CASE 
 
LOCKED 
 CASE 
 
 r 
 
GENERAL 
 
 INDICATIONS, 
 
 WHICH RELATE TO 
 
 THE LAWS 
 
 OF THE 
 
 ORGANIC LIFE. 
 
 BY 
 
 DANIEL PRING, 
 
 MEMBER OF THE ROYAL COLLEGE OP SURGEONS, 
 LONDON. 
 
 Uontion: 
 
 PUBLISHED BY JOHN CALLOW, MEDICAL BOOKSELLER, 16, PRINCES- 
 STREET, SOHO. 
 
 1819. 
 
Wood and Co. Printers of the 
 Bath $ Cheltenham Gaiettc,Bath. 
 
PI 
 
 TO ALL THOSE, 
 
 WITH WHOM THE LOVE OF SCIENCE IS A PASSION, 
 INDEPENDENT OF PECUNIARY GAIN; 
 
 WHO HAVE SUFFICIENT ZEAL TO PURSUE IT 
 THROUGH ALLOTS INTRICACIES, 
 
 AND 
 SUFFICIENT PATIENCE TO SURMOUNT ITS DIFFICULTIES 
 
 TO ALL THOSE 
 
 WHO PREFER TRUTH TO A SPLENDID EQUIPAGE 
 OR LUXURIOUS ENTERTAINMENTS: 
 
 foHotinng Dagre are, 
 
 WITH ALL POSSIBLE RESPECT, 
 
 BY THEIR SINCERE FRIEND 
 
 AND MOST ZEALOUS ADMIRER, 
 AND VERY HUMBLE 
 
 AND OBEDIENT SERVANT, 
 
 THE AUTHOR. 
 
 Hath, December 15th 1819. 
 
 M 
 
ERRATA. 
 
 9, 4, for not, read now. 
 52, 2, for methink, read methinks, 
 56, 28, read from " or" to " inference," 
 
 line 29, in a parenthesis. 
 56, 35, for these, read there 
 72, 36, for entric, read entire. 
 91, 16, for parieties, read parietes. 
 95, 30, read as are all other growths,&c. 
 
 101, 20, for parts, read poets. 
 
 102, 8, for contended, read contented. 
 139, 13, for recollection, read memory. 
 143, 17, read from " be" to " that," line 
 
 20, in a parenthesis. 
 
 149, 44, for ovum, read ova. 
 
 155, 37, read with those precisely form- 
 ed, &c. 
 
 160, 40, for these, read them. 
 
 165, 31, omit comma; to be placed at 
 through. 
 
 167, 17, omit second comma. 
 
 Page Line 
 
 177, 19, for is, read it. 
 
 178, 25, for effect, read effecti. 
 
 179, 7, for our, read due. 
 186, 35, for latter, read natural. 
 199, 2, omit in. 
 
 214, 3, omit but. 
 
 216, 19, for distension, read distentioft. 
 222, 4, for independently, read inde- 
 pendent. 
 
 232, 34, for material, read matter. 
 239, 28, for particles, read particle. 
 259, 12, for Is, read are. 
 269, 26, for the, read an. 
 280, 17, for infections, read infectioui . 
 285, 44, for these, read this. 
 285, 44, for functions, read function. 
 312, 46, for seaton, read seton. 
 316, 46, for purgeing, read purging. 
 317, 45, for irritating, read imitating. 
 341, 27, for upon, read up. 
 

PREFACE. 
 
 To publish a work entirely speculative, appears 
 to be a great innovation upon the fashion of philosophising, 
 which prevails in these times. To those who take the present 
 fashion for a model, or who cannot conceive any other mode 
 of inquiring into physical subjects than by experiment, an 
 abstract or speculative work must appear at least imperti- 
 nent, if not absurd, or monstrous. Notwithstanding the 
 severity of these charges, I have ventured to write, and to 
 print such a book/ not with the design of altering the present 
 fashion, or of introducing a new one ; but rather with the view 
 of furnishing materials to the experimentalists, and of offering 
 some additional suggestions, on a neglected department of 
 inquiry, upon which their labours might be bestowed with 
 apparent advantage. 
 
 To state more precisely the design of this volume, it is to 
 trace, as far as may be done without the aid of new facts, the 
 share which those properties have in the operations and phe- 
 nomena of animal bodies, which are the causes of the distinc- 
 tion between the living and the dead states. With this view, 
 the influence of these properties is spoken of in the principal 
 relations in which it is liable to be exerted or to be considered. 
 The influence of these properties will form a distinct subject 
 of investigation in every process in which it is engaged. Such 
 distinct investigation refers to a complete development of a 
 single topic, or of any separate branch of the subject; and in 
 this respect differs from my present design, which aspires to 
 
VI PREFACE. 
 
 shew only the general agency of these properties, and, as a 
 consequence of this general agency, that no single process of 
 an animal body can be fairly and fully investigated, without 
 taking this agency into the account ; nay, without making its 
 exhibition a primary concern in the analysis of relations. 
 
 The work here proposed for the accomplishment of the 
 experimentalists, is by no means new, or foreign to their 
 habits: considerable progress has already been made in it; 
 but if this progress can be facilitated by any additional sug- 
 gestions, or by a more extended connection of the subject, the 
 cause of science will be greatly served, and my present 
 attempt will be amply rewarded, 
 
 The necessity and importance of the living principle in the 
 phenomena of animals, has been remarked from the earliest pe- 
 riods of observation. That the Ancients were aware of the 
 necessity of this principle, is proved by the fable of Prome- 
 theus, who having formed a man of clay, stole fire from 
 Heaven to animate him : in this fable the word " fire" is ob- 
 viously an allegorical allusion to a principle of life. Since 
 this earliest distinction between matter and life, the last has 
 been variously noticed ; and, until latter periods, has been 
 rather a subject for fancy or imagination than one of philoso- 
 phical inquiry, whether by experiment or induction. But, 
 without excepting any period, the operations of this principle 
 have been spoken of generally and vaguely, with but few ex- 
 ceptions, as will appear from a brief sketch of the light in 
 which this principle has been hitherto regarded. 
 
 The first notice of the existence of a living principle, such 
 as that suggested in the fable, assigned to it no precise im- 
 portance and no particular influence. Many crude and 
 fanciful conjectures were broached relative to an agency of life, 
 and they appear to have been indulged in equally by poets 
 and physicians. From one of the hitter order, a theory sub- 
 sequently arose winch might more consistently have origi- 
 nated with the poets : according to this theory, that of Stahl, 
 an intelligent spirit was said to animate bodies, and to direct 
 
PREFACE. vii 
 
 their operations with great method and design. This theory 
 was too loose, too indiscriminate, to engage long a serious 
 consideration. The fable of Prometheus shews that the in- 
 fluence of a living principle was esteemed necessary to the 
 phenomena of life: the theory of Stahl assigned every thing 
 to this principle : if it had assigned much, it would not have 
 greatly erred ; but in assigning any thing, it did not challenge 
 implicit belief, because it was a fancy, and not an induction ; 
 or because the inference was not supported by the sort of evi- 
 dence which philosophy requires. It strayed still further from 
 sober truth, by proposing an intelligent principle, when the 
 evidence upon the subject barely sanctioned the opinion of 
 the existence of a principle of any sort, distinct from the 
 material fabric. 
 
 Very little has since been added to the theory of Stahl con- 
 cerning the general agency of a principle of life. The exist- 
 ence of the principle was insisted upon with some particularity 
 by Mr. Hunter : and it was said by him, as by Stahl, that this 
 principle was interested in all the operations of living bodies, 
 which is almost reverting to the fable of Prometheus ; for, if 
 the mechanism of a man could not perform the operations of a 
 Hying body, these operations must of course be attributed to 
 the principle without which they could not be performed. 
 The history of the affair thus far is simply this : the Anci- 
 ents supposed the phenomena of animal bodies to be performed 
 by a principle superadded to mechanism ; Stahl endowed this 
 principle with intelligence : Mr. Hunter adverts to the princi- 
 pie generally, as a principle of life, although in one function, 
 that of the absorbents, he appears to fall completely into the 
 theory of Stahl, by making these vessels little less than in- 
 telligent artificers. It is obvious that, up to this period, no 
 great progress has been made in developing the nature or laws 
 of the liring principle ; so loosely indeed has the subject al- 
 together been remarked upon, that the opinions of men are 
 itili divided, whether the phenomena of the living state are to 
 be referred to a principle of life, or whether they result merely 
 from the material fabric. 
 
yiii 
 
 The advocates on either side of this question respectively, 
 assert, on the one hand, that life is produced by the co-opera- 
 tion of the corporeal functions ; on the other, that life is not 
 an effect of the material structure, but a principle superadded to 
 it. Without designing to enter deeply into this dispute, it 
 may be inquired, if life is a product of the functions, or of the 
 mechanism, what makes the mechanism, or the functions ? As 
 (he mechanism falls to decay, and as the functions cease, when 
 life is extinct, it may be fairly presumed that life is instrumen- 
 tal to the formation and establishment of both. If it be said 
 that the structures are formed, and the functions commenced, 
 from a nucleus of peculiar construction, produced from a pa- 
 rental stock ; I reply, that this is attributing more to con- 
 struction or mechanism than is agreeable with analogy. We 
 have no instance of a mechanism which can produce, or reno- 
 vate itself, from its elements. Is the action of the heart, or 
 (he action of any other muscle, or is the secretion of urine by 
 the kidneys, bile by the liver, mucus by the intestines, pus from 
 raw surfaces, &c. to be explained by any resemblance which 
 die construction of these organs bear to the known examples 
 of mechanical arrangements which produce motion ? At least, 
 it is incumbent on those who would assert the affirmative, to 
 shew by what powers in mechanics these animal movements^ 
 and these processes, arc accomplished. 
 
 It must be confessed that there are in animals peculiar pro- 
 perties, which are concerned in their functions : if it be said 
 that these are properties of the matter of which animals are 
 composed, intending thereby a contradistinction to a superadd- 
 ed vital principle, the difference of opinion upon this question 
 then becomes little more than verbal, to all the purposes of an 
 investigation of the laws of these properties. To state the, 
 argument more concisely, it may be asserted by one party that 
 the properties of life have no existence, except in connection 
 with matter ; and by the other party, that the properties of life 
 had an existence distinct from matter, and are, in the form of a 
 vital principle, superadded to matter. 
 
PREPACK. IX 
 
 On this, as on every question, it is proper that we should 
 consult our experience ; and appealing to this testimony, it 
 must be decided that we have no proof of the existence of life 
 in a form, capable of producing those phenomena from which 
 its existence is inferred, except in connection with matter. In 
 every stage of the existence of man, for example, beginning 
 from the ovum as the first perceptible nucleus of his formation, 
 our experience furnishes us with no proof of an independent 
 existence of the properties of life, or an existence separate 
 from matter. In this earliest stage, the future man consists of 
 a few molecules, of no assignable arrangement, in connection 
 with which are the properties which concur to the future de- 
 velopment and functions of the animal. We certainly have 
 no experience that these properties are superadded to a few 
 particles in the ovarium, which previously existed without 
 them, and received these properties subsequently to their own 
 material aggregation. We have no experience of this ; yet the 
 circumstance may hereafter be made to appear, on other 
 grounds, not improbable. Our experience upon the point is, 
 that, in the first recognizable stage of the existence of an ani- 
 mal, properties of life, or disposing to the future functions 
 which characterize life, are in connection with matter; and 
 this connection endures as long as the characteristic pheno- 
 mena of life continue to be displayed. 
 
 If it be asked, can the properties of life have a separate 
 existence from matter ? this question is to be discussed on 
 other grounds than those which apply to the question, do 
 the properties which accomplish the functions of life exist, 
 except in connection with matter ? With respect to the last 
 question, our reply is that the phenomena of life are the result 
 of a relation between certain properties and matter ; that we 
 have no experience of life, or of the existence of vital proper- 
 ties, except in connection with matter: this however may 
 happen for the same reason that we have no experience, or but 
 an equivocal one, of any thing else except in connection with 
 matter, viz. that the senses with which we are furnished have 
 a perceptive relation only with matter. But, in defect of ex- 
 
X PREFACE. 
 
 perience, we rely upon our inferences, our confidence in which, 
 as will hereafter appear, is sometimes very little less than that 
 which is yielded to the objects of positive experience. 
 
 Descending then from the appeal to experience, it is to be 
 inquired whether, upon the ground of analogy to our experi- 
 ence, we are furnished with any proof that the properties of 
 life may exist independently of matter ? Assuming the postu- 
 latum, which it is hereafter attempted to establish, that nothing 
 which has an existence can cease to exist, the question may 
 be thus answered : As the properties of life are real agents, 
 as their agency is proved by their being the causes of certain 
 effects which are imputed to them, it is to be inferred, in agree- 
 ment with an universal law, that although* these properties 
 might change their form, they cannot cease to exist. During 
 life, these properties, as they are consumed, either escape from 
 the body or else pass into the structures. If the former, their 
 existence then becomes separate or distinct from the organized 
 matter : if the latter, as the structures must possess these pro- 
 perties at the time of death ; as at this period not only the 
 arrangement of the material fabric is broken up, but the sub- 
 stance itself will in time become gaseous, or cease to be matter ; 
 so, under either alternative, it appears that the properties of 
 life may exist when they are no longer connected with a sub- 
 stance answering to the definition of matter. It appears that 
 the organized substance, matter itself, might change its form, 
 and cease to be material : and consequently, as the properties 
 formerly in alliance with this matter continue to exist, their 
 existence outlives their connection with matter. Leaving 
 however these questions, in which I feel no great interest, it is 
 proper here to make such apologies or explanations as the 
 pages of this volume may appear to stand in need of, rather 
 than to enter, in this place, upon the discussion of opinions 
 which will not be found hereafter to have been totally 
 overlooked. 
 
 It has been hinted that, whatever the order of the connec- 
 tion between life and the primitive material aggregation might 
 have been, whether the oyum >vas fust formed in the ovarium 
 
PREFACE xi 
 
 and life afterwards bestowed upon it, or whether the life of 
 the ovum originally inhered with the particles composing it ; 
 whichever of these alternatives is the true one is of no con- 
 sequence with respect to an investigation of the laws of life, 
 during those stages of existence in which life and matter are 
 united, and concur in their phenomena. It is x the object of 
 this work to sketch an analysis of some phenomena which are 
 produced by this co-operation. The terms employed to de- 
 signate the department of life are " vital properties, properties 
 of life, the vital principle^ the principle of life, the organic 
 spirit," &c. The two last only will require explanation. 
 By " the principle of life" it is meant to designate the collec- 
 tive properties of life : some properties, or one property, of life, 
 are terms which relate to an inferred analysis of the principle 
 of life. By the " organic spirit" it is meant also to designate 
 the collective, or aggregate, properties of life ; and this term 
 " spirit," which is almost obsolete, is chosen simply for the 
 reason that it ought not to be rejected, or to have become ob- 
 solete, since this term serves as well asany other to distinguish 
 inferred and invisible properties from those which are ob- 
 jects of the senses. This appears to be as much as is implied 
 by the old distinction between matter and spirit ; and my taste 
 is sufficiently gothic to prefer an old term to a new one, when 
 the old one has been disgraced without reason, and the new 
 one is a mere innovation, or an affected improvement, without 
 any real superiority. 
 
 It will be perceived that the preliminary chapters are the 
 groundwork of the subsequent inquiry ; that an application 
 of the principles, laid down in these chapters, is constantly 
 brought in aid of the development of the principal subject ; 
 and consequently these chapters could not have been omitted 
 without the inconvenience of referring perpetually to doctrines 
 which were no where distinctly stated. If it be said that these 
 preliminary doctrines are pushed too far ; that it would have 
 been sufficient to have laid down the principles, and applied 
 them merely to the subject of physiology ; 1 reply, that their 
 universality, upon which alone their credit is supported, would 
 not have been thus physically demonstrated, and consequently 
 
xii PREFACE. 
 
 both the principles, and their application to the subject of 
 physiology, would on this account have been liable to be 
 questioned. Besides which, it is an honester part to shew the 
 full extent of a doctrine, than to leave others to make their 
 own application or construction of it ; and I am the less dif- 
 fident in doing this, in the present instance, because I feel a 
 confidence that the cause which, by an ignorant or a superfi- 
 cial reader, may be supposed to be militated against by these 
 doctrines, is, to fhe extent to which they apply, in reality 
 served by them, as much as a cause can be served by placing 
 it upon a true and solid, instead of a false or fanciful ground. 
 In addition, it may be remarked that the vulgar are not likely 
 to be interested or swayed by a discussion which will not fall 
 in their way ; and which, if it did, they would not understand. 
 I would add, with respect to these preliminary chapters, that 
 they were composed as much as four years since ; and that the 
 work has been several months in the press. 
 
 Another query might suggest itself to the reader, in peru- 
 sing the following pages. How is it, it may be asked, that 
 there is not in the whole book a single quotation, when it is so 
 much the present fashion to publish books which contain 
 little else but quotations ? This question certainly places me 
 in a very unlucky predicament. In justification of myself, 
 however, I must observe, that I did intend to have made one 
 or two quotations from Don Quixote ; but it so happens, that, 
 much as I reverence the authority of Cervantes, I had no oc- 
 casion even for these. But although this custom of quotation 
 has not in the work itself been treated with much respect, the 
 deficiency may be thus made some amends for in the preface ; 
 where, indeed, I have great occasion for a reply to those who 
 would ask why there are no quotations in my book, when 
 works of fashion, and reputed erudition, are found to have 
 three authorities, and sometimes five, at the bottom of every 
 page ? This very deficiency Cervantes himself thus patheti- 
 cally laments : " Other authors can pass upon the public, by 
 stuffing their books from Aristotle, Plato, and the whole com- 
 pany of ancient philosophers; thus amusing their readers into 
 
PREFACE. 
 
 a great opinion of their prodigious reading. Plutarch and 
 Cicero are slurred upon the public for as orthodox doctors as 
 St. Thomas or any of the Fathers. And then the method of 
 these moderns is so wonderfully agreeable and full of variety, 
 that they cannot fail to please. Now I want all these em- 
 bellishments and graces : I have neither marginal notes nor 
 critical remarks ; I do not so much as know what authors I fol- 
 low, and consequently can have no formal index * of them,' 
 as 'tis the fashion now, methodically strung on the letters of 
 the alphabet, beginning with Aristotle, and ending with Zeno- 
 phon, or Zoilus, or Zeuxis, which two last are commonly 
 crammed into the same piece, though one of them was a famous 
 painter and the other a saucy critic." Under which afflic- 
 tion Cervantes is thus consoled by his friend : " As to mar- 
 ginal notes and quotations from authors for your history, 'tis 
 but dropping here and there some scattered Latin sentences 
 that you have already by rote, or may have with little or no 
 pains. These scraps of Latin will gain you the credit of a 
 gjeat grammarian, which, I'll assure you, is no small accom- 
 plishment in this age. And for the citation of so many au- 
 thors, 'tis the easiest thing in nature : find out one of these 
 books with an alphabetical index, and, without any farther 
 ceremony, remove it verbatim into your own. There are 
 fools enough to be thus drawn into an opinion of your work ; 
 at least such a flourishing train of attendants will give your 
 book a fashionable air, and recommend it to sale."* 
 
 Taking leave of the authority of the great philosophical 
 humourist, Cervantes, in objection to this plan of making 
 books out of books, 1 will add a plain reason or two of 
 my own ; to wit, that, except in those systems which profess 
 to comprise all that is already known on a subject, rather 
 than to make any additions to it, there is no great advan- 
 tage in multiplying the copies of books which have been 
 before read under different names ; that, generally speaking, 
 the object of a book of science is to make some addition 
 
 * Vide Author's Preface to Dun Quixote. Ozell's edit. 
 
. PREFACE. 
 
 to the subject of which it treats ; and if an author has no 
 more original thinking to impart than would fill a hand- 
 bill, it is scarcely fair, in order to dispose of so small a 
 commodity, to delude the public into the purchase of a 
 whole book. 
 
 
TABLE OF CONTENTS. 
 
 BOOK I. General Principles ...... ...... .. 1 
 
 Chapter I. Truth ...... . . . . I 
 
 II. Causation ...... ...... 15r 
 
 HI. Universal Scheme, in connection with the foregoing 
 
 principles .... .... 36 
 
 BOOK II. On the Organic Origin of Man . . 60 
 
 Chapter I. Maternal Ovum .... .... .. 64 
 
 II. Fecundated Ovum 77 
 
 III. Origin of Man by Constitution +* 103 
 
 BOOK III. Of Post-Foetal Life ,,117 
 
 SECTION I. General Relations 119 
 
 Chapter I. Condition of the Spirit, &c. . . . . . . 119 
 
 II. Of the Mode in which Life is maintained .... 124 
 
 III. Growth 131 
 
 - IV. Animal Heat ..148 
 
 V. General Relations of Vital, Chymical, and Mechani- 
 cal Agencies , .... - 153 
 
 VI. General Relation of the Spirit with itself, in different 
 
 Seats 162 
 
 SECTION II. On the Preparatory Organs 
 
 Chapter I. General Relations of Preparatory Organs . . . . 171 
 
 II. The Stomach .... .... .... 177 
 
 III. The Intestines .... .. 186 
 
 IV. The Liver .... .... 192 
 
 V. The Spleen .... 200 
 
 VI. The Pancreas .... 203 
 
 . VII. The Mesenteric Absorbents .... ...... 204 
 
XVI CONTENTS. 
 
 \ 
 
 SECTION III. Relations of Blood (and its Products) in its p.^ 
 
 Vessels, and in the several Places of its Distribution 211 
 
 Chapter I. Formation of Blood .... .... .... 211 
 
 II. The Lungs <. .. ..213 
 
 III. Arterial Blood 218 
 
 IV. Relation of Blood with the Heart 220 
 
 V. Other Relations of Blood . . 225 
 
 VI. The Absorbents ...... .. .... 239 
 
 VII. Secretion .... 242 
 
 VIII. Relations of the Organic Life in the Nervous System 251 
 
 SECTION IV. General Nature of Disease 261 
 
 Chapter I. Origin of Disease according to doctrines of Causation 261 
 
 II. Origin of Disease in one Seat .... 273 
 
 III. General Nature of Disease of the Spirit . . . . 278 
 
 IV. Disease of the Assimilating, of the Regular Depend- 
 
 ent, and of the Occasional, Properties of Life .... 284 
 
 V. General Nature of Related Disease 288 
 
 VI. Therapeutics .... 306 
 
 SECTION V. Death of the Organic Life .... 325 
 
 Chapter I. Death in Connection with Disease .... 325 
 
 II. Death, produced by External Causes 334 
 
 III. General Nature of Death of the Organic Life .... 337 
 
BOOK FIRST. GENERAL PRINCIPLES, 
 
GENERAL INDICATIONS, 
 
 Ssc. 8$c. 
 
 CHAP. I. Truth. 
 
 1. As the word "Truth" is used in general, there 
 is nothing further meant by it than that it is synonymous with 
 " belief." Our religion is called the true religion: we esteem 
 Christ to be above Mahomet: a Turk says his is the true religion, 
 yet he conceives Mahomet to be greater than Christ. Another 
 worships the Sun, a beast, or a devil of his own contrivance, and 
 each is ready to affirm that his own is the true religion. Our 
 notion of Truth certainly does not at first sight afford this latitude; 
 it certainly does not allow that things contrary and incompatible 
 can both be true.; and yet it is seen, as in the above examples, that 
 propositions which are contradictory may be respectively believed. 
 If we want more examples, we have them in this way : a merchant 
 hears that a great venture has miscarried; that his ship parted 
 company in a tremendous sea, was speedily lost sight of, and was 
 said to have gone down: this account seems well authenticated, 
 and our merchant (as we are not apt to discredit ill) believes him- 
 self ruined, until he receives intelligence from his captain, saying 
 how the ship rode through the tempest with slight damages, was then 
 safe, and her cargo entire. The case is, that the merchant believed 
 his ship lost, when she was safe. To proceed with fewer words 
 2. A question of Truth is a question of the existence of the 
 object concerning which such question might be proposed. Truth 
 then refers to existence, and may be applied universally as to the 
 existence of the world, or, with limitation, reduced to any par- 
 ticular department or form of existence. To go a little higher, it 
 must be inquired upon what foundation does our idea of existence 
 
rest? and, how far are we to depend upon this notion? To 
 answer these questions we must consider an example of that which 
 we call knowledge.* \ 
 
 3. I see the candle which burns before me : in other words, 
 I have a consciousness of the existence of such an object. Is 
 there any further proof than this consciousness of its existence? 
 If we are asked how we are assured, by such a reason, that the 
 candle really clo$s exist, \vhat can we reply? Shall we say its 
 existence is necessary to produce the idea? What tells us so? 
 Why the impression which we already have; or our consciousness 
 that it does exist. The only proof therefore which we have of the 
 existence of externals, is the consciousness of their existence. 
 
 4. Is it then true that an external exists? We must reply, that 
 we have a consciousness of its existence; by which we mean that 
 it is true. We cannot otherwise confirm the point, or establish it 
 by higher proofs: for any additional reason which may be assigned 
 to demonstrate its existence, must itself be founded upon this 
 consciousness as its only evidence. For example: we cannot pro- 
 pose, as further proof, that if the candle did not exist, we should 
 not be conscious of it; because this is assuming that it does exist 
 upon the evidence of our consciousness. If, therefore, the con- 
 sciousness of the existence of an object, is the only, and an ade- 
 quate proof of its existence, it follows that all those objects of 
 which we have a consciousness do exist. 
 
 5. But this conclusion does not appear to correspond with 
 our notion of -truth, for a man in his dreams may have precisely the 
 same consciousness as if he were in a theatre: his invention might 
 supply the whole drama, and he might criticise the expression of 
 the actors, the sentiments of the piece; he may be conscious of 
 the presence of a friend to whom he communicates his remarks; 
 he may be conscious of every thing that is false, as if it were a 
 reality; and the only truth is that of which he is unconscious, viz. 
 that the whole is the invention of his own mind. Or, a man in the 
 clearest moonlight, when his senses are awake, may have the 
 strongest perception of the figure of a relation who has been some 
 time dead; a consciousness so unequivocal, as to agitate the 
 functions of the organic life. It is to be presumed, that, upon 
 recollection, a sensible man would impute this perception to a 
 disordered state of his faculties, rather than believe in the reality 
 of such a presence. This evidence of consciousness then, in order 
 to prove an external, seems to be defective; or there appears to 
 be an inconsistency in the credit which is to be assigned to it in 
 different instances. 
 
 6. To take an example of another kind : a man, with an in- 
 cipient amaurosis, will say there are spots, motes, insects, or 
 
 * Throughout this chapter the kind of truth, or belief, referred to, is that 
 relating to positive existences; and where this is not expressed it is to be 
 understood, there is a truth, or belief, with respect to non-existence, which 
 is subsequently spoken of. 
 
5 
 
 cobwebs in the air; a man whose vision is, as we say, perfect, 
 pronounces the atmosphere to be clear, and that there are no 
 motes, insects, or cobwebs in it at all. Are there then spots, 
 cobwebs, &c. in the air because our man with the disordered 
 retina is conscious of theml We, who have the accustomed vision, 
 say, no ; but our evidence of the two is the weaker, it is that there 
 are no motes, &c. in the air because we do not see them. Now 
 if our testimony of the existence of an external be correct, viz. 
 that we are conscious of the existence of such external (and we 
 can cite no higher testimony), then it is also true that there are 
 motes, &c. in the air, for their existence rests upon the same 
 evidence which we admit, viz. that there is a consciousness of their 
 existence. 
 
 7. Thus then the difficulty stands: those things which we 
 see, feel, hear, &c. are true respectively, because we are conscious 
 of them; while there are also things, the cognizance of which 
 belongs to the faculties of seeing, feeling, hearing, &c. and of 
 which we are also conscious, but which are nevertheless not true. 
 The real nature of truth cannot be altered by this apparent con- 
 tradiction ; for nothing can be plainer than that, if truth is con- 
 sciousness, consciousness must be truth. 
 
 8. But, it may be said, we suffer conviction, or consciousness, 
 to be a test of truth only, in those instances in which such convic- 
 tion is immutable. I ask again, what is the proof of truth in the 
 immutable instances? It must still be replied, consciousness. 
 Then if that of which we are conscious is true in one instance, 
 why is it not true in another? The cases are identical; for if con- 
 sciousness is truth, and there is no example of truth, which is not 
 established by consciousness, how can we reject as false, that which 
 is itself truth? 
 
 9. It is said that conviction proves a truth only, when it is 
 uniform or immutable with respect to the object. This distinction 
 is generally allowed: but the distinction is an artificial one. The 
 natural testimony of truth is consciousness, conviction, or belief; 
 and that, in nature, must necessarily be always true, which we 
 believe, or of the existence of which we are conscious. The 
 artificial testimony of truth is founded upon the consent of man- 
 kind, by which truth itself, or consciousness, is sometimes rejected 
 as false. Our present business is with natural truth. 
 
 10. A man whose arm is paralyzed puts it into water of 130 
 degrees of heat, and he says the water is not warm : he immerses 
 the other arm in the same water, and he is ready to affirm that it 
 is hot. A person who has taken a dose of laudanum may wake in 
 the night, and see the head of an ox between the curtains: he may 
 recollect himself, and by the testimony of some other sense con- 
 vince himself that he is awake; still he sees the head of the ox, his 
 eyes fixed and flaming upon him: presently he sees the head 
 recede gradually, and perhaps disappear. His conviction in this 
 case was unequivocal ; yet the next day he rejects this testimony 
 
of consciousness, and considers the existence of such an object to 
 have been untrue. To ;i person viewing objects through coloured 
 glass, all filings may appear green: a madman may address his 
 plebeian friend as the Emperor of China, or as the Devil, or as 
 Jupiter, as a fish, or a lion. The real objects in these cases 
 giving rise to different convictions, are the same; our investiga- 
 tion of natural truth, or consciousness, requires that we should 
 say why the same objects produce different convictions. 
 
