relative proportion of fibrine in this fluid would PATHOLOGY NOT DEDUCIBLE FROM PHYSIOLOGY. 99 be found augmented; while in many other diseases, in continued fevers, for instance, it would be found diminished ? Is there anything in the healthy ac- tion of the kidneys, from which we could have in- ferred their power, under certain circumstances and by a perverted action, of separating from the animal fluids, sugar and albumen ? There can be but one answer to all these questions : and to hundreds of others, of a similar character, which might easily be asked, ^Xn no case, with the un- important and qualified exceptions, which have alrcudy been made, can the pathological processes, conditions and relationships of any organ, or tissue, of the body, be inferred or deduced from the known physiological processes, conditions and relation- ships of the same parts. The knowledge of pa- thological phenomena does not flow from the knowledge of physiological phenomena. The science of pathology is not built upon the science of physiology ; the former cannot be deduced from the latter. Each science consists in its own phe- nomena, and their relations; and these phe- nomena and relations can be ascertained in only one way, and that is by the direct study and observation of the phenomena and relationships themselves. There is one sense in which a know- ledge of the normal structure, and the physiologi- cal actions, of the body may be said to be neces- sary to a knowledge of its abnormal structure, and of its pathological actions. We need the former as a standard of comparison for the latter. In order 100 THE PHILOSOPHY OF MEDICAL SCIENCE. to know what constitutes a morbid alteration of structure, we must know in what the healthy con- dition of this structure consists; and the same thing is true, of course, of its physiological and of its pathological actions. But this, it seems hardly necessary to say, has nothing to do with the question, which I have been considering in the present chapter. CHAPTER VII. Relations of pathology to its causes. Etiology. Our knowledge of the causes of disease the exclusive result of observation. Etiology not to be deduced from pathology. Illustrations. Age. Sex. Season. The relations of pathology to all those sub- stances, agents and influences, which act as its causes, which convert physiological actions and conditions into pathological actions and conditions, constitute the science of etiology. I wish to show, that the nature and foundation of this de- partment of the science of life differ, in no degree, from the nature and foundation of those other departments, which have already occupied our attention. With certain unimportant qualifica- tions, our knowledge of the causes of disease is the direct and exclusive result of observation and study of the causes themselves. No attainable knowledge of the phenomena themselves of pa- ETIOLOGY NOT DEDUCIBLE FROM PATHOLOGY. 101 thology can ever lead us, independent of expe- rience, to a knowledge of the causes of these phenomena. The phenomena themselves can be ascertained only by observation; the same thing is true of all the relations of these phenomena. Let us illustrate the doctrine, thus stated, by a reference to some of these relations; and in the first place, to some that are simple in their character, and well ascertained. There are certain diseases, for instance, which sustain a very definite rela- tionship to certain ages, or periods, of life. That peculiar form of acute inflammation, which has received the popular name of croup, occurs much more frequently during a certain limited period of life, than at any other period. The same thing is true of acute inflammation of the pia mater. A large proportion of both these diseases are found in children, between the ages of two and of seven years. Tubercular depositions in the lungs take place much more frequently between the fifteenth and the thirty-fifth years of life, than at any other period ; and the same thing is true of typhoid fever. Apoplectic extravasation into the brain is much more common after the forty-fifth year of life, than it is before this age. In all these cases, there is nothing in the diseases themselves, which could have led, by any process of reasoning, inde- pendent of experience, to a knowledge of their respective relations to certain periods of life. No a priori considerations could have led to the conclusion, that any one of these diseases should 102 THE PHILOSOPHY OF MEDICAL SCIENCE. have been more frequent during one period of life, than at others. Again, some diseases are much more common in one sex, than in the other. In early life, for instance, it is found, that males are more subject to acute inflammation of the pia mater, than females; while females are more sub- ject to hooping cough, than males. Diabetes is much more common amongst males, than amongst females. Now, in all these, and in similar cases, so far as the simple and direct relationship between the disease and sex is concerned, no acquaintance with the diseases, themselves, could have indicated the relationship. The latter could not have been deduced from the former. The same remarks may be made in regard to the influ- ence of season in the production of various diseases. Prior to experience, and independent of it, no one could have known, that pneumonia and bronchitis would be most prevalent during one season of the year, and dysentery during another. If all this is true, so far as these simple and well ascertained relationships are concerned, it is quite unnecessary to multiply illustrations drawn from pauses of a more complex and obscure character. |No pathological process, or condition, can be referred to any agent or influence, as its cause, by any method of reasoning, independent of direct observation of the relationship itself.l The latter cannot be deduced from the former. A know- ledge of one does not, in itself, lead to a know- ledge of the other. CHAPTER VIII. Relations of pathology to its modifiers. Therapeutics. Rationalists. Empi- rics. Therapeutics not deducible from pathology. Inflammation. Peri- odical diseases. Cinchona and arsenic; Relations between them. Action of remedies on disease not deducible from their action in health. Opium. Cinchona. Calomel. Action of remedies on the human body not deducible from their action on those of other animals. The next relationship, the nature and character of which, I have to investigate, is that which exists between morbid processes and conditions, or dis- eases, on the one hand, and those substances, agents, and influences, on the other, which are endowed with the property of arresting, or con- trolling, or modifying these processes, or condi- tions. These substances, agents and influences constitute what has been called the materia medica. The science of therapeutics consists in their rela- tionships to disease ; and their application to their appropriate purposes and uses constitutes the art of therapeutics. Practical medicine comprehends, and consists of, the phenomena of pathology, and the relations of these phenomena, amongst them- selves, to their causes, and to these their modifiers. Writers upon the science and the art of medi- cine have always been, so far as the subject now before us is concerned, divided into two classes, or schools; those of the rationalists, and of the 104 THE PHILOSOPHY OF MEDICAL SCIENCE. empirics. The former have always been, and still continue to be, the most numerous and powerful. Their doctrines have pervaded and governed the medical world. They claim to be more philoso- phical, than their opponents, the empirics. They profess to be governed and guided, in their theory and practice, by what they are pleased to call rational principles. They allege, that their thera- peutics is founded upon rational indications. They claim, not merely to cure diseases, but to cure them philosophically, and in conformity to their rational principles. They claim, not merely to have ascertained the relationship, which exists between diseases and their remedies, but to under- stand the nature and the reasons of this relation- ship. They pretend to explain the mode and manner in which these remedies produce their results. Their doctrine is, that therapeutics is founded upon pathology; that the former is de- duced from the latter. They are very confident in their knowledge of the intimate modus operandi of their remedies. The empirics, on the other hand, deny all this. They say, that the whole science and art of therapeutics are founded upon simple experience. They say, that our knowledge of the relationship between diseases and their modifiers, is the sole and exclusive result of obser- vation of this relationship itself. They disclaim any knowledge of the intimate and essential na- ture of this relationship. They deny, that any acquaintance, however complete and accurate, with THERAPEUTICS NOT DEDUCIBLE FROM PATHOLOGY. 105 the phenomena of pathology, could ever, of itself, have led to a knowledge of the relations, which exist between these phenomena, and those sub- stances and influences in nature, endowed with the property of arresting or controlling these phenomena. They deny, that therapeutics is founded upon pathology. They deny, that by any process of reasoning, the former can be de- duced from the latter. This doctrine, I hardly need say, is the doctrine of this essay; and the remaining portion of the present chapter will be devoted to its statement and illustration.1 1 It is constantly alleged, by medical writers, that all rational and philosophical practice must be deduced from pathology. Some of these systematic practitioners would seem hardly willing that any disease either could be cured, or indeed ought to be cured, unless the cure could be effected rationally, and according to rule. Mr. Lizars, in a paper of vol. x. of the Edinburgh Medical and Surgical Journal, upon the nature and the cure of acute inflammation, says : " Many, I have no doubt, will contend, that the explanation of the order of these actions and phenomena is of no avail — of no practical utility; that when disease exists, we have a sufficient knowledge of it, and that our aim then should be to cure the malady. But to such rea- soning I have only to answer, that on the precise and correct know- ledge of the theory of any disease, must depend the treatment. It has been this taking for granted that has impeded the advancement of medicine. Thus, disease is described as it occurred to the practi- tioner, and his nostrums of treatment detailed ; but no accurate theory of the disease is given, and how the remedies did effect, or were likely to effect a cure, is never dreamt of. .... I shall now proceed to show how far a correct knowledge of the theory points out the treatment; for I conceive however satisfactorily prac- tice may establish the treatment of any disease, yet, if we do not clearly comprehend its nature, and the operation of the remedies employed, that we still labor in the dark, and are pure empirics." It would be difficult to find a fuller and clearer statement of the pre- 14 106 THE PHILOSOPHY OF MEDICAL SCIENCE. If there are any limitations to this doctrine, they are very partial and unimportant. I will al- lude to one of these limitations, which, however, valent false philosophy in medicine, than this. Mr. Lizars's theory of inflammation makes the first essential step in the series of morbid processes, consist in disturbance of the nerves; and then, by what he calls a process of rational induction, he arrives at his treatment, which consists in the application of hot, anodyne fomentations. It is curious to see with what complacency he regards this treatment ; not so much because it is successful, as because it is so rational — so philosophical — so readily comprehended and understood ! Again, in the same journal} vol. xxi. a writer, in speaking of the therapeutics of consumption, says: "It is indeed to be regretted, that the unsuccessful results of treatment, suggested by reason and principle, furnish a strong pretext for adopting the bold and blind measures of empiricism ; for when rules of science fail, it may be said, can the practitioner be censured for availing himself of those resources, the efficacy of which is demonstrated by experience ? This specious argument, we regret to say, has too often been resorted to as a principle of action." p. 160. I cannot well imagine a more extraordinary or monstrous proposition than this. No treatment sug- gested by " reason and principle," and founded in " rules of sci- ence," however disastrous and unsuccessful its results may have been, is ever to be abandoned for any other, " the efficacy of which has been demonstrated merely by experience ! " But, monstrous and extraordinary as this proposition is, it is exactly the doctrine of the rationalists in therapeutics, divested of its philosophical disguises, and exhibited in its naked and bald deformity. In a subsequent volume, I find the following statement of the same false doctrine: "This relinquishment of theory, however, is impracticable; and every one who knows the constitution of the human mind, is aware, that whatever professions of untheoretical views are given, are ne- cessarily incapable of being realized, and will manifest themselves in one way or another. The human mind naturally clings, in all ob- scure and unintelligible processes, to something like an explanation ; and it is quite as impossible to avoid theorizing about the causes of such processes, as it is impossible to avoid thinking. The man who disavows theory, and especially in medicine, is either a rash, thought- less, and insane empiric, or is utterly ignorant of what he ought to THERAPEUTICS NOT DEDUCIBLE FROM PATHOLOGY. 107 is more apparent than real. The connexion between diseases and their causes having been ascertained by observation, we might safely con- clude, without waiting for the positive knowledge of experience, that if the cause should be remov- ed, the disease would disappear. But this conclu- sion consists merely in an application to the parti- cular case, or class of cases before us, of the law of the invariableness of relationships. Having ascertained, for instance, that a certain degree of mechanical pressure upon the brain was followed, immediately, by a perversion or suspension of cer- tain functions of this organ, we might safely con- clude that, in conformity to the law of the invari- ableness of relationships, if this pressure should be removed, the perversion, or suspension of the functions of the brain, would no longer exist. But in this, and in all analogous cases, the rela- tionship must be direct and simple. There must exist no intervening phenomenon between one event and the other, to destroy the directness and simplicity of their connexion. Whenever this is the case, the application of the law wholly fails us; and we must remain entirely ignorant of the effects of removing, or destroying, the first link in the chain of relations, upon the last, until we have ascertained, by experience, these effects upon the intermediate links of the chain. know Avell — the laws of human thought — or is at best a hollow and specious deceiver." Edinburgh Medical and Surgical Journal, vol. xxiii. p. 181. 108 THE PHILOSOPHV OF MEDICAL SCIENCE. With the qualification thus stated, a qualifica- tion, as I have already said, more nominal than real, all our knowledge of the relations between diseases and their remedies, or modifiers, is solely and exclusively the result of direct observation. The very existence of any such relationship would be utterly unknown to us, had it not been re- vealed by experience. No a priori reasoning could ever have taught us the possibility, even, of arresting, or controlling, the pathological actions of the tissues and organs of the animal system. No conceivable process of logical deduction, un- aided by experience, could ever have indicated, or shadowed forth the fact, that the lips of an incised wound could be made to unite, by what is called adhesive inflammation, or that the pain of neural- gia could be relieved by opium. This doctrine seems to me to be so generally misapprehended, and it is, at the same time, so intimately connected with all practical medicine, that I wish to present it, as fully and as clearly as it is possible so to do, to the reader. With this end in view, let us proceed to examine it, some- what more in detail. In the chapter on the rela- tions between pathology and physiology, for rea- sons there stated, and for the purpose of illustrat- ing the true character of these relations, I referred, particularly, to the well known morbid process and condition, called acute inflammation. For the same reasons, and for the purpose of our pre- sent illustration, let us examine the true nature THERAPEUTICS NOT DEDUCIBLE FROM PATHOLOGY. 109 and character of the relationship, between this morbid process and condition, and those sub- stances, agents, and influences, which are endow- ed with the power of removing, modifying, or controlling it. Let us suppose, that our know- ledge of the phenomena of inflammation were such as it now is; and that our knowledge of all its relations, excepting those, which we are exam- ining, were such as it now is ; — is there anything in this knowledge, which could lead, in any way, independent of actual experience, to a knowledge of its relations to its remedies, or modifiers ? Is there any conceivable process of reasoning, by which the former knowledge could lead to the lat- ter ? Could we ever have deduced the therapeu- tical relations of inflammation from its pheno- mena, or from its relations to its causes ? In any rational, or intelligible sense, could the treatment of inflammation have been inferred from its pa- thology ? Is the therapeutics of inflammation founded upon its pathology ? Does the former flow from the latter ? Even if the phenomena of this morbid process, and its relations to its causes, had been much more simple than they are ; if it had never presented itself under different forms, in different organs and tissues, and under different circumstances, would this be the case ? Looking at the elevated temperature of an inflamed part, we might have been justified, perhaps, in the pro- bable supposition, or conjecture, that by the direct application of cold, we might be able to diminish, HO THE PHILOSOPHY OF MEDICAL SCIENCE. or to remove, the morbid heat; and, by this ac- tion upon one of the elements of this morbid pro- cess, to modify or to destroy the others, and so to mitigate the severity, to modify, or to remove, the disease. But this act of a priori reasoning would have consisted, merely, in a conjecture, or suppo- sition, more or less probable. Actual trial of the application itself could alone determine the real relationship between the proposed remedy and the disease. This trial might have shown, not merely that the supposed relationship did not ex- ist, but, on the contrary, that the true relationship was quite different from the supposed one. It might have shown, that the rational and a priori remedy, instead of diminishing the morbid heat, acted only to increase it; and further experience might have established the fact, that this morbid heat might, under many circumstances, be dimin- ished, or removed, by the application of warmth ; all which, I need hardly say, has actually hap- pened.1 Positive observation has ascertained, with a considerable degree of certainty, the rela- tions, which do exist between the phenomena of inflammation, and the more or less direct applica- tion of cold and of warmth to the seat of the dis- ease. These relations differ very widely, under different circumstances, varying with the seat, the 1 Mr. Lizars said, in 1819, "for ten years I have used, invaria- bly, hot, anodyne applications to every acute inflammatory disease, and have never found them fail, in either mitigating or arresting the disease." Edinburgh Medical and Surgical Journal, vol. x. p. 408. THERAPEUTICS NOT DEDUCIBLE FROM PATHOLOGY. HI character, the stage, and the complications of the inflammation ; and they are such as no method of reasoning, or induction, could ever have ascer- tained. Again, looking at the accumulation of blood in the tissue of an inflamed part, or organ, we might have been justified, perhaps, in the sup- position, or conjecture, that the removal of a por- tion of this accumulated fluid, from the part, or from its immediate neighborhood, would be fol- lowed by a mitigation of the severity of the dis- ease, or by some modification of its phenomena. But in this case, as in the other, the reasoning, if such it can be called, would have consisted merely in a supposition, or conjecture, more or less pro- bable, of the existence of a relationship, which observation alone could determine. This rela- tionship, like the other, observation has, in a good degree, determined; and like the other, also, it is found to differ very widely under different cir- cumstances ; varying with the seat, the character, the stage, and the complications of the inflamma- tion ; and such as no process of reasoning, inde- pendent of direct experience, could ever have ascertained. An examination of all the other therapeutical relationships of inflammation will render the prin- ciple, which I am endeavoring to illustrate, still clearer and more evident. There is not one amongst them, which could have been indicated, even, by any method of deductive reasoning. How could any such reasoning have ever led to the 112 THE PHILOSOPHY OF MEDICAL SCIENCE. conclusion, that the abstraction of blood from the general circulation would have diminished the intensity, or shortened the duration, or in any way changed the action of this local morbid process ? How could any such reasoning have led to a knowledge of the circumstances, in which this ab- straction of blood would be followed by beneficial results ? How could any such reasoning have led to a knowledge of the relationships, which exists be- tween inflammation, and the operation of calomel, antimony, and opium ? Could the effects of these substances have been deduced, or inferred, from any knowledge, however accurate, of the pheno- mena of inflammation ? Manifestly, and indisputa- bly, not. All these effects have been ascertained by simple and direct observation of the effects themselves. It is not possible, in the nature of things, that they could have been ascertained by any other method, or in any other way. There are certain pathological processes and conditions, one characteristic element of which consists in a distinct and well marked periodicity in their recurrence. These processes and condi- tions differ very widely from each other in many important particulars ; but they agree in this. The most common of these are intermittent fever, and periodical neuralgia. Perhaps there is no therapeutical relationship better established, than that which exists between these diseases, on the one hand, and cinchona and arsenic, on the other. These substances, when introduced into the sys- THERAPEUTICS NOT DEDUCIBLE FROM PATHOLOGY. H3 tern, are endowed with the power of arresting, or of modifying, the above-mentioned diseases. Is there anything in this periodical element of these diseases, which, by any process of deduction, could have led to a knowledge of its relationship to these substances ? Do these substances possess any other known property in common, excepting this of their relationship to these diseases ? There can be but one answer to all these questions. No attainable knowledge of the morbid element; no attainable knowledge of these substances, could have ever led, independent of experience, to a knowledge of the relation, which exists between them. Who could have anticipated, that the action of an emetic would relieve the difficult breathing of croup ? What rational connexion is there between syphilis and the preparations of mercury; or between scrofula and iodine ? It would be a very easy matter to multiply these questions, and to extend these illustrations. Every portion of pathology, and every corresponding portion of therapeutics, would furnish us with material. I hope, however, that I have gone far enough to show, clearly and conclusively, that all our knowledge of the connexion between morbid processes and conditions, on the one hand, and those substances, agents, and influences, which are endowed with the property of arresting, con- trolling, or in any way modifying these processes and conditions, on the other, is solely and exclu- sively the result of observation. Therapeutics is 15 114 THE PHILOSOPHY OF MEDICAL SCIENCE. f not founded upon pathology. The former cannot I be deduced from the latter. It rests wholly upon I experience. It is, absolutely and exclusively, an I empirical art. There is but one philosophical, or intelligible, indication; and that is to remove disease, to mitigate its severity, or to abridge its duration; and this indication never grows out of any a priori reasoning, but reposes solely upon the basis of experience.1 1 In the early numbers of the Edinburgh Medical and Surgical Journal, there was published a series of anonymous papers, under the title of The Inquirer. The subject of No. XVI. of these papers is contained in this question : — " Does a minute knowledge of anatomy contribute greatly to the discrimination and cure of diseases ? " The paper was suggested by the circumstance, that Dr. Beddoes, in a plan of medical education, addressed to Sir Joseph Banks, proposed that four out of six years should be devoted principally to anatomy! The whole article is compact and solid with the soundest philosophy. I quote from it the following remarks, which, although referring particularly to the supposed connexion between anatomy and thera- peutics, are still sufficiently applicable to the subject of the text to justify me in transferring them to my pages. " For our knowledge of the virtues of opium, and cinchona, of mercury, and antimony, we cannot be indebted to the dissecting knife. Observation and experience, grounded generally on accident in the outset, have been the sole foundation of our acquisitions respecting the nature of these our instruments, without which all our anatomical and physiological information were vain. It was not from anatomical considerations, that Sydenham was led to adopt the cool treatment in small pox, that Currie learned the advantages of cold affusion in fever, or that Rollo deduced the utility of animal diet in diabetes. In a word, the greatest anatomists have not been the greatest improvers of medicine, nor among the most eminent of its practitioners. On the contrary, the most distinguished physicians and acknowledged benefactors of the medical art, have not been remarkable for the cultivation of anatomy. Sydenham, Morton, Mead, Fothergill, Home, Huxham, Lind, Heberden, Pringle, were THERAPEUTICS NOT DEDUCIBLE FROM PHYSIOLOGY. H5 It follows, from what has been said in the fore- going pages, that the therapeutical action of the substances and agents of the materia medica is not to be inferred from their effects upon the body in a state of health. Their pathological relations not minute anatomists.....Let a man be the most correct and minute anatomist, if he have not long and laboriously attended to the appearances and the treatment of diseases, however plausibly he may reason on the processes and functions of life, and explain their interruptions and modifications, which constitute health and disease, his knowledge will be but the vain speculations of the theorist, he will be practically more ignorant than many an uneducated nurse in an hospital. Let us not mistake the plausibilities of physiological and pathological reasoning, for actual knowledge, for they have their epidemic periods of change ; nor let us believe that the curious part of our inquiries are always absolutely useful.....Can a physician be directed to prescribe blood-letting judiciously by a knowledge of the particular course of the arteries and veins? or to recommend with skill the administration of purgatives and emetics, by an acquaintance with the structure of the stomach and bowels? Would he not apply, with equal propriety and success, the stimulus of the aspersion of cold water, or the pungency of hartshorn, to a person in syncope, although he were ignorant of the nerves of the skin, or of the Schneiderian membrane1? Were pleurisies and peri- pneumonies more successfully treated, after the arteries and veins of the lungs were described, and their cells injected with quicksilver?" Edin. Med. and Surg. Jour. vol. v. p. 70, et seq. It seems difficult to account for the fact, that such seeds as these should have produced so little fruit, except that they have been choked by the tares of a false it priori, and miscalled rational philo- sophy. Why else have not such sentiments taken deeper hold of the British medical mind? In a letter to Dr. Jenner, dated May 14th, 1806, Thomas Jefferson says, — "Harvey's discovery of the circulation of blood was a beautiful addition to our knowledge of the ancient economy; but on a review of the practice of medicine before and since that epoch, I do not see any great amelioration which has been derived from that discovery." Baron's Life of Jenner, vol. ii. p. 95. 116 THE PHILOSOPHY OF MEDICAL SCIENCE. are not to be deduced from their physiological relations. After having ascertained, that the effect of tartrate of antimony, or ipecacuanha, taken into the stomach, is to excite vomiting, we might, to be sure, independent of experience, have been led to administer one of these articles, for the purpose of removing, from the stomach, by the act of vomiting, any poisonous, or irritating, sub- stance taken into it. So, in cases of disease, attended with long-continued vigilance, having ascertained the power of opium to produce sleep, in a healthy condition of the system, we might be led, by a priori reasoning, to the use of the same substance, for the purpose of overcoming the morbid wakefulness. But even in these, and in all analogous, instances, excepting, perhaps, where the action of the article is to remove the cause of disease, as in the case of offending matters in the stomach, just alluded to, or where the action of the article may be strictly chemical, or mechanical, it is only by actual experience, that we can ascer- tain the effects of the remedies upon the system laboring under disease. It does not necessarily follow, that because opium usually occasions sleep when taken into the healthy system, it will always remove the vigilance of disease. The philoso- phical reason of this is obvious. Therapeutics consists in the ascertained relations between the substances and agents of the materia medica, and morbid actions and conditions of the body; not between these substances and agents, and the THERAPEUTICS NOT DEDUCIBLE FROM PHYSIOLOGY. H7 healthy actions and conditions of the body. And the philosophical reason is sustained by experi- ence. There are many circumstances, in which the morbid wakefulness attending upon disease is not removed, nor mitigated, by opium, in whatever quantity it is administered. Look at delirium tremens. It is now very well settled, that opium has but little effect, in procuring sleep in this disease. And what a rebuke is contained in the action of this remedy, under these circumstances, upon our complacent a priori philosophy, and our boasted rationalism in therapeutics! By what method of what we are pleased to call rational induction, could it have been ascertained, that in a disease, strictly functional in its character, not attended with inflammation, and marked especially by nervous excitement and wakefulness, not only would opium be found to be nearly destitute of any power; but, further, that this substance might be given in enormous doses, without producing any perceptible effect, whatever, either upon the disease, or the system generally ? Is there any- thing in the physiological relationships of cinchona, that could have led, without the teachings of direct experience, to a knowledge of its pathological relationships ? Does it produce any effect upon the healthy system, which could have indicated, even, in the most indefinite manner, its power of arresting, or controlling, intermittent fever ? Calo- mel, when introduced in moderate quantity, into the system in a state of health, occasions severe 118 THE PHILOSOPHY OF MEDICAL SCIENCE. local inflammation, attended with general febrile excitement. Is there anything in this action of calomel, which indicates the power of the same substance to arrest and control extensive and intense local inflammation ? On the contrary, so far as mere a priori reasoning is concerned, would it not have been more philosophical to have con- cluded, that this new inflammation, with the gen- eral disturbance of the economy attending it, would tend to increase, rather than to diminish, the severity of the original disease ? The most that can be said in favor of the doctrine, the unsoundness of which I am endeavoring to show, is this ; — that, in a few instances, the therapeu- tical properties of the articles of the materia medica may be, to a certain limited extent, and with many qualifications, inferred from their actions on the healthy functions. But in these instances, the inference is only more or less probable ; and its correctness can be tested and ascertained only by the results of actual experi- ence. The inference is not to be relied upon any farther than as an indication of an experiment or trial; the only foundation of our therapeutical knowledge consists in the result of the experiment or trial itself.1 1 Sir Humphrey Davy says, in a letter to a young friend, — "I have heard of some experiments you have made on the action of digitalis, and other poisons, on yourself. I hope you will not indulge in trials of this kind. I cannot see any useful result that will arise from them. It is in slates of disease, and not of health, that they are ACTION OF REMEDIES ON ANIMALS. H9 Remarks similar to the above, and for similar reasons, may be made in regard to the effects of the articles of the materia medica upon animals. The action of these substances upon the human body, in a state of health, is not to be positively inferred from their action upon the bodies of other animals in a state of health. So far as the struc- ture and functions of the several organs and tis- sues of these animals resemble the structure and functions of the corresponding organs and tissues in man, the action of these substances must be the same. But, in many instances, there is more or less difference in the structure and functions of these corresponding organs; and just in propor- tion to the degree of this difference, will the rela- tions, between the organs and the substances of the materia medica, differ. It is perfectly well known, that some animals, high in the scale of organization, take, with impunity, into their sys- tems, substances that are fatal to the life of man. For reasons precisely similar to these, the thera- peutical action of substances upon the human body is not to be inferred from the therapeutical action of the same substances upon the bodies of other animals. So far as the morbid actions and conditions of the several organs and tissues, in these animals, resemble the morbid actions and conditions of the corresponding organs and tis- to be used ; and you may injure your constitution without gaining any important result." John Davy's Life of Sir H. Davy. Vol. i. p. 104. 120 THE PHILOSOPHY OF MEDICAL SCIENCE. sues in the human body, these therapeutical ac- tions must be the same, according to the great law of the invariableness of relationships, of which I have so often had occasion to speak. But, cer- tainly, in many instances, it may be in all in- stances, these morbid actions and conditions are not absolutely identical in their character; and just so far as they differ from each other in cha- racter, must they necessarily differ in their thera- peutical, as well as in their other, relationships. Each class of animals has its own structure ; is endowed with its own properties ; has been made subject to its own laws; is connected with all sur- rounding substances, and agents, by its own rela- tionships. This structure, these properties, these laws, these relationships, can be ascertained only by studying them in each separate class of ani- mals, to which they belong, and with which they are connected. It is as unsafe, as it is unphiloso- phical, to attempt to infer, or deduce, positively, and independent of experience, those which may exist in one class, from those which are found to exist in another. Analogy may indicate or sug- gest the direction in which our researches should be carried; it can do nothing more, neither here nor elsewhere ; and to this very humble process should its functions always be limited. CHAPTER IX. Diagnosis: its importance, and its relation to Therapeutics. Illustrations. Pleurisy; Typhoid Fever. The considerations, contained in the preceding chapter, lead directly and obviously to a distinct and clear conception of the nature, the import- ance, and the relations of diagnosis. Diagnosis is an art, depending upon a knowledge of patho- logy. Just in proportion as this knowledge is positive, accurate, and complete, is our diagnosis positive, accurate, and complete. The two are correlative conditions. The philosophical reason of the practical importance of diagnosis, is simply and manifestly this ; — it is the expression of one of the terms in every problem of cure ; — it constitutes what may be called one of the elements in every the- rapeutical operation, or analysis. It is the only term, the value of which it is difficult to ascertain; it is the great element, upon a full knowledge of which, the certainty of every therapeutical operation de- pends. Therapeutics consists in the relationships which exist between pathological actions and con- ditions, on the one hand, and the articles and agents of the materia medica, on the other. These relationships, like all others, are fixed and invariable. The properties of the articles and agents of the materia medica are easily ascer- tained. It is not from any difficulty in ascertain- 16 122 THE PHILOSOPHY OF MEDICAL SCIENCE. ing these properties, that the uncertainties of the- rapeutics arise. These uncertainties grow out of, and rest in, the imperfection of our diagnosis; the incompleteness of our knowledge of patho- logy. Just in proportion to the perfection and absoluteness of our diagnosis; just in proportion to the completeness of our pathological know- ledge, will be the certainty of our therapeutics. All practical medicine depends upon a knowledge of three things, to wit: pathology; the articles or agents of the materia medica; and the rela- tions between these two elements : and nearly all the difficulties, the obscurities, the uncertainties, the imperfections of practical medicine, grow out of the difficulties, the obscurities, the uncertain- ties, the imperfections of our pathological know- ledge, or, in other words, of our diagnosis. Let us endeavor to illustrate the doctrine thus stated. For this purpose, it is of very little importance what pathological conditions, or diseases, we make use of. Let us, in the first place, however, choose some one of these conditions, least obscure, and least complex, in its character ; and in this respect, there is no one that can answer our purpose better than acute pleurisy. There is no disease of an im- portant organ better known than this. There is none less complicated in its pathology, and in its re- lations ; there is none, the diagnosis of which, in its several stages, and in its different degrees of severi- ty, can be more clearly or positively made out. We can ascertain, with a great degree of accuracy, the DIAGNOSIS —ITS RELATION TO THERAPEUTICS. 