 11. The palsy of the arm does not affect the temperature of 
 the water; the laudanum has no power to form such an external 
 as a bullock's head ; the disorder of the mind of the madman 
 cannot convert a plebeian acquaintance into an emperor, a fish, &c. ; 
 the colour of the glass, through which objects are viewed, does 
 not change the colour of the objects, &c. If then the same 
 objects produce different convictions, it follows that the difference 
 is in the constitution, or properties of the faculties, which are 
 susceptible of the conviction, or in the medium through which 
 this conviction is obtained. Hence it follows, further, that the 
 consciousness of an existence is the result of a relation between 
 the external world and the faculties by which we become 
 acquainted with it; that the conviction is according to this 
 relation; that if the object is changed, the consciousness of it will 
 also be changed; that if the object is the same, but produces in 
 different persons, or at different times, a different consciousness, 
 that then it operates upon a different disposition of properties, or 
 upon a different state of faculties. The consciousness then, or 
 idea, which we have of an external is according to the nature of 
 the external, and the state of the faculties, or of the intellectual 
 constitution with which it is related. 
 
 12. As consciousness is always the result of a relation, so the 
 consciousness will always be according to the nature, or state of 
 the constituents of the relation. If the external objects are the 
 came, in relation with the same senses or faculties, they will pro- 
 duce the same convictions; but if the same external objects are 
 related with other senses or faculties, they will produce different 
 convictions. Now the evidence, so far as it respects truth or 
 reality, is the same in every case; and consequently all conscious- 
 ness, and therefore all truth, is relative. But it is agreed among 
 mankind, that the only consciousness which shall be admitted as 
 truth, is that which is produced by the operation of externals 
 upon such a state or pre-disposition of the senses as is general, 
 though not universal, among mankind. This is artificial truth, 
 which is a limitation only of the natural truth, and being both 
 produced in the same way, and resting upon precisely the same 
 foundation, they are in nature of course both equally true. The 
 difference between a madman who errs in his senses, and one of 
 an otherwise diseased or defective sense, is that the consciousness 
 of the madman is admitted without respect to artificial truth; that 
 is, he does not acquiesce against his conviction in the truth which 
 
is founded upon the consent of mankind, which consent arises not 
 of a similar constitution or pre-disposition (and hence a similar 
 relation with the same externals) of their faculties. 
 
 13. If all truth is relative, it might be asked, what assurance 
 have we that things are in reality such as we apprehend them ? 
 that our notions of the external world are correct? There is no 
 other ground of this assurance than our own consciousness or 
 belief. Truth is immutable when the constituents of the relation 
 are the sanae ; it changes when the constituents on either part are 
 varied. If the senses of an individual are constituted differently 
 from those of the rest of his species, his perceptions will be diffe- 
 rent from theirs. If the mind of an individual is elevated by 
 genius or education very much above the level of the rest of his 
 species, his opinions of what is true will be differeiat from theirs. 
 If the taste of an individual is highly cultivated, or peculiarly 
 refined, he will pronounce things to be bad which others esteem. 
 good, and the contrary. 
 
 14. Now if it be asked which of these contradictions is 
 true, I reply, they are all true ; they are all true in regard to 
 those who entertain the respective convictions; but they are not 
 all true with respect to the artificial standard, by which, in a 
 general way, truth is decided by the majority which concur in the 
 same belief. Yet this concurrence is so far from making out a 
 standard by which truth becomes fixed and immutable, that the 
 general belief of nations is many times changed, often reversed, in 
 the course of civilization. This happens in matters of opinion, in 
 taste, in our estimation of good and bad; and it would also happen 
 in matters of sense, if the senses were liable to be changed by 
 education, in the same manner as the understanding is changed. 
 If the descendants of the present race for three generations should 
 be destitute of the sense of hearing, they would l>e very apt to 
 reject, according to the artificial standard, the truth of the 
 existence of sounds; or if their senses should be so changed thai 
 they should be conscious only of some of the abstract, and not of 
 the aggregate, properties of matter, the existence of the spiritual 
 world would be adopted as true, and that of the material would b 
 rejected as false. 
 
 15. In all our attempts, in all our arguments to establish a 
 truth, we aspire only to produce a conviction; and our appeal is 
 successful or not according to the susceptibility of belief, in rela- 
 tion to the proofs which are designed to produce it. The same 
 external objects operating upon, or in relation with, the same 
 senses will produce the same convictions of truth and reality; the 
 propositions which are believed as true by one, will be adopted 
 as true by another, provided they are related with the same con*- 
 stitution of mind. If the senses are modified, the convictions ia 
 regard to the objects with which they are related, are also modified. 
 If the mind is so disposed, it may reject the evidence of a. modified 
 sense, and conclude that it is false, because it is not the accustomed 
 
8 
 
 impression, or because it does not agree with the consent of 
 mankind, with regard to the same object. But if there is not 
 this disposition of mind to belief, against the evidence of a modi- 
 fied sense, then, as in the madman, it is wholly trusted. We can 
 in no instance cite a higher evidence for a truth than that we 
 believe it; yet, often, that which we believed at one time, we find 
 at another to be false. These are two results, produced by two 
 different relations: the evidence for that which we now adopt, is 
 precisely the evidence which we before had for that which is 
 rejected. 
 
 16. The nature then of truth is that it is an effect, the causes 
 of which we can generally assign ; and, like every other effect, it 
 varies as its causes are modified. An external, in relation with 
 our faculties, produces consciousness, or a belief of the existence 
 of such external: change the external, and our consciousness is 
 changed; let the external remain the same, but let, in matters of 
 sense, our senses be modified, or, in matters of opinion, let our 
 understanding be modified, and the same objects or the same 
 arguments produce a different consciousness, or a different belief. 
 The result of this relation is, that things, with the subjects of the 
 relation, are what they appear; the results of investigation are an 
 increase or substitution of matters of belief. The highest objects 
 which we propose, by communicating the results of investigation, 
 are to substitute fixed for wavering belief, and to make individual 
 convictions acknowledged generally, or universally, as truths. If 
 convictions, with regard to some objects,, or propositions, are per- 
 manent, it is because, the objects remaining the same, the faculties 
 with which they are related undergo no change. 
 
 17. Truths or convictions may be variously divided: they 
 may be divided into those which are uniform and constant, those 
 which are liable to change, those which are sensible, those which 
 are inferential, those which belong to the memory, those which 
 are calculated to be popular, those which can be adopted only by 
 a few, those which are entertained only by an individual, &c. 
 My business is not with all these. 
 
 18. Conviction, or belief, is sometimes positive, and some- 
 times mixed with doubt. Positive convictions are the effect of 
 certain evidence so related with our senses or understanding, as 
 to produce unequivocal belief. Belief mixed with doubt is the 
 effect of another kind of evidence, so related with our senses or 
 understandings as to produce only a degree of conviction. Ac- 
 cordingly, evidence is esteemed or depended upon in proportion 
 to the conviction which it is capable of producing. 
 
 19. The evidence of the reality or truth of externals is con- 
 sciousness or conviction ; and when we assert things as true, we 
 affirm only our own consciousness or belief. The evidence which 
 produces conviction, consists of the external objects, which, in 
 matters of sense, are so related with our faculties that their 
 existence is perceived ; or in matters of reflection, of the 
 
9 
 
 arguments, which are also so related as to produce physically, in 
 the common way of cause and effect, partial convictions, or per- 
 haps most commonly, belief mixed with doubt. The latter kind 
 of evidence, viz. the means by which belief is produced, is not to 
 be considered. 
 
 20. We gain the belief of an existence either by the imme- 
 diate operation of an external object upon our senses, or by a 
 process of our own minds: the strength of evidence must always 
 be proportionate to the strength of belief. In our examinations 
 respecting the existence of things, our object is to improve our evi- 
 dence, to substitute that which produces a certain for that which 
 produces a doubtful conclusion. We can look for no higher 
 satisfaction, with respect to things, than that we should possess 
 with regard to them the most perfect belief; we can propose to 
 ourselves no higher object of investigation. 
 
 21. It may be objected that universal scepticism must be a 
 consequence of this doctrine : for if, it may be urged, there is no 
 other testimony of the existence of externals, but our belief of 
 such existence; and if the strongest belief is liable, perhaps in 
 rare instances, to be superseded by a different one; how, ad- 
 mitting this principle, can we feel assured of the reality of any 
 thing beyond ourselves, or even of our own existence? I reply, 
 such a doctrine does not lead to scepticism, but quite the reverse ; 
 we cannot help believing: and the negative reason why we believe 
 is very often because we cannot help it: we can no more help 
 believing than we can help feeling: evidence is related with 
 credibility just as the causes of sensation are with sensibility; the 
 necessary effect of the relation in one case is to produce unavoid- 
 able belief, as it is in the other to produce unavoidable sensation. 
 If the relation is frustrated, then indeed neither effect takes place; 
 and a certain belief is no more producible by certain evidence on 
 a deranged understanding, than the usual sensations are producible 
 by certain excitants in the seat of a modified or impaired sensibility. 
 
 22. The modes by which we acquire a belief are three: by 
 an impression on the senses, by recollection, by inference. Belief, 
 or truths, simply of memory, are not produced by a present im- 
 pression upon the senses, or by analogy ; they are merely the 
 recollection of former witnessings, and never produce belief of 
 present existence. But the events or circumstances which are 
 thus furnished by memory, may become the basis of an inference 
 of a present existence. Thus it is a simple act of memory to 
 inform me that my father was alive when I was last at his house, it is 
 an inference that he is alive now; I recollect that he was alive, but I 
 cannot recollect that he is alive, although I conclude it by a process 
 in which this recollection is concerned. I do not think it necessary 
 to say any more about the evidence of memory, except that in 
 point of force it is, when clear and unequivocal, equal to that which 
 produced the belief which memory renews, and which might have 
 been the result either of aniropression on the senses or of an inference. 
 
10 
 
 ^ 23. There is a vulgar axiom which says " seeing is believing ;" 
 so also is tasting, bearing, feeling, &c. It is plain that things 
 which are perceived by the senses become objects of belief. 
 Belief, produced by an impression upon the senses, is rarely 
 superseded by a different belief with respect to the same object, 
 the relation of the senses with the external world being more 
 uniform and less complicated than that of the understanding. 
 But in sensible matters we are apt to believe more than the senses 
 inform us of; and as it passes under the authority of sensible 
 evidence, in this way the infallibility of the senses is brought 
 under question, and perhaps into disgrace. Thus a man, who, for 
 the first time, should see a shadowy representation of men on 
 horseback, would believe them (his judgment not being otherwise 
 instructed) to be men and horses of flesh and blood ; and he 
 would fancy that he believed no more than his senses informed 
 him of. It would scarcely occur to him that he did not see the 
 solidity of these men and horses, or their warmth, or their organiza- 
 tion, or the character in some other respects by which they are 
 identified. But our inexperienced man connects all these latter 
 particulars (whose only relation is with another sense) with that 
 which he sees, or with the effects produced on his faculty of vision, 
 and he would quote the perception of this sense, as the testimony 
 of these particulars. This distinction brings us up to the other 
 mode of acquiring a belief, which we propose to consider: the 
 first has been mentioned above ; but lest by this digression it 
 should be forgotten^ we will repeat, that the first mode of acquiring 
 a belief of the present existence of things, is by the influence which 
 related externals exert upon the senses. 
 
 24. The second mode of acquiring a belief of a present 
 existence, is by a process of the mind termed an inference, the 
 foundation of which is resemblance. The general nature of this 
 evidence may be thus briefly exemplified : a person who should 
 be shewn a black fluid in a bottle, having the taste, the smell, 
 the appearance, and in the common use of ink, would conclude 
 the fluid to be mere ink; and under this belief it would be no 
 great matter of apprehension with him to drink a tea-spoonful or 
 so to oblige a friend, who might assure him that ink was good for 
 his cough; he would, I say, from this resemblance to ink, the 
 composition of which he well knew* infer that the fluid was ink, 
 and might be taken in a small quantity with impunity. The ink, 
 however, may contain arsenic; it may be a black arsenical solu- 
 tion, instead of common ink. Again : a man who keeps a splendid 
 establishment, a fine equipage of carriages and servants, and is, 
 as people say, liberal in all his transactions, would be inferred to 
 be rich; because these are the signs of riches, or these demonstra- 
 tions resemble those of people, who, front a closer acquaintance 
 with their concerns which might amount to an experience, are 
 known to be rich. Yet our man with the equipage may be spend- 
 ing hjs last shilling, or possibly may not have a shilling to spend. 
 
11 
 
 Inference always proceeds upon analogy, it assumes things which 
 the senses do not witness in the present instance, from the 
 similarity of those which they do witness with some which have 
 been perceived before with which the adjunct, the matter of the 
 inference, was found to be connected. In fewer words, we 
 believe things not seen upon an experience of their connection 
 with things seen; or, from analogy which is perceptible in some 
 respects, we infer analogy in others. To multiply our examples 
 
 25. Fire is luminous and hot: whenever we see the former 
 property we infer the latter. Now on what does the truth (by 
 which I would be understood, when I employ this term, that belief 
 which is not likely to be superseded by another), on what does 
 the truth of this inference depend ? If heat is necessary to a 
 luminous body, that is, if a luminous body cannot exist without 
 heat, then we should be right in concluding always their con- 
 nection; but if a luminous body may exist without heat, then we 
 are not certain of the presence of heat in such luminous body 
 until we have examined it by another sense. As a body may be 
 luminous without being hot, we may be deceived in this inference. 
 
 26. When we see water congealed into the form of ice, we 
 infer that it is cold. In this inference we are not likely to be 
 deceived, because we are aware beforehand that ice cannot exist 
 without the coW which we expect to find. We have ascertained 
 that there is a relation of cause and effect between cold and the 
 congelation of the water. Where this relation is known we can- 
 not be deceived, if we infer the cause from seeing the effect. This 
 then is a necessary connection: but there are connections which 
 are not necessary, and it is in our affairs with these that we are 
 so liable to error. 
 
 27. What proof, it will be asked, have we of the necessity of 
 a connection? Briefly, universal experience. But if it should be 
 discovered that there is a property in nature, hitherto unobserved, 
 capable of producing such a congelation of water, in a summer's 
 atmosphere, without diminishing its temperature, we should then 
 conclude that the property producing the congelation of the water 
 was commonly associated with cold; that cold was not essential to 
 this property. Such a property being discovered, our inference of 
 the coldness of the substance, from seeing a piece of congealed 
 water, could not be free from the possibility of error. 
 
 28. But notwithstanding the discovery of a property capable 
 of congealing water, independent of cold, we should be very 
 much disposed to believe a piece of ice to be cold; and as the 
 independent property had not been noticed in the lapse of 
 previous ages, the sense of feeling would confirm our inference, 
 perhaps, every time it was made in the course of most men's lives. 
 And why should we be right so often? Because the association 
 of cold with the property of congelation would be proportionally 
 frequent. 
 
12 
 
 29. Here, then, we distinguish a different kind of force 
 belonging to two descriptions of evidence, viz. certainty, which 
 proceeds from the direct testimony of the senses; and probability, 
 which consists of the frequency of the connection between the 
 thing seen, and the thing unseen, which latter is inferred from 
 witnessing the former. 
 
 30. Probability always implies some doubt, as an inference may 
 always be superseded by a perception : but the degree of doubt 
 belonging to probable evidence is proportioned to the compara- 
 tive frequency of the association inferred, and the absence of such 
 association. Thus a man who should conclude a luminous body, 
 looking like fire, to be hot, would be less likely to be wrong, than 
 one who should conclude such a person to be a Christian, merely 
 because he goes to church; heat being most commonly conjoined 
 with a luminous body, and perhaps not one person in a hundred 
 of those who go to church being a Christian, except just when 
 it suits his humour or his convenience. Experience, or the 
 testimony, in this case, of another sense, would confirm the former 
 inference ; and the latter inference would be liable to be super- 
 seded, in a proportionate number of instances, by the belief of 
 experience. 
 
 3J. Upon this simple plan the immense fabric of human 
 reasoning is constructed. We appeal to the senses for wjequivo- 
 cal proof, or a testimony, the impression of which, while the 
 senses preserve common relations, cannot be superseded; and in 
 the absence of such proof we act upon probability, and we rely 
 upon it with a strength proportionate to the following gradations 
 of evidence: 1st, when the connection is universal, we on this 
 account are apt to suppose it necessary; 2nd, when the exceptions 
 bear but a trifling proportion to the frequency of the association; 
 3rd, when the exceptions are not so frequent as the association ; 
 4th, the judgment is suspended by a recollection of an equal 
 frequency of the associations and of the exceptions; 5th, the 
 inference is negatived, or probability inclines us to the opposite 
 belief, when the exceptions are more frequent than the associa- 
 tions. This gradation appears necessarily true, because we give 
 credit to the inference of a connection, from our past experience 
 of it; and the probability of its occurrence, under apparently 
 similar circumstances, must be in proportion to the times which it 
 does occur, or has occurred. This seems no more than a 
 definition of the common sense of mankind on this subject. 
 
 32. In examining the truth of a proposition, our business is 
 to take account of the evidence, which we shall often find to be 
 most complicated; a knot which the understanding ties perhaps 
 involuntarily, and which the understanding by any effort can 
 scarcely again untie. We shall find the facts, authority, or basis 
 of the evidence to be sometimes doubtful; we shall find it 
 ecessary to examine on what the truth of the evidence depends: 
 
13 
 
 but we shall not take this trouble, unless the probability of the 
 inference is clearly suggested; which will be judged of according 
 to the above estimate of probabilities. 
 
 33. If we think that the evidence of an inference which, as 
 far as we know, is founded on an universal connection, merits the 
 appellation of proof, we must denominate that evidence which is a 
 direct result of an influence on the senses, perceptive, or sensible 
 testimony. The kinds of evidence may then be enumerated ac- 
 cording to their force, in the following order: 
 
 1st. Perceptive evidence. 
 
 2nd. Proof; or that founded on analogy, to which we know of no 
 exception. These two are almost equal in their degree, and gene- 
 rally produce unequivocal belief: the 
 
 3rd. May therefore be called probable evidence ; as when the 
 analogy is rarely excepted against: thus designating this class of 
 inferential evidence by the term which has been employed to 
 denote the whole species. 
 
 4th. Indicative evidence; as when the association inferred, is 
 more frequent than the absence of such association. 
 
 5th. The evidence of possibility; when the connection or 
 association is known sometimes to occur. These three last, which 
 may be considered as different grades of presumptive evidence, 
 give rise to the diversities of opinion ; for as facts are pre-sup- 
 posed to be in opposition, so their comparison will be attended 
 with a different result, according as one or the other set of facts 
 is recollected. 
 
 34. The estimate of probability in all its range is to be 
 made by a comparison of the frequency of association with that of 
 exception. We must also remember that our judgment i^ best 
 qualified to make a comparison between things with which it is 
 most familiar; things with the collaterals of which, with the circle 
 of whose connections, we are best informed, and have treasured up 
 the greatest number of facts; things, in short, of which we have the 
 most common and extensive experience. Thus we are better quali- 
 fied to estimate probabilities (or our inferred belief is less likely to be 
 superseded), with regard to events which occur in the world every 
 day, than with regard to things of which we have had but three 
 examples: for though two of these may be in favour of our 
 inference, yet if these examples were more common, we should 
 perhaps find, as we often do, by progressive acquaintance, that 
 such a preponderance was anomalous; that that which in our con 
 fined knowledge appeared to be an exception, was in truth the 
 most common order of occurrence. 
 
 35. The object of seeking probable evidence, is to produce 
 a belief which comes as near as possible to that produced by 
 perceptive evidence : and the end of our examination of evidence 
 is, that we should not confuse the degrees of credit which are to 
 be assigned severally to propositions; but that we should think 
 according to the best rules we can devise, for making our opinions 
 
14 
 
 such a? would be confirmed by our senses, provided they were 
 qualified to take cognizance of the objects, or that the objects 
 were within this sphere. He is best qualified to make a com- 
 parison, whose experience is the most extensive ; or who makes 
 the best use of it, so as to comprehend in his judgment the 
 greatest number, and the most pertinent facts, which apply to the 
 question. 
 
 36. As inference is founded on supposed analogy, the whole 
 business of the examination of evidence, and the right of deduc- 
 tion, revolves upon the truth of the analogy, or of the points of 
 similitude upon which the inference is founded. If the analogy 
 between two things is perfect, the two things are identical, and 
 are to be distinguished from one another only by some associated 
 properties or circumstances. Hence an inference which is true of 
 one must necessarily be true of the other, provided the dis- 
 tinguishing properties or circumstances are not in either case 
 essential to the truth of the inference : if they are, a difference 
 may exist in these respects which may render the analogy imper- 
 fect, and the inference untrue. 
 
15 
 
 CHAP. II. Causation. 
 
 1. THE most that can be done in order to verify the 
 several particulars of information of which the human understand- 
 ing can be possessed, is to place them upon such a footing that 
 they are entitled to belief; in doing which, those proofs must be 
 admitted which agree with the relations before spoken of, by 
 which belief is produced. This agreement constitutes the only 
 ground of the validity of arguments, and of our appeal to the 
 judgment of others; and it must be confessed that the various 
 compositions of men's minds afford considerable latitude and 
 variety to the forte of the same evidence. 
 
 2. The effect of the operation of externals upon our senses 
 and understandings, is to produce an idea of some presence, of 
 something real, to produce the belief of an existence. 
 
 3. By an operation of the mind, this idea might be con- 
 trasted ; and as on the one hand the belief of an existence takes 
 place, so, on the other, a conception of nihility seems to be formed. 
 Now it is granted, and it must be granted, that we have no ideas 
 but those which are originally furnished by some presence, 
 operating on the senses: and seeing that the senses are impressed 
 only by positive existences, it will be very naturally inquired how 
 we come by the idea of the absence of existence? I reply, that 
 this idea is founded upon some part of our experience. 
 
 4. If a body of large dimensions, of a striking figure, and 
 cognizable to all the senses, but which from an inherent constitu- 
 tion, of from some concealed properties in its constitution, were 
 disposed to pass spontaneously from a solid into a gaseous form 
 (and such things do Occur); I say if such a thing were placed 
 before a man, examined by his eyes, his hands, and all of a sudden, 
 without perhaps the interference of any external cause, were to 
 begin to change its form, to expand in its dimensions, to take leave 
 of its solidity, to get thinner and thinner, until it disappeared 
 without a vestige; the witnessing of a phenomenon of this kind 
 would give rise to the idea of nihility, or the cessation of existence; 
 for something was present to the eye, and this something has dis- 
 appeared : we should say it was, and it has ceased to be. It was, 
 because we were conscious of it through the medium of the senses; 
 this is experience, it has ceased to be, because we are conscious 
 
16 
 
 that we are no longer conscious of its existence ; this is also ex- 
 perience. Our terms of knowledge express very little more than 
 the consciousness which the mind has of its own state: thus it is 
 conscious of being under some sensible impression ; the cause of 
 this impression being removed, it is conscious that it is not under 
 the past, but some present, some other impression. 
 
 5. The belief of the absence of existence is founded upon 
 a presumption with which the mind is possessed, of the ability of 
 the senses to perceive whatever external objects do exist. If the 
 senses perceive nothing in any place or direction, it is concluded 
 that there is nothing in such place or direction. If the proof of the 
 truth of this conclusion should be inquired for, I reply that such 
 is the conviction which the mind has, and which is synonymous 
 with truth, and is as much as can be offered for the truth of a 
 real presence, or for the existence of positive properties. 
 
 6. There are exceptions to this intuitive assurance which the 
 mind feels of the ability of the senses to discover whatever is 
 within the sphere of their relation. When we regard what might 
 be called an unoccupied atmosphere, those who know any thing 
 of chymistry would be convinced that they did not regard mere 
 vacuity, that the field of their vision was in fact occupied by 
 oxygen and azote, real existences. This belief is acquired in the 
 way before mentioned, viz. by inference: but when an inference 
 does not help us to the conviction of some real presence, and our 
 senses also fail to discover such real presence, then we trust to 
 the presumed sufficiency of the senses, and believe that there is no 
 real presence: and we act upon this belief: and we seldom err in 
 consequence of this reliance, because our sensible relations are in 
 general uniform and consistent. 
 
 7. An ignorant man need not go far for his example, if I may 
 so say, of nothingness: not knowing the nature, properties, laws, 
 &c. of the atmosphere in which he lived, he would be ready to 
 affirm that there was nothing in a bell glass, because it contained 
 nothing cognizable to the senses. Antecedent to that knowledge 
 which constitutes the base of our inference, about the constitu- 
 tion of air, the presence of properties, &c. we also should attain 
 the same conviction of nihility in the same example. But as the 
 case stands, if we remove the air from the bell glass, we then have 
 a specimen of the entire absence of any thing existent, there being 
 no substance contained in it, according either to the testimony of the 
 senses or of the understanding. It is an ancient, and, as it ap- 
 pears, an indisputable truism, that no real existence can arise in 
 this vacuum unless it should be admitted, or unless something, as 
 its elements, should be admitted from without: it is hence 
 concluded, 
 
 8. That as nothing (or the vacuum) must for ever remain 
 nothing, so this state of nihility can be changed or interrupted 
 only by some positive cause. Thus far the matter is very clear. 
 But the inference proceeds to affirm, that as a real existence 
 
17 
 
 cannot arise out of nothing, so every thing must be produced by 
 a cause. 
 
 9. In examining' the history of any particular existence, our 
 first question is with respect to its origin: it is how came it to be? 
 could it make itself] no: for it must be before it can act, or have 
 any force or virtue; which is supposing it to be already made. 
 Could it have existed from all eternity without having been created, 
 or without having assumed its present form at any period? no; for 
 these, as appears above, are the terms of a form of existence, viz. 
 that it would not be, unless something had made it; that it cannot 
 arise out of nothing, or exist of itself: from whence it follows that 
 it must be indebted for its existence to something else. 
 
 10. But on what grounds do we make this conclusion, that a 
 thing cannot exist of itself, or without a cause? Do we see this 
 universal law? Have we a sensible testimony in all instances, that 
 we thus presume to include all instances in our dogma? It must 
 be replied, no: we arc but very imperfectly informed of instances; 
 our sensible acquaintance with nature goes but a very little way, 
 we do not pretend that our knowledge is universal ; but where the 
 senses fail us we make inferences, which come sometimes very 
 near to the force, or conviction, of sensible witnessings. The 
 present axiom is allowed to be an inference ; the proper examination 
 of it is according to the grounds of inference before-mentioned: 
 let us take the result of such an examination. 
 
 11. It has been said, that next to the testimony of the senses 
 that proposition comes best recommended which agrees with all our 
 experience: it has been said, that a proposition, so enforced, is not 
 to be doubted ; that if such a one is doubted, or rather if it is pre- 
 tended to doubt such a one, we may with more reason reject totally 
 nine-tenths of the conclusions upon which we practise every day, 
 and are seldom deceived: for we are aware of some, though per- 
 haps rare exceptions to the truth of most conclusions; but in our 
 strongest degree of evidence, where from no known exception a 
 necessary connection seems to be exhibited, I say in this evidence 
 we must acquiesce, how forcibly soever we may be inclined other- 
 wise: we cannot chuse; our will may oppose, and we may make a 
 different profession; but our understandings will accept as a truth 
 a proposition so supported. Let us see whether our first principles 
 of causation rest upon a testimony of this kind. 
 
 1*2. Our views are confined to the departments of nature and 
 of art : of the works of art we have a conviction, acquired by much 
 labour, that they do not make themselves; that they would never 
 exist, as works of art, but by the means which produce them. We 
 have then, in this department, no example of any thing that exists 
 which* is not made by something else. In nature, all the several 
 instances will conform to one pattern. As this is more especially 
 our theme, let us pursue closely the thoughts connected with one 
 familiar example. 
 E 
 
18 
 
 13. A tree: why does it exist? upon what does its existence 
 depend? or, why is it a tree? It is made such by its roots, trunk, 
 and branches; without these it would be no tree: these are the 
 parts of a tree ; and if these parts are necessary to the definition of 
 a tree (which may be arbitrary, and is of no consequence), to the 
 identity of a tree, why then the tree could not exist without them. 
 But then these parts what makes them? The aggregation and 
 arrangement of ligneous fibres. What determines this aggregation 
 and arrangement of fibres? Certainly some cause; for the fibres, 
 if not endowed with this property, or if not affected by some agent, 
 would never aggregate or become arranged. We come at last to 
 examine the origin of the fibres: what makes them? Their par- 
 ticles of the same nature make their bulk; and other constituents, 
 which chymistry to some extent can display, make their nature. 
 Then these particles how are they made? Shall we say by par- 
 ticles still more minute, and by chymical properties? Thus far we 
 may go with the witness of the senses, at last we shall arrive at what 
 are termed elements; and if these elements can exist without the 
 condition of existence before expressed, viz. that they also must be 
 produced by some cause, why then we must give up the universality 
 of our axiom. 
 
 14. As far as our experience goes of the origin of things (and 
 we have an ample experience in this way, no less than that which 
 comprises all our knowledge of processes or of occurrences), we do 
 not know a single example in which the condition of existence is 
 not this, viz. that the thing would not exist, but for a process of 
 formation, or unless it were made by appropriate causes. The 
 elementary substances and particles, it will be said, are exceptions; 
 what then, do we know that these are truly elements^ mere units, 
 comprising in their existence only a single property ? No, it must 
 be replied, we do not know this; but here our analyses end. This 
 then is the state of the argument : nine tenths of the objects of 
 which we have any cognizance, are made perceptibly by causes; 
 that is, all the objects, the terms of whose existence we are ac- 
 quainted with, acknowledge this necessity of a causation, without 
 which they would not exist (and where shall we apply for a know- 
 ledge of these terms, but where they are manifested to the sensesT). 
 There are other objects whose origins we know nothing about, and 
 by which, consequently, we are furnished with no experience (and 
 therefore with no grounds for a conclusion); objects, of whose con- 
 ditions of existence we are not qualified for a sensible testimony ; 
 and the inference is, that these latter require the same process of 
 causation as the former. 
 
 15. The strength of the inference is this : from things seen (or 
 witnessed by a sense) we infer things not seen; we do this as 
 before explained, upon the ground of analogy. In the present 
 instance, is the analogy perfect ? It is unexceptionably perfect : for 
 what are the terms of existence? is the question; and it will not be 
 denied that the existence is mutual, that it obtains throughout, and 
 
19 
 
 is the property of every thing to which our question can be applied, 
 which of course does not respect non-entities. The analogy then is 
 perfect? It must be granted, in all instances? an exception is im- 
 possible. And the conclusion which is transferred upon the ground 
 of this perfect analogy, as far as our knowledge goes, is also with- 
 out an exception ? it must be allowed. Then the general pro- 
 position, viz. that nothing can exist without a cause, is one esta- 
 blished upon the first order of inferential proof; which in point of 
 authority has been shewn to be but little below (scarcely a definable 
 inferiority) the direct testimony of the senses. 
 