123 seat and the extent of the inflammation. We can follow, with a considerable degree of positiveness, some of the most important changes, and pheno- mena, which accompany this inflammation. We know very well the condition of the lung, lined by the inflamed membrane, and compressed by the effused fluids; and we can measure, with a good degree of accuracy, the quantity of fibrine and of serum, deposited in the cavity of the pleura, and estimate the variations in this quantity during the different stages of the disease. This inflammation is not often complicated with other serious pathological conditions; and when these complications do exist, they are generally easily ascertained, and their importance easily appre- ciated. In short, the diagnosis of acute pleurisy, in all its elements, is very complete and positive ; and in exact correspondence to this complete- ness and positiveness is the accuracy of our know- ledge of its therapeutical relationships. A quart of blood, drawn in a given time, from the arm, will always, under the same circumstances, pro- duce precisely the same effects. Two grains of calomel, or half a grain of opium, or a quarter of a grain of tartrate of antimony and potassa, or the three substances in combination, introduced every three or six hours into the system, will al- ways, under the same circumstances, be followed by precisely the same results. All true and direct relationships are invariable. The circumstances of the system, in acute pleurisy, are susceptible of 124 THE PHILOSOPHY OF MEDICAL SCIENCE. more accurate estimate and appreciation, than they are in many other diseases ; and just in pro- portion to the accuracy of this estimate and ap- preciation, is the certainty of our knowledge of the therapeutics, or the treatment, of this disease. If our knowledge of these circumstances could be made perfect and absolute ; if it could be made as nearly so as our knowledge of the composition and properties of calomel, tartrate of antimony and potassa, and opium is, then our knowledge of the relations between these circumstances, on the one hand, and these substances, on the other, would become, also, perfect, and absolute. The imperfection of our knowledge of the relation- ships between these two elements — the disease, on the one hand, and the therapeutical agents, on the other — must grow out of, and depend upon, the imperfection of our knowledge of one of the elements themselves. And here, as everywhere else in practical medicine, this imperfection is in the knowledge of the disease ; not in that of the composition and properties of the remedies. This composition and these properties we are sure of; they are positive ; they are constant. We may be entirely certain, that the calomel, the tartrate of antimony and potassa, and the opium, which we administer in a case of pleurisy to day, are identical in composition and character with those which we administered in another case of the same disease yesterday. And if the two cases of disease were alike, the effects of the remedies DIAGNOSIS —ITS RELATION TO THERAPEUTICS. 125 must necessarily be the same. The difficulty, and the only difficulty, consists in ascertaining this identity, or the degree of similarity between the two cases of disease. But even in a disease so simple as acute pleurisy, occurring in a person otherwise in a state of entire apparent health, it is difficult, perhaps it would be nearer the truth to say impossible, to find two cases in all respects alike. The obvious and appreciable elements, which are united to constitute the disease, differ in many respects in different cases; and these ele- ments are also constantly changing, in themselves, and in their relations to each other. The state of the system, at the commencement of the disease — a state, or condition, which is the aggregate result and product of physiological and pathological ac- tions and relations, that have been going on, and have existed, ever since the life of the individual commenced — must also be widely different in different cases ; and in no two, probably, precisely alike. Then, in addition to all this, there are pe- culiarities in different individuals, less obvious in their character, of a more subtle and recondite nature, and known only by their effects, which would more or less powerfully modify the disease itself, apart from the differences already enumer- ated. For these reasons, even in that simple form of disease, which I am now speaking of, our di- agnosis, in all its elements and relations, can never be absolute and complete ; and for this sin- gle and simple reason, our therapeutics must par- 126 THE PHILOSOPHY OF MEDICAL SCIENCE. take of the same character of imperfection. The actual degree of certainty, to which our therapeu- tics is capable of being carried, and the real ex- tent and power of our remedies over disease, will be made the subject of a separate chapter. A few remarks, similar to the foregoing, in rela- tion to some morbid condition, or disease, of a mere complicated and obscure character, will be sufficient to answer the end of the present chapter. Let us take that disease, which is now generally known in this country by the name of typhoid fever, — the dothinenteritis of many French wri- ters, and the abdominal typhus of the Germans. The pathology of typhoid fever is very compli- cated. Nearly all the functions of the body are more or less seriously disturbed during the course of the disease ; and very extensive and numerous structural alterations are found, on examination, in fatal cases. In the present state of our know- ledge, the therapeutical relations of this disease are very imperfectly known. It is not yet ascertained, that any of the articles, or agents, of the materia medica are possessed of any considerable power over it. It may be, that there are no articles, or agents, in nature, endowed with this power, to any very positive or great extent. This is a ques- tion, which can be settled only by further observa- tion. But be this as it may, and on the supposi- tion, even, of the existence of these substances, endowed with this power, our ability to apply them with success will depend upon the accuracy and NOSOLOGICAL, OR SPECIAL, DIAGNOSIS. 127 positiveness of our knowledge of the disease. Every peculiarity in its pathology, in any given case; every variety in the combination and pro- portion of its numerous and complex elements ; every change in these elements, and in their rela- tive proportions, will necessarily change, in a cor- responding degree, the relations between the dis- ease and its therapeutical modifiers. CHAPTER X. Diagnosis, twofold : — Nosological and Therapeutical. Elements and means of nosological diagnosis. Diseases not to be required to be wholly unlike each other. Typlmktal fever and congestion common elements. Locality of disease. Nature, or character, of disease. Combination and succession of certain phenomena. Symptoms. Relative value of these several elements. Tendencies of modern researches. Therapeutical diagnosis. Diagnosis is twofold, to wit, nosological, and therapeutical. It is the object of this chapter to point out the character of each of these kinds of diagnosis, and the differences between them. No- sological diagnosis is that to which this term is usually applied; to which, indeed, it is generally confined. Considered as a science, it consists in the individuality of each separate morbid process, or series of processes; or of each separate morbid condition ; considered as an art, it consists in the power and the act of distinguishing between these several individual processes, or conditions. The 128 THE PHILOSOPHY OF MEDICAL SCIENCE. number of these separate processes, or conditions, thus distinguished, and individualized, is the num- ber of separate diseases, to which the human body is subject: their classification, or arrangement, according to their differences and resemblances, constitutes systematic or methodical nosology : — the names, which are applied to them, constitute medical nomenclature. The elements of all diagnosis are to be found exclusively in pathology and its relations. The opinions of medical men have always been, to a great extent, confused, indefinite, and contra- dictory, in regard to the true principles of nosolo- gical diagnosis. I am not speaking now of the nosological arrangement of diseases ; this subject will be more fully considered in another place. I mean, that there has been no general agreement amongst medical men, in regard to the true prin- ciples, and the philosophical foundation, of noso- logical diagnosis. There has been no common and clear recognition of these principles. Nosolo- gists, and other systematic writers, have differed very widely amongst themselves in regard to what should and what should not constitute a separate disease. Many of them have elevated to this im- portant position a large number of comparatively trifling symptoms, merely, even of a single disease: others have confounded, under the same name, diseases essentially dissimilar. It may be very true, that these differences of opinion are, to a certain extent, unavoidable; that they grow out of diffi- NOSOLOGICAL DIAGNOSIS-ITS TRUE GROUNDS, ETC. 129 culties inseparable from the subject with which they are connected. Many diseases are so com- plicated in their pathology; they are so frequently constituted, in part, by processes and conditions, which enter largely into other related, but dissimilar, diseases; these diseases approach and touch each other in so many respects, and at so many points, that it may not be possible, always, in the present state of our knowledge, to fix upon positive means, and to lay down positive rules, for distinguishing between them. Let, us endeavor, however, to do this, as far as the actual state of science, and a correct view of the subject, will enable us. Let us endeavor to ascertain the true character; to enumerate and to appreciate the legitimate means and elements of nosological diagnosis; to see, as far as is possible, in what the identity and dissimi- larity of individual diseases consist. Before proceeding to do this, and as a prelim- inary step to our endeavor, let us notice one con- dition, or circumstance, of a negative character,— or which, in other words, ought not to be recog- nized and admitted as an element of diagnosis. I mean, that diseases must not be required to be utterly and in all respects, unlike each other, in order to constitute them distinct, individual spe- cies. There are several very important morbid conditions, which are common to a large number of separate diseases; a circumstance which neces- sarily deprives these conditions of any considera- ble degree of diagnostic value. This is especially 17 130 THE PHILOSOPHY OF MEDICAL SCIENCE. the case with that series of morbid actions, which we call fever. This term is strictly generic, and it ought always to be so used. The associated phenomena, to which this term is applied, cannot, with any propriety, be said to constitute a specific, or individual, disease ; they enter as elements merely into the composition of a great number of separate and widely dissimilar diseases. Inflam- mation of the pia mater; inflammation of the kidneys; inflammation of the pericardium, — are all alike attended by fever; and there is nothing, whatever, in the character of this latter element which distinguishes one of these diseases from the rest. The fever, then, is strictly common to them; and so far as their diagnosis, amongst themselves, is concerned, is of no value. Furthermore, this morbid condition, which we call fever, may be marked by certain very prominent and striking peculiarities, and still remain of very trifling im- portance as an element, or means, of specific diagnosis. There is one form of fever, which is called inflammatory: it usually accompanies acute inflammations of an open, frank, or sthenic character; and is marked by a strong, hard pulse, moderately hot skin, thirst, a moist, whitish tongue, and no very striking degree of muscular debility. This form, as has already been said, is present in many separate diseases. There is another form of fever, to which the terms typhoid, or adynamic, or asthenic, have been applied, and which differs in many respects from the former. NOSOLOGICAL DIAGNOSIS-ITS TRUE GROUNDS, ETC. 131 Now what I wish to say is this, —that the presence, in fever, even of these strongly marked peculiari- ties, still fails to impart to the fever any considera- ble value in nosological diagnosis. The inflam- matory, or sthenic, form of this morbid condition attends many dissimilar diseases; and the same thing is true of the typhoid, or asthenic, form. The latter is usually present in the diseases, which have received the names of typhoid and typhus fevers; and it also very frequently accompanies small pox, scarlatina, some forms of pneumonia, and other local affections. This typhoid element, thus common to many diseases, unlike each other in several or in all other circumstances, cannot, certainly, be regarded as an element of great or primary importance in diagnosis. The diagnosis of these several diseases, thus marked by the presence of this common condition, must rest upon other circumstances peculiar to each. Remarks, in every respect similar to the fore- going, may be made in regard to that obscure, but most grave, morbid condition, to which the term congestion has been applied. This condition, marked especially, by great disturbances, or rather by an entire loss, of what may very properly be called the balance of the circulation, and by pro- found but unknown modifications of innervation, is frequently witnessed at the onset, or in the early stages, of diseases; while the typhoidal form of fever more commonly shows itself, during their progress, or in their later periods. The former 132 THE PHILOSOPHY OF MEDICAL SCIENCE. morbid condition, like the latter, may be present in many dissimilar diseases, and cannot, for this reason, be relied upon as a means, or instrument, of diagnosis. It accompanies Asiatic cholera, ma- lignant intermittent and remittent fevers, the grave forms of scarlatina, yellow fever, plague, and so on; so that the diagnosis of these diseases, and of others, under similar circumstances, must depend, not upon this common element, but upon others, with which it is associated. The foregoing con- siderations are sufficient, — although many others of a similar character might be added to them, if it were necessary, — to show, that different dis- eases may possess certain very prominent and important elements in common, without hindering, in any degree, their separation into perfectly dis- tinct, individual species. They may also agree, in many respects; in regard to their causes ; their march, and duration ; their relations to remedial measures; and in other respects, and still be sus- ceptible of clear and positive diagnostic distinction. It is quite evident, then, that diseases must not be required to be wholly and in all things unlike each other, in order to constitute them distinct species. The positive elements of nosological or specific diagnosis are quite numerous; and they vary very widely in their number and character, in different diseases. They are to be found, as in the case of plants and animals, in all the phenomena and relationships, which unite to make up the natural NOSOLOGICAL DIAGNOSIS —ITS TRUE GROUNDS, ETC. 133 history of diseases. In some cases, they are few, simple, and absolute ; in others, they are numerous, complicated, and less positive in their character. They may be found in the seat, or locality, of dis- ease ; in the nature, or peculiarity, of the essential lesion in which it consists ; in certain symptoms or combinations of symptoms ; in its relations to its causes and its modifiers; or in several, or all, of these circumstances, variously united. One of the most common divisions of diseases; one that has been almost universally recognized, is that which separates them into two classes ; — those which are local, and those which are general. This division, let me observe, cannot be regarded as absolute. Some diseases are much more cir- cumscribed in their extent, and much more limited in their actions and influences, than others ; there is a very wide and manifest difference in this respect; but, still, it is not easy to show, that any disease is absolutely local, on the one hand, or absolutely general, on the other. In the simplest cases of local disease, there may be more or less complexity of pathological action ; in those diseases, which are regarded as most general in their character, there are tissues and functions of the body, which, so far as we have means of as- certaining, are in a healthy condition. But, not- withstanding all this, the anatomical locality, or situation, of many diseases constitutes one of the chief, and fundamental elements in their nosologi- cal diagnosis. There are many diseases, the pri- 134 THE PHILOSOPHY OF MEDICAL SCIENCE. mary and essential seat of which is in certain organs, or tissues, of the body; in which their processes are carried on, and to which they are mostly confined. This circumstance is, of itself, and independent of other circumstances, sufficient to settle, so far as it goes, the nosological diagno- sis of certain diseases. If these diseases agree in all other circumstances, but differ in this, of their anatomical locality, they are different, and dissim- ilar, diseases. This circumstance alone establishes their nosological diagnosis, and fixes one element, at least, of their nomenclature. Inflammation of the kidney is not the same as inflammation of the liver; hemorrhage from the vessels of the brain constitutes one disease, hemorrhage from those of the lungs constitutes another ; dropsy of the peri- cardium is not the same disease as ascites. This locality may have reference to an entire organ, or to the anatomical elements, or tissues, which enter into the composition of the organ. Thus, inflam- mation of the internal lining membrane of the heart constitutes one disease, and inflammation of the external lining membrane constitutes another. This is one of the simplest and most positive ele- ments of diagnosis, in all cases where the locality, and the primary character, of the disease are suffi- ciently manifest and certain. There are other cases, in which the localization of a morbid pro- cess in any given organ, or tissue, may constitute only a secondary means of diagnosis, or in which it may be rejected almost entirely. This will hap- DIAGNOSIS —ITS GROUNDS AND PRINCIPLES. 