 This is a point upon which we must be very scrupulous : it is 
 not to be admitted \vithout undeniable evidence, and that adduced 
 it cannot be cast aside. It is an important conclusion: a single 
 axiom founded upon it is equal to a volume of principles, in the 
 extent of its application ; on this account I think it right on one 
 occasion to be a little prolix. 
 
 16. If the hour-hand of a watch now points at the figure 
 twelve, and presently stands opposite to the figure four, would any 
 one doubt but the hour-hand of the watch had moved? no. But 
 was the motion of it seen or felt ? is it known by a direct testimony 
 of the senses ? no : the progression is too slow to be perceptible. It is, 
 notwithstanding, concluded that there has been progression ? certain- 
 ly, there is no doubt of it. How is this firm conviction attained ? thus, 
 when a body changes its place, the course of its progression in 
 other examples may be perceived; it may be seen to move (changing 
 the place is the point of analogy}: when therefore a body has 
 changed its place, though, as in the instance of the hour-hand of 
 the watch, it proceeds too slowly, or, in the case of a musket-shot, 
 it goes with too great velocity, to be seen ; yet the body has 
 changed its place in either instance ; and this is a point of analogy 
 between the latter instances and those of bodies whose progression 
 is perceptible, upon which we found an inference that it would be 
 absurd to doubt. Yet there is no other testimony of its truth, but 
 the universality of the occurrence of motion in bodies which are 
 seen to move when they do change their place. This is a parallel 
 with the basis of our first principle of causation ; and many others 
 may be cited, some hundreds or perhaps thousands, all of them 
 affording, according to common sense and received opinion, indu- 
 bitable inferences. 
 
 17. But in addition to the proof of analogy upon which our 
 first principle has been shewn to rest, and which is on other oc- 
 casions rather less abstract, considered sufficient, there are not 
 wanting other proofs. I would ask, does not our experience in 
 those which are called elements, prove that they are not elements? 
 A supposed elementary particle of matter, for instance: does it not 
 possess weight? does it not exhibit a power of attraction? Inde- 
 pendently of these common properties of matter, has it not some 
 nature? has it not some chymical properties, perhaps some vital 
 ones, or properties holding with life an additional relation? all of 
 
20 
 
 which are essential to identify this particle of matter. Take away 
 any one of these ; make our elementary particle thus much defi- 
 cient, and the dependence of this particle for its identity will also be 
 shewn to be upon its causes; for the same chymical property, sup- 
 posing it to be that of an alkali, may exist without solidity, or it 
 may exist with a different property of attraction, with altogether an 
 altered relation with other substances. The same may be said of 
 the gaseous elements: who has decomposed oxygen? yet is not 
 oxygen capable of maintaining flame, of producing acidity? It 
 possesses weight, it may assume a tangible or a visible form ; and 
 united with another element, with hydrogen, does it not constitute 
 combustion? and in another form, as that of water, does not the 
 same union prevent ignition, or counteract it, having taken place? 
 Do not all these operations exemplify different, numerous, pro- 
 perties of the same thing? and if one of these properties were taken 
 away, would not our elementary oxygen be something else ? would 
 it not want one property by which it is identified ? Who shall tell 
 me then that we have experience of an elementary particle? But I 
 rest not the argument upon this basis. I will even suppose there 
 are elements, five or six hundred elements, to our perception; and 
 will trust, as has been done, the proposition to the support which it 
 finds in the right of inference. 
 
 18. Now if nothing can exist without a cause, it follows that 
 all things are effects. It also follows, that every thing which exists 
 is made by more than one cause ; a principle which if it can be made 
 clear, disposes very readily of oijr question about elementary 
 substances. 
 
 19. What is a cause? The term implies a relation: it is that 
 which is capable of producing something different from itself, which 
 something is called an effect. This also is a relative term, it im- 
 plies that which results from the operation of a cause. 
 
 20. What virtue is there in a cause which enables it tp pro- 
 duce something different from itself? a question well urged : why 
 truly, none. If a cause could produce an effect which is different 
 from itself, that in which the difference consists, if it be superadded 
 to the cause, must originate from non-entity : which is contrary to 
 our established principle. If it be only a part of a cause, some 
 properties having been abstracted, why then there is no act of pro- 
 duction; for that only i emails, and is tlje effect, which was before 
 produced. A single cause is no agent, it is an identity, but capable 
 of no transaction: for a thing cannot supply or confer what it does 
 not possess ; all it can supply is itself, or its own identity. How 
 then do effects comprise the cause, and still be something different 
 from the cause? 
 
 21. As a single cause can produce nothing different from itself, 
 and as the effect, according to the relative signification of the word, 
 is more than the cause ; and as this difference cannot originate out 
 of ijon-entity ; so the difference must on these accounts be supplied 
 by something else. The effect then depeuds, not upon one, but 
 
21 
 
 upon more than one cause ; and as all things are effects, there can 
 be nothing simple and elementary, but all things must be produced 
 by causes. 
 
 22. The causes which make an effect can supply nothing but 
 themselves, nothing but that which pre-existed the effect there- 
 fore is no new existence, but it js a new form : called new, from its 
 having taken place at some known period. Surely, it will be said, 
 an effect appears to be very different from its causes? It must be 
 different from its individual causes, but is that which it is made fry 
 them all ; the causes must be different individually from their effect, 
 or the whole; and this, in some respects, is a gigantic principle. 
 
 23. The mode by which a cause acts has nothing mystical in it, 
 it is itself, and no more than itself, and it can do no more than exist. 
 But it may exist separately, that is, as an effect dependent only 
 upon its own causes. When it performs that which characterizes a 
 cause, viz. when it produces an effect, it is by combining with some- 
 thing else. 
 
 24. In this combination there is no new production ; bqth 
 causes (or if they were a thousand it would be the same thing) are 
 changed, so as to exist, still preserving every property which belongs 
 to them, in another form. This other form is the effect which is 
 thus conjointly produced. 
 
 25. Causes do not lose their existence in changing their form : 
 although in the effect the causes separately may not be recognized, 
 they cannot lose their existence; the whole is a different combina- 
 tion, and of course possesses a double set of properties, which will 
 individually have some share in determining its character. Every 
 thing is liable to be considered as an effect: and all those things are 
 liable to be considered as causes, which, from a relation between 
 themselves and others, might change their form and produce effects. 
 
 26. The relation just mentioned is an effect, and of course 
 determined by its propei causes. 
 
 27. There are effects in which the causes are lost to our 
 senses, as in most or all chymical mutations. These causes are 
 nevertheless discovered in such effects by analysis; and when these 
 causes are withdrawn, the existence which they helped to compose, 
 ceases, or these effects cease. There are other effects where the 
 causes are separately recognized: such are the effects produced by 
 arrangement of causes, where the parts are seen individually, but 
 where the effect results, a$ in other instances, from the combination 
 of the whole. 
 
 28. Single effects in a body are an arbitrary limitation : they 
 are so if the mind chuses to consider them as such. But the whole 
 body may be regarded as an effect, and then these minor ones come 
 to be regarded as causes. Thus our earth is an effect, so is the 
 meanest particle which helps to compose it. 
 
 29. Consistently with the definition before given, and as a test 
 of the relation therein mentioned, a cause is that without which the 
 ffftct cannot exist: it is identified with tlie effect, and by this cir- 
 
22 
 
 cumstance is distingnished from all associations ; a distinction, how- 
 ever, which it it is sometimes most difficult to make, but which, for 
 the purpose of accurate reasoning, is of all other distinctions the 
 most essential. 
 
 30. The test of a mere connection is the abstraction of the 
 thing, or property, constituting perhaps a supposed cause, and the 
 permanence or cessation of the effect. If, upon the removal of a 
 connected substance, the effect remains unchanged, the substance in 
 question is an associated or connected one only, and no cause; and 
 the contrary. 
 
 31. The relation between causes, disposing them to unite and 
 form effects, is sometimes called an affinity ; it is, however, an act 
 of causation produced by properties inherent, though seldom or 
 never perceived in the causes. This act has also its effect, which 
 is among the latent combinations of the causes of bodies. 
 
 32. Thus we see that causes are identified with effects, that 
 there is no cause which is not contained in the effect, for a cause is 
 that without which the effect cannot exist. There are in the sciences 
 many instances which I could point out, and most likely a great 
 many more with which I am not in the least acquainted, where 
 associations are currently considered as causes. Indeed nobody has 
 been at the pains to define this matter, and it is therefore no won- 
 der that such a mistake should prevail. A person sees at a distance 
 a horse, and he is ready to affirm that the horse is the cause of this 
 instance of vision; but it is net so ; the cause which produces vision 
 in this case is, according to the common theory, the modification of 
 light; and the same vision (as by the shadowy representation of a 
 horse) may be produced by the same modification of light, where 
 there is no horse. Now this example would be urged as an ob- 
 jection to my principle; but examples should be scrutinized before 
 we give them an application. It will be said (pursuing the objec- 
 tion), the horse is the cause of the idea we have of a horse ; yet we 
 have this idea when the horse is not present: and certainly this 
 cause, viz. the horse, never entered into our minds, and became a 
 cause of the effect by existing in it, in the way described. Let us 
 follow this matter to the extremity. 
 
 33. The mistake is this, that a whole series of processes of 
 causation is considered only as one act. The stomach and digestive 
 organs, the lungs, the heart, the blood, and the blood-vessels ; the 
 brain, the spinal marrow, and the nerves; the bones, the muscles, 
 the skin, and all other parts, and minutest constituents of the parts 
 of the animal, are the causes of the identity of the horse; by these 
 and by its life, it has certain properties of solidity, colour, figure, 
 &c.: these latter have a relation with light, that is, they conjoin 
 with it to produce an effect; while the internal viscera, all parts 
 beneath the surface, have no relation with light: light has a relation 
 with the eye and acts upon it, while of course the internal viscera, 
 not being concerned in this relation, are not comprised in the effects 
 of it. The cause of vision is the modification of light, producing a 
 
23 
 
 certain perception. Now in this stage remove all these things be- 
 fore mentioned, remove the horse, let also the modification of light 
 be absent, and with it let also the perception vanish ; the perception 
 has taken place: this effect has been produced, and another series 
 of causation is commenced. The perception is related with intel- 
 lectual faculties: the idea of the horse is at this time produced ; 
 this idea has its relations with other ideas, and if we want the horse 
 we perhaps look for a halter in order to catch him. All these 
 things originated from the horse, we say; true: and the horse, where 
 did he originate from? We may as well begin to date the origin 
 of our notion, of our idea, from thence ; because it is plain that 
 unless the horse had first been made, we could have had no concep- 
 tion of him. According then to the ordinary signification of the 
 word CAUSE, the blood which circulates in the horse's ears is the 
 cause of our idea of the horse, yea, and the chymical properties of 
 that blood ; and, to go higher still, the manure which produced the 
 grass from which that blood was made; and, to look still further, 
 the animal who excreted that manure, and all his causes for some 
 generations back, were all causes of our idea of the horse, since we 
 never should have seen the horse if these things had not been. 
 
 34. But the remote existences and relations exhibited in the 
 above account do not agree with our definition of a cause; which 
 is, that without which the effect cannot exist. Now as the effect, 
 viz. the idea, can exist without all these things, and does exist when 
 they are all removed, we cannot say that the effect depends upon 
 them as causes, for the effect is when they are not, or are entirely 
 out of the way of influencing it. If we want a short expression for 
 convenience, we may call these " remote causes," of various degrees 
 of approximation to the effect. But if we desire to know what they 
 really are, we shall find them to be nothing more than a series of 
 changes, which lead to others by processes of true causation, 
 through many intermediate relations. Each of these changes is a 
 distinct act of causation. Each individual change exists inde- 
 pendently of all those which went before it (provided such is the 
 relation), and has no ability to maintain the existence (which is the 
 business of a cause) of any of those which might succeed to it; but 
 depends only on such causes as agree with our definition. 
 
 35. It will be urged, an effect cannot take place without those 
 which are termed " remote causes." This is true: yet these 
 remote causes do not necessarily help to constitute the effect, the 
 effect takes place as the act of its immediate components; the 
 cause which brought them together was the effect also of its im- 
 mediate components. The difference between such a series of acts 
 of causation, and one single act, arises from the multiplicity of 
 related existences. Examined in this manner, there will be found 
 no example in opposition to our principle, viz. that there is no 
 cause which does not enter into, is present in, and combined with, 
 the other causes of the effect. If any such should be supposed, it 
 will be found upon closer scrutiny to be a connection, but not a 
 
24 
 
 cause; not indispensable to the existence of the effect: and this 
 must of necessity be true, since a cause can operate only by sup- 
 plying its own self; and of course where it is not, there it can have 
 no influence. 
 
 36. Now although this appears to be a true account of those 
 which are called remote causes, yet there are some difficulties in- 
 volved in it which require to be further explained ; no less for the 
 sake of consistency, than for the purpose of exhibiting more fully 
 the true extent of the relation. 
 
 37. It is acknowledged that a cause always exists in the effect; 
 or if the effect can exist without it, the supposed cause is none, but 
 merely a connection. But an effect cannot exist without these 
 remote causes ; is it not therfore necessary, it may be asked, that 
 any single effect which we contemplate, should participate in the 
 causes, however remote, which led to it? Thus, for example, if a 
 steeple should fall in consequence of being struck by lightning, and 
 a justice of the peace (as a brief specification of an example), passing 
 by at the time, should be killed by a stone which fell upon his head, 
 would not the lightning be the cause of the death of the justice? 
 To pursue the objection, it may be said, stating the case more fully, 
 the lightning precipitated this stone from the steeple, which cause 
 was contained in the stone as long at least as it was actuated by it ; 
 still urged by the lightning, the stone fractured the justice's skull; 
 the fractured bone, driven by the force of the lightning contained in 
 the stone, lacerates the brain, in consequence of which its function 
 ceases, and the justice dies. The question is, whether the lightning, 
 by fair constitution, in the true way of causation, converts a living 
 principle into the condition of death 1 
 
 38. As we find that death may arise from a somewhat similar 
 accident, where there is no lightning in the case; so we must con- 
 clude that the effect, namely, the condition of death, mav exist, and is 
 identified without lightning, and that therefore lightning does not 
 in this instance mix with the living principle, changing its identity 
 from the living to the dead state. By this coarse illustration 
 (chosen because the processes are obvious) we are furnished with a 
 general distinction explanatory of the laws by which remote agency 
 is governed: the distinction is this, the lightning is a cause only in 
 respect to concurrent agents with which it is so related, as to pro- 
 duce an effect conjointly with them. The extent of the causa- 
 tion of the lightning is dependent upon its relation; which 
 relation, as before explained, is settled by the presence of 
 causes: thus, allowing that the stone contained lightning at the 
 time that it fractured the justice's skull, yet the relation between 
 the agents might be, that the bone received properties only common 
 to an impulse of any kind, and had no relation with the lightning 
 by which it might be derived to itself from the stone; or, supposing 
 that the bone participated in the lightning, and thus furnished, 
 entered the brain ; yet the effect upon the vital principle would be 
 caused by other parts of the agency, and iu no degree by the 
 
25 
 
 lightning, provided the relation of the latter with the series 
 ceased with its passing into the bone. 
 
 39. But although this distinction seems a very obvious one, 
 yet there is often much difficulty, nay, it is sometimes impossible 
 to make it: we may define the principle of the distinction, and 
 have no doubts about it; but we cannot assert the truth of our 
 limitation, if it should be required, in all particular instances. 
 Thus, for example, a drop. of oil of vitriol, applied to the sciatic 
 nerve pretty near its origin, would produce a convulsion of all the 
 muscles, and perhaps destroy life. Now the properties of the 
 oil of vitriol are related with those of the nerve, these latter with 
 those of the spinal marrow, these last with those of the whole 
 muscular system. Where then, I would ask, does the agency of 
 the properties of the oil of vitriol cease? They produce a change 
 in those of the nerve, which change is communicated to the pro- 
 perties of the spinal marrow, producing a change in them; what 
 then is the relation between the oil of vitriol combined with these 
 changed properties of the nerve, and the properties of the spinal 
 juarrow? The mode itself of causation is extremely simple, yet, 
 from the interchange of the process in phenomena, it becomes 
 inscrutably complex. Let us however pursue the question a little 
 further. 
 
 40. The properties of the oil of vitriol are so related with 
 those of the nerve, that the latter are made, by combination with 
 the former, an altered identity: this identity has relation with the 
 properties of the spinal marrow. Now this relation must agree with 
 the modes of causation: it may be, that the spinal marrow is in- 
 fluenced by more properties than usual, or by fewer properties 
 than usual: it may be influenced by addition or by privation. 
 Thus, in the natural state, properties of the nerve may be per- 
 petually passing from the nerve to the spinal marrow, as they are 
 from the spinal marrow to the nerve; the combination which is 
 produced by the oil of vitriol and the properties of the nerve, may 
 have no relation with the spinal marrow; the office of this last 
 would then be changed for want of the usual influence : or the 
 relation of the oil of vitriol may be only with some of the proper- 
 ties of the nerve, admitting the usual communication of others to 
 the spinal marrow, this partial supply of usual properties would 
 derange the function of the spinal marrow by privation ; or, the 
 relation of the acid may be with all the properties of the nerve, 
 and the combination thus formed, may be related with the spinal 
 marrow ; then the relation of the properties of the oil of vitriol, 
 thus communicated to the spinal marrow, may be with all or with 
 some of its properties, thus modifying the result; and the relation 
 of the acid may either stop with all, or some of the properties of 
 the spinal marrow: or the properties of the former, conjointly with 
 those of the latter, may be extended to the muscular system. 
 Thus we see what difficulties oppose the attainment of a precise 
 philosophy, which emulates the knowledge of the causes which 
 
fix identities, however minutely the analysis might be attempted, 
 It is plain, from this exhibition, that if we cannot be content with 
 the looser or more general information, we are likely to remain 
 dissatisfied for a very long time. 
 
 41. This part of the subject naturally leads to another topic: 
 the connection is this, we have talked about a single drop of oil 
 of vitriol producing such diffused and mighty effects, and we see 
 on other occasions how agents, apparently of inconsiderable 
 bulk, operate upon a wide field, and still preserve some title to 
 the appellation of causes. This then naturally brings us to a 
 more detailed view of the relation of quantities. 
 
 42. It is scarcely necessary to say that by the word " quan- 
 tity" is to be understood, the repetition of parts possessing the 
 nature of the whole. 
 
 43. It has been admitted by those who have written speci- 
 fically upon matter, that the smallest quantities are infinitely 
 divisible. This notion has been said to be come at only by a 
 process of the imagination: but the proposition is further sup- 
 ported by the application of those laws which determine the 
 properties, to the quantities, of things; for, as every property has 
 a certain sum of its nature which is inseparable from its existence, 
 and as every property is constituted by other properties, and these 
 likewise being of certain sums, so it follows that quantity is in all 
 instances, infinitely compounded, the larger, or the more con- 
 siderable, of the lesser or fewer parts. 
 
 44. But this theory seems to carry with it its own refutation: 
 for if the quantities composing the smallest particles are infinite, 
 what shall we say of those which belong to the largest masses? 
 The direct reply is, that they are infinite too. Thus then we have 
 two specimens of infinity, of which one is the greater and the 
 other the less. Now if an infinite divisibility is true in all in- 
 stances, the difference between our specimens is this, that sup- 
 posing the division of the parts of the two specimens to proceed 
 together, ad infinitum, the parts of each will continue to preserve 
 the same relation as their whole respectively. 
 
 45. If we take, for example, so immense a bulk as the half of 
 our globe, from our actual experience of the divisibility of matter, 
 the visible minuteness of its particles, &c. it will almost be allowed 
 without the aid of inference, that the contents of this bulk in 
 minute particles are infinite; especially when we consider that 
 those of a single grain of sand, reduced to powder, are too nume- 
 rous for our calculation. Yet it is obvious that the particles com- 
 posing one half of the globe, though they are allowed to be in- 
 finite, are not so numerous as those which compose the whole. 
 
 46. My business is not with verbal inconsistencies, nor shall 
 I trouble myself to examine whether they exist; it is sufficient for 
 the purposes of correct information to accept the truths which are 
 proved by experience ; the only commentary therefore which I shall 
 offer upon the facts respecting this apparent difficulty is as follows : 
 
27 
 
 47. Every quantity may be considered positively, as an 
 identity determined by. its contents: every quantity may be con- 
 sidered relatively, or in comparison of its contents with those of 
 another. The two quantities, though different, agree in the cir- 
 cumstance of an infinite divisibility, which is the positive property 
 of each ; but they differ relatively in the proportion of their parts. 
 
 43. Infinite divisibility is a property common to all quanti- 
 ties; but, for purposes of convenience, it is necessary that we 
 should make a suppositions ultimate quantity of the lowest per- 
 ceptible minuteness : thus in numbers we have an unit, in sub- 
 stances a particle. Now the largest bulks are made up of those 
 particles, and by them the largest bulks possess the property 
 which they themselves possess. If the particle be an ultimate 
 quantity, the divisibility of the bulk, it being reducible into par- 
 ticles, and made up of the repetitions of finite quantities, must be 
 finite; but if the particle be divisible in infinitum^ then the bulk, 
 being composed of the repetitions of infinite quantities, must itself 
 be infinitely divisible, the whole possessing the quality of the 
 parts, and the parts of the vyhole; the whole being more than the 
 parts, because the whole contains more of the infinitely divisible 
 particjes. 
 
 49. It is possible to pursue these thoughts much further, and 
 to start many other difficulties: but to do so would only be to ex- 
 hibit some subtile reasoning, by which they must at last be recon- 
 ciled, and the argument would terminate with something like the 
 following conclusion, viz. that every quantity is made finite by 
 synthesis, and is infinite in analysis; that divisibility is a property 
 common to all quantities, and therefore belongs to the least as 
 well as to the largest; that the difference between quantities con- 
 sists in the various repetitions of infinitely divisible minute quan- 
 tities, whjch compose the respective masses. 
 
 50. The closest definition of the facts will not permit our con- 
 sidering a given quantity as infinite. But when we use this term, 
 \ve speak of its contents: thus, if the body of a man or a horse 
 were the given quantity, when the analysis had proceeded so far 
 as to have divided him into four or eight parts, we should scarcely 
 say that, pursuing the analysis, upon cutting one of the legs in two 
 we had made another division of the man, the quantity composing 
 the man having ceased; nor should we imagine ourselves making 
 a further division of the leg when we were about the fourth section 
 of a toe-nail. The quantity which belongs to an identity is divisi- 
 ble, this being a common property: that quantity reduced to halves, 
 the former identity, so far as depends upon quantity, has ceased; 
 then the parts come to be divided and lose their identity, then 
 other parts; a common property of all things being divisibility. 
 Thus, it is not an infinite divisibility of things identified by quan- 
 tity; but the term infinite is applicable only tq their contents. 
 In this account I am scarcely aware of having digressed at all 
 from the enumeration, of facts : or if I have, it is only in making u 
 
m 
 
 choice between the two suppositions, of whether the particles, 
 which are too numerous and minute for calculation, shall be sup- 
 posed to be finite or infinite. Having said thus much of the 
 nature of quantities, it remains to discuss a few points which 
 belong to the subject of proportion. 
 
 51. Proportion may be considered, first, as it belongs fo 
 things existing separately ; and, second, as they are conjoined in 
 agency. An example of the former is, as when we compare the 
 size of two mountains, existing perhaps in different quarters of 
 the globe; an example of the latter is, as when two agents com- 
 bine to produce an effect, in that which has been called the true 
 inode of causation : my business is with the last. 
 
 52. A small quantity appears capable of influencing the whole 
 contents of a large one: thus a single drop of sulphuric acid will 
 acidulate slightly a pint of water, containing perhaps 7,680 drops. 
 There are still more striking examples to the same purpose, but it 
 is unnecessary to enumerate them. Now as the amount of infinitely 
 divisible particles is, between these two, very disproportionate, how 
 comes it that the contents of the single drop should be capable 
 of a divisibility corresponding with that of the 7,680 drops? 
 
 53. Supposing (as we may for the sake of the argument, though 
 it is not quite correct) that one drop of the water were equal in 
 its contents to the drop of sulphuric acid, then if each were re- 
 duced to a million parts, and were reducible no further, the oil 
 of vitriol would be capable of imparting its influence to no more 
 than the contents of one drop of the water. Nor is the conclusion 
 different, upon the supposition of an infinite divisibility belonging 
 to each; for if one half of the drop of oil of vitriol were removed, 
 or diffused, the remaining half drop, upon being divided and 
 mixed with the whole drop of the water, would riot influence the 
 whole of its contents, because the quantum of divisible particles 
 in the water would be always double those of the sulphuric acid; 
 notwithstanding which, the whole pint of water will be influenced 
 by the drop of the acid, and each drop, each particle of the 
 mixture, will appear to possess the same properties as the whole. 
 
 54. But in this case it is necessary to infer that the propor- 
 tion of the ingredients in their division is equal to their pr0- 
 portion when aggregated ; that is, however comminuted and diffused 
 the drop of the acid might be, there will be contents of the 
 quantum of water which are not influenced by the particles of 
 the acid : if the drop of acid be infinitely divisible, so is a drop 
 of the water; if the mixture were confined to the two drops (of 
 the acid and of the water), there would be an agreement or 
 equality of proportion among the particles; but if the acid is 
 diffused among many drops of the water, then its particles can 
 apply only to combinations of particles of the water. 
 
 55. The law therefore of proportion between conjoined 
 agents appears to be simply this, namely, that a given quantum, 
 of one agent can affect only the same quantum of another. Hence 
 
29 
 
 it must follow that when a small quantity appears to influence the 
 whole of a large one, there must be some deception in the cas 
 which it is proper to examine. 
 
 56. The relation of place between substances is one, the full 
 efficacy of which I will not attempt to define; rather because it 
 would be long and superfluous than because it would be difficult. 
 However, to sketch the leading points of this relation, it may be 
 observed that when things conspire to produce an effect, the 
 agents, though mutually influential, occupy various degrees of 
 intimacy in their combination. The loosest relation of this de- 
 scription is that of the mechanical kind, where the parts preserve 
 their identity without intermixture of particles, and may respec- 
 tively be contemplated independently of the whole, as the parts 
 of a house, a table, an animal, &c. Next to these grosser 
 mechanical instances come those of mixture, where the parts are 
 mingled together in minuter proportions, but still not so intimately 
 as to prevent the separate recognition of different components; 
 as, for example, in an imperfect mixture of powders of different 
 colour and sensible properties. The third example is that of 
 combination, where the intermixture is not by recognizable parts, 
 but between the infinitely, or, to speak more cautiously, the in- 
 visibly subdivided particles. In this last class of the relation of 
 place, all traces of separate components are lost, and the thing 
 appears altogether of one nature, as in the instances of chymical 
 union. 
 
 57. Now this relation of place between agents is settled as 
 before explained by the causes which belong to the agents, they 
 being various and producing the varieties of the relation. But to 
 return to the present topic: the tendency, in the state of combina- 
 tion, of the minutest possible divisions of particles is to separate 
 from the aggregate which they before constituted, and to diffuse 
 themselves to an extent corresponding with their divisibility, and 
 the relation subsisting between their particles, and those of the 
 agent with which they are combined. 
 
 58. In this manner, to recur to our former example, our drop 
 of oil of vitriol, if divided into 7,680 minuter portions, would fur- 
 nish one to each drop in the pint of water: and if this division 
 were again subdivided, one portion to each half drop of the water; 
 in this way, pursuing a division (which in possibility we have 
 before stated the grounds for believing infinite), we may conceive 
 how each thousandth part of a drop of the water may come to 
 possess a portion of the acid proportionately (according to the 
 aggregate differences) less than itself. This then is the solution 
 of the difficulty: by whatever test we examine this acidulated 
 water, whether directly by the sense of taste, or by a cyhmieal 
 agent, the acid will be discoverable in the minutest portions; not 
 because there are not particles of the water which are unaffected 
 by the acid, but because there is no test adapted to our faculties 
 or comprehension, the minuteness of which is sufficient to dis- 
 
30 
 
 cover those vastly divided particles of the water, which are not 
 influenced by the still more minutely divided portions of the acid. 
 
 59. But a larger is sometimes totally changed, to all appear- 
 ances, by a lesser quantity : here the proportions of the real 
 agents are in fact the same. Thus a lesser agent may be diffused 
 in the way just described among the particles of a larger, ap- 
 parently changing the qualities of the whole; and another agent 
 being combined equal to the lesser already combined, may have a 
 relation of influence only with the lesser, and by destroying its 
 influence in the general mass, may appear to aftect the whole 
 quantity, so much greater than itself. 
 
 60. There is yet another, and perhaps a more striking class 
 of examples of an influence communicated by a minute, apparently 
 to the whole of a considerable, quantity: I allude to those of con- 
 version. Thus a single spark of fire will ignite a whole barrel of 
 gunpowder. This cannot be, according to our law of proportions, 
 by a communication of the divided portions of the spark to all 
 the divisible particles of the gunpowder: what then is the mode 
 of this instance of causation? 
 
 61. It is simple increase by affinity. To describe the process 
 more minutely : gunpowder contains latent fire (made latent by its 
 combination in this form); eliminated fire (as the spark) is related 
 with its own quantum of the latent fire, and unites with it by the 
 force of superior affinity. The single spark is thus increased by it* 
 union; these conjoined quantities have a similar relation with the 
 latent fire within their sphere, and the ignition of the whole is 
 produced by a quick repetition of the same process. These points 
 will be still further scrutinized when we come to speak of the sub- 
 jects to which they apply. To proceed at present with the other 
 topics of causation: 
 
 62. An effect is identified by its causes; but it is so closely 
 connected with other things, that, from meeting with them con- 
 tinually in this close connection with the effect, we are apt to 
 regard them as causes. Every individual cause of an effect, 
 unfortunately, is liable to have these adjuncts and associations, 
 which, from the regularity and frequency of their alliance, are apt 
 to be mistaken for the causes which are necessary to the existence 
 of the effect. There is no way of evading this obstacle to a just 
 discrimination in our pursuit of science, but by defining exclusively 
 the particular effect we mean to consider, and then examining its 
 real dependences. Thus, for example, we may say, atmospherical 
 air maintains life, or is a cause of life; if atmospherical air should 
 be found to consist of three constituents, the real relation with, or 
 real cause of, life may be only one of these; while, previous to an 
 analysis of air, the whole properties, or their combined result, may 
 be assigned as the cause of life; or, after such an analysis has been 
 made, the concurrence of these three properties may be assigned 
 as necessary to life, and they may, from the effect which they pro- 
 duce in their union, be equally considered as causes, until the 
 
31 
 
 relation is analyzed, as well as the atmosphere ; until it is ascer- 
 tained that only one of these constituents of the atmosphere 
 maintains life or is the cause of life, while the others are merely 
 associated. This is merely a supposed example, not true through- 
 cut, but chosen because it is familar. 
 