135 pen where the peculiar nature and tendencies of the morbid process constitute its fundamental and most important element; and where its seat, or locality, is of secondary or accidental value. Thus we may have tubercle, or cancer, constituting, each an individual, and identical disease, in whatever organ, or organs, of the body, it may be mostly, or exclusively, situated. In the second place, we find an important ele- ment of nosological diagnosis in certain charac- teristics of disease, independent of its anatomical locality. The same organ, or tissue, may become the seat of morbid processes, and conditions, dif- fering, so far as their phenomena and relations enable us to judge, essentially from each other. These differences may be radical and absolute, in the nature of the morbid process itself; or they may depend upon the combination and the rela- tions of different morbid actions in the different elementary tissues of the organ, or part, which is the seat of disease. Thus, there may be many distinct and separate diseases in the same organ or tissue. The kidneys, for instance, like most other parts of the body, are subject to acute inflammation, constituting a well-marked, distinct, individual disease, characterized by its own appro- priate phenomena ; and called, in classical nomen- clature, nephritis. Again, the same organs are subject to another morbid process, the results of which show themselves, locally, in a great aug- mentation in the quantity, and in certain striking 136 THE PHILOSOPHY OF MEDICAL SCIENCE. alterations in the quality, of the peculiar secretion of these organs ; which changes are also attended with other pathological conditions of a more gen- eral character, constituting all together another distinct, well-marked, individual disease, to which we give the name diabetes. Once more, the same organs are subject to still another morbid process, characterized by its own peculiar phe- nomena, both local and general; differing from either of those already mentioned ; and constitu- ting a third distinct, well-marked, individual dis- ease, which is called albuminuria, or BrigWs disease. Softening of the cerebral substance constitutes one disease ; an extravasation of blood into it, another. In the third place, a very important element of systematic diagnosis is to be found, not so much in the principal locality, or the peculiar nature, or character, of the disease, as in a certain combina- tion, and succession of morbid processes and con- ditions. Many of the diseases, belonging to this class, possess certain features, more or less promi- nent or striking, in common, which give them a family resemblance ; but each individual member of the group, or family, to which it belongs, is marked by certain traits, or by some peculiar com- bination of features, which distinguishes it from the others to which it is allied. The character and value of the diagnostic element of which I am now speaking, may be very clearly shown by a reference to the exanthematous fevers. The NOSOLOGICAL DIAGNOSIS- ITS TRUE GROUNDS, ETC. 137 most common, and the most important, of these are, small pox, scarlet fever, and measles. What are our means of distinguishing, nosologically, between these several diseases ? In what are the elements of our diagnosis to be found ? Not in any anatomical locality of either of the diseases ; not in any ascertained peculiarity in the nature, or character, of the morbid processes, or condi- tions, in which they consist. In each of these diseases, our diagnosis depends upon, and consists in, a certain combination and succession, or series, of morbid processes and conditions, characteristic of the individual disease in which they occur. In small pox, these diagnostic elements are to be found, principally, in a series of morbid processes, which take place in the skin. This series of processes is not found in any other disease. Ifc consists in an eruption of a we)l defined, and peculiar character, commencing at a definite pe- riod after the occurrence of other morbid phe- nomena, and going through a regular succession of changes. This eruption, thus constituting the fundamental element of specific diagnosis, is asso- ciated, as has just been intimated, with certain other phenomena, more or less characteristic of this particular disease. Amongst these, are the specific nature of its cause, the determinate dura- tion of the several stages, or periods, of the disease, and its peculiar relations to another allied affec- tion, — the cow pox. The diagnosis of small pox consists in the presence of all these associated 18 138 THE PHILOSOPHY OF MEDICAL SCIENCE. phenomena, and in their more or less regular suc- cession and development. Similar principles of diagnosis are applicable to all the exanthemata, — to the several forms of periodical, and continued, fever, to plague, and to some other diseases. In all these cases, we rely, for our diagnosis, upon the combination and succession of certain phe- nomena, more or less numerous and characteristic, and differing from each other in the several indi- vidual diseases. There is another class of diseases, the positive, diagnostic elements of which consist entirely, or nearly so, in certain symptoms, — the nature of the diseases, and in many cases their causes, also, being wholly unknown. Amongst these, may be mentioned, as types of the class, epilepsy, teta- nus, chorea, hydrophobia, and delirium tremens. Each of these diseases is distinguished from the rest of the same family, and for still stronger rea- sons, from all other diseases, by certain peculiar and characteristic symptoms, and by these alone, or in connexion, as in the case of the two last- named affections, with their specific causes. The elements of diagnosis, which have been thus indicated, must be definite, fixed, and con- stant, — each single element, or combination of elements, constituting the diagnostic marks of a given, individual disease, not being interchangeable with those of any other individual disease. Sepa- rate and distinct diseases may exist together in the system; and in consequence of this coexist- NOSOLOGICAL DIAGNOSIS - ITS TRUE GROUNDS, ETC. JS9 ence, they may be somewhat modified in their character, and manifestations; but they cannot properly be considered as convertible into each other. They may approach each other very closely, or become quite identical, so far as their analogous or common elements are concerned; but their diagnostic conditions must not be subject to this mutual conversion, or blending together. The exact value of these several conditions, or elements, — actual and relative, — is a matter, not susceptible, perhaps, of very positive deter- mination ; but I will venture to remark, that amongst those, which are most absolute and dis- tinctive, is the seat of local diseases, and the presence, in those of a more general character, of some obvious, and peculiar anatomical lesion, like that of tubercle, and cancer, the pustular cutaneous eruption in small pox, and the follicular ulceration of the intestines in typhoid fever. Such I believe to be the fundamental and true principles of nosological diagnosis ; by the appli- cation of which, the individuality of all diseases, and their character, as distinct species, are to be determined. It is important to observe here, that our ability to apply these principles successfully has nothing, whatever, to do with the soundness of the principles themselves. This ability will depend upon the knowledge, the sagacity, and the skill of the individual observer. The exist- ence of individual diseases is one thing; the power of ascertaining this existence is another: — 140 THE PHILOSOPHY OF MEDICAL SCIENCE. the former is not dependent upon the latter. It is only within a few years, that we have been furnished with means of distinguishing, with clearness and certainty, between pleurisy and pneumonia; but these two diseases have always been as distinct from each other as they now are. Besides this, it should never be forgotten, that almost all diseases are occasionally so impressed and modified, by inappreciable or unknown influ- ences, that their usual diagnostic signs are want- ing, or very much obscured, — the diseases being latent, as it is called. Cancerous disorganization of the stomach, in some instances, gives no indi- cation of its existence, sufficiently distinct to render its detection possible, during life, even by the most competent and careful observers: and the same thing is true in the case of most other diseases.1 1 In my History of Typhoid and Typhus Fevers, after stating that there are few general diseases, susceptible of a more certain and positive diagnosis, than the former, I added the admission, that cases might sometimes occur, so enveloped in obscurity, as to baffle the skill of the most careful and experienced observers, — that the dis- ease might occasionally be so nearly latent, or so poorly defined, as to be overlooked or mistaken. In a somewhat ungracious review of my book, in the Edinburgh Medical and Surgical Journal, this admis- sion of the difficulty, or impossibility, in a few exceptional cases, of distinguishing typhoid fever from other diseases, and especially from its allied affection,—typhus fever,—is gravely cited as sufficient proof, that the two diseases, — typhoid and typhus fever, — cannot be distinct species! Let me add here, that this question, of the essential likeness, or unlikeness, of these two diseases, —one of the most important and interesting questions of specific diagnosis, that has ever occupied the attention of physicians, — if submitted to the NOSOLOGICAL DIAGNOSIS —ITS TRUE GROUNDS, ETC. 141 Let me add, in conclusion, that the tendency and result of that accurate, minute, and compre- hensive study of disease, which distinguishes the school of modern medical observation, and which marks the advent of a new era in our science, have been altogether and uniformly in favor of a nicer and more positive discrimination between diseases, than has heretofore existed. The oppo- site tendency, especially in Great Britain and in this country, has been principally owing to the vi- cious spirit — so generally prevalent, and so po- tent in its influences — of gratuitous and unwar- rantable generalization ; — a spirit which gave birth to the preposterous dogma of the absolute unity of all disease, and which led Dr. Armstrong, Dr. Boott, and many others, equally distinguished for learning and ability, to advocate the doctrine test of the principles which I have laid down, and fairly tried by them, — cannot fail, I think, to be settled in favor of the doctrine of their fundamental dissimilarity. The two diseases will be found to approach each other, very closely, in the possession of those morbid processes and phenomena, —I mean general fever of the typhoidal type, certain changes in the composition and quality of the blood, and certain nervous symptoms, — which are common to many dis- eases, and, for this reason, of but small value as diagnostic or dis- tinctive characters ; while they are separated clearly and broadly from each other, by the presence in one, and the absence from the other, of very strongly marked and constant anatomical lesions, and of groups of symptoms, equally striking, constant and characteristic. Any principles of diagnosis, or any rules of reasoning, that make true typhus fever, and typhoid fever essentially one specific disease, will make small pox and oriental plague, also, nothing but varieties, or modifications, of the same single disease. This result will be found to be absolutely unavoidable. 142 THE PHILOSOPHY OF MEDICAL SCIENCE. of the essential, specific identity of all the various kinds of continued and periodical fever — of ty- phus, of typhoid, of intermittent, bilious remit- tent, congestive, and yellow fever. It can hardly be owing to anything else, than the influence of this disposition, that the great majority of British physicians of the present day refuse to admit, or to endeavor to ascertain, even, by a thorough and impartial investigation of the subject, the true distinction between the two great forms of con- tinued fever — a distinction that was clearly re- cognized by such men, amongst their illustrious predecessors, as Huxham, Darwin, and Pringle.1 1 The opinion of Huxham upon this subject has often been quoted, and is well known. Those of Darwin, Dr. Vaughan, and Sir John Pringle, are probably less familiar to most of those who may be my readers; and I cannot forbear citing the authority of these English observers of the last century, in support of the views stated in the preceding note. In a letter from Dr. Darwin to Dr. Lettsom, dated Derby, October 8th, 1787, there is the following pas- sage : — " If your society proposes questions, I should wish to offer for one, 'Whether the nervous fever of Huxham, —or fever with debility, without petechia? or sore throat, or flushed countenance, or pungent heat, —be the same as petechial fever, or jail fever? ' The former of these, viz., the nervous fever of Huxham, prevails much over all the country at this time." Life and Correspondence of Dr. Lettsom, vol. iii. p. 118. Dr. Vaughan, of Leicester, in a letter to Dr. Lettsom, dated July 27th, 1783, in reference to the same subject, says : —" There is surely a peculiarity in the species of fever you had the goodness to send me an account of, protracting itself to such a length as thirty- five or forty days ; it certainly agrees very much with Huxham's Febris Nervosa, which, notwithstanding Dr. Cullen, is a very differ- ent disease to the Febris Carcerum, in its attack, progress, termination, and cure:' Ibid. vol. iii. p. 161. THERAPEUTICAL DIAGNOSIS. 143 I mean, by what I have chosen to call thera- peutical diagnosis, the distinction between indi- vidual diseases, or morbid conditions, depending The testimony of Sir John Pringle to this point is much fuller. "In the description," (Observations on the Diseases of the Army, Phil. Ed. p. 298,) he says, " I have endeavored to distinguish them" —malignant or pestilential fevers — " from all others, as far as I could do it, in distempers whose symptoms are so much alike. The nervous fevers are frequently accompanied with miliary erup- tions, which have no resemblance to the petechia; nor have I ever happened to see miliary eruptions in the malignant kind." In reply to some strictures of De Haen, (Ibid. p. 384,) he says, still more explicitly : — "I have never considered the jail or hospital fever, and the miliary fever " — meaning the low, nervous — "as similar ; and, indeed, I may venture to say, that, as the symptoms of the two are so much unlike, they ought to be treated as different in specie; and, consequently, that neither the theory nor the practice in the one ought to be regulated by analogy from the other." Again, he says : — "I have therefore all along considered the jail, or hos- pital fever — in regard to others that commonly occur in these parts — as a fever sui generis, at least as different from either the scar- let, the miliary, or any other eruptive fevers, which are known." Ibid. 385. The strictures alluded to above, by De Haen, had reference, par- ticularly, to the treatment of fever by Huxham and Pringle. De Haen charged these glorious old British observers — the types and ornaments of a school never since surpassed by their countrymen — with bad practice; with a too stimulating and incendiary method in the management of fever. Pringle, in his reply to De Haen, says expressly, that the fever treated by the latter at Vienna was of a different kind from that treated by himself; and in a note to this reply, he makes the following very interesting remarks, in regard to the dissimilarity of the cutaneous eruptions in the two diseases. " After publishing what is above, relating to the distinction, which I conceived was to be made between De Haen's petechial and mine, I was confirmed in my opinion by Dr. Huck, who, in the year 1763, was at Vienna, and was favored with admittance into all the hospi- tals there, and in particular had the satisfaction of attending Dr. De Haen himself, and seeing, with that celebrated physician, some of 144 THE PHILOSOPHY OF MEDICAL SCIENCE. upon the relations of these to the articles and agencies of the materia medica. Nosological diag- nosis constitutes one of the elements of therapeu- his patients in that very fever, which he calls petechial. Dr. Huck examined those spots in Dr. De Haen's presence, and assured me, that they had hardly any resemblance to those which I have called petechial, and which he himself had so often seen in the hospitals of the army ; but that they were so like flea-bites, that he was apt to believe, that one must be often mistaken for the other." (Observations on the Diseases of the Army, p. 384.) Let me say here, that I do not know anything in the annals of medical polemics, imbued with a finer temper, or a more philosophical spirit, than this reply of Pringle to De Haen. It is every way equal — and there can be no higher praise than this — to Louis's defences against the attacks of Broussais and Bouillaud. In place, or out of place, I cannot forego the pleasure of gracing a page of my book with the following passages — truly, words of wisdom, " fitly spoken — like apples of gold in pictures of silver " —from the reply of Prin- gle : " In fine, Dr. De Haen may be assured, that the regimen, which I propose, stood at first on no other foundation than expe- rience, after my having seen the bad effects of a contrary method, whether by too large or too frequent bleedings in the beginning ; or by giving hot things too early, in order to raise the pulse, when it began to sink, or to force a crisis before the common period of the disease. Some of the medicines are superfluous, but I am pretty sure, that none of them are hurtful.....But having once got into a method, which brought about as many cures as seemed otherwise consistent with the circumstances of my patients, lying in a foul air, amidst a constant noise, and often neglected by the nurses, I did not attempt to reduce my practice to more simplicity, than what is mentioned. Yet whatever confidence I may have in the directions, which I have published, I am still ready to alter any part of them, upon a fair representation from those, who have had equal opportunities with myself of seeing and treating this fever. But to oppose either mere theory, or analogy from other fevers, where the similarity is so disputable; or to oppose some general maxims from Hippocrates or Sydenham to the observations, which I have offered, as the result of a long and painful experience in a distemper, that no physician could well know but in such circumstances as mine, is THERAPEUTICAL DIAGNOSIS. 145 tical diagnosis, but the latter includes, also, many other elements in addition to this. The first con- dition of therapeutical diagnosis is a knowledge of the individual disease ; but many other, and frequently much more important, conditions of this diagnosis, are to be found in other circum- stances. Amongst these may be mentioned, for the purpose of illustrating my meaning, the fol- lowing, to wit; —the extent, and severity, of the individual disease — its period—in many cases, its occurrence in a sporadic or an epidemic form — the age of the patient — and the general con- dition of the patient previous to the attack of the individual disease. These circumstances do not enter into our nosological diagnosis; but they fre- quently constitute altogether the most important elements in the therapeutical relationships of dis- ease. The nosological diagnosis of acute pneu- monitis, confined to the lower portion of a single luno-, does not differ from that of the same dis- ease, involving the whole of one lung, and half of the other; but this difference in the extent of the disease will affect very essentially its therapeutical relationships, and the diagnosis depending upon these. And the same thing is true of the other circumstances, which have just been enumerated __the period of the disease — its sporadic or epi- demic form — the age of the patient — his condi- a manner of writing, I must say, more fitted for disputations in a school of medicine, than for the instruction of a practical physician." Observations on the Diseases of the Army, p. 395. 19 146 THE PHILOSOPHY OF MEDICAL SCIENCE. tion at the time of the attack, and so on. Each of these circumstances has an important bearing upon the therapeutical relationships of disease ; and the latter will be influenced by every modifi- cation in the former. The paramount importance, in practical medi- cine, of as complete and positive a knowledge, as is attainable, of all the circumstances, which can influence diseases, so far as the effects of reme- dies upon them is concerned, is so obvious, that I need not insist upon it. This knowledge is, in- deed, in many cases more absolutely essential to the safe and proper management of disease, than nosological diagnosis itself. CHAPTER XI. PROPOSITION THIRD. AN AliSOUTi: LAW, OR PRINCIPLE, OF MEDICAL SCIENCE CONSISTS IN AN ABSOLUTE AND RIGOROUS GENERALIZATION OF SOME OF THE FACTS, PHENOMENA, EVENTS, OR RELATIONSHIPS, BY THE SUM OF WHICH, THE SCIENCE IS CONSTITUTED. THE ACTUAL, ASCERTAINABLE LAWS, OR PRINCIPLES, OF MEDICAL SCIENCE, ARE, FOR THE MOST PART, NOT ABSOLUTE, BUT AP- PROXIMATIVE. The character and conditions of principles in medical science. These princi- ples approximative, and not absolute. This approximative character fixed and determinate. Its degree of fluctuation confined within certain limits. Illustrations. Proportion of sexes at birth. Law of great numbers. Cal- culation of probabilities. Laws or principles of therapeutics; their com- plexity ; difficulty of ascertaining them. Gavarret. Conditions of these laws. Facts must be comparable. True value of therapeutical experience. Mistaken notions. The constituent elements of a law, or principle, in the science of life, do not differ from those of a law, or principle, in physical science. I mean by this, that in the former case, as truly as in the latter, the law consists in the constancy of a phenomenon, or the invariableness of a relation- ship ; or in the nearest possible approximation to this constancy and invariableness, and in nothing else. The law, or principle, is not an element lying back of the phenomena and their relation- 148 THE PHILOSOPHY OF MEDICAL SCIENCE. ships, or interposed between them, or superadded to them, by any act of the reason : — it consists in the phenomena and their relationships, and is identi- cal with them;—it is the expression, merely, of these phenomena and relationships, generalized and classified. But, notwithstanding this essential agreement in the nature and composition of these two classes of laws, there is one fundamental difference be- tween them, which it is necessary fully and clearly to exhibit. With certain limited exceptions, the laws of physical science are positive and absolute, both in their aggregate, and in their elements, — in their sum, and in their details; but the ascer- tainable laws of the science of life are approxima- tive only, and not absolute. This difference I have called fundamental; it runs through almost the entire science of life, and impresses upon its phenomena, and its laws, peculiarities, which require to be fully developed, and thoroughly understood. To aid the reader in the accomplish- ment of this desirable object, — to point out and illustrate the true character of these laws,—the conditions of their legitimacy and their value, and the true methods of arriving at them, — is the object of the present chapter. I have already said, that in physical science, all genuine and direct relationships are invariable. This is as true in the science of life as in physical science ; but there is this great difference in the two cases. In the latter, these relationships are, PRINCIPLES AND LAWS. 149 for the most part, susceptible of such analysis, and separation from each other, as to be ascertainable in their singleness and simplicity ; in the former, they are, almost universally, so numerous, and complicated, so involved and so intricate, as to defy all such analysis and isolation ; and it is this circumstance that gives to the laws of the science of life the peculiar character of Avhich I am speak- ing. The sum of the phenomena and relation- ships, in any and in every given instance, is not positive and constant, but contingent and variable. This character and peculiarity of the elements of the law are, of course, extended to the law itself; rendering it, as I have said, approximative only, and not absolute. But this contingency, or variableness, is not indefinite and unbounded; it is confined within certain limits : and these limits are susceptible of very accurate measurement. Within these limits, the law becomes absolute ; their extent determines the degree of its possible fluctuation, or variable- ness. It is to the existence of this appreciable and ascertainable limitation, that we are indebted for the comparable character of the facts, and relationships, which constitute the elements, or materials, of our laws. These facts and relation- ships are not identical, one with another, but their resemblances are sufficiently fixed to render them available as positive data, in the prosecution of our researches. For instance, one important series of these facts, and relationships, is consti- 150 THE PHILOSOPHY OF MEDICAL SCIENCE. tuted by individual life, — or the sum of the organ- ization and its functions, with their relations, in the individual. Now, although this sum, or aggre- gate, of phenomena and relationships, constituting one individual, is never absolutely equivalent to the similar sum, or aggregate, constituting any other individual, still the difference between them never surpasses certain determinate limits; the resem- blances between them are sufficiently constant and fixed to render them comparable elements, and to give them a character sufficiently definite, to consti- tute them legitimate data for scientific comparison and study. Thus, the continuance of the functions constituting life, in the several classes of vegetable and of animal being, although contingent and va- riable, in each individual; and not susceptible, in any given instance, of being certainly known, in advance, never exceeds certain limits; and its average period, for each species, is ascertainable with great accuracy. The distribution of births between the two sexes constitutes a law of physi- ology of very great positiveness and uniformity, the individual elements of which are altogether contingent and uncertain; and the positiveness of the law depends upon the fact, that this contin- gency is strictly confined within certain limits. The same thing may be said of the number of births to each permanent union of the sexes by marriage. This number, in any given instance, is entirely uncertain ; but the uncertainty is always limited in degree, so that each single fact, consti- PRINCIPLES IN MEDICAL SCIENCE. 151 tuted by this variable number, is still sufficiently fixed and definite, to render it subject to compari- son with other similar facts, and so to convert it into a legitimate element of a law of the science of life. Similar remarks may be made in regard to the phenomena and relationships of pathology. Every law, or principle, of pathology consists solely in a generalization of certain phenomena, or relation- ships. These phenomena and relationships, in each individual of a class or series, constitute a sum or aggregate of uncertain and variable quan- tity ; and the law, which results from their general- ization, must partake, in some degree, of this character. But the degree of this variableness, both in the individual sum, or aggregate, and in the whole of these, classified and arranged, con- stituting the law, or principle, is confined within certain limits, susceptible of being ascertained and measured. This limitation gives to the indi- vidual facts a character sufficiently fixed and determinate, to render them susceptible of being compared with each other, and so to convert thern into legitimate elements, or constituents, of a law. Were it not for this circumstance, there could be no such thing as science in pathology. There is, for instance, a certain number of phe- nomena and relationships, the sum of which con- stitutes a disease, to which we give the name of pleurisy. This sum or aggregate is not absolute, and uniform, but contingent, and variable. No 152 THE PHILOSOPHY OF MEDICAL SCIENCE. one of these aggregates, constituting the disease, is ever exactly equivalent to another; no two cases of pleurisy are ever precisely identical. Still, the differences between them are not unlim- ited and indefinite ; they are always confined within certain degrees. The resemblances between these individual aggregates are sufficiently fixed and positive, to render them determinate and compara- ble facts; capable of being used as data, and dealt with in our researches and generalizations, subject to the qualifications already made, as we deal with the data of physical science. The same thing is true of all the other groups of morbid phenomena and relationships, constituting the va- rious individual diseases of the nosology. The sum of these phenomena is more variable and fluctua- ting in some groups, than in others; our know- ledge of these phenomena is more accurate and extensive in some groups, than in others; but the degree of fluctuation is always confined within certain limits, which are susceptible of determinate measurement. . Let us now endeavor to see by ivhat method, these individual facts, phenomena, and relation- ships, can be generalized, so as to constitute the laws or principles of the science of life. Let us see how rigorous and positive this generalization of contingent and variable, but still comparable, facts, can be made, — by what process it is to be accomplished, — and what the conditions are, to which it is subject. I have spoken of the law of PRINCIPLES, OR LAWS —WHAT THEY ARE. 153 the distribution of births between the two sexes. What is this law ? and how is it ascertained ? Certainly, nothing can be more doubtful or con- tingent, in any single instance, than the birth of a male or a female child. One event is almost as likely to happen as the other. And even where the number of births is considerably increased, the relative proportion of the sexes is a matter of very great uncertainty. Large families of children are sometimes born of the same parents, consist- ing exclusively of either one sex or the other; and very frequently the proportion between them is utterly unequal; so that the whole matter might seem to be one of unlimited chance and uncer- tainty. During the first three months of 1843, the whole number of children born in the obstet- rical department of the Philadelphia Dispensary was forty-five : of these, twenty-nine were males, and only sixteen, females; the difference in favor of males being almost equal to the proportion of two to one. But as we extend our investigation, we shall find this difference gradually diminishing, until, at length, the true law of this proportion of the sexes at birth is seen gradually evolving itself from the study and analysis of a great number of facts. The number of legitimate births in Paris, during the year 1836, was 19,309. Of these, 9,785 were male; and 9,524 were female: the male births being in proportion to the whole, as 5068 to 10,000. The whole number of legiti- mate births in France, during the year 1825, was 20 154 THE PHILOSOPHY OF MEDICAL SCIENCE. 904,594. Of these, 468,151 were male; and 436,443 were female ; the male births being in pro- portion to the whole, as 5175 to 10,000.* But this average result is not to be taken as the positive and absolute expression of the law before us. The result is still subject to a certain degree of varia- bleness, or fluctuation ; the amount of which can be ascertained by an arithmetical process, the elements of which are to be found in the numbers themselves, and which is known as the calculation of probabilities. The result of the application of this process to the two illustrations, just given, is as follows. In the first instance, although the positive result showed the chance of a male birth to be 0.5068, a calculation of the probabilities shows, farther, that this chance may vary, in either direction, above or below the observed result, to the extent of 0.0102 : — so that the law derived from these numbers would be, not that the chance of a male birth in Paris, during the year 1836, was rigorously as 5068 to 10,000 ; but that this chance varied between 5,170, and 4,966 to 10,000: or, that it might have been considerably more, or slightly less, than even, or equal. In the second instance, although the positive result showed the chance of a male birth to have been 0.5175, an application of the calculation of proba- bilities shows, further, that this chance really varied 1 Principes Generaux de Statistique Medicale. Par Jules Gavar- ret. p. 76, et. seq. PRINCIPLES OF MEDICAL SCIENCE. 155 in both directions, above and below the observed result, to the extent of 0.0015 ; so that the law derived from these numbers would be, not that the chance of a male birth in France, during the year 1825, was rigorously as 5175 to 10,000; but that this chance varied between 5,190, and 5,160, to 10,000. It will be noticed, that the extent of the fluctuation is very much less in the second, than in the first instance; and the reason of this is to be found in the vastly greater number of facts, constituting the law. The law of proportion between the sexes, at birth, in France, during the year 1825, is absolute, within the limits, thus ascertained, by an application to the observed data of the calculation of probabilities; and the law approaches absoluteness and invariableness, just in proportion to the multiplication of the data, or facts, from which it is derived, and by the analysis and generalization of which, it is consti- tuted ; and although it may never, from the very nature of its elements, acquire the positive char- acter which belongs to many of the laws of physi- cal science, the degree of its uncertainty may be rendered almost indefinitely small, and so unim- portant, as to be practically disregarded. There is one condition of the legitimacy of the laws, or principles, resulting from the process, and established by the methods, just described, obvious enough, to be sure, but which it may be well to point out and to illustrate. This condition is — in the words of M. Gavarret — that the sum, 156 THE PHILOSOPHY OF MEDICAL SCIENCE. or aggregate, of possible causes of the facts, which constitute the elements, or materials, of the law, must remain the same. When this condition fails, the law will be modified, in correspondence with the new element, which has been introduced into the sum of the possible causes of the facts, or phenomena, with which it is concerned. And such a modification, when it exceeds in extent the limits of variation within which the law may os- cillate, is to be taken as evidence, that the sum of possible causes has changed, and that some per- turbating element has been introduced amongst them. Thus, during the years 1824 and 1825, the number of legitimate births in France amounted to 1,817,572. Of these, 939,641 were male ; and 877,931 were female. During the same years, the number of illegitimate births amounted to 140,566. Of these, 71,661 were male; and 68,905 were female. Amongst the legitimate births, the proportion of males is as 51,697 to 100,000 ; while amongst the illegitimate births, the proportion is only as 50,980 to 100,000. Now, the difference in the foregoing results might have amounted to 391 in 100,000 births, without surpassing the limits, within which the law may oscillate : but the actual difference very much ex- ceeds this, and amounts to 717 in 100,000 births. This result shows, that some important difference exists in the sum of the possible causes of the two series of facts ; and this difference really consists in the fact, that the births constituting one series PRINCIPLES OF MEDICAL SCIENCE. 157 were in wedlock, and those constituting the other, out of it.1 The law of the average number of children, born to each family, is to be ascertained by the same methods, and is subject to the same condi- tions. The sum of the phenomena and relation- ships, upon which, in each single instance, this number depends, is uncertain and variable ; but the degree of this variableness is strictly confined within appreciable limits; so that the individual facts, although not identical with each other, are still comparable with each other. When a very large number of single instances have been accu- mulated, the average number to each ascertained, and the limits within which this number may oscil- late measured, by an application of the calculation of probabilities, the law of which I am speaking is determined. But this law is uniform and perma- nent on condition, that the sum of possible causes of the number of children to each family remains the same. This sum may be materially affected by changes in the physical, the political, the mo- ral, and the social condition of the people ; and in this way the law itself, which is only the aggre- gate expression, or the generalization, of this sum, will be also affected. It follows, of course, that this law may vary at different periods of time, and amongst different people. The foregoing doctrines are just as applicable 1 Principes Gen^raux de Statistique Medicale. Par Jules Gavar- ret, p. 93, 94. 158 THE PHILOSOPHY OF MEDICAL SCIENCE. to many of the phenomena and relationships of pathology, as they are to those of physiology. Now, the laws, or principles, of pathology, of etiology, and of therapeutics, are ascertainable by the same methods, and subject to the same condi- tions. Each series of facts, or relationships, con- stituting the elements of the law, although not absolutely identical with each other, must still be sufficiently fixed and determinate in their charac- ter, to render them comparable facts ; each series must consist of large numbers ; and the limits, within which the observed average may oscillate, must be ascertained by an application of the cal- culation of probabilities ; and the sum of possible causes must continue uniform. The law, what- ever it is, — whether physiological, pathological, etiological, or therapeutical, — will be positive and absolute — the limits within which it may oscillate will become smaller — just in proportion to the degree of comparableness, or similarity, of the individual facts, the greatness of their number, and the fixedness, or uniformity, of the sum of their possible causes. It is important, however, to observe, that there is a wide difference, in the readiness, facility, and positiveness, with which different laws may be de- termined. The aggregate of appreciable lesions, for instance, furnishing one of the elements in a group of morbid phenomena constituting a given disease, may often be ascertained with great cer- tainty from a comparatively small number of ob- PRINCIPLES IN THERAPEUTICS. 