 63. In the business of analysis we can specify only this rule, 
 in order to distinguish causes from mere associations (and this rule 
 must frequently be inadequate, owing to our defective means of 
 analysis), namely, to develop dependences as far as we are able; 
 to reject as causes all those things which may be separated from 
 the effect without changing its identity; and still to regard those 
 as causes which we cannot discover to be separable from the identity 
 of the effect. 
 
 64. It is affirmed by some, and the doctrine I believe is 
 almost a fashionable one, that causation is nothing more than the 
 succession of phenomena; that we know nothing more of causa- 
 tion than that there are certain antecedents, which are regularly 
 followed by certain consequences. It is affirmed, that we cannot 
 tell why effects should succeed to causes. I do not wish to spend 
 many words upon this doctrine: to consider it then briefly: 
 
 65. An acid and an alkali are causes, a neutral salt is their 
 effect: that is, a neutral salt succeeds to the combination of an 
 acid and an alkali. But would the neutral salt exist without the 
 acid and the alkali? To answer this question we must appeal to 
 our experience; and no one will object to this appeal, because it 
 is the best that can be proposed. Our experience tells us that the 
 neutral salt cannot exist without the acid and the alkali; hence 
 we infer, that the causes, viz. the acid and the alkali, are necessary 
 to the existence of the effect, viz. the neutral salt; and we infer 
 that the causes are necessary to the effect, simply because the 
 effect cannot exist without them : and this is agreeable to our ex- 
 perience in every example, in which the cause and the effect are 
 witnessed by the senses. 
 
 66. Our ideas of the necessity of one thing to the existence 
 of another are derived from, or have their strongest illustration in, 
 the relation of cause and effect. Thus, we say, blood is necessary 
 to the life of a man: we mean it is necessary to the life of a 
 man, because without it the man would die. Thus food also is 
 necessary to the life of a man. If any one doubts this necessity for 
 food in order to preserve life, let him try to live without it, in 
 which he will certainly succeed if there is no necessity for it. 
 Thus, muscles are necessary to voluntary motion; thus, too, air is 
 necessary to combustion. We have no notion of a case of necessity 
 which does not respect the relation of cause and effect. If, then, 
 causes are necessary to the existence of effects, the next question 
 is, why are they necessary? and this is what certain philosophers, 
 as they call themselves, or as either in derision, or in the way of 
 civility, they might be called ; this is the question which they 
 tell us we cannot answer. Let us try 
 
82 
 
 67. If- a cause is necessary to the existence of an effect, th 
 effect cannot exist without it; if the effect depends upon the 
 cause, and cannot exist without it, then there must be some virtue 
 in the cause, by which the effect is produced. So far, so good: 
 we next come to this virtue in a cause. 
 
 68. A cause is a form of existence. A form of existence has 
 no virtue to be either more or less than itself; the most then that 
 a cause can do, is to exist. Thus, an acid can be neither more nor 
 less than an acid; or if it ceases to be an acid, it is because this 
 form of existence unites with another, as, recurring to our example, 
 with an alkali; and conjointly they produce another form of exis- 
 tence, which other form of existence is the effect; and the causes 
 are necessary to the existence of the effect, because the effect it 
 the existence of the causes, and the existence of the causes is that 
 of the effect. The reason why a cause appears to produce some- 
 thing different from itself, is that in the effect there is a double 
 relation of existences with our faculties of perception; that is, an 
 effect is made by the union of differential forms of existence. 
 These forms of existence in their separate state have a separate 
 relation with our faculties of perception : in their united state, the 
 relation of two forms of existence with our faculties is comprised 
 in one ; and hence an effect appears one form of existence, different 
 only from its causes, because the causes when separate have an 
 individual relation with our faculties, and when united they have 
 only one or an aggregate relation with our faculties of perception. 
 The perception of this one undivided relation of causes, comprised 
 in an effect, is frequently superseded in matters of experimental 
 philosophy .by inference. Thus atmospherical air appears one form 
 of existence; but our inferences teach us, while contemplating a 
 sphere of vision without sensible objects, that the atmosphere 
 which occupies this range consists of oxygen and azote ; and if 
 our means of analysis were more perfect, we should ascertain it 
 to consist of fifty thousand things besides. From the same quar- 
 ter may be drawn many similar examples, which, as they are 
 similar, it is unnecessary to mention. 
 
 69. Succession is admitted to prove causation; but we dis- 
 tinguish between succession which does, and which does not im- 
 ply dependence. When one form of existence regularly succeeds 
 to another, and regularly ceases when that other is removed, thqn 
 we experience that the existence of one is dependent upon that of 
 the other;. and that the effect will succeed to the causes, and will 
 not exist when these are absent, in all future instances, is an in- 
 ference founded upon universal past experience. This is the suc- 
 cession which proves the relation of cause and effect; and the 
 .proof is established upon these, analytical and synthetical tests. 
 
 70. But when an antecedent is occasionally only followed by 
 a certain consequence; or, more .satisfactorily, when the conse- 
 quence may .exist without the antecedent ; then this succession 
 does not prove causation, uor .cau it be admitted, as a proof. But 
 
33 
 
 mere succession indicates causation by its analogy to the order 
 in which we experience dependence: this analogy is to the syn- 
 thetical proof of dependence; but is often invalidated by the 
 analytical test: that is, the consequence which succeeds in a few 
 instances to a certain precursor, is found, upon further experience, 
 or a closer investigation, to be capable of existing without it. This 
 doctrine will be further enlarged upon in a future instance, where 
 the truth of its application is a matter of some importance. 
 
 71. Although in the gross we contemplate an effect as a single 
 thing, yet its properties are infinite, or it includes within itself an 
 infinity of forms of existence. The causes of one part of an effect, by 
 pursuing an analysis, in possibility, justly supposed, are without num- 
 ber: and the relation of the causes causarum of one part, with those of 
 the other, produce individual effects which are also incalculable, and 
 serve to diversify to an astonishing extent the forms of existence. 
 The reason why we do not see all these things is, because only cer- 
 tain properties of things have a relation with our faculties; the 
 others of course have no influence upon them ; as an arm is to us 
 a sound arm, though it should be undergoing the preparatory 
 changes of an erysipelatous inflammation, which may shew itself in 
 two hours. Now the arm had digressed from health when we 
 thought it healthy ; but the relation of that act of causation was 
 not with our senses. The relation of the vesicles and the redness 
 is with our senses; and accordingly these phenomena are taken 
 account of by them. This is a clumsy example where the choice 
 lies among ten thousand. 
 
 72. The chief end of investigation is to understand relations; 
 and these are the more complicated, the more extended the series 
 is which forms the subject of inquiry: but there are few men who 
 have the talent of combining, so as to comprehend in their view a 
 whole system of facts, or who are capable of connecting the parts of 
 an extensive chain; and fewer still who are adequate to the arduous 
 business of just analytical discrimination : and consequently, the rela- 
 tions even of familiar things are still but imperfectly understood. 
 
 73. Investigation is of two kinds; analytical and synthetical: 
 and our inquiry observes these modes, whether it is conducted with 
 ocular testimonies, or by inference founded on analogy. 
 
 74. The modes by which new forms are produced are two, 
 viz. by addition of properties or parts ; and by subtraction of pro- 
 perties or parts. The former gives what the subject of the addition* 
 or the other causes conjoined in the effect, did not before possess; 
 the latter leaves the subject such an identity as is determined by the 
 remaining causes. The proof of this proposition is, that an effect 
 will always remain the same if its present existence is not disturbed ; 
 and that no change can happen but by something added, or by 
 something taken away. 
 
 75. Identity of effect requires identity of the causes. This is a 
 proposition to which there are many apparent exceptions, which 
 have never been explained ; it is my business to reconcile them, 
 a 
 
34 
 
 Example of exception : the prick of a pin will produce pa in ; so will 
 that of a needle, so will hot water, or caustic, or an incision with a 
 knife, with a razor, or a scythe; all these things produce pain: all 
 these things are causes, yet they are not the same. But have they 
 no relation with sensibility which is common to them all ? Why 
 truly they must: and for this reason, viz. that pain can be identified 
 only by its causes. Those causes must be operative which can 
 make pain: if they are not these causes, if they are more or less, 
 they will make something else corresponding with ivhat they are, 
 and not pain ; or else such a modification of pain, as will agree with 
 the diversity of the real causes. If, therefore, the causes are diffe- 
 rent, the effect also will be different, or those which we suppose to 
 be causes are none. 
 
 76. To take another example: a ligature on a nervous trunk 
 will paralyze the parts to which its branches are distributed. This 
 effect will be produced by thread, by silk, by cotton, by a piece of 
 whipcord or catgut, or horse-hair; by pinching the nerve between 
 the finger and thumb, by applying a red-hot wire to it, by dividing 
 it with a knife. These causes, as they are called, in the gross, are 
 all very different, yet the effect is the same; and. why? It is, that 
 they possess in common one relation ; or, that the real cause, that 
 which is productive of the effect, is the same in them all : the other 
 appearances, properties, &c. which identify these nominal causes, 
 and distinguish them from each other, are mere associations, or 
 adjuncts, which do not produce the effect, having no relation with 
 the subject of the influence, although connected with a real cause. 
 And what is this common relation? Why, the ligatures, whether of 
 hair, or silk, or catgut, &c. having in common a certain figure, a 
 certain tenacity and strength, which admit their being drawn tight, 
 and thus making a certain degree of pressure, are capable, each, by 
 these properties, which are common to all, of compressing the 
 theca of the nerve, and of displacing a circle of the medulla : this is 
 their share in the effect ; the phenomena are then left to other causes ; 
 and the relation afterwards is, that no nervous influence is com- 
 municated beyond a place in the nerve so circumstanced. But 
 what shall we say of the knife, which is different from all the 
 ligatures? The knife produces one effect in common with the 
 ligatures; and as it is a different cause, or as different causes act, it 
 produces other effects which the ligatures do not. By it the nerve 
 is divided what follows? The law with respect to the function of 
 the nerve is, that it requires a perfect continuity of the entire 
 structure of the chord. Is not this continuity interrupted in both 
 instances, is not this the common effect? or the common relation 
 in which all these agents stand with respect to the nerve, and the 
 phenomena of their application ? It must be allowed that it is: and 
 the same does obtain, must obtain, if there is any truth in our first 
 principle, in all instances. This confusion of real causes with their 
 connected properties is a great stumbling-block in matters of 
 science: but as the principle has never been reconciled and ex- 
 
35 
 
 plained, it is sometimes respected, as it were, intuitively, and it is at 
 others set aside without ceremony. 
 
 77. The cause always exists in the effect. Here we are liable 
 to be misled by successive acts of causation. Thus, to extend in 
 this place a former illustration, a man made a watch : the man is 
 the cause, as may be said, the watch the effect. But surely the man 
 is not included in the watch? Why, no; truly the man has an habi- 
 tation in England, and the watch may be lying upon the dressing- 
 table of a gentleman at Calcutta. Here we must trace a process of 
 causation ; and though an example more palpably opposed to our 
 doctrine will not readily be devised, we shall still find that our 
 principle is untouched by it. 
 
 78. The vital organs of the man, his animal powers, his 
 mechanic knowledge, his facility in the art, all concur to produce 
 one effect, which is the exertion of that ability which is produced 
 by this complicated causation; this effect, in its turn, becomes a 
 cause, by which the parts of the watch are adapted to each other; 
 the intelligence of the artificer is related with volition, or produces 
 and modifies volition ; volition is related with the muscles of the 
 arms and fingers; and modified motion (motion modified according 
 to the volition) is the result ; by this motion the parts of the watch 
 are prepared and adapted. So that it is not a man with which a 
 watch holds a relation as with a cause, but with a certain moving 
 power, which is the first cause, proceeding from the man, which 
 is exerted upon the works of the watch. If we would know 
 whether this power of motion, or its properties, communicated to 
 the works of the watch, still exist in them, we can scarcely answer 
 this question, without a better understanding of the relations of 
 moving powers in general. The power of motion appears to be 
 expended in the act to which it gives rise. And whether it enters 
 into the substance moved, or whether it is communicated from the 
 subject moved to the surrounding medium, in the course of its pro- 
 gression, is a point which in this place it is superfluous to discuss. 
 The watch being thus produced, is then identified as an effect by 
 its own constituents, and is maintained by relations subsisting be- 
 tween its parts. The powers which concurred to produce it are its 
 remote causes, and these may be withdrawn, or cease, while the 
 watch preserves its identity ; its real, true, or efficient causes are 
 ihose by which its identity is preserved, when its connection with the 
 remote or concurring agents has ceased ; and these causes cannot 
 well have a place in England, while the watch is at Calcutta. All 
 this is very obvious, and requires no more to be said about it. 
 
 These principles of causation furnish the true basis for inquiry, 
 and are sufficient to lay down here. I shall hereafter see what 
 light they throw upon a particular application ; or rather I shall en- 
 deavour to shew how we ought to philosophize, in order to be agree- 
 able with these apparent truisms. In the mean time, it may not 
 be uninteresting to see how the general affairs of this world agree 
 with these notions, which I shall do after a looser fashion; intending 
 this rhapsody rather as a interlude than as a regular part of the piece. 
 
36 
 
 CHAP, ill, 
 
 The Universal Scheme considered in Connection with tlkt 
 foregoing Principles. 
 
 1. NATURE and education have produced in man * 
 restless and enterprising spirit. He is delighted with the know- 
 ledge he possesses ; and acquiring by this a glimmering of some of 
 a more exquisite kind which is further in the back ground, with- 
 out perhaps sufficiently examining how far he is qualified to attain 
 his desires, he adventures to push boldly on, and had rather sub- 
 stitute fictions for truths than consent to have the scope of his infor- 
 mation abridged. In no instance has this spirit of speculative 
 cnterprize prompted a bolder research than that in which it has aspired 
 to the discovery of the origin of the world in which we are placed, 
 and of the primitive condition of things. It cannot be disputed but a 
 more perfect information on this matter would be highly gratifying 
 to us: in some respects such an information must also be acknow-* 
 ledged to be of the very highest importance. But we have supposed 
 that the limitation of our faculties excludes us from this rich pos- 
 session; animated, however, by the hope of throwing upon the 
 subject one additional ray, notwithstanding past failures, I shall just 
 examine how far the question is affected by the preceding notions: 
 ome of which appearing to be new either in their conception or 
 arrangement, promise at least to add to our results in the present 
 application. 
 
 2. The axiom " ex nihilo nihiljit" has been by some cited in 
 support of theism : how far its services in .this way extend, or 
 whether it possesses a tendency of a different description, will per- 
 haps hereafter more fully appear. The principle that " nothing can 
 exist without a cause" has been before shewn to rest upon analogy; 
 as a principle, it can certainly be no part of our experience ; but 
 though not amounting to an ocular testimony, it is found to be an 
 inference which deserves consideration. The evidence for the 
 principle amounts to this, viz. none of the examples of the origin of 
 an existence, of whose origin we have an experience or sensible 
 testimony, take place spontaneously, or in any way but by an act of 
 causation which has been before described. Without affirming that 
 this evidence is sufficient to establish the principle, or without 
 affirming the truth of any of the principles which may be hereafter 
 
37 
 
 employed, we will just, by way of experiment, examine the scheme 
 which must be acknowledged by those who admit them. But we 
 will not do this, without first bestowing a few thoughts upon the 
 converse of the principle, in order that they might be occasionally 
 compared as we proceed. 
 
 3. If nothing can be without a cause, distinct from itself, or, in 
 other words, but by a process of causation, the agency of a first 
 cause is absolutely precluded. But the prevailing system supposes a 
 first cause. If it is asked how this world, those things which we 
 see around us, and we ourselves, came to exist! It will be replied, we 
 were created by the power of an intellectual being, who is selff 
 existent. In consonance with a system of natural evidence, founded 
 upon the preceding data, let us examine how much is implied by 
 this work of creation. 
 
 4. Creation is another word for production. This world was 
 produced at a certain period, and until then did not exist, it is said. 
 Did then the intelligent being with whom this creation originated 
 supply the materials of the world? For we know that things are 
 made by their causes, however we may be at a loss to conceive 
 fiom whence these causes sprung. Did this universal artificer sup- 
 ply the materials of this world? If he did, then the materials must 
 have been included in him, must have been identified with him; 
 and the world (as an effect must exist in its elements, or in the 
 sources from which it is supplied, although in them its form is 
 perhaps not conspicuous), must have been coeval with its creator, 
 and consequently could not be produced de novo. If the materials 
 of this world were not supplied by an intelligent author, then 
 either it exists without them, or else they are furnished from some 
 other source, or in some other way. It does not exist without them ; 
 for we perceive these materials in all our analyses, and we presume 
 upon them and work with them every day, and almost in every act 
 of our lives. 
 
 5. But, it will be said, the mistake lies in the examination of 
 the first question: it will be said, the things of this world do 
 not' exist without their materials or their parts; nor were these 
 materials co-existent and identified with their author, but they 
 came into existence at his command. What then, is a command an 
 oak, or a rock, or the sea, or a mountain, or a continent? No; but it 
 will be said, by a command these things were produced. In \vhat 
 manner produced? Our experience of a command is, that it can 
 produce nothing, or no effect, except in relation with something 
 else. Asa sole agent, a command is totally inefficient; but its effi- 
 cacy is powerful in a circle of relations, which it holds with cp- 
 temporary existences. The case we are considering supposes it to 
 be a sole agent, for it supposes its efficacy to have been exerted 
 before other things were made. The exclusive efficacy of a com- 
 mand is then to be examined; and what says our experience? A 
 command is something, a power is something, a virtue is something, 
 If they are nothing, they can do nothing : then they are confessedly 
 
38 
 
 something. Can that something be different from what it is? 
 Why, truly, no; a thing cannot be, and not be, what it is; it seem? 
 not allowing too much to say that a thing is what it is. This com- 
 mand, then, this power, this virtue, can they be different from what 
 they are, and still be the things themselves? Can they, without the 
 aid of any thing else, be at the same time a command, a power, a 
 virtue, an elephant, and a rhinoceros? Can they be any thing more 
 than themselves? No, it will be said ; but, in the stupidity of repeti- 
 tion, it may be urged again, they can produce something different 
 from themselves. How produce? It must be answered, because 
 there is such a command, there will be also the rhinoceros, or 
 an elephant, or the sea. Then a thing may do more than be itself; 
 and this too without possessing the properties or the materials by 
 which something different from itself is constituted. A thing is a 
 certain identity; it is an existence; it must remain that existence, 
 unless altered by something else, in which case the product will be 
 a mixture of identities ; but, left to itself, its only power, its only 
 faculty, is to exist as itself. What is the proof? Every example of 
 existence of which we are informed by our senses. Against so uni- 
 versal a testimony shall we indulge a supposition which is made 
 without any example, without any sanction from our experience? 
 There are two ways, which have been before stated (and which, to 
 obviate some false examples which might be cited, may here be 
 differently expressed), in which new forms arise. One, as when 
 certain parts or properties of an aggregate are separated, and ap- 
 pear as distinct effects; the other, as when two or more aggregates 
 combine to produce a distinct effect: whichever of these is the 
 mode of causation, the effect can in no instance be any thing more 
 than a modification of present existences, which, whether in sepa- 
 rating parts and properties, or uniting with parts or properties, 
 must still produce new forms. 
 
 6. It is true, it must be replied by one who is neither a fool, 
 nor disingenuous, the argument is not without weight: but we are 
 led to embrace one difficulty for the purpose of obviating another, 
 which is to conceive an origin of things without referring their exis- 
 tence to the agency of that which is called a first cause. Perhaps 
 this supposed difficulty, which thus becomes an excuse for a belief 
 without natural evidence, may be an imaginary one: whether, or 
 how far we are necessarily obliged to accept it, has been before in 
 part shewn, and we shall have occasion for some further examina- 
 tion on these points. 
 
 7. For the sake of stating the argument clearly, we will not 
 fear the danger of a little repetition. We will suppose a period 
 before this visible world was created: what existed at that time? 
 An intelligent and powerful principle, a designing author. Then 
 this intellectual being, by a volition, or by a virtue, as it is said, 
 produced this visible world. What do we know of a volition, what 
 is our experience of such a thing ? for all our thoughts must. 1 
 brought to this test. It is a mere volition, a mere desire: hovr 
 
39 
 
 does it become influential? By its relation with something else 
 upon which it acts. How is a result produced? By the conjoined 
 agency of the will, and some other causes, as in man, the material 
 organs, the muscles, &c. with which it is related. Does a mere 
 volition produce any thing which is not a volition; which is an 
 effect of volition? Our experience of the efficacy of volition is, that 
 it can act upon organic substances; and as most of those substances 
 which are said to be under the controul of an universal mind are 
 inorganic, so do they not belong to that class, of the subjection 
 of which to mind and volition we have an experience. 
 
 8. It appears sufficiently plain that a mere volition can be 
 neither more nor less than what it is, that is, a volition, its own 
 identity, and that it can do nothing unless through the medium, or 
 with the concurrent operation, of something else. And of a virtue: 
 how far is this operative? Why, truly, as far as it supplies itself, as 
 far as it contributes its existence or its identity. Then it is evident 
 that if neither a volition nor a virtue is either an elephant or a 
 rhinoceros, that they can of themselves become neither one nor the 
 other. If they should lead to these results, such results arise from 
 them by the conjunction of causes; in the aggregate producing, or 
 forming, or bring such constitutions, the parts of which (or the 
 disunited existences of which) are pre-formed. This is our expe- 
 rience, our universal experience, our perceptive information in every 
 case in which an origin falls under the observation of the senses. 
 Have we a right to imagine any thing in opposition to it? 
 
 9. It seems then that a creator can produce nothing tfe novo; 
 that he is either identified with things, or concurs only with them to 
 determine the order and combination of effects: and it necessarily 
 follows, if the argument be admitted, that things were coeval with 
 inch concurring agent, which latter can have only the force of a 
 cause; that is, can supply only itself or its own existence. 
 
 10. There is in the universe a harmony that cannot be con- 
 templated without filling the soul with delight; there is a stu- 
 pendous scheme of agreement exhibited in all its parts; it is a 
 world that is admirable; and astonishes one no less in the con- 
 templation, than by the wonderful rapture which the contemplation 
 occasionally inspires. This harmony, this perfect agreement, this 
 mutual subordination, cannot be fortuitous, it is said; it must have 
 been so determined by the designing of an intelligent artificer. 
 Whether or not such a world was created, not having existed before, 
 by such an artificer, has been examined above: we are next to con- 
 sider whether such a one (an intellectual principle) mingles its influ- 
 ence among causes which were coeval with itself. 
 
 11. Before we proceed to shew what sort of a world might be 
 produced in consonance with the preceding axioms of causation, we 
 will examine the grounds on which an intelligent designing creator 
 has been inferred from the harmony and adaptation displayed in 
 the parts and structures of the world. Regularity of constitution, 
 adaptation of causes to effects, and effects to final purposes, prove, 
 
40 
 
 it is said, contrivance ; and contrivance proves a designer. This, I 
 take it, is a mode of reasoning which has been employed ; and it 
 must be confessed that the reasoning is not chargeable with 
 prolixity. 
 
 12. How, it is fair to ask, do we come at the inference that 
 nothing can be constituted properly, so as to bear an exact relation 
 with other things, and to work with them for a general effect, but 
 by a previous designing by intellect? or, shorter, thus : what is the 
 proof that nothing regular can be accomplished without design? 
 Why it is so concluded, because we ourselves can produce little 
 better than confusion, unless we think, and frame to ourselves some 
 model of our purposes. Then it is concluded that nothing regular 
 and consistent can take place without design, because we are under 
 the necessity of designing in order to produce that which is consistent 
 and regular. This is the testimony for the inference, which must 
 also be examined. 
 
 13. Is this then the whole sum of our experience in the mat- 
 ter of regular and harmonious production? Why, truly, no; if we 
 wish to compose a book, or a sentence, or construct a piece of 
 mechanism (the perfection of which will consist in its relation with 
 something else, which for the sake of distinction we may call a final 
 purpose), we must think and design for it. But in all the spon- 
 taneous operations in which we are not concerned, and which are far 
 more numerous than those in which we are concerned, we have no 
 evidence of a designing principle; we see nothing but the operation 
 of causes, we perceive no other dependence: and it is upon our ex- 
 perience of a diversity, that we make a distinction betweeen artificial 
 contrivances, and natural productions; that is, from our experience 
 of the works of design, we trust to the analogy between them to 
 infer the direction of design, where the conduct of it is not wit- 
 nessed; and relying upon this analogy, we pronounce all works of 
 art to be those of design, in opposition to the works of nature, 
 which being different from those of art, give rise to a distinction 
 rather than to an extension of the same class. 
 
 14. Sticking close, then, to our experience, the question comes 
 to this issue, viz. as regular production is sometimes a consequence 
 of design, and sometimes the result of causes, in which design does 
 not appear, are we to conclude that regular productions are 
 necessarily dependent upon design, or that they sometimes only pro- 
 ceed from design, or that they invariably ensue, as has been hinted, 
 merely from causes, in the way of causation which has been before 
 described ? We find, in considering those questions, that the ex- 
 perience which should guide our decision is rather contradictory, as 
 we have examples of regular production in each way. But if there 
 is any truth in some former predications, design itself should ope- 
 rate in the general way of causes ; at any rate we cannot even grant 
 the distinction implied by these questions, without first ascertaining 
 how design itself is formed, and in what way it operates to produce 
 this harmony, upon which the proposition we are discussing It 
 
41 
 
 chiefly rested. I would merely add, what an objector might 
 in this place urge, that we can have no experience of negative 
 existence ; but at the same time we are not to supply this deficiency 
 of experience by inference, unless the analogy upon which it is 
 founded is at least perfect in essential points. This matter has 
 been before discussed in our examination of the grounds and 
 nature of belief. 
 
 15. Intellect is no designing principle until it is furnished 
 with ideas, the capacity for designing is produced in the usual way 
 of cause and effect: the intellect which we bring into the world 
 with us is a mere pre-disposition : it is constituted a designing 
 principle by the operation of those causes which fill it with ideas, 
 and by familiarity with which it becomes instructed in the relations 
 of causes with effects (the production of these latter being the 
 general purpose of design). The very capacity for designing, in 
 every example we have of it, is a mere effect: it is itself the result 
 of a process of causation. And what is its force? Simply that 
 of becoming in its turn a cause, and of having the same relation 
 with the consequences which result from it, as any other prevail- 
 ing cause might have with the circle of effects in which it is liable 
 to be interested. What then must we conclude from this fact in 
 conjunction with a principle before expressed, but that there are 
 causes which precede and constitute the designing capacity itself, 
 rather than that the designing capacity must precede every act of 
 formation 1 
 
 16. Will it be said this is true in regard to ourselves, but 
 those causes which we suppose so perfectly free from any design- 
 ing principle, and which excite our ideas, are themselves governed 
 and directed by an universal principle of intelligence? I ask for 
 the proof, or even for evidence of a much weaker degree; and so 
 fond am I of the notion of such a presence that I will almost force 
 mvself to believe it upon weak grounds: of course the proofs I 
 require are those of natural evidence. It must be replied as 
 before stated, that as we can do nothing that is worth the doing 
 without designing for it, so nothing worth doing can be done 
 which is not designed. To this it must be answered, that such an 
 assertion is not consistent with our sensible testimonies, which 
 amount to this, that causes (viz. the intellectual radicle and those 
 objects which instruct it) produce in man a designing capacity: 
 that these causes operate and produce this effect without being 
 themselves actuated by design, and that then the designing capacity 
 so produced operates in its turn, and produces effects which are 
 conformable with their causes. Are we to conclude that design 
 actuates every process of causation, because we perceive that it is 
 concerned in some? 
 
 17. If this question should be answered in the affirmative it 
 must needs be an arbitrary decision, a mere ipsedixit; for it is 
 contrary to the rules of reasoning which we acknowledge and 
 observe in similar cases. We might as reasonably tack up a 
 
 H 
 
42 
 
 syllogism of this kind, viz. it must be allowed that the sea is good, 
 so is this which is usually denominated a house, therefore a house 
 is the sea. This is in fact an assumption similar to thai above; it 
 is arguing the perfect identity of two things from an agreement in 
 one single quality, while there is a vast difference in all the other 
 properties which belong to and distinguish them. 
 
 18. It appears then that the proposition, that all the pheno- 
 mena in nature are produced and regulated by an universal mind, 
 is founded upon the analogy between these productions of nature 
 and the productions of art, in which latter we experience the in- 
 fluence of mind to be concerned. This is the point of analogy: 
 but the inference upon this ground of analogy is liable to the ob- 
 jections before stated, the principal of which may be summed up 
 in the two following : 
 
 1st. Mind produces volition: through this medium its con- 
 ceptions or designings are executed ; and we have no experience 
 of the efficacy of volition, except in its alliance with organic sub- 
 stances. Hence there is a dissimilarity between the subjects on 
 which the operation of mind, through volition, is experienced, and 
 those on which such operation is supposed, and an argument of an 
 analogy cannot well be founded on dissimilitude. 
 
 2nd. It is inferred that mind is necessary to produce regular 
 phenomena, because those are disorderly which mind does not 
 produce. At the same time it is affirmed that all phenomena are 
 produced by mind: and if this is true, it must follow that no argu- 
 ment can be founded on the contrast between regular and con- 
 fused productions, or designed and chance productions, seeing 
 that of the latter we can have no possible examples. 
 
 19. But if we find that this exposition has no better success 
 than to leave the point at issue still in doubt; if there are those 
 who will assume the title of arbitrators, and substitute affirmation 
 for proof, intending to carry the point by authority where some 
 sort of choice appears to be allowed them; we must then confess 
 that some further satisfaction is required; and, with a view to 
 obtain it, we have only to recur to a principle of causation in 
 order to put the present question upon the same footing as that 
 upon which the principle itself stands.. 
 