159 servations. In the same way, the diagnosis of many diseases is susceptible of a comparatively ready and positive solution and settlement. The reason of this difference is to be found in the fact, that the phenomena and relationships, constitut- ing the last-mentioned series of facts, are simpler and fewer, than in the more difficult cases ; they approach nearer to the character of physical phe- nomena and relationships. Amongst these laws, there is no one of so much interest and importance, as that of the therapeuti- cal relationships of disease ; and there is no one, the determination of which requires a more rigorous adherence to the methods and conditions laid down in the foregoing pages. Medical science has no problem, the solution of which is at the same time a matter of so much difficulty, and so much importance, as that involved in these rela- tionships. For these reasons, I shall enter into a somewhat detailed exposition of the subject before us, in its connexion with therapeutics, or the treatment of disease ; for the materials of which exposition, I am almost entirely indebted to the admirable treatise of M. Gavarret, on Medical Sta- tistics. The first condition, in the establishment of any therapeutical principle, or law, is this — that the facts, or phenomena, the relationships of which are to be investigated, shall be sufficiently fixed and definite to be comparable. The elements of this condition are thus stated by M. Gavarret. The 160 THE PHILOSOPHY OF MEDICAL SCIENCE. subjects of the disease, whatever it is, which is to be studied, ought to be taken from the same loca- lity, and from the same classes of population; and the hygienic circumstances surrounding these subjects, during the treatment of the disease, should also be the same. These precautions, it is easy to see, are necessary, in order to render the individual cases of disease comparable. If the cases are taken from localities, differing in any important circumstances from each other, and also from classes of the population, differing, in like manner, from each other, it is obvious enough, that, from these circumstances alone, such peculiarities may be impressed upon the dif- ferent cases of the disease, coming from one class and locality, or from another, as entirely, or in great part, to destroy their comparable character. Let us suppose, for instance, that the typhus fever of Ireland is the disease, the therapeutical rela- tions of which we wish to ascertain. Nothing can be clearer, than that the law of these relations might be found to be quite different in subjects belonging to the lower orders, and living in insa- lubrious situations, and in those belonging to the higher classes, and living in healthy situations. The average physiological condition of these two classes, resulting from their very different habits and modes of life, might be so widely dis- similar, as to give to their diseases a wide dis- similarity. In the second place, the disease, to be studied, THERAPEUTICAL PRINCIPLES-HOW ASCERTAINED. IQJ should be susceptible of a clear and positive diag- nosis. It should be distinctly and accurately dis- tinguished — nosologically, or as a species — from all other diseases ; and it should be readily sepa- rable into its several varieties, so far as these are strongly enough marked to be of any importance. The necessity of this condition is so obvious, and the reasons of this necessity have been so fully pointed out in another place, that there is no oc- casion for insisting upon it any further here. I will only add one or two remarks from Gavarret. When the law that we are in search of is that of the effects of any given plan of treatment, upon any given disease, considered nosologically, or as a whole, every case of the disease that presents it- self should be taken into account, whatever may be its stage, its degree of severity, or its compli- cations. There should be no selection of cases. The object before us is to ascertain the law of relationship between a given disease, as an inte- gral morbid species, and a certain mode of treat- ment ; and of course the disease should be taken as it presents itself, in all its varieties of degree, of period, and of complication. Under these cir- cumstances, and when this is our object, the condi- tions in regard to locality, the occupation, and social position of the subjects, and so on, are of course to be disregarded. But instead of wish- ing to determine the results of any given method of management upon any given disease, as a whole, embracing all its possible varieties and 21 162 THE PHILOSOPHY OF MEDICAL SCIENCE. complications, we may wish to confine our inves- tigations to these results, in regard to certain varieties, or forms, of the disease. The solution of this latter problem is indeed of much greater practical importance, than that of the former ; and at the same time it includes the elements of the former. Observation has long ago established the fact, that different forms, or varieties, of the same nosological affection, often require to be managed by methods more widely different, than are re- quired by many dissimilar nosological diseases. The practical value of most therapeutical rules will be found to depend upon their applicability to certain forms, or varieties, of disease. When the object before us is to ascertain the effects of treatment upon these several forms of the same disease, it is necessary, to the legitimacy of our conclusions, that the cases, constituting these forms, should be arranged in their several categories, at the earliest possible period of time in their pro- gress. Each individual case must be placed in its appropriate series, or sub-division, constitut- ing the particular form, or variety, to which it belongs, as soon as its character can be deter- mined. In the third place, the method of treatment which is to be applied should be defined as dis- tinctly and as clearly as possible ; both in its fixed and its fluctuating elements. When the foregoing conditions are fulfilled — when the subjects of the disease to be studied are taken from the same THERAPEUTICAL PRINCIPLES. 163 general localities, and from similar classes of the population, thus securing a general similarity in their physiological condition, and in their patholo- gical tendencies, and susceptibilities — when they are exposed to the same hygienic influences during the continuance of their treatment — when the disease, whatever it is, is clearly and positively distinguished from all other affections, and suscep- tible also of being divided into its several forms and varieties, depending upon its extent or seve- rity, — the period at which it was subjected to treatment, — the age, and sex of the patient, or any other appreciable circumstances; — and when, finally, the method of treatment is itself distinctly marked out, and well defined, we have secured our comparable facts, the legitimate data, and the only legitimate data, for our subsequent opera- tions. It is not pretended, that these individual facts — any two of them even — are absolutely identical. The physiological condition of each single subject of the disease may have some pecu- liarity ; this condition may differ in some respects from that of every other individual in any given series of cases — the disease itself may not be, and probably will not be, absolutely the same in extent and severity, in any two cases, even of its most distinct and well defined variety; — and, finally, the method of treatment may be subject to certain modifications in its application to each single case;—but notwithstanding all this, the facts are still comparable facts. Their degree of 164 THE PHILOSOPHY OF MEDICAL SCIENCE. difference is limited ; this degree never surpasses certain definite and appreciable boundaries. The phenomena to be compared having been thus ascertained and determined, we apply to them the methods, which have already been described. The law of relationship between the group of morbid elements, on the one hand, and the par- ticular method of treatment, on the other; or, in other words, the effects of the treatment upon the disease can result only from an examination and analysis of a great number of individual instances, and by an application to the average result, of the calculation of probabilities. The law, whatever it is, may be relied upon, as positive and absolute, just in proportion to the fixed and uniform char- acter of the compared facts, and to the greatness of their number; and, on the other hand, the law, if such it can be called, will be valueless, just in pro- portion to the opposite conditions. A failure in any one of the conditions destroys, just so far as it goes, the value and the legitimacy of our conclu- sions. It is not necessary to the purposes of this essay, that I should enter into a full exposition and de- velopment of the principles of statistics in their application to the different branches of medical science. It is only by the aid of these principles, legitimately applied,' subject to the conditions already pointed out, that most of the laws of our science are susceptible of being rigorously deter- mined. I shall conclude this portion of my sub- THERAPEUTICAL PRINCIPLES. 165 ject with one or two illustrations, taken from the work of Gavarret, showing the necessity of an examination and analysis of large numbers of cases, in order to arrive at any safe or positive results in regard to the effects of any particular remedy, or mode of treatment, in any given disease ; and the danger of receiving the average observed result of any given treatment, as the true expression of the law, in all cases where the number of instan- ces is small. Louis, in his researches on typhoid fever, cites one hundred and forty cases; fifty-five of which were fatal, and eighty-five of which were not fatal; the mean mortality being equal to 0.37143, — or, in general terms, to 37 in 100. Now, an applica- tion, to this result, of the calculation of probabili- ties shows, that this average mortality derived from so small a number of cases may fluctuate between the proportions of forty-nine, and twenty- six, to a hundred; so that in comparing any other method of treatment with that of Louis, the aggre- gate sum of the conditions, or circumstances, re- maining the same, it is not to be taken as settled, or certain, that the method is better or worse than his, unless the difference in the result surpasses, or exceeds, these possible limits. Let us suppose, that five hundred cases of a given disease have been subjected to a given treatment, with the result of one hundred deaths and four hundred recoveries ; and that the same number of cases of the same disease have been subjected to a different 166 THE PHILOSOPHY OF MEDICAL SCIENCE. treatment, with the result of one hundred and thirty deaths, and three hundred and seventy re- coveries. In the first class the ratio of mortality is as 20,000 to 100,000 ; in the second class, this ratio is as 26,000 to 100,000 ; the difference be- tween the two being 6000 in 100,000. An appli- cation to these numbers of the law of probabilities shows, that the limit of possible variation is equal to 7,508 in 100,000 ; so that, although the second method of treatment may be better than the first, the number of cases by which the two methods have been tested is not sufficient to demonstrate, positively and rigorously, the fact of its superiority. By extending this observation to twice the number of cases, the ratio of mortality in each class re- maining the same, we have the following results. The limit of possible variation, ascertained by the calculation of probabilities, when applied to a thousand cases, instead of five hundred, sinks from 7,508 in 100,000 to 5,306 in 100,000, which is considerably less than the observed difference in the ratio of mortality, this being as 6000 in 100,000. The result in this case, owing simply to the increase in the number of cases from which it is derived, demonstrates, positively, the superi- ority of the second method of treatment over the first. It has already been stated, that in certain de- partments of medical science, the phenomena and relationships, with which the departments are con- cerned, may be more readily and certainly gene- THERAPEUTICAL PRINCIPLES. -[Qf ralized ; and the laws, or principles, constituted by these generalizations, may be established by the study and analysis of a much smaller number of cases; and that the reason of this is to be found in the greater degree of fixedness and uniformity in the phenomena themselves. Thus the diaonostic characters of many diseases, — of small pox, of measles, of scarlet fever, of pleurisy, of pneumonia, of rheumatism, of tetanus, of epilepsy, and so on,__ are so constant and uniform, — the limits of their variableness are so narrow, — that it requires com- paratively only a small number of complete and accurate observations to settle them definitely, and to establish their laws. The same thing is true of the appreciable lesions of many diseases, — of phthisis, of true apoplexy, of pleurisy, of pneumo- nia, of pericarditis, and of others. But when we come to apply the foregoing rigorous doctrines to what are commonly called the laws, or principles, of therapeutics, how will these laws come out of the trial ? Subjected to the ordeal of these doc- trines, what becomes of the great mass of medical testimony to the efficacy of medical treatment? In how many instances, and to what extent, have the fundamental conditions of the establishment of any therapeutical law been fulfilled ? How far have the facts been really comparable facts ? In how many series of observations, has the nosologi- cal diagnosis, even, been established beyond any reasonable doubt; and, what is still more impor- tant, how accurately and clearly have the varieties 168 THE PHILOSOPHY OF MEDICAL SCIENCE. or forms of the disease been arranged in their ap- propriate categories? And even where these and the other essential conditions have been fulfil- led, in how many instances have the observations been extended to a number of cases sufficiently large, to determine, with any positiveness, the ac- tual results of the treatment upon the mortality of the disease ? Alas ! my brethren, there can be but one answer to all these questions ; and humiliating as that answer may be, it is much better to make it, to hear it, and to give heed to it, than volunta- rily to shut our ears and our eyes, and still stumble on in the dark. What is the character of the great mass of medical observation, in regard to the treat- ment of diseases, recorded in books and in medical journals? Dr. A. gravely reports a series of cases of what he calls tubercular consumption, all cured by his new method. But not a syllable is said about any evidence of the actual existence of the disease in any of his cases, derived from its physical signs ; it may be only a year or two since the commencement of his observations; and no information is furnished as to the number of cases which have terminated fatally under the same management. Dr. B., with the same gravity, and apparent honesty, boasts, that he has been re- markably successful in the cure of scarlet fever; because he has not lost one of eight or ten, or it may be twenty cases, or about this number, of the disease, that have fallen into his hands, during the last season. With great self-complacency, he THERAPEUTICAL PRINCIPLES. 169 compares the wonderful results of his own skill, with those of a neighboring practitioner, who, he has understood, — and he has no doubt of the fact, — has lost all, or nearly all of the cases of the same disease, which have unfortunately come under his care. The idea of inquiring how far the two series, or classes, of cases have been comparable, never seems to have entered his mind. Not a word is said, about the form or variety of the disease, which either he, or his neighbor, has been treating : although, supposing the results to have been as he has stated them, the probability is, that his own cases belonged to the simple form of the disease, and those with which he compares them to the anginose, or malignant form. Dr. C. announ- ces to the medical world, that for the last year and a half, perhaps for the last four or five years, even, he has been uniformly successful in his treatment of croup. He says not a syllable about the form of the disease in the cases which he has managed; he has not ascertained whether they were cases of true membranous, or non-membranous, croup. He may not be aware, that there is any such dif- ference in the forms of this disease. On a further investigation into the real state of the facts, it may be found, perhaps, that the number of cases, of which he had kept no positive record, but which he really thought was very considerable, after all only amounted to some eight, or ten, or a dozen; and that from amongst these, even, he had ex- cluded one case, because the child had been 22 170 THE PHILOSOPHY OF MEDICAL SCIENCE. scrofulous and feeble ever since its birth; and one other, because he did not see the patient till a day or two after the first appearance of the disease ; and still a third, because it had not been properly treated by the physician who first had the care of it; and, finally, it frequently comes up, at last, that one case, which he had treated from its com- mencement, had terminated fatally, but it had en- tirely escaped his recollection. This sketch of the general character of medical testimony as to the effects of treatment, in these diseases, and in many others, is neither exaggerated, nor falsely colored. I appeal to the experience of all close and philo- sophical observers, now living; and to the multi- tudinous records on the pages of medical books and journals, for the proof of its faithfulness and its accuracy. There is one remark of some importance which ought to be made here ; and containing, as it does, a partial qualification, of one amongst the many difficult conditions, conformity to which is essen- tial to the establishment of any therapeutical law, or to the settlement of the positive and compara- tive value of different methods of treatment, it is a matter of no little consolation, that we are justified in making it. This remark is, that the number of cases, necessary to the determination of the actual or relative value of these different methods of treatment, is much less in certain dis- eases than in others. This is especially true, wherever the diagnosis is positive ; and where, at THERAPEUTICAL PRINCIPLES. 171 the same time, the issue of the disease, either in recovery, or in death, has already been ascertained to be very uniform and constant. Traumatic tetanus, hydrophobia, tubercular consumption and membranous croup, for instance, under all modes of treatment, have, thus far, in an immense majority of instances, terminated fatally. In these, and in all analogous cases, a widely differ- ent result, derived from the application of a new method of treatment, even to a limited number of cases, might be sufficient to determine, very posi- tively, the superiority of the method. The extent of the difference here, notwithstanding the small- ness of the numbers, may exceed the limits of possible error, or fluctuation. Thus the recovery, under the application of a new method of treat- ment, of ten cases out of twenty, of hydrophobia, or traumatic tetanus, would constitute very posi- tive evidence of its advantages, when compared with any other known methods. So, the applica- tion of a new method to a disease, the common termination of which in recovery, under other methods, had already been ascertained, with widely different and unfavorable results, even in a small number of cases, would be sufficient to deter- mine very conclusively, its inferiority to the other methods. But the extent to which these qualifying re- marks are applicable is not very great. In a large proportion of the serious diseases, to which the human body is subject, the issue of the disease, 172 THE PHILOSOPHY OF MEDICAL SCIENCE. either in death or recovery, is a matter of much greater contingency and doubt. The ratio of mortality ceases to be extreme, in either direction ; and in proportion as this happens, does it become necessary to augment the number of observations, from the study of which, any therapeutical law is to be derived. It may very naturally be asked, what, if these things are so — if this hard doc- trine is sound — is the practitioner of medicine to do ? Is he to fold his arms, and to wait, till those who have the means and the ability, have gone through with these long, laborious, delicate and difficult investigations, — requiring so much time, and toil, and cooperation, — and have ascer- tained, positively, the actual and relative value of different modes of treatment in all the important diseases, which he is daily called upon to manage ? Is his present knowledge of the effects of his remedies without positiveness and without value ; and because it has not been obtained precisely by the methods, and subject to the conditions, above stated, is it to be distrusted and thrown aside ? Is he no longer to bleed in acute pleurisy, or to give calomel in syphilis, or opium in spasmodic colic, or quinine in intermittent fewer, because the the- rapeutical laws, in all these cases, have not been duly established and authenticated, according to the formulae of the foregoing doctrine ? Such ques- tions, I say, will very naturally suggest themselves; it is proper that they should be answered; and the answer is this. The foregoing rules of medi- THERAPEUTICAL PRINCIPLES. 173 cal treatment, and most others like them, have been ascertained and established, so far as they are ascertained and established, by a series of observations of such vast extent, as to compensate, in a good degree, for the absence of the other conditions. In regard to many of them, the testi- mony of observers, for successive ages, has been nearly unanimous and uniform. The good effects of bleeding in most cases of simple, acute inflam- mation of the lungs, the pleura, the peritoneum, the pia mater, and other organs and tissues, are so constant, as to leave no room for doubt or uncertainty. And the same thing is true of most of the generally admitted rules, or methods, of practice. This kind of observation has been sufficient to establish, in a general manner, these therapeutical maxims. They rest upon the con- current testimony of immense numbers of wit- nesses ; they are the results of an almost indefinite number of observations. It is to be taken for granted, that if these generally admitted rules, growing out of this very extensive observation, had been false and imaginary, the sagacity and experience of this host of witnesses could not have failed to detect their falsity. These rules have been, in this matter, ascertained with a suffi- cient degree of positiveness, to render them our most valuable guides, in the management of disease. Although in very many instances the diagnosis of the disease, or the diseases, in ques- tion, must have been equivocal or mistaken; — 174 THE PHILOSOPHY OF MEDICAL SCIENCE. although the circumstances in which the patients were placed, and their individual conditions, must have been exceedingly diverse, still the aggregate number of cases has been so enormous, as to neutralize, in a great degree, the effects of these elements of imperfection and error. But it ought still to be added, that even in these cases, it is only by a faithful adherence to the rules and methods, which have been described, that the exact value of the several remedies, or modes of treatment, can be ascertained. These generally- received maxims of therapeutics are all still sub- ject to revision. It is only by subjecting them to the rigorous discipline of the doctrines of this chapter, that their value can be absolutely and positively determined; and the actual and rela- tive positions which they ought to occupy, defi- nitively assigned to them.1 1 wish now, in concluding this chapter, once more to call the attention of my reader to the 'It may even be said, I think, that the school of observation, whose principles and methods, I have endeavored to vindicate, in the present chapter, denies too peremptorily, and with too little qualifica- tion, the value of all results which have not been obtained in con- formity to its own rigorous processes. One of my medical friends, says to me, in a letter, — " Perhaps there is one point that 1 may venture to caution you upon, — may I do so? I have sometimes thought that Louis and some of his disciples were a little rough in their treatment of unproved opinions ; and that they showed rather too much pleasure in demonstiating that anything which seemed particularly probable, was not true. But I do not believe you will fall into this ultraism of the rigorous school." The remarks in the text will save me from this imputation. THERAPEUTICAL PRINCIPLES. 175 remark which I made at its commencement, to wit; — that the constituent elements of a law, or principle, in the science of life, do not differ from those of a law, or principle, of physical science. In both instances, the law, or principle, whatever it may be, consists solely and exclusively in the generalization, more or less rigorous and absolute, of the phenomena and relationships to which the law refers. The law, or principle, is not a cre- ation of the reason ; it is not the product of any a priori processes of the mind ; it does not consist in any intellectual deduction, as it is termed, from the phenomena, or their relationships ; it does not consist in any explanation, or interpretation, of these phenomena, or their relationships ; — it is not to be found in anything superadded to them, or interposed between them ; — it is the simple expression of their generalization, and nothing else. It may be well enough, perhaps, to remark here, although the grounds upon which the re- mark is founded must be sufficiently obvious, that the positiveness with which these principles are thus susceptible of being ascertained, applies to the principles themselves, and not to the individual phenomena and relationships, by the aggregate of which, they are constituted. Each of these sepa- rate elements of the principle, whatever it may be, is, in its very nature, contingent and variable, and must for ever continue to be so ; and no pos- sible degree of absoluteness in the principle can ever deprive these elements of this character. 176 THE PHILOSOPHY OF MEDICAL SCIENCE. How great soever may be the accuracy with which the average duration of human life, under all conditions, and in all circumstances, may be determined; the duration of any individual life will still remain, as before, altogether uncertain and contingent. And the same thing is true of patho- logical phenomena, and therapeutical relation- ships. How definitively soever the laws of these phenomena and of these relationships may be settled; the individual instances, or elements, of which they are composed, must still continue fluctuating and indeterminate, always, however, within certain limits ; — the positiveness of the law cannot apply to the individual instances. The exactness of our appreciation of these instances, and our ability to estimate their precise value and conditions, may be aided by an acquaintance with the law ; but this appreciation and estimate must still depend mostly upon the extent and accuracy of our knowledge of the several elements, which unite to make up the individual instances them- selves. Thus although the ascertained law of the ratio of mortality in a given disease, under given circumstances, may assist us in predicting the ter- mination, in an individual case ; still this prediction must depend, in a great degree, upon our know- ledge of the fluctuating and variable elements of the case itself. No acquaintance, however per- fect, with the laws of pathology and therapeutics, can ever remove, or in any degree diminish, the necessity of a thorough and discriminating study PRINCIPLES AND LAWS OF MEDICAL SCIENCE. 177 and knowledge of the single instances which unite to make up the materials of the law. Our diag- nosis, prognosis, and management of individual cases of disease must depend, not so much upon the laws with which the diseases are concerned, us upon an accurate knowledge of the individual cases themselves; so that no perfection, or abso- luteness, of the law, can ever lessen the necessity and importance of sagacity, discrimination, and skill, on the part of the physician, in the practical application of his art. A vague and indefinite notion seems to have been long and extensively entertained, that some great principle, like the fact of gravitation, is yet to be discovered in physiological science, leading to results as new and magnificent, as those that flowed from the discovery of that simplest and sublimest of all known relationships. Even Cu- vier exclaims, " Why may not Natural History one day have its Newton? " And Whewell says: — " The idea of the vital forces may gradually be- come so clear and definite, as to be available in science, and future generations may include, in their physiology, propositions elevated as far above the circulation of the blood, as the doctrine of universal gravitation goes beyond the explanation of the heavenly motions by epicycles."x If the philosophy of this essay is not altogether mistaken and erroneous, the fallacy of all such expectations 1 Hist. Ind. Sci. vol. ii. p. 405. 23 178 THE PHILOSOPHY OF MEDICAL SCIENCE. must be sufficiently obvious. I trust that Natural History, including physiology and all its relations, will yet have, not one Newton, but many. Medi- cal science — one of the branches of Natural His- tory — has already had, indeed, not one Newton only, but many ; and it is to their labors, that it is indebted for its existence, and for the degree of perfection, which it has been enabled to reach. But not to the development of any abstract idea of the vital forces; not to the discovery of any single and novel principle, as it is termed, has it ever been indebted, or will it ever hereafter be indebted, for its advancement. The " elevated propositions," of which Whewell speaks, whether in strict physiology, pathology, therapeutics, or whatever section of the science of life, are to be reached, not by any of the means, or processes, to which he seems to allude ; but by the methods, and subject to the conditions, which have been already stated. These are the Newtons of medi- cal science —■ Hippocrates, Haller, Morgagni, Sy- denham, Hunter, Laennec, Andral, Louis, Cho- mel, Du Chatelet,— and others, — their worthy compeers, — who, imbued with the same spirit, guided by the same principles, and steadfast in their allegiance to the same doctrines, have resisted the influences of a fascinating but false philosophy, and have worked faithfully and diligently in their only true vocation, — the study and analysis of phe- nomena and their relationships; and the Newtons of our science, who are yet to come, must work PRINCIPLES AND LAWS OF MEDICAL SCIENCE. 179 in the same direction, and their labors will be crowned with similar, but still nobler, more posi- tive, and more valuable results.1 1 I have devoted no separate chapter to a formal exposition of what has been called the "numerical" method of observation. The reason of this omission must be obvious to every reader of my book. The doctrines of the numerical method, in its full develop- ment and application, are simply the doctrines of the foregoing chap- ter. This method is no new thing. Its elements are as old as Hip- pocrates : and there is hardly an individual writer on practical medi- cine, of any authority or importance, from his period to our own — including those who have been most unsparing in their abuse of the method — who has not used it. Every man, in every age, who has stated numerable facts in anatomy, physiology, pathology, or therapeutics, in specific numbers, has made use of the numerical me- thod. Every observer, who counted accurately his cases of disease, or any of the phenomena connected with these cases, and gave the result in numbers, instead of resorting to the more common and indefinite terms — a small number, or a large number, frequently, or rarely — so far made use of this method. Its application to the facts and relationships of medical science had long been becoming more general and extensive, before the full measure of its value was practically exhibited by Louis, and its true principles philosophically developed and demonstrated by Gavarret. Although very slowly and reluctantly admitted by British physicians, as a formal and sys- tematic method, it is nevertheless true, that some of the most distin- guished and worthy amongst them, had adopted and used it some- what extensively, many years before the publication of the researches of Louis. It is sufficient for me to mention, here, the names of William Woolcombe and John Cheyne, two stars of as steady and bright a lustre as any in the galaxy of British medical observers. This method, notwithstanding the opposition which it has met with from those who claim to be preeminently the disciples and champions of Hippocratic and rational medicine, has been constantly, though slowly, advancing in estimation, and pushing its way to favor in the British islands. CHAPTER XII. PROPOSITION FOURTH. MEDICAL DOCTRINES, AS THEY ARE CALLED, ARE, IN MOST INSTANCES, HYPOTHETICAL EXPLANATIONS, OR INTERPRETA- TIONS, MERELY, OF THE ASCERTAINED PHENOMENA, AND THEII5 RELATIONSHIPS, OF MEDICAL SCIENCE. THESE EXPLANATIONS CONSIST OF CERTAIN OTHER ASSUMED AND UNASCERTAINED PHENOMENA AND RELATIONSHIPS. THEY DO NOT CONSTITUTE A LEGITIMATE ELEMENT OF MEDICAL SCIENCE. ALL MEDICAL SCIENCE IS ABSOLUTELY INDEPENDENT OF THESE EXPLANA- TIONS. The nature and value of what are called Medical Doctrines. Universal pre- valence of medical hypotheses. Their bad influences. Methodism. Cul- len's theory of fever. Homoeopathy: Statement of its principles. Standard by which they are to be tried. Evil effects of Medical Doctrines upon the minds of medical men, and upon the interests of medical science. Brous- sais : His History of Chronic Inflammations, and his Examination of Medical Doctrines. Sydenham. How far interpretations may be al- lowed. I hope, that the chapter on the nature of hypo- theses in physical science, and their relations to science itself, has prepared the reader, if any such preparation was necessary, for what I have now to say upon the same subject, in its connexion with the science of life. The doctrines, which were advanced in that chapter, are, if I am not mis- MEDICAL DOCTRINES, OR HYPOTHESES. 181 taken, all of them, for still stronger reasons, and with less qualification, applicable to all the depart- ments of the science of life. The essential character of all hypotheses, — both physical and physiological, — is the same ; the nature of their constituent elements is the same; their relations to the respective sciences, with which they are connected, are the same. In the science of life, as in physical science, they consist, exclusively, in explanations, or pretended explanations, of appre- ciable phenomena and relationships, through the assumption of other unknown and imaginary phe- nomena and relationships. The science of life, in all its departments, is wholly independent of these pretended explanations; they do not enter into it, as one of its elements — they are, in no degree, and in no sense, one of its constituents. It is also true, farther than this, that theory, or hypothesis, has played a much wider and more prominent part in the science of life, than in phy- sical science. It has followed the former, like its shadow, from its birth, in the early ages of the world, to the present time. Under all circumstan- ces, amongst all nations, in every stage and phasis of human progress, under the reign of all philoso- phies, and all religions; in all times, and every- where, within the range of civilization, has medical science been attended with its protean hosts of hypotheses. These hypotheses have pervaded and ruled the science, and, to a great extent, deter- mined its character. It is true, also, that the 182 THE PHILOSOPHY OF MEDICAL SCIENCE. influences of these hypotheses upon medical science have been more inauspicious and malign, than the influence of hypotheses upon physical science. Their effects have been bad, and only bad. The praise of having guided our researches, of having suggested new courses and new methods of investigation, of having assisted us in the con- ception and comprehension of phenomena, and in the expression of our ideas concerning them, which has been given to physical hypotheses, does not belong to these. They have only rendered more obscure and difficult what was sufficiently so before their intervention; and they have ever impeded the progress of the science which they professed to promote. Not only so, but they have almost always acted injuriously upon the practical application of the science of medicine. They have often destroyed, or neutralized, its efficacy as an art for the relief of human suffering. They have done more than this, even ; — they have, in many instances, converted the science from an instrument of good, to an engine of positive ill — a means of inflicting upon men the very evils, which its true objects and aim are to remove. And these observations are, to a very considerable extent, as true of the present, as they are of the past. Hy- pothesis, in medicine, still passes for science — the former still usurps the functions, and claims the prerogatives, of the latter. After the full consideration, which was given to this subject in the chapter on the hypotheses of MEDICAL DOCTRINES, OR HYPOTHESES. 183 physical science, it is unnecessary to repeat the general remarks, which were then made, in their bearing upon the science of life. It will be suffi- cient for my purpose, to refer to some few of the hypotheses themselves; and, in this way, to try the truth and soundness of the doctrines, which I have ventured to lay down. In physical science, the number of these leading hypotheses is small, and they are generally characterized by a great degree of beauty, simplicity, and what, in a certain qualified sense of the word, may be called verisimilitude. In the science of life, they are without number; their name is legion; and, in most instances, they are as remarkable for their ill-adjusted complexity, clumsiness and improba- bility, as the theories of physical science are for the opposite qualities. These theories, or hypotheses, in the science of medicine, are generally dignified with the title of doctrines. Thus, we have what are called the doctrines of the vitalists, and the organists ; the doctrines of the humoralists, and the solidists ; the chemical, and the mechanical, doctrines; the doctrine of irritability; the doctrine of contro- stimulism; the Cullenian, the Brunonian and the Broussaisian doctrines ; the doctrines of homoeo- pathy, of hydropathy, and so on, from the begin- ning to the end of the long and heterogeneous chapter. It is not my purpose to write a history of medical doctrines, or, in other words, of medi- cal hypotheses, — for all these so called doctrines 184 THE PHILOSOPHY OF MEDICAL SCIENCE. are only hypotheses, — and I shall speak of them, only so far, as may be necessary to the illustration of my own views. It is hardly worth my while, and it would aid but little in the direct elucidation of my subject, to say much of the medical theories of the Greek philosophers, either before or after the time of Hippocrates. The medical theories of these philosophers generally constituted apart of their more comprehensive theories of the universe, and consisted of similar elements. Hippocrates him- self held no general doctrine in regard to diseases, which can properly be called a theory ; a circum- stance which now constitutes one of the highest and most legitimate titles to the preeminent posi- tion, which he occupies. One of the first medical doctrines, or hypothe- ses, which was formally stated, and fully devel- oped, was that of the methodists, as they are called; and it is in this doctrine, that we find one of the earliest manifestations of that tendency to dualism, in pathological theory, which has never ceased to show itself, from that time to the present. Ac- cording to this doctrine, the whole body was made to consist of a porous tissue, through which, fluids were constantly passing ; and all disease was made to consist in the relaxed, or the constricted, state of the pores. This was a simplification of the doctrine of Asclepiades, according to whose system, many diseases depended, not merely upon the state of the pores, but upon the changes, and MEDICAL DOCTRINES, OR HYPOTHESES. 185 the various actions upon each other, of the mole- cules passing through them. The latter doctrine was a mixture of humoralism and solidism ; the former was pure solidism. The state of the pores, throughout the whole body, was inferred from the state of the skin, and from that of the natural out- lets of the body. When the pores of the skin, or these outlets, were relaxed, or open, giving issue to the fluids of the body, the disease was said to belong to the class designated by the term laxum ; when these pores and outlets were closed or con- stricted, the disease was said to belong to the opposite class, designated by the term strictum; and when some of the pores, or outlets, were closed, while, at the same time, others were open, the disease was said to belong to the class, desig- nated by the term mixtum. Such was the doctrine, or hypothesis, of the methodists; and their thera- peutics flowed necessarily from it; being founded exclusively on the double indication, of removing the two opposite conditions of the pores. This, although one of the oldest medical doctrines, or hypotheses, is, so far as its essential character and elements are concerned, an exact prototype and representative of all its successors. In order to interpret, and account for, the appreciable pheno- mena and relationships of morbid actions, certain properties and conditions of the body, wholly un- known and imaginary, are assumed; then, these supposed properties and conditions, by a second 24 186 THE PHILOSOPHY OF MEDICAL SCIENCE. assumption, are said to be connected with certain obvious states of the skin, and the natural outlets of the body, and, through this connexion, suscep- tible of being ascertained ; and, finally, by a pro- cess of a priori reasoning, the treatment of all diseases, thus ascertained, is made tos consist in the removal of these assumed and imaginary con- ditions ; the therapeutics of the methodists nat- urally, necessarily, and rationally, as it is called, flowing from their pathology. Such, I say, when analyzed, and reduced to its actual elements, is the character of all medical hypotheses. Some of these may be more ingenious, than others, — some it would be more proper to say, may be less absurd, and preposterous, and improbable, than others ; but they are all essentially alike ; they all consist in certain unknown and imaginary pheno- mena and relationships, assumed for the purpose, as is vainly supposed, of rendering more intelli- gible to our comprehension, of explaining, inter- preting, and accounting for, the phenomena and relationships, which are obvious and appreciable. They constitute, in no sense, and in no degree, any legitimate element of the science of life. It is curious to see, in this ancient and venera- ble hypothesis, some of those more strongly marked features, which have never ceased to reappear in the successive members of the prolific family to which it belongs. Thessalus, like his modern dis- ciples, and in strict keeping with the spurious but seductive simplicity of his pathological creed, said, MEDICAL DOCTRINES — THEIR TRUE CHARACTER. 