 20. An act of causation, such an one to which may be at- 
 tributed contrivance, cannot take place, it is said, unless regulated 
 by a designing principle. But design itself, abstractedly, what is 
 necessary to its existence? what but the ideas of those things with 
 which it works, or for which it projects? and can these ideas pre- 
 exist their objects? We have in truth no example of it. Where- 
 ever we can contemplate the designing faculty, we perceive that 
 the objects themselves must exist before the corresponding ideas 
 can exist: that is to say, those things must first exist which furnish 
 the analogies, or models of design. This experience obtains in that 
 which we call invention, and is without an exception; have we 
 then a right to conclude against it? If we allow it force, and con- 
 
43 
 
 cede the proposition it indicates, then those things (or their pro- 
 totypes) which it seems were made by design, are antecedent to 
 design, and so far from being the effects are the causes of design. 
 
 21. And now to recur to ou; principle, which we state to be 
 this, as nothing can exist without a cause; as this principle is 
 founded upon every known instance of origination; so one cause 
 cannot produce it, for one cause must remain as such, and cannot 
 be different from itself: it is therefore necessary that the effect 
 (which is always different from a single cause) should comprise in 
 itself causes, different individually from such effect, but the same 
 in the aggregate. Hence it follows that the principle of intelli- 
 gence, this same designing principle, must be made by causes, or 
 is their effect; and as the causes individually must be different 
 from the effect, so there were agents which preceded design, and 
 without the guidance of design formed the designing principle 
 itself: and yet it is said that nothing good, excellent, or regular, 
 can be produced without design; while it must be admitted, 
 agreeably with natural evidence, that design itself must have been 
 produced without it. 
 
 22. According then to the preceding principles, which are 
 merely exhibited as a sketch of the indications of nature, the fol- 
 lowing is the state of the question with respect to the influence 
 of a pervading intellect, or universal mind: 
 
 1. This visible world cannot have been produced, de novo, 
 not having existed in any form before, by mere intellectual influ- 
 ence; since no cause can supply that which it does not possess, 
 or be either more or less than itself, or contribute any other influ- 
 ence than that which is comprised in its own existence. 
 
 2. Such universal mind itself must have been produced by its 
 causes; and these latter, determining all effects*, determining all 
 operations (since nothing can take place but by them), must govern 
 such universal mind, making it that which it is, and making it in 
 its turn concur in the general scheme of causation. 
 
 3. That such an intellectual principle might have been formed 
 in the way mentioned; that it may pervade all nature, direct] the 
 operation of other causes, mingle with them for final purposes of 
 its own; and that it may arrange and direct every part for the 
 good of the whole (which is as much as we can imagine of the ex- 
 cellence of such a nature); I say, all this may be true, for any thing 
 urged to the contrary in the preceding sketches: but it behoves 
 one who worships truth (or, to speak more philosophically, who is 
 desirous of obtaining and resting upon firm convictions), and who 
 knows how liable human nature is to be deceived by false appear- 
 ances, to examine this matter rigidly as a question, before he yields 
 to it an implicit belief. 
 
 23. It has been asked, first, if there were no such universal 
 mind, how came we to have the notion of such a thing? It has 
 been further inquired, secondly, how the notion of an intellectual 
 and moral presence came to be so prevailing, that there is perhaps 
 
44 
 
 no people who have not the idea of some powerful and intelligent 
 being who governs the world? For the first question, it is sufficient 
 to remark, that there are such things as fictions, and in the same man- 
 ner as they arise might originate any notion, and consequently the 
 one we are considering ; the notion is formed by the combination 
 of ideas from sensible impressions, and by the assumption of 
 analogies. Thus much is sufficient to shew that the origin of a 
 notion is no proof of its truth, for by the same processes we are 
 originating notions, some false and some true, every day. And for 
 the second question, it is only to be observed, that if a fiction is 
 one to which human nature, from similarity of constitution, is 
 prone, it will be very likely to be an universal one, without being 
 the less a fiction. Thus in the more ignorant times, and now 
 among ignorant nations, spiritual agencies were perpetually oc- 
 curring in nature, and affecting the concerns of men : the influence 
 of the planets over certain affairs has likewise been a prevailing 
 fiction, which however is discredited by men of sense and reflec- 
 tion, because they find no evidence for the opinion ; and without 
 this support it is not consistent with their character to fill their 
 understandings with bad conceits, when the value they set upon 
 good ones is shewn by the pains they take to find them. Thus 
 much for the questions; I proceed to shew that the belief of some 
 universal governor is one which men must be prone to slide into 
 by an easy gradation from the common observance of causes. 
 
 24. The notion of such an existence might arise out of the 
 almost intuitive assent to a principle which has hitherto appeared 
 to be the basis of a different argument: the principle is this, that 
 nothing can exist without a cause; and now for the application. 
 It is observed, that things do not make themselves: this observa- 
 tion disposes us to look for their causes. As one instance, we will 
 take a human bone (or any other bone), but, for the sake of pre- 
 cision, a human tibia: what produces it, what constitutes it? It 
 will be replied, a bone is made by the union of phosphate of lime, 
 phosphate of magnesia, carbonate of lime, sulphate of lime, gela- 
 tine, fat, and cartilage; blood-vessels, &c. exist in bone, and our 
 tibia has a certain arrangement. Now urge the question further, 
 which is very natural, and ask what determines this arrangement? 
 We are not acquainted with the agents, and therefore supposing 
 the necessity of a cause, as observed above, we say, GOD. Again, 
 the phosphate of lime, if first detected in bones, would be con- 
 sidered a simple substance: if it should, during this opinion, be 
 asked how this phosphate of lime came to be? still retaining the 
 necessity of some cause, it would be replied, it was created by 
 GOD. But another step of analysis would give rise to a different 
 reply ; for when the two materials of which this substance con- 
 sisted were known, the question, how it came to be, would be 
 answered, " by the union of lime and phosphoric acid/' Every 
 example tends to shew that a Divine agency is assigned to begin 
 where analysis, or the knowledge of causes, ends. Thus it happens 
 
45 
 
 that the assigned extent of the influence of the Deity is absolutely 
 abridged as science advances; for as known causes are developed, 
 the unknown cease to be supposed. In this way then the idea of some 
 general antecedent cause conies to be obtained, and it is founded 
 upon the acknowledged necessity of such a cause, which necessity 
 must obtain equally (or the necessity is limited without reason, 
 and in a case in which the universal analogy holds good) with 
 respect equally to the existence of the Deity as of other things: 
 this is a point which has been discussed. 
 
 25. The notion of a first cause being in this way acquired, 
 men very soon and very naturally extend their imaginations, and 
 they next conclude him to be a moral agent. This conception is 
 as easy as the other, and equally fitted to become prevalent, with- 
 out natural evidence of the stricter sort. Thus, all those things 
 by which we are liable to be affected, are related with us in such 
 a way as to produce either agreeable or disagreeable sensations: 
 the causes of the former we call good, those of the latter, evil. 
 Now who dispenses these? Why, no other than the first cause 
 which made them to exist. Then we come to invoke this cause to 
 bestow upon us what is good, and remove that which is evil, and 
 it is very seldom that we are gratified, except as an ardent desire 
 for the possession of an object induces us to make strenuous 
 efforts to obtain it. Deities are in this way formed by the per- 
 sonification of causes, and, as in the Mythology, a particular GOD 
 may be*assigned to each department of causes. 
 
 26, But the main question is this, viz. as it has been shewn 
 that a designing principle is not necessary to creation and order, 
 is there any evidence which proves the existence of an intellectual 
 principle which mingles with the ordinary causes; and directs 
 them with a moral government, dispensing good and evil con- 
 sistently with our notions of right and wrong? We must examine 
 the evidence for such a moral government. 
 
 27. There is a harmony and beauty in the universe, which it 
 is said prove the existence of something intellectual which 
 designs for the good of the whole. That there is such an unity and 
 concord in the operations of nature in a general way, is not 
 to be disputed: but how does it follow that this agreement is 
 made by design? I shall not discuss this matter over again, but 
 refer to the preceding pages in which it has been already discussed. 
 Is there any other proof? In reply, it may be inquired, if this per- 
 vading mind, as a regulating principle, be not admitted, how else 
 shall we account for the order and regularity which have just 
 been confessed? In order to answer this question, we niu>t pro- 
 ceed in the exhibition of the consequences which ensue from our 
 first principle. 
 
 28. It has been shewn that nothing takes place without a 
 cause, and that effects are made what they are by their causes.* 
 
 See Chapter II. 
 
46 
 
 Tilings, then, are either causes or effects: they are, however, 
 liable to be considered in three ways: first, by themselves, as 
 positive identities; second, in relation to other things, in which 
 light they are regarded as causes ; and, third, as effects, in rela- 
 tion to their own causes. AH virtue or power is comprised in 
 causes, for nothing can influence which does not become a cause. 
 All effects are produced by many causes; and all things are what 
 their causes make them. Thus much for the present, in the way 
 of recapitulation. 
 
 29. If a thing which was before, as we say, ugly, should be- 
 come beautiful, what is it that makes it so? Plainly the influence 
 of some cause, or the possession or combination of that in which 
 it was before deficient. But then, it will be asked, what is it that 
 makes this addition, or, rather, who is it that projects a change 
 the result of which is beauty? To this I reply, a cause. Aye, 
 but what cause] One that held such a relation with the agents 
 concerned in the change, as to accomplish the end we have sup- 
 posed. But is it not necessary that design should interfere in the 
 process? How, I would ask again, does the design act? It can 
 have only the force of a cause ; and what is the proof that it is 
 capable of becoming a cause in such an instance, or, in other 
 words, that the agents concerned hold such a relation with design ? 
 We will define an example by way of illustration : let it be an 
 imaginary one. 
 
 30. It is now February, and this extensive wood looks naked 
 and poor; Nature is asleep in the trees, and she cuts but an indiffe- 
 rent figure. Presently, it is May, and the wood looks smiling, 
 cheerful, luxuriant : the naked branches are covered with leaves, 
 and the appearance is as gay and beautiful as the shade is inviting. 
 Why do the branches shoot forth leaves? Shall we say, because 
 design moves the sap? Is it known then that design is capable of 
 putting sap in motion? In truth, we have no experience of it; 
 our experience of the power of design is simply this: that it has a 
 relation of re-agency with the parts and properties of animal 
 bodies; and its influence is never extended beyond the subject in 
 whom it exists, except by a volition which acts on the material 
 organs. Now I cannot prove that design is not capable of moving the 
 sap; but it is easy to shew that this is not deduced from our ex- 
 perience, or necessary to be supposed for the purpose of obviating 
 any other difficulty: and it will be seen, at the same time, that 
 nothing is gained by this intervention of design, as it will appear 
 that the same difficulty for which design was imagined will occur 
 again in the questions respecting itself. 
 
 31. Ask how the whole is made? By its parts: how the 
 whole earth is made; or, what makes the whole earth? That 
 without which it cannot be the whole earth, viz. by its two halves : 
 and these? By their parts. In this way we may descend to par- 
 ticular bodies, as a stone by what is its identity determined? 
 By its parts also but then its figure? Its figure is conformable 
 
47 . 
 
 with the arrangement of its parts, and depends upon them for it* 
 identity. After all, what shall we say of its properties'? It is a 
 peculiar sort of stone: it may contain iron, sulphur, &c. in addi- 
 tion to the common properties of matter. Then it is made this 
 peculiar kind of stone by these peculiar constituents. And these, 
 how are they made? Certainly not from nothing: they are not 
 elementary, as already shewn. Or, take a part of an animal, as 
 an arm what makes its identity? Plainly that without which it 
 would not be identified, viz. bones, muscles, blood-vessels, nerves, 
 &c. What constitutes their identity? The chymical analyses 
 have severally gone some way towards answering this question. 
 But then what brings these together, and arranges these elements, 
 as they are called, in such a way as to make a muscle? The 
 causes which have a relation with these elements capable of pro- 
 ducing such an effect and what are these causes? They are not 
 known ; they are not cognizable to the senses. Here, then, the 
 intervention of design is supposed, while our experience furnishes 
 us with no example of a relation which subsists between the de- 
 signing principle and inanimate particles; for such they are until 
 they are joined together, and obtain a reciprocation of function, 
 as in the form of an animal body. But then, further, this design, 
 how came it (allowing it for the present) to project a muscle? By 
 itself, it must be said. And where did it gain its instruction 1 
 The intelligence was produced by what? By that without which 
 its identity could not exist, by its causes and what are these? 
 Properties which we infer to be different from itself individually, 
 but in the aggregate forming it; properties which, in our expe- 
 rience of the history of design, are external or distinct from the 
 intellectual pre-disposition, but which unite with it, and form with 
 it, ideas; and furnish it with the models of design. That, then, 
 which we attribute to design, results from causes: of the design 
 we have no evidence ; and if it is supposed, this also is governed 
 by causes, an endless chain. It is the business of analytical science 
 to discover these. 
 
 32. Such a state of things as that which has been hinted at 
 would be called a mere jumble and contention of the elements of 
 nature; it would be asked, what order, what regularity, what per- 
 fection, &c. can ensue from such a tumult? such heterogeneous 
 materials without any directing sense? First, let us examine what 
 that is to which we give names of regularity, order, adaptation, 
 contrivance, perfection, &c. 
 
 33. Why is a good watch a regular piece of mechanism? 
 Because its parts all concur to indicate time, in correspondence 
 with the motion of the earth; in other words, because they have 
 a relation with an end, or are capable of producing a certain effect, 
 which is to indicate time. Now supposing that the parts of the 
 watch were different, or differently arranged, so as to make the 
 hands move round the dial-plate sometimes three times in an hour, 
 and sometimes only halfway round it in three hours; what should 
 
48 
 
 we say of the order of its parts? It would be said of them, they 
 want order altogether. If it is inquired why they want order? it 
 must be answered, their relation is not to indicate time correctly. 
 But in this reply we make some addition to our first proof of 
 order, viz. that which says it is the relation of parts with a certain 
 end, for the parts, &c. of our lying watch have a relation with a cer- 
 tain end, viz. with that which they accomplish. It is not, then, the 
 arrangement of parts, agreeably to any purpose which constitutes 
 order; but agreeably to the purpose we desire, regard, or like best. 
 34. We say then that is orderly and regular which suits our 
 convenience, or which pleases us. And is this any deviation from 
 the other processes of causation which we do not call orderly and 
 regular? Let us see. Certain things have such a relation with us 
 as to please or suit us; other things, acknowledging other rela- 
 tions, perhaps displease or do not suit us: what is there in either 
 instance but a common act of causation? The causes which we 
 dislike, perfect something else, or agree with another end; those 
 which we like, are equally disagreeable in another relation; there 
 is in both instances an order or concurrence, the same in charac- 
 ter, but the instances (or the causes) are themselves different ; and 
 very naturally, and very orderly, belong to different purposes. 
 
 35. But order, it may be said, is exhibited wherever there 
 are any traces of method, whatever may be the end produced. 
 And what is method but an arrangement for specific effects? 
 And what effects ever do result from an arrangement, whether of 
 the sands upon the sea-shore, or of the fibres of a leaf, which is not 
 equally specific in regard to them? 
 
 36. It appears, then, if by the word " order" is meant the 
 subserviency of parts to an end, that " order" must obtain in every 
 process of causation ; since it is the peculiar or inevitable business 
 of causes to produce an end. If by the word " order" is meant a 
 similitude to the works of art, this similitude exists but partially ; 
 and the reason why it exists at all is that certain specimens only 
 of the works of nature are so related with our faculties as to in- 
 duce imitation, and to furnish the models: we shall not, however, 
 be able to discover a difference of character between those wor!;s 
 of nature which have certain points of resemblance with our imi- 
 tations, and the universal results of causation. The difference is 
 in the end, not in the character; for the most that can be said of 
 the parts in either instance is that they concur, or are subservient 
 to the end. It is plain that the distinction implied by the words 
 order and confusion is arbitrary. If the materials which make a 
 man should be so arranged as to make a pig, we should say that 
 the arrangement was disorderly for making a man, but quite 
 orderly for making a pig. 
 
 37. The same is to be observed of perfection, which is also a 
 relative term. Every identity must be perfect, because it is itself. 
 In this sense there ^is a positive perfection: if the thing were 
 changed, it would be imperfect compared with that which it was 
 
49 
 
 before, but perfect in another identity. Thus, a man is perfect as 
 such, while he retains the identity of a man; and the worms into 
 which he degenerates are perfect worms, but imperfect men. The 
 word perfection is most commonly used in the relative or compara- 
 tive sense. 
 
 38. Now supposing it possible that an entire change were to 
 take place in the world ; suppose that the causes of which it is com- 
 posed were, in every instance, to make a different combination or 
 effect; suppose that roots, now nutritious, imbibed from the earth 
 poisons; suppose that trees contained, and were capable of 
 evolving the bodies of elephants; suppose that men had more than 
 five senses, and as many heads as ringers, and these latter doubled; 
 what would be the consequence? Why, perfection. If all the 
 parts comprised in such a slate did not agree, if there was not 
 absolute harmony of relations; what then? Why then such a state 
 of things could not exist; but another in which there was this har- 
 mony of relations: for if there is not agreement and compatibility 
 in one state of things, things will be compelled to adopt another, in 
 which there is agreement and compatibility: this is a truism. There 
 must be agreement then with any state of identities; when 
 there is disagreement with present, there is agreement with a 
 new state of identities, and that new state is adopted ; otherwise, if 
 the past subsists, there was agreement in the past: this also is 
 obvious. 
 
 39. What shall we say more than this for the present state of 
 things? We can do no more than insist upon this harmony, which 
 is a necessary one under all circumstances. But it will be asked 
 whether the present condition of the world is not the best? This 
 is a different question, which is answered thus: if by " best" is 
 meant most agreeable to the present state of man, we perhaps 
 should not err in asserting the affirmative ; but if by " best" is meant 
 any positive excellence, which is independent of man, why then it re- 
 mains to be known what this excellence is. It cannot be affirmed that 
 in another state of things, man, preserving in an altered identity some 
 characteristic traces of his present nature, may not be better off, 
 and the state of things be better for him, than at present; for his 
 faculties may be improved, if his means of knowledge, or his senses, 
 were multiplied: his body would be improved if his strength were 
 greater; if its causes were permanent, not apt to run into disease, 
 and indissoluble; and his happiness would be enhanced if there 
 were such an agreement between his sensibilities and his circum- 
 stances as to ensure great and unremitting felicity. [ would urge, 
 further, that man does not know how far he ought to consider the 
 present state of things as the " best," according to the meaning be- 
 fore conjectured to belong to this word: I say he does not know 
 this ; for though he is acquainted with a condition of existence 
 which is neither wholly happy nor wholly miserable, yet he is 
 totally ignorant of his future fate, which is of the greatest impor- 
 i 
 
50 
 
 tance. But suppose that man had never been? why then his 
 materials would have been otherwise combined, and they would 
 then have held true relations, though different from those which 
 they now acknowledge. In saying thus much with respect to man, 
 J am anticipating another part of the subject. Our business is not 
 to conjecture whether things may be changed for the advantage of 
 man; but to gain a rational understanding of how things exist as 
 they are, and to what forces are to be assigned the determination of 
 existences. 
 
 40. If it should be said, although in another state of things 
 there must be the order or relation between causes and effects, yet 
 things may nevertheless be very disorderly; the active principles 
 may be for ever changing the form of the passive materials, there 
 would be no stability, no permanency: I reply, if stability and 
 permanency are necessary to order, then it now exists but partially ; 
 for combinations are now perpetually shifting their forms, changing 
 their alliances; and man himself, all confident and important as he 
 appears, is but the creature of a day. 
 
 41. Granting, then, that agreement exists now, and must exist, 
 under every form, it remains that we should examine to what this 
 agreement is to be attributed, either in the acknowledged, or in the 
 apparently objectionable instances. 
 
 42. The senses can instruct us a considerable way in the solu- 
 tion of this question; common inferences will instruct us still fur- 
 ther; and the principles before mentioned, will leave us but little to 
 expect from further investigation. Thus, a clock would be no 
 clock without the wood, brass, &c. of which it is composed. What 
 makes the wood and the brass? Causes of which chymistry can 
 perhaps shew us one division. And what makes these? Other 
 causes which analysis has not reached. But these parts require ar- 
 rangement? True, this is necessary to the identity of a clock. 
 And how is this arrangement acconiplished ? In the usual way of 
 causation; thus, from a relation of agency between the hands of 
 man (as causes) and the brass, and wood, ^c. And how is such a 
 precise arrangement formed? By a relation between the muscles 
 and volition (as causes). And how is such a particular series of 
 volition determined upon? By the designing faculty. And what 
 produced this? An intellectual predisposition instructed, or made 
 the designing faculty which it is (from whence results this particu- 
 lar act of design), by the causes or things which surround it, and 
 with which it is related. But what made this intellectual predis- 
 position? Causes not analysed. (Ex nihilo nihil, #c.) 
 
 43. Now if it be inquired what determines the universe to be 
 orderly or disorderly? what makes it such as it is, or what would 
 make it different? I reply, causes. I repeat the manner of causation : 
 it is this : things are certain forms of existence ; they remain separate, 
 and are contemplated as effects ; they unite with others, and become 
 causes; the materials of their original state are not lost when 
 
51 
 
 causes produce effects; but they are disguised to us> because two 
 things have not the same relation with our perceptive faculties, as 
 one thing; and after a process of causation, we contemplate a ter- 
 tium quid, which is an aggregate of the causes. This is clearly, 
 and, what is more, truly illustrated in numerical changes : two and 
 two make four. Why? Because two and two are four, or four is 
 the existence of two and two ; if one is added we make tive, for the 
 same reason ; if one is taken away the identity is what the remaining 
 causes make it, or is the existence of the remaining causes, or three, 
 &c. Things are what their causes make them, for where there is 
 not production, and where there is no cause, there is unchangeable 
 nihility. The foundation of this principle has been before fully 
 discussed. 
 
 44. The causes of the universe determine its harmony, or its 
 seeming discord. If it be asked why this fine arrangement is ap- 
 parent? it must be answered, because such is the force of the 
 existences which make it what it is ; and if they were otherwise it 
 also would be different. Thus then we may venture to exhibit the 
 views which would agree with the principles unembarrassed by our 
 duller reasonings; and, in some such form, of soliloquy as the fol- 
 lowing, we may suppose an enthusiast in these views to express 
 himself, 
 
 45. Great Nature, by whatever name expressed, it is to thee I 
 address myself! thee I contemplate! thou art my theme: but 
 where begin to think, where begin to speak of thee ! I view, at 
 night, a large expanse of hill and dale, shaded with trees, clad in 
 luxuriant verduie; or naked, sighing at the rude attacks of wintry 
 blasts. Imagination paints the extent beyond, where earth is mottled 
 by other shapes and clothing ; with other animals to enjoy her 
 fruits. From this terrestrial scene, the view ascends to those re- 
 volving orbs, this lofty dome, adorned with stars and planets. These 
 things I contemplate, and wonder, Nature, at the vastness of thy 
 space and works; thy silence breathes into my soul; all is im- 
 mensity, engendering wonder. Yet this first impression once abated, 
 a speck of thy production, with faculties, the offspring of thy bounty, 
 presumes to scan thy methods, and pry impertinently into ways 
 which thou hast studied to conceal. But forgive the trespass, it 
 is love of thee that prompts this curious zeal, and guides my 
 thoughts astray; it is thy work, that they should adore thee ; take 
 it, therefore, not amiss, that falling from the amazement which is 
 first inspired by thee, I seek to know at least thy scheme, ihougli 
 ignorant of thy means, thy instruments, and subtler agencies. 
 
 46. Thy movements give birth to time, yet thy existence ac- 
 knowledges no period ; thou hast made time, and wilt not. be 
 obedient to thy creature : we boast some records of thy existence, 
 and presume to fix a date to thy beginning ; but if then thou didst 
 commence, from whence derived? or how start forth from nothing? 
 Thy own nature, thy inherent and proper forces, had no share m 
 
52 
 
 thy origination, for that would be to date thy actions previous to 
 thy birth. How then didst thou begin? Methink, the spirit of the 
 hills, at the question, shakes from him his beloved repose ; himself, 
 apart, speaks with a commissioned voice the language of the whole ; 
 yet it is a voice sweet and soft, it floats like a zephyr, and is heard 
 only in the stillness of the world ; it is a whisper to the soul, which 
 swells when it comprehends the great idea, and echoes thus the 
 truth, in accents of its own : " Search not when that began which 
 always has been ; ages and ages have revolved, myriads of changes 
 have been wrought, forms have been made, endured, and vanished; 
 destruction has succeeded quickly to creation : yet Nature was, be- 
 fore all this; her processes were repeated in periods infinite, which 
 thou, with a capacity for finite purposes, understandest not, but 
 must still think true." 
 
 47. Is then great Nature indebted to no other power but her 
 own] Say what this other power is, and try if here our thoughts 
 of infinite duration succeed more happily; something had no be- 
 ginning then; the voice is surejy no chimera: hark! it speaks again: 
 48. " What in this world, which so excites thy admiration, 
 canst thou perceive but an assemblage of forms? Thou wouldst 
 know when and how they came to be. Oh! dull perceiver! little 
 dost thou deserve to rise to universal truths, if thou so readily canst 
 overlook what in thine own experience is without exception. 
 Observe of things which are y but were not: thyself observe. The 
 sun has not yet thirty annual courses run, since the creatures which 
 are like thee knew thee not: ask how thou earnest to be, what has 
 produced the thing thou art? Thy history is clear; thy formation 
 has, throughout, been passive; that which thou hast, by which thcu 
 dost exist, is given thee; nought hast thou but what is conferred; 
 conferred by whom, or what? A form thou hadst prepared for 
 change, from others like' thyself derived, but most imperfect. And 
 what made this? thy curiosity would ask. It is plain, an assem- 
 blage of existences, of occult forms or properties, whose being is 
 inferred, because existence is their effect, but which to develop will 
 yet for centuries to come make full employment for the restless 
 spirits of thy kind. But this imperfect form derived, the earth 
 feeds with constituents, animals, and plants: these transfused sup- 
 ply thy growth with its materials, and thy accessions are as they are 
 furnished ." 
 
 49. Yes, this is the manner of it: existences all related; and 
 their relations fixed, not by themselves, but by the force of the 
 existences which are included within themselves; existence still 
 maintains existence, and nought begins where no existence is. 
 
 50. What sum of admiration is sufficient for this grand world, 
 enclosing in itself an endless series of forms and combinations! 
 Existence still springing from itself, and by itself perpetuated; 
 whose beginning no time has witnessed, whose end no period will 
 define; existing without our knowledge how; describing various 
 
53 
 
 shapes, pursuing various changes, none occurring but existence 
 still compels; all enduring in their present, or in other forms, be- 
 cause existence has no poiver to be nothing. 
 
 51. The stars are yet upheld ; great bulks we must acknowledge 
 them, apparently above us; and they fall not, though propped only 
 by light etherial columns. Who shall say why they keep their 
 spheres? who shall say what they are; whether constant, or at 
 periods produced by agents which we do not know, in worlds 
 teeming with things and processes of which we here find no 
 examples? They govern not themselves, but are obedient to their 
 own constituents; there, too, existences are causes, and all we 
 contemplate in them is yet compelled, effected by existence. 
 
 52. The sun is present, and imparts to us both light and heat; 
 it is formed by its own causes; these, or its grosser forms, by others, 
 an endless chain. In turn it sends to us some causes, which it 
 well can spare: to us it sheds existence, which mingles with our 
 substances and creates new forms. 
 
 53. The sea possesses by a natural right, the deep dominions 
 over which it rolls. This vast property it claims by force of causes 
 which with it abide; it seeks the lowest parts, and terrifies its con- 
 fines all around by bold incursions on the soil which man calls his; 
 it foams and dashes against great rocks, a bulwark formed to check 
 its aggrandizing spirit, and make its waters still recoil upon itself. 
 Fruitless ambition! thy powers have but their scope; and further, 
 earth is too mighty for tliee, as it, in thy dominions, and all its 
 fine productions, are but a weakness, serving for thy pastime. 
 
 54. Myriads of waves roar and froth, or, gliding smoothly, 
 glitter in the sun upon thy melting bosom. Not one of these that 
 moves, but moves as 'tis impelled; it, passive, an effect; in turn 
 impelling, then a cause; all more minutely propertied ; each par- 
 ticle which we suppose, but cannot see, of the same quality with 
 the whole: fluid and salt; one while upbearing, then yielding; at 
 one time pleasant and salutary for those of a different element, at 
 another, threatening, overwhelming, and destructive; now, trans- 
 porting rich freights in safety to the shores, dispensing wealth and 
 luxury, then swallowing without remorse, this merchandize (the 
 sovereign curse of nations), and bringing ruin, as indeed is just, on 
 those who rest their hopes and fortunes on such trash. Thou, too 
 great sea! endless in thy relations. 
 
 55. Thy movements observe a method even in their roughness : 
 one while thy waves overstep their present limits, the pebbles on 
 the strand are seen no more, thy presence hides them, and they 
 chafe and fret, obscurely warring with each other, where no witness 
 is to tell the fate and history which must belong to each. They, 
 by their causes, are, where we observe them, still passive; they are 
 removed, or broken, or rest, or remain a whole; or are collected, 
 some fused, some ground on roads and then manure the fields; or 
 else are washed along, DOW backwards, then onwards again, 
 
54 
 
 traversing the uneven bottom of the deep from shore to shore. 
 Again the waves retire, the sand is wet, the sun compels rom it a 
 contribution, and it is dry; these changes regular, flux nnd reflux, 
 marking periods, and obedient to some other power. What other 
 power? The moon, they say; but this is perhaps a fable, coinci- 
 dence is not causation; still by some power governed in this regu- 
 lar work; again connecting the great sea with unknown things, 
 an 'iidieKs series of relations. 
 
 5f>. But our parent earth supplies to us more varied interests : 
 our native soil is quite familiar, and we are told of worlds abroad, 
 desolate or rich, where animation fails for want of means; or 
 where nature, prodigal, spontaneous, yields more goods than can 
 be enjoyed. 
 
 57. Africa, scorched by the sun which should but warm, 
 presents varieties of her own. Here woods* water, fruits, men, 
 beasts; there, oceans of sand, which mingle with the wind, and 
 bear rapidly distress and ruin: but here the inanimate causes sport 
 mostly for their own amusement ; while the wind howls in the 
 desert, and the sand flies in columns, sometimes upwards, then in 
 vast clouds onwards borne, the tiger crouches, unconscious, in 
 watch for his prey, and the savage is asleep in his hut ; each, each, 
 and all, governed by existence, forcing existence, by causes. 
 