187 that he could make of the most illiterate artisans excellent practitioners in less than six months. Ccelius Aurelianus, with all his merits, like other members of his sect, denied the existence of speci- fics, because their effects could not be attributed either to constriction or relaxation ; and banished purgatives from his materia medica, because their action could not be referred to either of his two imaginary modi operandi. There are treatises on therapeutics, still fresh, both from British and American presses, imbued and pervaded by the same a priori rationalism. Passing over the chemical, mechanical, and humoral doctrines, with their various modifications and combinations, let us come down nearer to our own times, and look at some one or two of the more recent pathological theories, and see if they have any better claim, than their predecessors, to be considered as anything more, than gratuitous conjectures or speculations. One of the most cel- ebrated of these, — constructed with great care and skill, all its parts adjusted and arranged with a formal and elaborate exactness worthy of its famous author, — is the Cullenian theory of fever. This theory begun by assuming, that the cause of the cold stage of a febrile paroxysm is the cause of all the subsequent phenomena. The doctrine assumed, in the second place, that this primary cause is to be found in the weakened energy of the brain, oc- casioned by the application, and action upon it, of certain sedative influences, or agents. Then, it 188 THE PHILOSOPHY OF MEDICAL SCIENCE. was further assumed, that this diminished energy of the brain produces a state of debility in all the functions of the body, but especially in the heart and arteries, and in the extreme vessels; in con- sequence of which it was again assumed, that these vessels become the seat of spasm. In conse- quence of the cold stage, and of this spasm of the extreme vessels, it was finally assumed, that the heart and arteries are excited to increased activity, and by this activity, the spasm of the vessels is overcome, the energy of the brain is restored, and the series of morbid actions thus entirely destroyed. With all this, the vix medicatrix natures is so strangely mixed up, that it is not easy to get at the exact ideas of the author himself, in regard to its functions and agency. But such, at any rate, briefly stated, is Dr. Cullen's doctrine of fever. He seemed to think, that it was a very sound, a very philosophical, and a very useful doctrine. " I flatter myself," he says, " that I have avoided hypothesis, and what have been called theories ! " Now, I have no intention of entering into any examination of this doctrine, as its author calls it, or of indulging in any comments upon it. I cite it only as an illustration of the doctrine of this chapter. Certainly, the wildest dreamer in patho- logy, and the loosest a priori reasoner, even, could hardly have gathered together a jumble of assump- tions, more utterly gratuitous. They are as im- probable, each in itself, as they are altogether in- coherent and heterogeneous. But the entire the- MEDICAL DOCTRINES — H0MO20PATHY. 189 ory differs, in no way, so far as its essential char- acter, and its relations to true science, are con- cerned, from those of the methodists, the chemists, the mechanicians, amongst the ancients ; or from that of Brown, of Rasori, of Broussais, of Hahne- mann, or of Samuel Thompson, amongst the mod- erns. I have spoken of Hahnemann ; and I will con- clude this kind of illustration, by a short examina- tion of what is called the homoeopathic system of medicine. It is possible, perhaps, that some of my readers may be surprized, that I should thus recognize the claims, or pretensions, of this system to the character of a medical doctrine. But its claims are just as legitimate, as those of any of the systems, of which I have already spoken. They are of the same nature; they rest upon the same grounds; they differ, in no respect, from the claims of Methodism, Cullenism, Brownism, or Broussaisism. Whether there has been, or has not been, more charlatanry amongst its disciples and practitioners, than amongst those of other doctrines, it in no way concerns my present pur- pose to inquire. The system, I have said, claims our suffrages, on the same grounds, that are set forth by all other systems; and I intend to test its soundness by an application to it of the same philosophical principles, by which those other sys- tems have been tried. This, certainly, its friends and advocates cannot complain of. I will not condemn it, on the ground of any apparent im- 190 THE PHILOSOPHY OF MEDICAL SCIENCE. probabilities, or absurdities, which it may involve. I am ready to admit and to believe any and all of its assertions, on the same conditions, upon which I admit and believe any and all other assertions. I shall not endeavor to ridicule its infinitesimal doses, nor that element, in its pathology, which refers hysteria, mania, epilepsy, every species of spasm, softening of the bones, cancer, fungus haematodes, gout, haemorrhoids, dropsy, epistaxis, haemoptysis, asthma, suppuration of the lungs, impotence and sterility, deafness, cataract, gravel, paralysis, all kinds of pains ; and very many other chronic diseases, besides a large majority of acute diseases, to psora, or itch, as their only true, fun- damental and productive cause ! All this, and much more, even the assertion, that a homoeo- pathic dose of mesmerism will snatch from im- pending death a case of uterine hemorrhage,1 1 am quite ready to admit and receive, as true and sound doctrine, whenever it is so established, according to the philosophy of this essay, — but not till then. The leading principles of the homoeopathic doctrine may be thus stated. I derive them from the French translation of Dr. Hahnemann's expo- sition ; and whatever modifications they may have undergone, in the hands of his successors, can in no way affect their relations to the true philosophy of medical science. I may say the same thing of 1 Exp. de la Doc. Homceop. p. 292. MEDICAL DOCTRINES — HOMCEOPATHY. 191 the details of these principles; these details have no bearing upon my present purpose. 1. To the entire human organization, is super- added an immaterial principle, — a dynamical, or moving, force, — active in itself, — by which, the organization is ruled and controlled. It is this dynamical force, or principle, upon which, all morbific causes or influences act; and the disturb- ance, which these causes occasion in this princi- ple, operates of necessity upon the organization, deranging its healthy actions, and perverting its natural sensations. 2. Every modification of this immaterial and independent principle, through the altered actions and deranged sensations of the organs, which it governs and moves, manifests itself by external signs, or symptoms, which are always recognizable and appreciable, by the attentive and careful observer; so that the totality of the symptoms, in any given case, becomes an absolute and infallible index and exponent of the changes in the organs, or, in other words, of the disease. These changes, themselves, are beyond the reach of our investigation, so that the study of anato- mical lesions is only a vain dream. 3. The vital force being a dynamic power, the morbific causes, occasioning its disturbance, can do this only in virtue of a like dynamic power in themselves; and these disturbances, thus produ- ced, can be removed only by modifiers, or reme- dies, equally dynamic in their character, and acting on the vital force. 192 THE PHILOSOPHY OF MEDICAL SCIENCE. 4. The effects of all modifiers, or remedies, upon this force can be certainly and positively ascertained, only when the force itself is not already disturbed by the action of morbific causes, — or, in other words, — when the body is in a state of perfect health. The action of these modifiers is constant and uniform ; so that when they act as remedies it can only be by modifying the vital force precisely as they do in health. 5. The totality of the symptoms, and the dis- ease, being, so far as our knowledge is concerned, equivalent terms, or the same thing; the former being removed, it follows, of necessity, that the latter is cured. 6. This cure can be accomplished only in two ways, — first, by exciting, through the agency of modifiers, or remedies, actions in the vital force like those which already constitute the dis- ease; or, second, by exciting actions in this force unlike, or opposite, to those constituting the disease. 7. All pure experience, and all careful trials, show that the latter is impossible; and that even when the symptoms are diminished, or removed, by it, they never fail to reappear in an aggravated form. It follows, then, that there is only one method by which the totality of the symptoms, representing the disease, can be certainly and permanently re- moved ; and that is through the agency of those substances and influences, which so modify the dynamic force of the healthy body, as to produce MEDICAL DOCTRINES —HOMCEOPATHY. 193 a totality of symptoms like those which represent the disease. 8. The artificial action, constituting this total- ity, must be a little stronger, or more powerful, than that representing the disease. 9. Pure experience shows, that all true reme- dies do act in this manner ; and do cure diseases. All opposite, or allopathic experience, as it is called, is false and deceptive. Diseases are never removed by substances, which do not act in this manner. 10. Remedies, or modifiers, in order to pro- duce the desired effect on the disturbed vital force, must be introduced into the body in ex- ceedingly minute, and almost infinitesimal quan- tities. Such I believe to be the fundamental princi- ples of the homoeopathic doctrine. I have en- deavored to state them as clearly, and explicitly, as possible. Their details, their practical applica- tion, their illustrations, and the reasoning by which they are supposed to be supported, do not at present concern us. My single purpose is to see how far they are conformable to the philoso- phy, which it is the design of this essay to vindi- cate and establish. Are these principles, as they are called, true principles, according to the legit- imate and philosophical meaning, which ought to be attached to this word? Do they consist of phenomena and relationships, of an appreciable 25 194 THE PHILOSOPHY OF MEDICAL SCIENCE. and positive character, ascertained by absolute and extensive observation ? Let us see. How is it with the first, fundamental proposi- tion, upon which all the others are made to de- pend, and from which they flow ? What is the material of which this foundation consists; upon which the entire homoeopathic superstructure is made to rest ? Is this proposition, fact, or fancy ? Is this foundation wrought from the adamant of positive phenomena, or is it woven with the tissue of dreams ? It is not possible that there can be but one answer to these questions, unless the an- swer comes from a dreamer. There is no evi- dence, whatever, of the existence even — to say no- thing of its alleged properties and relations — of this independent, dynamical force, presiding over, and moving, the organic structure. The existence of this force is an assumption, just as perfectly and entirely gratuitous, as it is possible to ima- gine. It is more so than that of the strictum and laxum of the methodists, or the spasm of Cullen. The whole doctrine of this dynamical force is nothing but physiological transcendentalism. Life is the sum of the organization, and its actions. This is all we know — this is all we can know, about it. What the vital force is — how it is con- nected with the organic structure — the nature of the bond between them — the intimate manner in which each is acted on by its modifiers — is ut- terly unknown to us; and the probability is, that this ignorance will never be removed. This ele- MEDICAL DOCTRINES—H0MCE0PATHY. 195 ment in the doctrine of Hahnemann is no new thing ; it is very much like the archeus of Van Helmont, and other old systematists, and the evi- dence of its existence is of just the same cha- racter. In regard to the second proposition, it is not enough to say that it is gratuitous; it is worse than this. It is in direct and unqualified opposi- tion to the most extensive and positive observa- tion. It is not true, that every modification of the condition of the living structure and powers has its invariable and characteristic external sign, or manifestation, through which the modification is made known. Certainly, it is by their signs and symptoms, that internal diseases are revealed to the physician. But daily observation shows, that there is no uniform and invariable relation- ship between the extent and intensity of disease, and its external signs. The prominency, the number, and the combination, of these, depend upon many circumstances beside the disease with which they are connected. Has no change taken place in the condition of the living struc- ture, or its actions — in the relations, susceptibili- ties, and tendencies, of one or both — during the latent period of the contagion of small-pox, yel- low fever, or hydrophobia ? Is this independent vital force of homoeopathy — admitting it to be present, with all its assumed properties — in no wav affected by this poison of terrific energy, that has crept into the system ? It is impossible 196 THE PHILOSOPHY OF MEDICAL SCIENCE. to suppose, that such can be the case ; but the modification, whatever it may be, gives no out- ward and intelligible sign of its existence. Neither is it true, as is alleged by homoeopathy, in con- nexion with this subject, that the internal changes in the organs themselves, are wholly beyond our means of investigation. To a very great ex- tent, they are entirely within our means of inves- tigation, and they constitute one of the most val- uable and positive elements in our knowledge of disease. The third proposition, asserting the existence of certain properties and susceptibilities of the dynamic vital force, is like the first, in regard to the separate and independent existence of the force itself, wholly gratuitous. The fourth principle in the doctrine of homoeo- pathy is, that the remedial action of all substances can be ascertained only by the effects which they produce upon the dynamic power, in its un- disturbed state. The doctrine, that all thera- peutical laws consist in ascertained relationships between morbid conditions, on the one hand, and their modifiers, on the other, has been so fully stated, that it is unnecessary to say anything fur- ther upon this opposite principle of Hahnemann. I will not comment in detail upon the several other propositions, as I have arranged and num- bered them. The principles which they profess to set forth are not principles, but assumptions. There is no proof, that diseases can be removed MEDICAL DOCTRINES—HOMCEOPATHY. 197 in only two ways, or in only one of two ways. There is no proof, that remedies act on the as- sumed vital force, by producing a modification like that in which the disease consists. We have no knowledge, whatever, of the intimate and ulti- mate action of modifiers, or remedies, on the structure or susceptibilities of the body. All these elements of the doctrine before us, so gravely set forth as facts, are anything but facts. They are all "such stuff as dreams are made of," and nothing else. The whole system of Hahnemann, from beginning to end — in its prin- ciples, and in its details — is one of unadulter- ated and arrogant dogmatism, resting exclusively upon a priori reasoning, or, in other words, upon mere speculation. But, it will probably be said, — the doctrine is sustained by facts; its soundness and correctness are corroborated and demonstrated by the results of observation, — it professes to rest upon experi- ence, as well as upon reason, and the nature of things. The experience upon which Hahnemann founds his doctrine, and by which he professes to sustain it is, if this is possible, more fallacious, and less philosophical, than the doctrine itself. I only insist, that this experience shall be tried by the same test, as has been applied, in this essay, to all medical experience. Let my readers exam- ine the experience which Hahnemann calls in to support his doctrine, and refer it to the rules, which have already been laid down, as applicable 198 THE PHILOSOPHY OF MEDICAL SCIENCE. to all experience in medical science. His work is full of bold and unqualified assertions upon this subject, I admit; but the evidence of the experi- ence itself is utterly wanting. In the entire history of medical doctrines, there is not one in regard to which the proof of their soundness derived from experience is so entirely defective and unsatisfactory, as it is here. Perhaps the most striking fact running through the whole exposition, or Organon, of Hahnemann, is the absolute nullity of all conclusive observation. He says, with no qualification, whatever, "the allopathic method never really cures ;" — " the homoeopathic method never fails to cure ;" but when we look for any evidence of the truth either of one allegation, or the other, it is nowhere to be found. There is no evidence, in the first place, at all conclusive, of the power of the remedies themselves, to pro- duce, in the healthy body, the effects that are so confidently attributed to them. The author of the system lays down a general law, which he wishes us to regard as invariable and absolute, — for instance, that similar diseases must and do cure each other, — the stronger disease always curing the weaker, — and then he gives such facts as the following to prove it. Small pox is often complicated with opthalmia and dysentery, — they are similar diseases. Dezoteux and Leroy report each a case of chronic opthalmia, cured by inoc- ulation ; and the occurrence of small pox cured a dysentery in a case reported by Wendt. Then MEDICAL DOCTRINES —HOMOEOPATHY. 199 another law, — equally universal and absolute, — is established by the following evidence, and by a few other similar cases: — Tulpius tells us, that two children, having contracted tinea, were free from attacks of epilepsy, to which they had been subject, so long as the tinea continued.1 The worthlessness of all such experience has been fully shown in another part of my essay; and it is upon such experience, that homoeopathy, — apart from its a priori doctrines, — urges its claims to our consideration. The efficacy, and advantages, of its mode of treating disease, can be established in only one way, — by only one method. Let it produce its comparable facts, — its cases of dis- ease, clearly distinguished, and separated from other diseases, both in their nosological diagnosis and in their varieties, — and let it produce these in large numbers, — not in groups of twos and threes, or of twenties and fifties, even, but of hundreds ; — let it conform to the rigorous and indispensable con- ditions, which have already been so fully stated, 1 The value attached by Hahnemann to simple experience is very unequivocally manifested by a direct admission in his Organon, of the subordination of its authority to that of his rational, or