 58. Asia, wide separated, is yet joined to Europe by inter- 
 mediate causes and relations. Man, adventurous for he knows not 
 what, brings from this soil materials of luxury and corruption. 
 Here the earth teems with new varieties: here the elephant, 
 nourished and developed by the productions of the land, is 
 domesticated by man, and rendered by this connection more mis- 
 chievous than nature would have made him ; he, by this new as- 
 sociation learns to fight battles not his own, and is taught a 
 treachery to his species, which should belong alone to man. 
 
 59. America too has her phenomena. In all these quarters 
 of the globe myriads of inanimate processes, of the peculiar kind, 
 take place, all governed by their proper causes. The animate 
 creation is also wonderfully variegated, and nature seems to have 
 et apart districts and countries for the reign of animals, all things 
 concurring to their wants, as in the more civilized parts she, 
 suffering the dominion of man, appears to have niade every thing 
 subservient to his purposes. 
 
 60. Europe presents a more familiar scene. Here nature and 
 man work more conspicuously together: the former prepares ma- 
 terials, the latter works them into forms ; their operations some- 
 times mixed, sometimes exclusive. The trees in the forest bend as 
 the wind impels, or their leaves are made wet by the storm ; they 
 shoot forth their branches and grow rich in foliage, and they stand 
 erect in their majesty ; their present causes yield to others, the 
 green twig withers, and the strong arm becomes sapless, their leaves 
 are no longer sustained, and they return to the earth; or their 
 
55 
 
 whole bulk; their uprightness, and their majesty, arc all levelled by 
 the woodman. Then begins with them another series of causation, 
 61. But of all productions of the earth the most interesting to 
 man are those which come nearest to himself, the various tribes of 
 animals: these, all curiously endowed, by other causes first dis- 
 posed, the earth maintains them; they for a while enjoy their 
 faculties ; effects produced : causes, producing, they then exchange 
 their properties, and return to earth, assuming new forms, and be- 
 come the actors in another scene. 
 
 62. What in a general way shall we observe of man? In 
 truth he is a theme too complicate for general remark : lie, how- 
 ever, pursues in every point of view, in every single act, and in their 
 combinations, the universal order; related with his own causes; 
 these infinite ; he, an effect. His causes and associated attributes, 
 with surrounding existences allied, affected by, or changing them : 
 still an effect; or in turn a cause. How he is built up, we need 
 not say; the drama of his life need not be told ; what he returns to 
 is also plain. Thus then in more sober form the order of the 
 world proceeds. 
 
 63. The universe is identified by all its parts ; these last by 
 their constituents, in infinitum. The produced contains the pro- 
 ducing. 
 
 64. Causes have their sphere of influence ; that is, as they 
 operate only by supplying themselves, they are causes only where 
 they exist; further the subject of their past operation is taken up 
 by others, and a continuous history of its change* may be preserved 
 to all appearances, when no trace remains of the identity which was 
 formed by preceding causation. Thus 
 
 65. The sun encourages the growth of the stick which be- 
 comes the bludgeon of a highwayman, by which a man is killed : 
 his family is for a while supported by the parish ; a son enlists as a 
 soldier, and a shot from his piece occasions the death of a general 
 officer, whose widow and nation lament him. None of which 
 would have happened, had not the sun, all pervading, encouraged by 
 his influence the growth of the stick. Yet the sun-beams which 
 warmed the tree, are not the cause that one became a soldier, who 
 might otherwise have been a tailor, or of the death of the officer, 
 whose fate his country laments. These are distinct, though con- 
 nected acts of causation, and every cause concerned is to be con- 
 sidered as such only where itself exists ; to that which can exist 
 without it, it is no cause. (See Chap. IF. &c.) 
 
 66. The appellation of " remote cause" is given to express the 
 relation between the sun and the ultimate effect, viz. the death of 
 the officer, in the example just given. This appellation might as 
 well be retained, since its implication cannot be expressed without 
 more words; it must however be understood that there is no such 
 thing as a remote cause, of the description hinted at in our example, 
 simply for the reason that the expression implies a cause, that is 
 
56 
 
 not a cause. The man who plants an apple-free is not the cause of 
 an apple; he is concerned as a cause only in the planting of it, 
 which was an act accomplished by his powers; but the growth of 
 the apple is dependent upon the causes which constitute it, these 
 upon others; some are retained in them and are essential to the 
 identity of the apple, and still preserve the character of causes ; 
 others, of remote connection, have passed into different forms, and 
 as an apple is identified without them, so they, in respect to it, cease 
 to be causes. We will however admit the term for the sake of a short 
 expression, and thus conclude our exhibition of the order of the world. 
 
 67- Effects are portions of the whole, -which by us are con- 
 sidered separately, because such is the relation between them and 
 our faculties. These effects are the most conspicuous to us when 
 they appear in the shape of gross bodies. By analysis, combina- 
 tion, &c. gross bodies may be rendered some fluid and others 
 gaseous ; and then we only recognize certain properties which 
 belonged to them. Previous to this decomposition they appeared 
 homogeneous, and holding a perceptive relation perhaps with all the 
 senses, at least with those of vision and touch : subsequent to it, 
 they appear to be composed of properties which have a perceptive 
 relation with only some of the senses, or perhaps with only one par- 
 ticular sense, and then losing the characteristic of an aggregate of 
 the properties of matter, the body ceases to be material. These 
 component properties are not self-existent, if there is any truth in 
 the article on causation, but are constituted by others in infinitnm. 
 But analysis being imperfect, the force of the causes which make 
 these properties has remained unchanged, and their respective 
 identities are still preserved, or suffering, spontaneously, decompo- 
 sition, are no longer objects either of sense or inference, and are 
 therefore considered as elements. These, causes were not thrown 
 in the way of combination by themselves, but by that which has 
 been called a remote cause, but which might be no cause at all. 
 For every thing which takes place there is an adequate process of 
 causation, simple and undeviating, and the combinations which do 
 take place, are those of which these are the causes which produce 
 them. 
 
 These are the outlines of a mode of philosophising, the detail 
 of which will be best developed by extending the application ; for 
 which purpose I select the general history and condition of man, as 
 a subject which of all others stands most in need of elucidation, and 
 at the same time is more agreeable than any other with my habits 
 and pursuits, hoping that if these principles do not conduct us to a 
 satisfactory understanding of this complex subject, they will at 
 least serve as a clue to the proper manner in which its investigation 
 is to be attempted. 
 
 An apology or justification of another sort, may to some appear 
 to be required for the discussions which this section comprises. 
 
57 
 
 If it should be charged against these doctrines that they are 
 subversive of religion; I reply that such a charge is totally un- 
 founded. The Christian religion is proposed upon authority * the 
 ground of its adoption is faith } and this is a part of the religion 
 itself. If the truths of Christianity were such as were capable of 
 being made manifest by natural proofs, there would have existed no 
 necessity for a revelation in order that they might be embraced. 
 Christianity sets nature aside, and entirely out of the question: it is 
 proposed by its author that it should be accepted in the way of 
 confidence, or trust upon his authority; and whether natural testi- 
 mony concur with or oppose the system, is a point which does not at 
 all affect the grounds or terms upon which it is recommended. 
 The true and only source of proof, by which the existence and 
 moral government of the Deity can be consistently established, is 
 revelation : and the belief must be taken up upon this ground, in what- 
 ever point of view nature or physical testimony might be regarded. 
 It is allowed by the most orthodox, that the facts recorded in the 
 New Testament, as the miracles, &c. of Christ, are out of the com- 
 mon order of nature, and that they exhibit a power of which no man 
 has ever had the faintest glimmering of experience. Yet these 
 histories are believed, in the way that is proposed, viz. that they 
 should be accepted as matters of faith. If natural evidence 
 tended to produce the same belief as that enjoined by revelation, 
 nature would be referred to as a testimony of the truth of revela- 
 tion: the system of revelation would only be an exposition of 
 the system of nature. But revelation is proposed only upon one 
 ground, viz. faith : and it is even contrary to our religion to adopt 
 it upon any other basis. 
 
 I cannot help thinking that some who have cited natural evi- 
 dence in proof of the truth of revelation, have gone further than 
 they were sanctioned by the creed they professed. They have 
 endeavoured to establish Christianity, or some leading points of 
 this scheme, upon a different foundation from that upon which it 
 was proposed: and as their attempts, if they were even more 
 complete and successful in their issue, can make nothing in 
 favour of a scheme, which, to be adopted as the letter requires, 
 must be adopted upon another basis; so the total failure of these 
 attempts can detract nothing from the credibility of the revealed 
 accounts. In short, it matters not how nature is represented, in 
 what light she is made to appear, or upon what party her services 
 are engaged : her voice in the affair is protested against, and the 
 inadequacy of her testimony declared, by the proposition of a 
 system upon a higher authority, upon an authority superior to 
 that of nature. 
 
 The ground upon which Christianity is proposed, viz. faith, 
 
 is one, which, though founded upon our experience, as every kind 
 
 of evidence must be, is capable of superseding other evidence, 
 
 which is also founded upon our experience ; this happens every 
 
 K 
 
58 
 
 day; and therefore there is no reason why Christianity should not 
 be embraced, although its principles should not be agreeable with 
 our experience in other respects. It happens perpetually that 
 we believe accounts of strange, and, as we say, unnatural occur- 
 rences, upon our faith in the veracity of the narrator. Our only 
 commentary on these cases is, " unless I had every reason to 
 believe that what you say is true, I should scarcely credit asser- 
 tions so contrary to ordinary experience;'' but that the things 
 asserted are contrary to ordinary experience cannot be disguised, 
 though they are still capable of being accepted, and firmly believed, 
 upon the reliance we place on the competency and veracity of the 
 witness. So the case stands in some respects between natural and re- 
 vealed evidences concerning religion : we cannot disguise that one 
 part of our experience inclines us to a certain system of inferences; 
 but if these inferences are controverted upon what we esteem 
 better grounds, they must be rejected, and others accepted in 
 their stead. Where two systems are at issue, that must be pre- 
 ferred which is recommended by the best evidence; and the 
 general adoption of that of Christianity in this case, appears to 
 shew that, according to the common sense of mankind, the scheme 
 of Christianity, resting upon authority, and faith in that authority, 
 is better deserving of credit than that consisting of inferences 
 from the observation of nature, who is, it must be confessed, in 
 such intricate matters oftentimes a deceitful guide. In the mean 
 time physical truth or science continues to be investigated ; and 
 nations unite to complete the system of physical science, pro- 
 fessing only a design to augment the sum of their intellectual 
 attainments, and admitting still that there is an evidence above 
 that which rests upon a physical basis. 
 
 But although in the preceding sketches physical and revealed 
 evidences appear not entirely to agree, yet in fact their results are 
 not altogether so incompatible as may at first sight appear. If in- 
 stead of investigating physical topics as such, and merely taking ac- 
 count of the evidence of nature that is derived from the relations 
 of cause and effect; if, instead of doing this, I had been desirous 
 of exhibiting a system of natural Theism, the preceding views fur- 
 nish the materials, and the whole account, so far as it goes, might 
 have been made to agree with the implication of the letter of 
 revelation, merely by a nominal change. It would have precluded 
 fancy and gratuitous assumption ; but it would have made those 
 who thought proper to accept it Theists upon physical proof. I 
 profess myself (as the nature of my profession may by some be 
 not understood) with all sincerity to be a firm believer in the 
 existence of a Deity; and I ascribe to this Deity, even on phy- 
 sical testimony, perhaps all that revelation strictly requires, 
 assuming, as is allowed on all hands, that some licence is ad- 
 missible in the interpretation of the letter ; that some expressions 
 are adapted to the sense, and to human views, and are not to be 
 
59 
 
 understood literally. But although with this sanctioned limitation 
 J profess myself a Theist, my notions differ perhaps from those 
 of others in the nature of the real agency of a Deity, and, as I 
 can perceive, in this respect only; and if the question belonging 
 to this real agency were proposed to ten of our most orthodox 
 religionists, I am confident that they would, by giving a different 
 answer, or perhaps no answer at all, at least by not agreeing in 
 their accounts, shew that my difference of opinion was upon 
 points on which they themselves are not agreed. However, all 
 this is foreign to my purpose, which is to investigate the laws of 
 physiology, to which I am pledged by my calling legally and 
 morally. For this purpose it is necessary that every sort of light 
 which can assist in their elucidation and development should be 
 brought into the service. If I am reproached with having thrown 
 a false light upon the subject, let this be proved, and I am ready 
 to acknowledge it; my consolation then will be that even the 
 promulgation of error is one step towards the advancement of 
 science, more especially when it serves to lead the pursuit. 
 

BOOK SECOND ON THE ORGANIC ORIGIN OF MAN, 
 
SECTION I. 
 
 JL HE constitution of man has been divided into the 
 organic, animal, and intellectual departments. As these are 
 variously blended in the subject, giving rise to complex relations, 
 so thte precise definition of three parts, where the whole seems to 
 form but one, must be confessed to be in some degree arbitrary. 
 But as the division is indispensably ^convenient, though in some 
 respects imperfect; and as it is, to a great extent, conformable 
 with the division of which nature has on other occasions furnished 
 us the examples; we appear warranted in adopting it, provided 
 the detail does not assume, in consequence of the classification, a 
 distinctness which is not agreeable with truth. 
 
 The title of " organic* life" includes all the phenomena of 
 living bodies, which are independent of sensation and voluntary 
 motion. The principal phenomena expressed by this term are 
 those of digestion, chylification, respiration, sanguification, cir- 
 culation, secretion, absorption, &c. 
 
 The animal existence is one which is joined to the organic, 
 and has a relation with it. It is identified by the faculties of 
 sensation, by which it is liable to be affected by, and motion, by 
 which it is capable of affecting, the external world. 
 
 The intellectual existence is joined with the organic and ani- 
 mal existences; it is identified by the faculties of remembrance, asso- 
 ciation, comparison, inference, &c. Perhaps these faculties are not 
 so distinct as they appear: it is possible to regard them all only as 
 modifications of the first ; of this we shall speak at a future time. 
 The degree in which these faculties are possessed seems to dis- 
 tinguish men from brutes; rather than the perfect possession of 
 them by the one, and the total absence of them in the other. 
 
 My present design is in general to exhibit the state of evi- 
 dence upon the several topics. If this evidence furnishes a series 
 of satisfactory conclusions which agree with each other, and with 
 other things, the value of the evidence will not be diminished by 
 its being conjoined with the conclusions it supports, even though 
 these last may assume the form of a system, for which I give no 
 pledge : my only pledge is, to make out a few truths if I can. 
 
64 
 
 CHAP. I. Maternal Ovum. 
 
 1. THOSE who wish to know of what constituents the 
 textures of animals are formed, may consult the systems of 
 chymistry, in which their analysis, to a certain extent, might be 
 found. But to us, who are just entering upon a different inquiry, 
 chymistry can furnish but little aid ; our research is not concern- 
 ing the proportions of fat, earth, salts, &c.; but it entertains con- 
 nection with their result: we have not now to consider the visible 
 fabric in its elements; it shall suffice for us to notice, with respect 
 to these elements, their tendencies, and some few of their 
 phenomena which are exhibited under different alliances. 
 
 2. There is no distinction more obvious than that between 
 the living and the dead states. If we wish to know in what this 
 difference consists, it will be necessary to express so much of the 
 difference as we are capable of perceiving, trusting afterwards to 
 our inferences for supplying what is further to be desired. 
 
 3. As, in the definition of the organic life, the processes of 
 digestion, circulation, respiration, secretion, &c. are said to consti- 
 tute it; so, in the absence of these, the organic life ceases ; this cri- 
 terion of the difference between the living and the dead states, can 
 be neither overlooked nor doubted. Organs then, during life, in a 
 state of action, at the period of death fall into a condition of rest. 
 Is there no other difference between the living and the dead states, 
 but that the one is matter in motion and the other matter at rest? 
 
 4. It must be replied, that the difference, so far as we have 
 traced it, consists in this, viz. that in the living state there is the 
 presence of an efficient cause of these actions, of a peculiar nature, 
 and giving rise not to mere motion, but to peculiar motions con- 
 nected with other phenomena, which it will be our future business 
 to consider: in the dead state there is no such efficient cause; if 
 its properties are retained in the textures, its form is inefficient. 
 
 5. That this cause is one which belongs neither to the 
 mechanical nor the chymical constitution of the textures is shewn, 
 to the very utmost extent of observation, by the fact that these 
 processes, characteristic of organic life (before mentioned), cease, 
 while the mechanical arrangement and chymical constitution of 
 the textures remain. In the ordinary instances of death, scepti- 
 cism may urge, it is possible that some change takes place either 
 in the chymical constitution, or in the material arrangement, which 
 occasions the cessation of the actions. As in a piece of machinery, 
 
65 
 
 the motion of the parts ceases when their arrangement is disturbed, 
 notwithstanding all the causes remain which before produced the 
 motion. 
 
 6. The objection is an absurd one: we will, however, remove 
 it by an instance which is not one of ordinary death : arterial blood 
 contains the chemical elements: amputate a limb, wash out the 
 blood, let the textures be carefully preserved, transfuse arterial 
 blood into its proper channels: the phenomena of the living state 
 will not take place, as circulation, secretion, &c. the blood will flow 
 to a certain extent, as in any other dead tubes, until it coagulates. 
 
 7. If, however, it were proved that life consists in a modifica- 
 tion of chymical or mechanical properties, the phenomena of this 
 modification are so different from the ordinary phenomena of these 
 properties, that they furnish a centra-distinction: and as the pheno- 
 mena are thus distinct, so also must be the cause by which they 
 are produced; the former therefore would be designated vital phe- 
 nomena, or the phenomena of life; and the latter, the vital principle, 
 or the principle of life. The nature of the principle is thus put 
 upon the footing of the universal laws of causation ; and whatever 
 might be its origin or connections, the same investigation is applica- 
 ble to it, as a cause peculiarly constituted, whether, indifferently, by 
 a modification of the common or of the chymical properties of 
 matter, or wholly by another class of properties which are essen- 
 tially connected with neither of these departments. 
 
 8. It is not necessary in this place to connect all the processes 
 of organic life with the cause just adverted to, or with that which 
 has been called the vital principle. It is sufficient to indicate a 
 general efficacy which belongs to it, and return to the operations of 
 it which are connected more strictly with our present design. 
 
 9. During life, or during the continuance of the cause above 
 spoken of, the identities of the structures are preserved; when this 
 cause ceases to act, the structures are disposed for change, and they 
 gradually run into chymical decomposition. It is then by the in* 
 ihience of the cause called the vital principle that the structures are 
 kept together: this cause ceasing to act, it is the tendency of the 
 textures to disunite, and return to what have been called their ele- 
 mentary constituents. 
 
 10. As the constituents of the textures when left to themselves* 
 so far from having any disposition to unite, exhibit clearly the con- 
 trary tendency to separate; so the cause of their union, in the living 
 subject, is not to be looked for in their own nature, or their own 
 properties (which are mutually repulsive), but in something diffe- 
 rent from their chymical elements. 
 
 11. As the chymical elements remain united only so long as 
 the principle of life is with them, and separate when the efficacy of 
 this principle is no longer displayed; so we appear warranted to in- 
 fer, that the vital principle ; or the condition of it in which it is 
 capable of the processes of life, is that which produces the union of 
 the elements of the textures; since by it alone this union is main- 
 tained, and it ceasing, the union is dissolved: than which double 
 L 
 
66 
 
 test, in a matter of inference, there can be no higher proof of 
 causation, as will hereafter be shewn. 
 
 12. This principle, which we do not see, I call inclusively the 
 organic spirit; thus distinguishing it from the chymical and 
 material alliances; and for this purpose only, and having expressed 
 how much is meant by the term, there can be no objection to the 
 use of it, provided the distinction it implies be agreeable to truth, 
 which I have begun by endeavouring to prove. 
 
 13. In our view of the principles of causation, it was shewn 
 that there is nothing strictly elementary.* We are therefore taught 
 to expect the agency of properties in phenomena, where we are not 
 even acquainted with -their effects; that is, we are taught to infer a 
 series of causes which has no end: bodies, compounded of proper- 
 ties, related with the senses; these latter, of others, not related with 
 the senses; and to a great extent we can trace, satisfactorily, as in 
 the present instance, these relations between a visible and an in- 
 visible world. Without however examining here what we are to 
 think of the extent of these relations, it shall suffice to have re- 
 marked that of the spiritual alliance with the animal textures to be 
 in mere conformity with the principles before laid down. Before 
 connecting then the formation of the textures with the agents by 
 which it is said they are formed, it will be proper to inquire a little 
 concerning the origin of the cause itself, which appears to have a 
 natural precedence. 
 
 14. We distinguish, among others, two modes of the produc- 
 tion of an apparently new form; one, by perceptible constitution, 
 where the components are brought together and combined, as in the 
 example of the union of an acid and an alkali, and the formation of 
 a neutral salt ; and the other, as where a form previously consti- 
 tuted detaches from itself a portion of its own identity, giving rise 
 to a distinct being: the former mode may be called the origin by 
 constitution, the latter an origin by derivation. 
 
 15. If we examine how the spirit of a man came to be, we 
 must recur to the first mode, and pursue the history of its forma- 
 tion and growth : if we inquire how it is perpetuated, we shall find 
 strong traces of the latter, and at the same time shall not altogether 
 overlook the former; in other words, we shall find these modes to 
 be mixed in this business, and the examination alluded to belongs 
 to our present subject. 
 
 16. The organic spirit is formed like gross substances, viz. by 
 its constituents; if it be asked what these constituents are? it must 
 be replied, 
 
 17. The properties by which it is identified, and without 
 which it cannot exist. 
 
 18. The organic spirit exists in various forms: in some in- 
 stances, as in the lowest tribe of animals and vegetables, it displays 
 but little more than a single property, or else a combination of pro- 
 perties subserving to one similar end ; that is, it does little more than 
 
 Chapter II. 
 
67 
 
 maintain the connection of an homogeneous structure. As we 
 ascend in the scale of the animal creation, the complexity of the 
 spirit increases, though not in the same ratio as the complexity of 
 the animal and intellectual faculties increases; for the organic spirit 
 of a horse exhibits in its effects as great a complexity, or as many 
 properties, as that of a man. 
 
 19. On account of the irregularity adverted to, the laws of the 
 organic spirit cannot be generalized, except in some few points of 
 agreement, and they therefore require to be considered specifically 
 in the several examples. The life of man is the example here 
 chosen, and the only general laws to which it is necessary to remark 
 its subserviency are those universal ones of causation before 
 spoken of. 
 
 20. The first sensible origin of man is his existence in the 
 ovum; and it it here that the history of his perpetuation must 
 commence. 
 
 21, The organic particles of the ovum, life being extinct, fol- 
 low the fate of those of the other textures; that is, they become 
 separated from each other. The tendency then of the organic 
 particles of the ovum is not to aggregation, but to decomposition: 
 their aggregation is maintained by life: without life their union can- 
 not be preserved: but for life, their union would not have taken 
 place, they separating when life has ceased. 
 
 22. The organic spirit of the ovum has then this property of 
 life, viz. to be competent to produce and maintain the union of ils 
 organic particles. It has also other properties of life, although it 
 wants those which are subservient to growth. 
 
 23. If the organic particles, which this spirit forms and unites, 
 are homogeneous; or if it performs only one action; then the 
 organic spirit is an identity which has only one relation, and this a 
 mediate relation with our faculties of perception. But if it pro- 
 duces particles which are not homogeneous, and if their arrange- 
 ment is diversified, then the properties concerned in the formation 
 of this spiritual identity have several relations with our faculties. 
 This is a common distinction in the relations of causes, and it has 
 been before explained. To give a familiar example of it: thus a 
 chymical substance in its state of combination appears to be but one 
 nature; in the state of analysis it exhibits different natures, these 
 were contained in the homogeneous body, but in that state they had 
 no relation direct or mediate with our faculties of perception. 
 
 24. The organic spirit of the ovum produces the sensible effects 
 of but few properties, but it has many properties which are latent^ 
 perhaps tending to influence the organic particles: of these we are 
 imperfectly instructed by facts of the description which follows. 
 
 25. An ovum, which at first displays only the property of life, 
 of preserving the integrity of its material alliances, is capable of 
 running through a series of changes, by which the character of its 
 material aggregation is changed; numerous combinations take 
 place, parts become distinct, their arrangement is determined, finally 
 
68 
 
 all the characteristics of the most complicated state of life are 
 manifested. These processes in the crustaceous ova are more con- 
 spicuously applicable to my purpose; these ova are detached 
 totally from the parent, and are at this period in the simple con- 
 dition which has just been remarked, they are afterwards exposed 
 to the operation only of a single external cause, viz. heat, and the 
 spirit begins to manifest its complexity, the textures are elected, 
 evolved, and arranged. 
 
 26. The respective causes, corresponding with the individual 
 changes, are not conferred from without, they are therefore in- 
 herent in the ovum; when they are not exhibited, as in their earlier 
 stage, their combination prevents an individual recognition, and 
 they are said then to be latent. 
 
 27. This state is a predisposition to after-life. 
 
 28. The organic spirit of the ovum possesses either all the 
 properties of the organic spirit of the parent, or other properties 
 having a relation with the external causes by which the identical 
 properties of the organic spirit of the ovum are subsequently 
 assumed. This question is not to be discussed here: but the proof 
 of one or other of these alternatives is this, viz. that the ovum be- 
 comes, in a general way, which is sufficient for the purpose, the 
 similitude of the original from whence it was derived ; that is, a 
 substance nearly homogeneous and destitute of any visible arrange- 
 ment, is capable of attaining all the complication of the structures, 
 as bones, cartilages, ligaments, membranes, muscles, nerves, arteries, 
 visceral organs, skin, hair, &c. and the same thing obtains with 
 respect to vegetables. Let it be remembered that the tendency of 
 the matter is to dissolution, and consequently its parts could never 
 unite but for that which prevents dissolution and counteracts the 
 force of a natural tendency, viz. the organic spirit. This is the 
 antecedent to these visible phenomena; or this is a governing 
 agency, amidst concurring causes; and this it is whose history we are 
 now to trace. 
 
 29. It has been said by some, that the primordium of every 
 individual of the human race was contained in Adam, or in first 
 parents, and that the succession of persons has been maintained by 
 an evolution of original seeds. To this opinion I cannot assent, in 
 consideration of the following circumstances: 
 
 1. An entire ovum is but the assemblage of a very few organic 
 particles. As the rudiments of procreation hold but a very insigni- 
 ficant proportion to the rudiments of the whole body, so we cannot 
 imagine that a single ovum, which was developed into the first 
 offspring of the primo-genitors, should contain the identical elements 
 of an endless perpetuation of the species. 
 
 2. It is contrary to analogy to suppose even that the identical 
 embryon of the third, was contained in the first, generation; for the 
 ovum, in its primitive condition, contains none or but very few of 
 the identical parts, which make the future animal : these are per- 
 petually changing, and increasing hy the processes of growth; and 
 
as the properties of the ovum, when the shape, &c. of the animal 
 are attained, are capable of a wonderful increment of their own 
 nature, it is little better than absurd to refer a series of generations 
 to one ovum, to so diminutive a source, when it appears that every 
 animal is endowed with a capacity of increasing*, almost indefinitely, 
 the elements of procreation, as well as those of the structures. 
 
 3. The procreative agents, so far from appearing to be possessed 
 in anticipation by a single ovum for all generations, do not appear 
 to be possessed identically, that is, such as they were obtained 
 from the progenitors, even for one ; for the procreative faculties 
 are not manifest, or exercised, until many years after the formation 
 of all the organs and structures, and must therefore be allowed to 
 be a product mainly attributable to the animal in whom they are 
 considered. So far then as the observation of facts is permitted 
 us, the supposition does not appear to agree with them ; and if it is 
 proposed on any other grounds, it is not worthy of consideration. 
 Indeed, it would be as reasonable in every respect to say that all 
 the bones as well as all the seeds of the human race were contained 
 in Adam, or in first parents: the arguments, on both suppositions, 
 as hinted above, might be founded on the same analogies. Other 
 reasons for a contrary opinion upon this point will appear in the 
 detail of my own views, to which 1 therefore proceed. 
 
 30. That the maternal ovum contains all the properties of the 
 original, that is, of the mother, or a predisposition to these proper- 
 ties, appears, as before remarked, from the general similitude which 
 the offspring bears to the parent. The question, whether the pro- 
 perties which at a future time are to produce bones, muscles, c. 
 are contained in a peculiar combination in the ovum, or whether 
 they are acquired from without, by relations which certain proper- 
 ties in the ovum have with the external influences, is not so easy to 
 settle in regard to the human race; but the fact, that the crustaceous 
 ova are developed by changes which takes place among their own 
 constituents, appears to sanction the former conclusion, which I 
 shall therefore assume to a certain extent for the present, and I 
 trust not farther than is allowable. 
 
 31. The condition of the maternal ovum is this: it is a smalt 
 aggregation of matter, formed by some properties of the organic 
 spirit, and it becomes the receptacle of an organic spirit. This 
 spirit itself is a combination of many properties; these in the con- 
 dition of the ovum are for the most part latent, but they afterwards 
 become causes, and are displayed in effects. These properties in 
 the condition last mentioned, under which they are exhibited, are 
 similar to those possessed by the original. The proof that such 
 latent properties belong to the spirit of the ovum is this, viz. 
 
 32. That the processes of constitution take place in the pro- 
 gress of the ovum towards foetal life; constitution is no single act, 
 or is not the act of an element, as explained before. There is no 
 bone in the first stage of the existence of an ovum. Blood supplied 
 to any organic molecule will not be formed into bone : for this 
 
70 
 
 purpose something else is required, viz. the existence of properties, 
 whose relation with the constituents of blood is to form bone. 
 The same thing is still more clear in the crustaceous ova, as before 
 remarked. 
 
 33. A great apparent difficulty may possibly be started in this 
 place: it may be asked how is it possible for so small a body as the 
 ovum to contain so vast a diversity of properties as is thus sup- 
 posed ? We must answer this question by citing as much as we are 
 able to observe of the nature of properties. 
 
 34. Matter is constituted by a combination of certain proper- 
 ties. No one property is material ; but the aggregate of properties is 
 recognized as that which has a well-known relation with our facul- 
 ties of perception, and which we agree to call matter, just as we 
 agree to call the united existence of an acid and an alkali a natural 
 salt. Now matter itself, in the gross, is said to be infinitely divisible, 
 and yet the individual properties of matter, which are recognized 
 only by a single sense, as its colour or its smell, are constituted by 
 other properties with which we have no perceptive relation at all. 
 (Chap. II. &c.) It may be doubted whether the properties related 
 with smell and vision possess figure; but supposing that properties 
 do possess figure (which is supposing what cannot be invariably true), 
 merely to facilitate our conception of the divisibility of properties, 
 it may be observed (to borrow an illustration) that a substance may 
 continue for a long time to emit an odour sufficient to fill a con- 
 siderable space, without any sensible diminution of its bulk or 
 weight. The odour existing in the minuter spheres of this exten- 
 sive space is of the same nature with the whole; the space may be 
 divided into ten millions of spheres, the property of odour in each 
 of these spheres may be infinitely constituted by other properties, 
 yet all these are emitted from a substance which may perhaps 
 weigh only a single grain. 
 
 35. If then a property is thus divisible, if the property which 
 resides in the smallest perceptible bulk may be divided into ten mil- 
 lions of portions, and each portion comprising an infinity of consti- 
 tuents, we shall have no difficulty in conceiving how a sufficient 
 number of properties for the future development of the animal may 
 reside in an aggregation of matter, as an ovum, which itself appears 
 to consist only of a few particles. 
 
 36. We have said that there is no limit to the diversity of 
 causes, by which the minutest effect is produced, from the necessity 
 of what have been called the causa causarum. It will be allowed, 
 the faculty of vision is as perfect in its kind at a mere point of the 
 retina as it is on the whole surface (there are a thousand instances 
 of the same force if this should be denied), now this faculty is made 
 of many properties; some of them are analyzed in our experiments. 
 There are then, confessedly, many properties 0:1 a scope of matter 
 not bigger than the point of a needle. Now supposing that these 
 properties, instead of remaining combined and minute, as they are, 
 should have a tendency to separate, and being supplied respectively 
 
71 
 
 with their similitudes, each should aggregate and repeat its own 
 nature, themselves being thus developed, and by force of relations 
 developing a sensible bulk, in correspondence with their own in- 
 crease. Why this is a parallel to all that we are supposing of the 
 properties possessed by the ovum. We object to its minuteness for 
 the possession of so many properties, and yet it is clear that more 
 properties than we can enumerate in the ovum may exist upon the 
 minutest point of matter; and the reason why in the latter case they 
 are not conspicuous, is precisely the one which explains their con- 
 cealment in the former, or in the instance of the maternal ovum, 
 viz. that the properties want the processes of growth in order to 
 become conspicuous. This matter is too obvious to require another 
 word in explanation: it may, however, be added, that as much as 
 has been here remarked is agreeable with the whole of our expe- 
 rience of the nature and laws of properties. 
 
 37. As the spirit of the maternal ovum, for succeeding genera- 
 tions, has been said not to have been contained in rirst parents, but 
 to be formed in each de novo, the question next to be considered is 
 in what manner it is formed ? And now we must recur to a ques- 
 tion which has been anticipated. To define it in regard to its 
 present application, we will ask, Is the organic spirit of the ovum 
 constituted for the purposes of perpetuation, in the same way in 
 some respects as it was in the first of the species] or is it formed 
 in the way of derivation? 
 
 38. To suppose the constitution of the human organic spirit 
 in the primitive way, would most probably involve a long history of 
 changes and accessions, on which, as we understand not spiritual 
 relations, we have no grounds for conjecture. Further, in such an 
 original constitution we cannot but suppose the occurrence of many 
 accidents which would render its identity irregular, much more so 
 than we find it. Upon the whole, it does not appear necessary to pre- 
 serve a distinct discussion of these questions. 
 
 3D. The maternal ovum was no more formed in the ovum from 
 which the mother herself was produced, than the bones: it was then 
 produced subsequent even to foetal life, which furnishes no ova. 
 The maternal ovum is found to have properties correspondent 
 with the properties which belong to all the parts of the mother; 
 the manner in which it is produced in the mother, is the subject of 
 our immediate consideration. 
 
 40. The alternatives of the manner in which the spirit is pro- 
 duced which forms the maternal ovum, are the two following: 1st, 
 whether the seat of the formation of the ovum is a point to which 
 every order of structure, or every part in the mother, sends identi- 
 cal properties, which thus reside in the ovum, requiring only the 
 development which they obtain by the processes of nutrition and 
 growth in order to form a new being, which resembles the one from 
 which it was derived, and which is constituted by the possession of 
 the identical properties of the parent? or, 2nd, whether, without 
 any contribution of identical properties from remote structures, the 
 
72 
 
 ovarium exercises a function, independent of other seats, of pro- 
 ducing a certain aggregate of organic molecules, and of endowing 
 them with properties which are similar to those possessed by the 
 parent, in every seat 1 
 
 41. In order to settle these alternatives, I devised an experi- 
 ment which, if it had succeeded, would have been conclusive. The 
 object of the experiment was to preclude the possibility of identical 
 properties from remote seats in the ovum. For this purpose, I pro- 
 cured two young rabbits, a male and female, and cut off both their 
 ears. The rabbits attained maturity, grew old and fat, but did not 
 breed. This experiment was repeated with two other rabbits, but 
 it so happened that they did not breed. These experiments are 
 not sufficient to prove that rabbits will not breed when their ears 
 are cut off, but I did not feel disposed to multiply my examples : 
 this therefore is the result, which leaves the question undecided. 
 I can assign no reason for this defect of procreation in these in- 
 stances, unless that the rabbits did not, with their ears cut off, 
 know each other to be rabbits.* Here it will perhaps be sagacious- 
 ly observed, there is no need of such a proof as this experiment 
 tends to furnish; for we see human beings variously mutilated, 
 having lost an arm, or a leg, or both arms, or both legs, getting 
 perfect children every day. This is true, but is no parallel to my 
 experiment : for if the father of a child has no arms, the mother has, 
 and either parent can furnish the radicles of resembling structures. 
 If the annals of human procreation, which are tolerably diversified, 
 can furnish any instance in which both parents has lost both fags, 
 l)oth arms, or both ears, or had no teeth, such an instance, if 1 had 
 been acquainted with it, would have superseded the necessity of my 
 experiment ; which, as it failed, the subject to which it refers re- 
 mains to be discussed upon the few imperfect data which are 
 currently known* 
 
 42. Every part of the mother possesses its organic spirit ; 
 every muscle, every bone, every nerve, every artery, every particle, 
 have their organic spirit; by it they are produced, maintained, and 
 governed; all these are possessed likewise by the ovum. Now these 
 parts of the entric organic spirit are modified in their several seats ; 
 that is, where they produce different phenomena: and their seats 
 are, respectively, fixed with precision; or else we should every now 
 and then find toes in the stomach, nails on the forehead, liver in the 
 hands, kidneys on the face, &c. The parts then of the spirit, or its 
 several modifications, have their respective seats. 
 
 * Let it be borne in mind in the subsequent discussion that only one result 
 of this experiment can be conclusive : that is, if the offspring should be de- 
 ficient in ears, it will prove the derivation of the ovum from the precise seats 
 of properties in the mother; if the offspring should possess ears, they may in 
 like manner be obtained by derivation from those undeveloped properties which 
 exist in amputated surfaces and afterwards are exhibited by the production 
 of new growths. For the elucidation of this note the chapter on Growth is 
 to be consulted. 
 
73 
 
 43. The seats of properties are determined by spiritual rela- 
 tions, for at first the existence of properties is not manifested ; they 
 afterwards assume their identities and seats, giving rise to aggre- 
 gations and arrangement of matter; which change is accomplished 
 by the causes by which the properties producing visible effects 
 are governed. When a modification of the organic spirit has 
 assumed its sphere, it exerts a function ; one of secretion, for ex- 
 ample. Now this function has so many properties as are deter- 
 mined by its relations with those other spiritual properties with 
 which it co-exists. 
 
 44. The precise nature of the function which produces the 
 secretion, is determined by a causation between the parts of the 
 spirit, which we can in no instance understand, because we are in 
 no instance acquainted with the relations it involves. The secre- 
 tion will be according to the function. 
 
 45. Every secretion is endowed with precise properties ; and 
 the same only can be said of any other production, which we may 
 or may not call a secretion. How these properties precisely, and 
 no others, came to be assembled, will be as difficult to pronounce 
 upon in one case as in another, because in all cases there are ante- 
 cedent processes of causation, of which we are totally uninformed ; 
 and it is sufficient for the present thus to shew the correspon- 
 dence of these processes with the general order of causation 
 which they also observe. 
 
 46*. Thus then the product of a function may possess chymi- 
 cal properties, and matter of a common kind, and latent constitu- 
 ents of life which may originate new forms; such a function as 
 this is displayed even by the kidneys, and sometimes by the 
 skin, &c. whose secretions generate animalcules. In each part 
 the function is precise, and not to be explained but by the know- 
 ledge of antecedent processes. 
 
 47. So in the ovarium, the function of this part is to produce 
 Ova. These ova are only a determinate constitution, the effect 
 of a determinate function, governed by processes of causation, 
 obeying spiritual relations, which are antecedent. 
 
 48. These ova, like any other product of a process of causa- 
 tion, have their identities, their causes, their relations, their pro- 
 perties, &c. some of which we shall endeavour to develop. 
 
 49. The only properties of the maternal ovum, before its 
 elimination from the ovarium, which are manifested in effects, are 
 those which produce and maintain a few organic particles. 
 
 50. The latent properties of the ovum, in this condition, are 
 those which correspond with the parts of the organic spirit of the 
 mother; and there is so ready a communication between them, 
 that is, between the properties of the mother and those of the 
 ovum, that we are inclined to suspect, as stated in our first alterna- 
 tive, that the formation of the organic spirit of the ovum is by a 
 derivation from all the parts of the mother, and that the confluence 
 of all the organic properties of the mother to the ovarium is an 
 M 
 
74 
 
 established function, either regular or occasional ; rather than that 
 the ovuoi is a local production, independent of the diffused 
 maternal parts. It is difficult, without admitting such a supposi- 
 tion, to reconcile facts of the following kind : 
 
 1st. Local hereditary diseases. Thus a mother may be affected 
 with phthisis pulmonalis (a disease perhaps not before known in 
 her family): this local tendency existing in the lungs (for such 
 local tendency is necessary to the disease), is participated jin by 
 the ovum, and the subject which is matured from it may also 
 have, at some period of its life, ulceration of the lungs. 
 
 2nd. The same may be said of calculous disorders, of gout, of 
 cancer, &c. 
 
 3rd. I knew a case in point of the following kind: a woman 
 was constantly afflicted with intense pain in the head : it continued 
 for some mouths, occasionally so severe as to produce a state of 
 stupefaction, sometimes to threaten a loss of intellect, and was 
 mitigated by none of the means employed for its relief. At this 
 time she was delivered of an acepkalons fatus. The pain in the 
 head afterwards recurred irregularly, and with less violence; she 
 then had a child naturally formed, but subject to frequent con- 
 vulsions, which threatened its life; and at about the third year, at 
 which time my acquaintance with the history ceases, a fatuity is 
 remarked which renders doubtful the future possession of good 
 intellectual faculties. 
 
 51. Now these circumstances do not afford absolute proof 
 on tbe point in question; for the latent properties producing the 
 hereditary diseases, might have been formed in that which was 
 to constitute the ovum of the offspring, as well as in that which 
 was to constitute the lungs, the brain, the kidneys, &c. ; and these 
 formations might have been synchronous and independent in 
 the ovum from which the mother was developed. The case 
 of disorder of the head might have exhibited a coincidence 
 only, and not a process of causation. But, if we allow it not 
 proved, that the properties of the ovutn are derived from a 
 corresponding seat of properties in tbe mother by these facts, 
 we must admit that the ovum* if independently formed, is 
 liable to be modified by the organic spirit of the mother existing 
 remotely; because, diseases produced by accidents, or by habits 
 of living, have been participated in by the offspring, in which case 
 the independent predispositions of synchronous formation seem to 
 be precluded. Thus mania has been perpetuated, or has been 
 introduced into a family, where its origin was referable to accident 
 or habit; thus also gout, and consumption, which have originated 
 in habits of life, have been transmitted to offsprings who have not 
 eq rally subjected themselves to the same exciting causes. The 
 dis >ase in these instances was created subsequently to the forma* 
 tion of the ovum. 
 
 52. In addition to these testimonies, it may also be observed, 
 that the ovum has no life of its own capable of maintaining its 
 
75 
 
 texture ; that when the parent dies the decomposition which fol- 
 lows is universal, and the ovum shews no more the possession of 
 an independent principle than a portion of muscle or skin. As, 
 however, from the death of other parts, the circulation ceases, this 
 remark is less conclusive than it might have been if deduced from 
 experiments in which this objection would be fairly obviated. 
 From however a just estimate of this class of facts, we are war- 
 ranted in presuming that 
 
 53. A communication subsists between the properties of the 
 organic spirit of the ovum and the diffused one, occupying the 
 several seats belonging to the mother, and that by this intercourse 
 the former is liable to be modified. We appear warranted in pre- 
 suming thus much, although it should be refused to admit the regular 
 confluences of all parts of the maternal spirit to theovum, in the same 
 manner as properties of a defined number and nature are assembled 
 in the other parts by laws equally mysterious; as, for example, the 
 properties which constitute a sense. This latter opinion, although 
 I say it is not proved, I consider as probable,* and shall therefore 
 bestow a few paragraphs in its further illustration. 
 
 54. To suppose a centre which is related with all parts of the 
 hody, has in it nothing monstrous, nor, as above hinted, does it 
 want the support of analogy. The faculty of speech and the 
 agents of articulation are related with all the passions, with all the 
 operations of the understanding; they are even more extensively 
 related, and the influences they obtain are derived from one entire 
 system, of the properties of which no part of the material fabric is 
 wholly destitute. Thus, the eye may witness a shipwrick (or any 
 other catastrophe); hope, anxiety, fear, horror, &c. may be succes- 
 sively occasioned by this instance of vision : and as the feelings are 
 modified, so also may be the voice and speech ; one while an ex- 
 clamation of terror, then a recital of the chances or possibilities 
 of escape, then an exclamation of horror at the conclusion of the 
 tragedy, with an ensuing train of feelings, all of which might be 
 expressed by the voice. The catastrophe, or spectacle, being 
 finished, the mind might fall into a series of reflections perhaps 
 upon the precarious existence of man; and the train of actions in 
 which the organs of speech have been thus engaged, may termi- 
 nate in a disquisition upon moral conduct, and the reasonableness 
 of our expectations of a future state. The same thing in effect 
 may happen, though the operations should have been commenced 
 by the excitement of any other sense. Thus the organs of the 
 voice form a centre at which the variations of an extensive system 
 may meet, and by which the minutest of these variations, however 
 remote its origin, may be expressed. The same thing happens 
 with regard to the brain : and every organ i$ a centre, whose 
 
 * The additional alternative, expressed in the note at page 72, is to be 
 taken into the account, aud regarded as making only a modification of this 
 inference. 
 
76 
 
 function is not perfected in itself, but by remote influences and 
 distant relations. It does not appear therefore assuming too 
 much in the instance before us, to admit the possibility that the 
 organic spirit of the ovum is formed, maintained, or modified, by 
 a confluence, regular or occasional, of the spiritual properties of 
 the mother, existing in different seats, and which properties, as 
 may be demonstrated, are possessed also by the ovum. I have 
 stated the evidence which refers to this topic, or as much of it as 
 is apparent to me. I should be sorry to assume more than is 
 justified by it. I will therefore state, of the condition of the 
 maternal ovum, as much as appears to have been rendered probable. 
 
 1st. That the ovum, before its elimination from the ovarium, 
 contains properties which correspond with those which belong to 
 the mother. 
 
 2nd. That these properties are so combined, that they are, in 
 this stage, latent. 
 
 3rd. But that these properties constitute the predisposition 
 to future effects. 
 
 4th. That the properties of the ovum are liable to be influ- 
 enced by communicating with those of the mother. 
 
 5th. That the life of the ovum is not independent of that of 
 the mother in viviparous animals. 
 
 6th. That the matter of the ovum is an aggregation of no very 
 complicated kind, because only a few of the properties of the 
 organic spirit are exercised in this stage of its existence. 
 
 It is affirmed, that the ovum is not perpetuated by evolution: 
 but it is not decided whether the ovum is formed by derivation 
 from all parts of the mother, or whether the function of the ova- 
 rium is to produce resembling properties independently of their 
 diffused existence in the several seats; had the experiment before 
 detailed succeeded, it would have gone some way towards settling 
 this point ; in the mean time the former alternative is preferred, for 
 the reasons which have been just assigned. 
 
 Among other points, still doubtful, it is net proved also with 
 certainty, whether the osseous spirit, for example (or any other), 
 exists in the ovum, or whether the ovum possesses only properties 
 which determine the future existence of an osseous spirit, through 
 a series of processes and preparatory relations: if the former is 
 true, then the ovum is not the foetus by reason of peculiar combina- 
 tions of its properties ; if the latter, then it is for want of pro- 
 gressive causation. This however is a question which it will be 
 hereafter attempted to settle. 
 
 Thus much for the present for the organic spirit of the ovum, 
 previous to its escape from the ovarium. The order of our con- 
 siderations suggests, that we should next speak of it in its fecun- 
 dated state. 
 
77 
 
 CHAP. II.Fecundated Ovum. 
 
 1. THE maternal ovum is constituted for the preservation 
 of its identity in this state: and this identity is maintained, 1st, 
 as long as life continues to reside in it; or, 2d, until it receives an 
 extraneous influence of a peculiar kind. 
 
 2. This extraneous influence being obtained, sub coitu, that 
 which was the maternal ovum becomes the fecundated ovum; and 
 instead of a constitution disposed to preserve its present identity, 
 it is made one, disposed for change. 
 
 3. It has been matter of inquiry among naturalists whether 
 an actual contact of the ovum with seminal fluid is necessary for 
 its fecundation ? or, whether the communication of an aura subtilis, 
 from this fluid, to the ovum, is sufficient for the same purpose? 
 As is usual in questions of no importance, many experiments have 
 been made with a view to the decision of these questions. The 
 experiments are not worth comparing: the principal facts relating 
 to the question are the two following: 1st, that an ovum, in the 
 human subject for example, is fecundated in the ovarium, as in the 
 case of extra uterine foetuses; to which seat, it appears improba- 
 ble, from the structure of the parts, that the gross seminal fluid 
 should penetrate. 2nd, That the ova of fishes are fecundated 
 without coition by mere contact of male semen. If the first fact 
 indicates that the ovum is fecundated without seminal contact, or 
 by an emanation of its properties, or aura subtilis, the second fact 
 does not refute this conjecture, because, though an actual contact 
 may commonly take place, yet the properties which are efficient 
 in the result of this contact may be separable from the fluid to 
 which they belonged; or may be the emanating properties, or 
 aura subtilis just spoken of. If the argument were discussed 
 minutely, much might be urged on both sides: such a discussion 
 is however superfluous, because, as before hinted, the question 
 itself is one of very little importance; for the relation of the 
 ovum is not with a few gelatinous particles, but with the spirit 
 or vital properties of which the visible fluid is the mere vehicle or 
 medium. In this point of view, as the fluid itself can have no 
 efficacy, whether it does, or does not touch the ovum ; it seems, on 
 this account, scarcely worth while to bestow a grain of ingenuity 
 in settling the alternatives. 
 
78 
 
 4. The properties of the maternal ovum, receiving the ex- 
 traneous influence just mentioned, commence the processes which 
 terminate in the establishment of fetal life. As the maternal 
 ovum was indisposed for these processes previously to fecunda- 
 tion, so they must be considered as the result of a constitution 
 which lakes place in the ovum. 
 
 5. As it is proved that the material and chymical parts of 
 the ovum are not the governing but the governed,* so the con- 
 stitution which takes place, sub coitu, and which produces the 
 changes hinted at, respects the properties of the organic spirit of 
 the ovum, and not its material alliances. 
 
 6. It has been said that the properties of the maternal ovum 
 correspond either identically, or predisponently, with those of the 
 mother: the proofs of which are chiefly rested upon the following 
 description of facts : 
 
 1st. The offspring of a black man and a white woman is a 
 mulatto. 
 
 2nd. The offspring of a horse and an ass is a mule, &c. 
 Examples of this kind are familiar and the law obtains as far as 
 the procreative intercourse between varieties of the same species 
 is known to take place. 
 
 7. Hence it appears, that as much as has been remarked of 
 the properties of the maternal ovum may also be said of the semi- 
 nal constitution, viz. that this likewise contains an organic spirit; 
 that this organic spirit is, like the maternal ovum, indisposed for 
 the changes which end in foetal life; that it exhibits in its ma- 
 terial aggregation but few properties; that it has many latent 
 ones, which correspond either identically, or predisponently, with 
 those of the subject in which it resides; that these latent proper- 
 ties are in peculiar combination, &c. A parity of laws may be 
 remarked between the seminal production and the maternal 
 ovnrn, because these laws are deduced, with but few exceptions, 
 and those of no great importance, from the same facts. 
 
 8. But this subject, viz. the fecundated ovum, brings us to a 
 question which, in speaking of the maternal ovum, it would have 
 been anticipating the subject to have discussed fully. The ques- 
 tion is, whether the identical organic properties of the parent 
 reside in the ovum? or, whether its properties are only a predis- 
 position to those of the mother, existing in the several structures? 
 The same question, in the other case, may be tranferred to the 
 cause of fecundation. 
 
 9. This question must be determined by our principles of 
 causation. The properties, whether of the maternal ovum, or of 
 the seminal fluid, never singly commence the processes which 
 end in fcetal life. It appears, therefore, probable that the pro- 
 creative rudiments, respectively, furnish only one stage of predis- 
 position towards the properties which form bone, muscle, &c.; but 
 
 Book Second, Chapter I. 
 
79 
 
 this is not to be positively asserted, because the inactivity of these 
 properties may be explained by a peculiar state of combination, 
 which it may be one effect of fecundation to dissolve. 
 
 10. If the properties contained in the maternal ovum and 
 those of the cause of fecundation were precisely the same, it is 
 obvious that no change, save that of increment, could result from 
 their combination. But other changes do result from it, and those 
 of the most complicated kind: it is therefore equally obvious that 
 a condition of these rudiments takes place upon their union, 
 which was not previous to their union, and that this process is 
 one of causation, which has been said to be the combination of 
 differentials; or, in other words, something is supplied to the 
 ovum which it wanted, to commence the processes which end in 
 foetal life; and something is supplied by the ovum to the seminal 
 matter, which it wanted in order to commence the same processes, 
 these, singly, not being constituted for such an end. 
 
 11. Thus then we see that in order to exhibit the state of 
 feetal life, at which period, and subsequently, the resemblance of 
 properties to those of the parent is also exhibited, it is necessary 
 that something different should mutually be supplied. Whether 
 this difference, this process of constitution, belongs to all the 
 parts of the spirit, or only to some of them, is a question to be 
 examined. 
 
 12. As the offspring from ^ male and female, of varieties of 
 a species, is found to be modified in all its parts; as the develop- 
 ment of the bones, &c. in the mule, is not the same as either in 
 the horse or in the ass; as every difference in the progenitors is 
 expressed by a corresponding difference or modification in the 
 offspring; and as progressive causation in a body which is not 
 exposed to adequate external causes, consists only in the develop- 
 ment or changes of combinations of properties already possessed, 
 or latent; so we must conclude that the procreative rudiments on 
 either side contain all the properties of their originals; and that 
 as the offspring affords evidence of the possession of no other pro- 
 perties, but those which do agree with those of the originals, so 
 we must consider the change which occurs in the ovum, sub coilu, 
 as the effect of the combination of the differentials, which in every 
 ease appear to a greater or lesser extent in the progenitors. 
 
 13. It is then that process of constitution which takes place 
 in the ovum by the mixture of the properties of its organic spirit 
 with those of the male, which gives activity to the former, and 
 makes them commence the processes which terminate in foetal 
 life. But whether all the differentials concur in this effect, or 
 whether the activity of the ovum is produced only by a relation of 
 agency subsisting between the properties agreeing in either sex 
 with the generative organs (which are perhaps the only fixed and 
 constant differentials), is a point which cannot be decided, because 
 the difference is not confined to these organs, but might pervade 
 (irregularly, in the several examples) all parts of the constitutions* 
 respectively, of the male and female. 
 
80 
 
 14. There are some properties of the organic spirit (indeed 
 the principal part of them), which are common both to the male 
 and female: these may be called perfect resemblances: there are 
 others which are different, or their efficient union is different, 
 though bearing a resemblance in some respects; and there are 
 others which bear no obvious similitude. These properties in the 
 parents reside, according to the restrictions and alternatives be- 
 fore proposed, one set in the maternal ovum, and the other in the 
 seminal fluid, and it is in these productions that we are now called 
 upon to consider them. 
 
 15. The instances of the first, viz. those of perfect resemblance, 
 are found in the properties which develop common identical sub- 
 stances, as bone, brain, muscle, &c. in which the properties 
 derived from both parents agree perfectly to a certain extent; 
 those of the second, viz, where there is agreement in a general 
 character, but difference in some respects; as in the allied pro- 
 perties with the common ones just mentioned, which modify the 
 development of bone, brain, muscle, &c.; those of the third, viz. 
 properties that are totally differential, as those which develop the 
 organs of generation and those which supply, on either side, the 
 seeds of hereditary disease. 
 
 16. These properties on both sides are related according to 
 spiritual laws. But, in general agreement with the laws of causa- 
 tion, they may be classed under three heads: 1st, properties of 
 aggregation: these include the perfect resemblances; 2nd, pro- 
 perties of constitution, as where differentials unite and modify 
 each other; and, 3rd, properties differential, holding with regard 
 to the others neither the relation of aggregation nor that of con- 
 stitution, but which preserve singly their own natures. 
 
 17. It has been said that these rudiments of the future ani- 
 mal contain the properties which afterwards produce bone, &c. 
 that is, that these properties are not conferred from without. 
 But a question was started at the same time, viz. whether these 
 are precisely the properties which are to form bone, &c. or 
 whether they are only predisponent, and made perfect by ex- 
 ternal relations* It was also said the former would be presumed 
 upon to a certain extent, and I now repeat more fully the ground 
 of that presumption. The fecundated ovum of an oviparous 
 animal is consigned perhaps to a dunghill or the sand ; it obtains 
 here no accession of properties except heat, and a series of inter- 
 nal changes take place, which terminate in the formation of the 
 textures, &c. of the foetus, which are, in their nature, nearly those 
 of the adult. Now if a property to form muscle, another skin, 
 another bone, another stomach, &c. existed merely in a predisponent 
 state in the fecundated ovum; that is, not the perfect property, a 
 deficient identity, this one cause, viz. heat, could not supply to all 
 the deficient properties those differentials, agreeing in number, 
 which would render each perfect. For this would be to suppose 
 what indeed is possible according to the laws of causation, but of 
 which we have no single instance; it would be to suppose that 
 
81 
 
 caloric is capable of an analysis, by combination with an ovum, 
 into a thousand constituent properties, each of which made its 
 specific constitution. But we cannot indulge this supposition to 
 any extent, because we find that instead of being broken down 
 into all those constituents by which, according to our principle 
 of causation, it would cease to be heat; instead of this, we find 
 that it pervades all parts in its own form, and has no other per- 
 ceptible agency than that of increasing the temperature of the 
 ovum, thus operating by a general relation, and preserving its 
 entire nature, and not by a relation subsisting between its analysed 
 properties and those of the ovum. 
 
 18. But these proofs being, as thus stated, not unexception- 
 able, even with respect to our^laws of causation, it is right before 
 we admit an inference from them to scrutinize the matter a little 
 deeper. It is said in the last paragraph that heat cannot preserve 
 its own identity, and produce a great variety of effects by a true 
 process of causation; that is, by supplying the respective causes 
 which are necessary to different effects. But this observation holds 
 good only of the operation of heat upon substances which preserve 
 their identity, or which maintain the unity of their constitution 
 under its influence ; in such, their nature is still preserved, their 
 temperature only is raised, and is not applicable to compound sub- 
 stances, or those disposed to separate their constituents, among 
 which the ovum may be reckoned as one ; in these latter, heat, with- 
 out ceasing to be recognizable, may have several relations with con- 
 stituents, and produce several effects. Thus, as familiar examples, 
 heat may deliquate wax, which will still remain the same in consti- 
 tution, though rendered fluid by its combination with heat; or it 
 may fuse different metals, or ignite a combustible substance, or 
 deprive a fluid apparently homogeneous of its spirit, or its oil, &c. ; 
 that is, it will afford to each of these substances (which are dissimi- 
 lar) an agent by which they are respectively modified. In fewer 
 words, as long as heat preserves its own nature, the diversity of its 
 effects result, not from the analysis of its own constituents, but 
 from the superaddition of one common property to several proper- 
 ties. The relations of heat are various, but in an homogeneous 
 substance, or on one neither analysed nor divisible, it produces only 
 a single effect, which is to raise its temperature. As the question 
 concerning the ovum is, whether the properties in it, which are 
 subsequently to form the textures, are pre-disponent to, or identical 
 with, those properties which do form the textures, as this is the 
 present question, it appears that the argument cited in the last 
 paragraph is insufficient to decide it, because heat still retaining its 
 own nature, may supply to diversified pre-disponent properties of 
 the ovum that in which they are all deficient, in order to become 
 the identical ones of the textures. 
 
 19> As the question is not determined by these facts, and as 
 its determination appears to be of some importance, it is proper to 
 recollect facts of another kind, which are also related with the 
 
 N 
 
question, in the hope, of reflecting upon it some additional light. 
 The temperature of an egg may be raised in a few minutes to the 
 same degree as that which it attains during any period of incubation ; 
 and yet none of those formations, as bone, muscle, membrane, &c. 
 will take place, which happen eventually. If the properties of the ovum 
 were predisponent, waiting each for a cause which would perfect their 
 identities, it would appear that each being supplied with this cause, 
 should then be in a condition for commencing the operations which 
 terminate in foetal existence; it appears that this should be the case, 
 if the properties did not act because they were deficient identities, 
 that is, deficient in regard to the purpose which they ultimately 
 accomplish; and if heat, which, so far as we know, has no other 
 varieties but those of degree, perfected these identities, then the 
 temperature of incubation once attained, the properties should re- 
 quire nothing further in order to exert themselves to the end of 
 foetal existence. 
 
 20. But this is not the fact, for a continuation of heat is 
 necessary to the end of foetal existence ; from which it appears war- 
 rantable to infer, that heat does not operate on individual properties 
 by supplying a cause, in which they were deficient, in the way of 
 true or individual causation, but by continuing an influence which 
 maintains the series of processes which take place between the 
 .properties which are inherent in the ovum. 
 
 21. Thus then, in consideration of these preceding proofs, it 
 may be presumed as probable that all the properties of the future 
 .animal acg possessed by the ovum; that its changes are those of 
 combinations, among these properties, inherent processes of causa- 
 tion, which we are further to consider. 
 
 22. The maternal ovum by fecundation is advanced into the 
 second stage of pre-disposition* towards foetal life. Its latent pro- 
 perties are increased by the acquisition of the differentials spoken of 
 (at 11, 12, 13, &c.), and its acting properties are also increased by 
 the change of combination which the properties of its organic spirit 
 undergo. 
 
 23. The cause of fecundation makes the latent properties of 
 of the maternal ovum active; it unites its own properties with 
 them, and they proceed in a series of changes according to their 
 spiritual relations. 
 
 24. We can remark nothing further of these spiritual relations 
 than has been already remarked at 15, where they are reduced to 
 common principles of causation, on the truth of which they are 
 rested. But although we do not know all the agencies which are 
 involved in a single spiritual process, yet we are able to infer some 
 changes which display themselves in the visible alliances ; our busi- 
 ness will be to trace these changes, making such inferences. 
 
 $ 25. The escape of the ovum from the ovarium is probably 
 
 This pre-diiposition refers principally to future internal changes by 
 properties possessed. 
 
the effect of its expansion, by which the membrane which confines 
 it is ruptured. An expansion, sub coitu, may happen, from the 
 general determination to the uterine system at this time, and a 
 more particular determination to the ovum itself may be supposed, 
 in agreement with the theory before suggested, viz. that, sub coitu, 
 the semen of the male and the maternal ovum acquire, as points of 
 confluence, properties from every seat in the structure of the 
 parents. It is not supposed that these resembling or radical pro- 
 perties have a material bulk, by the addition of which to the ovum 
 it might be expanded ; it is, in agreement with this theory, con- 
 jectured only, that, as in other instances of spiritual determination, 
 as in cases of sympathetic irritation, &c. an increased determination 
 of fluids succeeds to that of the spiritual properties. But whether 
 the ovum escapes by an expansion which ruptures its capsule, or in 
 any other way, is for the present purpose of very little consequence. 
 Its escape is accomplished by an act, or change, of vital properties, 
 on the part either of the maternal contiguous structure or of the 
 ovum itself; since the same cause, viz. that of fecundation, would, 
 produce no escape of an ovum in the dead subject. 
 
 26. The ovum next passes into the uterus: which we may 
 imagine to result from the exercise of a faculty of contraction 
 possessed by the Fallopian tubes, propelling it to its destination. 
 We have no reason to think that this journey is one which the 
 ovum itself has wit enough to perform, seeing that it was never in- 
 structed of the road, and has not yet acquired its travelling members, 
 whether by wings, legs, fins, on horseback, or in a mail-coach. So 
 much for these matters: it is enough that this act too is one of 
 vitality. It is a function of the uterus to prepare a membrane for 
 the reception of the ovum, which is very civil on the part of the 
 uterus, but is nothing to us at present. It may however be re- 
 marked, that this formation of a membrane is another result of the 
 determination just spoken of, and exemplifies a common ending of 
 determination, in secretion. Our present business is with the growth 
 of the ovum. 
 
 27. The ovum, while it is yet an homogeneous aggregation of 
 animal substance, destitute of any intelligible arrangement, attaches 
 itself to the uterus in such a manner as to obtain blood or some 
 other fluid : and this forms another epoch in the causation which ter- 
 minates in foetal life. 
 
 28. Blood supplied to a dead ovum will not lead to the for- 
 mation of the textures, nor produce any change in it except that 
 perhaps of making it contain a little blood: and yet the organiza- 
 tion of the ovum might be preserved, so far as it is visible (the best 
 analogous example will be found in the crustaceous ova, &c.) It is 
 then, as demonstrated before in another way, the principle of life, or 
 the organic spirit, which leads to those changes, by which the tex- 
 tures, &c. are formed. 
 
 29. Nor are the properties of the spirit gradually conferred 
 upon the ovum by an intercourse of circulation, &c. which obtains 
 
in the uterus (supposing the ovum to be a mere nidus of no specific 
 properties, capable only of inheriting what is imparted to it), for 
 then the placenta would stand a good chance of being the foetus, and 
 a polypus would inevitably put in for the same honour. Besides, the 
 properties of the cause of fecundation are found to be conferred 
 upon the ovum, which are alone sufficient to establish its character 
 as something more than a mere nidus, into which the properties 
 which it afterwards exhibits are gradually transfused; for the inter- 
 course between the ovum and the male has ceased with the act of 
 fecundation. 
 
 30. Having now to speak of the influence which the spirit 
 exerts on the grosser materials of the ovum, in the course of its 
 progress to the next stage of its existence, it is proper that we 
 should examine, in the first place, by what kind of relation spirit is 
 able to produce those effects upon matter which have been all 
 along attributed to it. 
 
 31. The spirit has been said to be identified by its properties, 
 by the causes which make it, and which then extend their opera- 
 tions to things subjected to them, and with which they are allied. 
 We will first connect the question with some general instances of 
 constitution, of which process the one we are considering is, among 
 others, an example. Why does the ink with which I write adhere 
 to the paper, and why would it not adhere to it if the paper were 
 oiled? Why does an acid combine with an alkali and make a 
 neutral salt? Why do vegetables derive nourishment from the 
 earth and not from stones? Why does the needle follow the load- 
 stone, or a man feed upon beef? It must be answered, from the 
 force of causes. All these are effects, to which causes impel; 
 existence, forcing existence. But the name of this process will be 
 inquired for: and surely it will be said the mode of causation is 
 not the same in this confusion of examples. We will return to the 
 examples and ascertain this point. 
 
 32. Why does the ink adhere to the paper, &c.? it will be 
 said, by arj attraction of some sort or other; and when it is oiled 
 why does the ink run off? because there is no attraction, but rather 
 a repulsion; and why does an acid unite with an alkali, &c.? be- 
 cause there is ah attraction among the minute particles, so that they 
 are intermixed, past individual recognition^. And the other instances, 
 the loadstone and the needle, and the man and the beef, &c.? 
 attraction, if will be replied. And what is this attraction? a ten- 
 dency among substances to unite, of which there are various de- 
 grees and modes; but attraction is only one word, and expresses 
 this tendency to unite. 
 
 33. Is this attraction, this tendency of things to contact, mix- 
 ture, union, &c. an identical principle; is it the same in all in- 
 stances? Why, truly, no: things that are joined together agree, 
 however different they might he else, in being joined together; so far 
 the effect is alike. So all things in the world exist; but because they 
 have this quality, or effect, in common, it does not follow that allthc 
 
85 
 
 ce are the same, or that existence in this case, 
 or junction in the other, are precisely the same, or produced by the 
 same causes, in the several examples. 
 
 34. But, so far as the effect is common, the instances, how- 
 ever various their other properties might be, will be found to have 
 some common cause. Thus, a horse exists, and so does a tree; 
 but the causes which make the existence of the horse are not those 
 which make the existence of the tree; they are both examples of 
 existence, and the causes which produce mere existence are the 
 same; that is, they are in both existences. The same may be said 
 of the union of substances: different substances furnish alike in- 
 stances of the union of substances. If it be asked what is there in 
 common in the cause of union? it must be replied, a property in 
 the things united, the force of which is to produce their union. As 
 the effect, viz. an union of substances, is common in all the 
 examples, so also must the cause of the common effect be in all cases 
 identical. In opposition to this view, it may be urged, if the princi- 
 ple of union is identical in all cases, election among substances is 
 precluded, whereas the fact is otherwise; for the substances which 
 do unite are found to entertain, with respect to rach other, a par- 
 ticular and not a common or general relation. From this particu- 
 lar relation may be explained, why a property, to a certain extent 
 identical, in all the instances of union, gives rise to examples of 
 specific election. The property which produces the union of sub- 
 stances is no more elementary than any other agent, or form of 
 existence, but, like every thing else, is constituted ; one reason then 
 why some substances are disposed to unite with others, but not with 
 all, is that the causes of union exist variously in substances, and the 
 principle of union is thus formed only when the agreement of its 
 causes contained in the substances respectively subsists, so as to iden-r 
 tify the property, by supplying its causes in a way conformable with 
 the universal law of causation. Another reason why some substances 
 are disposed to unite with others, and not with all, may be found 
 in the modification to which the causes of union, existing in different 
 substances, are liable in common with all other causes. Hence it 
 appears that the property of union among substances is identical, 
 so far as the effect is common; that the difference of the principle 
 is expressed in the obvious modifications illustrated in the examples; 
 that the specific elections among substances depend first upon the 
 concurrence of the causes contained in the substances to form the 
 common property of union; and, second, upon a similar agreement 
 or concurrence of causes, when these causes are modified by allied 
 agents, resulting from particular and more complex relations. 
 
 35. The varieties or modifications of the principle of union 
 are grossly classed in books under the titles, " gravitation, simple 
 attraction, attraction of cohesion, &c." But the varieties, or modi- 
 fications of identity in the causes of union, which are included in 
 this classification, are perhaps endless. The chymists have indi- 
 cated another class of these uniting agencies, agreeing with another 
 
86 
 
 class of substances which appears to differ from the last, principally 
 in being of a more minute and intimate kind : they denote this class 
 by the term " affinity" 
 
 36. Thus far the words attraction, affinity, &c. are applied 
 only to substances which possess all, or some of the properties by 
 which matter is recognized. But properties, not known as material 
 or falling under the classes of chymistry, are capable of modifying 
 each other (which is the best test of a perfect union among sub- 
 stances); and this is no more than we observe even of chymical sub- 
 stances, for in them properties modify each other, which are neither 
 tangible, visible, &c. nor endowed with any faculty, by which the 
 belief of a material presence is made to arise, as among unions of 
 the gaseous or other peculiar properties, which are superadded to 
 the material substances of chymistry. 
 
 37. But, to avoid a cavil about words, we will not say that 
 these properties mix, unite, or combine; words that may be said to 
 apply only to things that are extended; but we will merely say what 
 we find to be the case, viz. that properties, different forms of 
 existence, may modify each other, and if the terms, " the union of 
 these properties, their combinations, &c." should be hereafter used, 
 it is now defined upon what conditions, and they must be allowed 
 to pass by favour, they being founded upon an analogy which in 
 some respects may be thought not unexceptionable. To return 
 then to our affinities. 
 
 38. Among other relations, properties have one with matter, 
 by which matter tends to an union with properties: and this it may 
 do though already restrained by some power of union, provided the 
 last be the weakest, as we say. This law is illustrated by a thou- 
 sand instances in chymistry ; it is also illustrated by the phenomena 
 of magnetism ; it is also illustrated in animal processes, of which 
 one example will suffice. The living kidney produces urine from 
 the blood, while the dead kidney will not by any force of injection 
 of blood into its vessels, although its texture is preserved, and its 
 chymical constitution is not yet decomposed. In the animal de- 
 partment, I call the properties hinted at, for the sake of distinction, 
 spiritual properties, and their exertion in such instances an act 
 of affinity. 
 
 39. The evidence of the resemblance of such an act of affinity 
 to those displayed in chymistry, is found not only in their apparent 
 analogy (with which alone we ought to be satisfied), but it is also 
 furnished a priori. The act in all instances is determined by 
 latent causes of union or separation, by which the relation is fixed. 
 These causes may differ, and the relation will be modified. Having 
 stated the grounds upon which the term affinity is employed, and 
 whal is meant by it, we are next to trace the processes which are 
 assigned to its agency. 
 
 40. Fecundation, it has been said, disposes the properties of 
 the ovum to be active. These properties have been divided (at 14) 
 into three classes. This clarification was made, as comprehending 
 
87 
 
 the relation between the maternal and the fecundating properties, 
 and as they exist and act so are the textures developed. 
 
 | 41. The identical properties of life afterwards manifested have 
 been shewn to exist in the ovum. As these properties do not sud- 
 denly form the textures they affect, though they should be perfectly 
 supplied with the only sensible material, viz. blood, so must they 
 undergo previous changes among themselves. The relations be- 
 tween these spiritual properties must be complied with in the first 
 pla'ce, their sphere of existence settled, their identities assumed, in 
 agreement with their proper function, which they then begin to exert. 
 
 42. It follows from the last paragraph, that the properties 
 Which are to form the structures have not in the ovum the same 
 individual sdats, or spheres, as those in which they subsequently 
 operate. It follows, that they gradually assume their spheres, iu 
 consequence of catenated processes of causation, which are internal, 
 and commenced by the influence of the cause of fecundation. 
 
 43. Pr6perties having assumed their spheres, their affinity Wffti 
 matter, which has been defined, and proved in many places, and 
 among others at 8, 4, 10, &c. Book 2, Chap, i., begins to be exerted. 
 
 44. The parts of the spirit in their respective spheres, by the 
 affinity mentioned, collect and aggregate materials according to the 
 nature and amount of the properties which compose them; every 
 particle of matter laid down has a property of the spirit whose 
 sphere is in correspondence With its size. 
 
 45. The fonriatton of the textures is not at once a perfect 
 process, which must happen (as the textures are governed by the 
 spirit) from the preparatory changes of the organic life. As these 
 lalter are modified, so the textures will be adopted : thus, the speck 
 in a partially incubated egg cannot at first or for some days be 
 recognized as the heart; even when it has become a punctum 
 saliens, its analogy to the perfect heart does but partially appear: 
 thus, also, the formation of cartilage precedes the formation of 
 bone in tlie same place, &c. 
 
 46. Now if these conversions are said to arise from different 
 functions of the vessels, I would ask the meaning of the expression, 
 I would ask in what a variety of function in any set of Vessels con- 
 sists? or, what is the cause of that variety? Why, truly, it will be 
 found in the principle which animates them, for without this princi- 
 ple they are no agents; they can do nothing; nay, so far from ac- 
 complishing further processes of growth, the stage of organization 
 already attained is dissolved ; the textures, so far from aggregating 
 or producing changes tending to the perfection of the structures, 
 separate in all their parts, and fall into decay. 
 
 47. The properties of the organic spirit determine, by the 
 affinity above-mentioned, what shall be its chymical and material 
 alliances. These properties then inhere and unite with the organic 
 particles, forming in conjunction another identity. 
 
 '48. As the materials admit of being influenced through the 
 medium of the organic spirit, so the spirit itself, as willhereafter 
 
88 
 
 appear, admits of being influenced through the medium of the 
 material alliances. It is difficult to say when the properties of the 
 spirit are changed by this latter mode ; but we may infer that the 
 conjoined result, the identity mentioned in the last paragraph, al- 
 ways suffers from the agency of a cause whose direct relation is 
 with either. This matter will in another place be more fully 
 Stated. 
 
 49. What the precise order of the formation of the parts of the 
 ovum is, cannot be asserted ; but of this we may be assured, that 
 there is always a perfect agreement in the acting properties : for 
 example, a large blood-vessel would not be suddenly formed, filled 
 with blood, set in brisk motion by a vis a tergo, before such a con- 
 tinuity of tube was established, as to provide against its extravasation. 
 50. The gradual formation of the textures corresponds with 
 the gradual development of the acting properties: the organization 
 already constructed concurs with the properties of life, but is not 
 itself productive of an increase of organization. It has been at- 
 tempted by some to explain the organization of a foetus, by sup- 
 posing originally some such simple matter as a tube containing a 
 fluid and situated in a bed of some sort of jelly, or any thing else, 
 without the inheritance of any of those peculiar properties which 
 constitute life. 
 
 51. We will allow the existence of such a tube, we will even 
 suppose it to be organized, no matter how; we will even grant that it 
 contains blood, no matter from whence deriyed ; we will even allow that 
 it has a faculty of pulsation, without being scrupulous about how it 
 came by this faculty of pulsation; we will grant an apparatus of this 
 sort, and then I would ask what is it capable of doing? Why simply 
 this : if the tube is open at both ends, it would, by its faculty of contrao 
 tion, very readily and at once expel the blood it contains, and as no 
 source is imagined by which more blood is poured into it, there is 
 an end of the business; or, if more blood is poured into it, why its 
 faculty of contraction will expel it, and the ends of its operations are to 
 receive, and to expel. But supposing that the tube is closed at one 
 end ? If the faculty of contraction were not strong enough to rupture 
 the tube (by which it would be in the condition just described), why 
 then the resistance would overcome the faculty of contraction, and 
 the advantage of this postulatum would be entirely lost, which 
 would be a great pity, inasmuch as the future feet us would remain 
 a mere tube with some coagulated blood in it ; and, as all such 
 things independent of a vital principle have a great tendency to 
 decomposition, our pulsating tube, blood and all, would stand a 
 very good chance of returning to its elementary dusl, before it 
 would have made any progress in the work of foatalization. And as 
 the argument would not be improved by supposing five hundred 
 such tubes, instead of one, which would be supposing as much as 
 we reasonably can suppose, I say, as the multiplication of tubes 
 does not improve the force of the argument, we ought to trouble 
 ourselves no further about it. 
 
89 
 
 52. But if it should still be required to shew that the growth 
 of the foetus is not a mere development of the same system of 
 organization existing in miniature as that which is afterwards mani- 
 fested, if it should be required to prove this, we shall not be dis- 
 appointed if we rest the proof on the following grounds. The off- 
 spring in every instance of connection between varieties of a species 
 partakes as much of the organization of the male as of the female. 
 How, I would ask, conies this mixture of organization? There is 
 no union of organization between the maternal ovum and the cause 
 of fecundation ; and if there were such an union, the mere textures, 
 independent of a principle of life, on either side, would tend to 
 decomposition. So that it is necessary we should admit the or- 
 ganization, which resembles in the offspring that of the male pro- 
 genitor at least, to be accomplished by the force of properties which 
 are distinct from organization. Further, there is no apparent 
 nucleus of organization in the first stages of the human foetus ; it is 
 a mere cloud : and if there is supposed organization here, it will 
 scarcely be supposed in the male semen ; and if there were organiza- 
 tion in both, it would be altogether inefficient, but for the govern- 
 ment of the properties of life. Enough of this. 
 
 53. The agreement or harmony spoken of (at 49) will be 
 more happy in its success, and less objectionable, by reason that 
 there is nothing in it, no agency supposed, which has not been 
 demonstrated a priori. 
 
 54. Without seeking for additional proofs, we have only to 
 recollect those which have already been adduced in numerous 
 paragraphs; where the total inefficacy of the organic materials, 
 their tendency, &c. independent of the properties of a princi- 
 ple of life, have been stated; and in which also it has been 
 shewn that the sensible materials are laid down by the force of an 
 affinity, which subsists between them and spiritual properties, pre- 
 existent, which have respectively assumed their spheres, and act in 
 them accordingly. From this principle it is to be inferred that the 
 mode of organization is as follows. 
 
 55. A combined organic spirit, subsequently to fecundation, 
 begins then to separate its properties; those whose affinity is to 
 form the heart, are not at once perfect relative identities, but be- 
 come such by many preparatory changes. Changes of the same 
 kind are taking place in the organic spirit destined to form the 
 other parts. Matter is aggregated according to the states of the 
 principle in its different seats, each change bringing the constitu- 
 tion nearer and nearer to the condition of foetal existence. While 
 one set of properties are engaged in the preparatory changes neces- 
 sary to the formation of the heart, others are occupied in the same 
 way with respect to the blood-vessels. Change succeeds to change; 
 all the properties working with each other, and preserving their true 
 relations in every stage ; until, finally, a permanent formation is at- 
 tained, and the foetus, hitherto living like a vegetable, deriving the 
 materials of growth by a root, connected with a source of nutrition, 
 o 
 
90 
 
 is by the force of its causes made independent of its original, and 
 capable of another stage of life. 
 
 56. It will be found that this enumeration of changes agrees 
 with the changes which we observe. None of these textures are 
 at once perfected. As the textures are what the properties of 
 the organic spirit make them, so we infer from these mutations of 
 the materials previous mutations of the living principle, and these 
 are the most satisfactory grounds of the inference. 
 
 57. The harmony of functions too is preserved in the same 
 way in all the stages of existence; it is preserved by internal rela- 
 tions, which only illustrate a principle of causation, stated at 
 38, &c. Chap. iii. Book 1. The relations of the ovum with the 
 mother, during the uterine connections, are next to be considered. 
 
 58. The ovum having passed through the Fallopian tube 
 into the uterus, speedily acquires an attachment to this viscus, 
 by which an intercourse is still maintained between the mother 
 and the offspring. It is not necessary, as has been before shewn, 
 that any properties of the organic spirit should be conferred by 
 the mother on the ovum at this stage. This conclusion is princi- 
 pally deduced from the phenomena of the crustaceous ova, which 
 are developed into the future animal without any vascular inter- 
 course with the mother, or, in some instances, without an inter- 
 course of any other kind, between the periods of their escape 
 from the ovaducts and their final maturation. 
 
 59. But although it is not necessary that the ovum should ac- 
 quire the vital properties in the stage we are considering, yet the 
 connection between the ovum and the mother is such that it cannot, 
 during this period, be dissolved without a cessation of the pheno- 
 mena which characterize the living principle in the ovum. We 
 find, also, that an arrangement, very similar, obtains with respect 
 to the crustaceous ova: thus, if the temperature of an egg is not 
 pretty equally maintained, or if a sufficient degree of heat is 
 withheld during the periods of incubation, the embryo, whatever 
 its present organization might be, dies. The facts, thus indicated, 
 appear to give the sanction of probability to the following infer- 
 ence, which is also supported by other facts to be stated subse- 
 quently, viz. 
 
 60. As soon as the organic spirit of the ovum has ceased to 
 be a constitution of properties at rest; as soon as the ovum has 
 commenced the actions characteristic of life ; that then it is, from 
 the force of its own causes, disposed for death, or a return to its 
 separated constituents. It has been quaintly said that " life is a 
 forced state." I am disposed to say of it, with less quaintness, that 
 it is a constitution disposed to change its form ; that its present form 
 is maintained by certain agents, in the usual way of causation; 
 and that its changes also are accomplished according to the same 
 general law. The organic spirit itself tends to change its form, 
 and the textures follow its fate; such is the force of internal 
 causes: the force of some which are external is to preserve the 
 
91 
 
 condition by which we recognize it as r a living principle.- At this 
 period of foetalization, which might be called the uterine period, 
 it is our present business to say what are the agents which main- 
 tain the living condition, and the enumeration will not be tedious. 
 
 61. It is necessary that the feel us should obtain from the 
 mother a fluid, which is either blood, or else convertible into 
 blood, by the foetal system. The office of this blood is inferred 
 in the case of the foetus in utero, in part, from the known uses of 
 it in the subsequent periods of life; but principally from the 
 consequences, such as the extinction of life, &c. in the foetus, 
 from an obstructed supply. It is hence believed that blood is the 
 external, which at once maintains the living state of the spirit, 
 and furnishes tiie materials of the structures. 
 
 62. The foetus in utero is also necessarily exposed to an ele- 
 vated temperature; whether it is mere heat, imparted from the 
 double source, viz. from the blood, and from the uterine parieties 
 which supports the living principle in its preparatory changes; 
 or whether, in the human ovum, this effect is dependent upon cer- 
 tain congenial and adapted properties of blood; is a question 
 upon which we will not assert peremptorily, at any rate until we 
 have recollected some circumstances of analogy. 
 
 63, The crustaceous ovum contains the substance which 
 supplies the materials of growth; so far it resembles blood in the 
 other case: this substance is not capable of commencing (although 
 it has the properties of blood) the processes of life, which are 
 begun and maintained by heat. 
 
 64. The relations then which we are considering, in respect 
 to the crustaceous ovum, are as follow: 1st, the substance which 
 furnishes the materials of growth can neither begin the actions ncr 
 maintain the properties of life; 2nd, heat is capable of beginning 
 and maintaining these processes; 3rd, if, as is proved by many 
 familiar facts, the material, viz. that which performs the office of 
 blood, were withdrawn, then heat could not maintain the pro- 
 cesses of life; 4th, neither heat nor blood, the vital principle 
 being extinct, are capable of supporting the processes of life, or 
 of renewing them when they have ceased. 
 
 65. It follows, therefore, from the facts in the last paragraph 
 and other preceding ones, 1st, that in the crustaceous ovum a 
 (quiescent (quiescent from the state of combination of its pro- 
 perties) organic spirit must exist in the first place; 2nd, that 
 heat makes its properties active; 3rd, that their actions are after- 
 wards preserved, and continued in a series of changes by the con. 
 joined influence, or energy, or causes, of the organic spirit, of heat, 
 and of the properties allied with the material of growth. 
 
 66. In the uterine ovum of viviparous animals, we have more 
 difficulty in discovering what share heat has in its growth, because 
 there is not, as in the oviparous animals, a state of rest in the 
 constituents of the ovum for any length of time subsequent to 
 fecundation. But we judge, from the iudispensability of heat 
 
92 
 
 (though differently obtained) in the after-periods of life to the 
 continuance of vital processes, and from the extinction of life 
 by a degree of cold which the internal calorific powers are inade- 
 quate to resist, that the influence of heat is truly essential to these 
 processes: and if this is a genuine relation between heat and the 
 agent of life, we appear justified in assigning such relation during 
 all the stages of the uterine ovum. 
 
 67. In addition to what we observe of the actual relation of 
 heat with life in the maturer periods of human existence, we have 
 the evidence of analogy tending to the same point, derived from 
 the crustaceous ova, whose processes of life, as above stated, are 
 found not to commence without the influence of a certain degree 
 of heat; and if this analogy is true, to the extent upon which it 
 might apparently be presumed, the following view, in regard to 
 the human ovum, will appear to receive its sanction. 
 
 68. The fecundated human ovum differs from the crusta- 
 ceous ovum in the identical properties which compose it, and in 
 the following circumstances: 1st, the crustaceous ovum contains 
 its material of growth within itself, while the human ovum is 
 dependent for the same upon a maternal source; 2nd, the crusta- 
 ceous ovum, fecundated and prepared for the changes which pro- 
 duce mature organization, waits for the influence of a cause, 
 giving activity to its properties, which cause is external heat; 
 while the human fecundated ovum does not rest for want of such a 
 cause, but is immediately supplied with it, and its properties are 
 rendered active, and they begin to form the textures. Much 
 more remains to be said, under a distinct title, on the subject of 
 animal heat, and indeed on most of the topics hitherto spoken of; 
 but as much is here said as belongs exclusively to the condition 
 of the ovum. 
 
 70. It was remarked that the fluid which the ovum obtained 
 from the mother, was either blood or convertible into blood by 
 the foetal system. The fostus, as is well known, or we might say 
 the placenta, cannot be injected through the uterine vessels. 
 Now, as the injections employed are as subtile as blood itself, it 
 is hence concluded that there is no communication of vessels 
 between the placenta and the uterus: how then (the question is 
 much hackneyed) does the foetus obtain the materials of growth? 
 
 71. There is no continuity of vessels between the uterus and 
 the maternal portion of the placenta; the foetal portion of which 
 is connected with the uterus only through the medium of the 
 maternal portion. The maternal portion has blood brought into 
 contact with it: from this blood it absorbs some fluid, which 
 passes into the foetal portion of the placenta, and thence to the 
 fcetus. The circulation of the fcetus is from itself to the placenta, 
 and back again to the foetus: these things are well known. This 
 provision prevents the ill consequences of excessive repletion, or 
 accumulation of blood, in the fcetus, which would happen if 
 arterial blood passed freely into it by a direct communication 
 
93 
 
 with the vessels of the mother. It hence appears that the acquisi- 
 tion of fluid from the uterus by the placenta must be exceedingly 
 slow, or it would be disproportionate to the growth of the 
 fffitus. It is probable that the fluid is thus obtained from the 
 uterus by the slow and well-adapted process of absorption, either 
 animal or capillary; the latter may perhaps be preferred, by 
 reason that fluid is absorbed before absorbent vessels are found 
 in the ovum. 
 
 72. That red blood is not absorbed by the maternal portion 
 of the placenta, appears probable from the circumstances, 1st, 
 that injections, which usually pass into all vessels carrying red 
 blood, cannot be made to pass through the maternal portion of the 
 placenta; and, 2nd, that in the crustaceous ovum red blood is 
 formed, as in the chick, unequivocally without any absorption of 
 this fluid from the mother; it is formed from a substance which 
 supplies nourishment to the chick, but which is nothing like red 
 blood. Assuming the probability that blood is formed by the 
 foetal system in the human ovum, and it being acknowledged that 
 such is the fact in the crustaceous ovum, it remains that we in- 
 quire how this conversion is accomplished. 
 
 73. That red blood is formed by the foetus from other fluids, 
 is an assumption which rests partly upon analogy; but if the 
 analogy should not be unexceptionable, the reasonings founded 
 upon it will at least be explanatory of some processes of the 
 crustaceous ova. 
 
 74. If an egg which has lost its vital principle, or which 
 was never endowed with the fecundating principle (in effect the 
 same), be exposed to a proper temperature (i.e. such a one as 
 would lead to the development of the chick, in an egg disposed 
 for the living processes), the egg in this condition will no more 
 form blood than it will form the textures or commence the other 
 functions. As it has been shewn that the latter are attributable 
 to the operation of vital properties, so it must also be inferred, by 
 parity of reasoning, that the conversion of substances which differ 
 materially from blood, into blood, is a result of properties which 
 belong to the organic spirit. 
 
 75. But we have reason to believe that a fluid may contain 
 all the materials of growth, indeed w r e have many direct examples 
 of it, without answering to the description of blood. And it may 
 be supposed that nutrition may be performed by such a fluid, 
 imbibed in the one case through the placenta, and in the other 
 from the albumen of the egg; the constituents of which fluid, as 
 those of other things, are infinite; requiring only the means of 
 analysis, of which we are ignorant, to shew them to be so. Then 
 the question seems to be, not how a fluid containing the elements 
 of the structures comes to be possessed by the embryon, but how 
 this fluid is made red blood? 
 
 76. This has been attributed to the agency of mere atmos- 
 pherical oxygen, but erroneously, as appears from the following 
 
94 
 
 facts: 1st, in the crustaceous egg there is only a very small space, 
 which is said to contain air: it is to be proved that the air thus 
 contained, is sufficient for the oxygenation of so considerable a 
 quantity of blood as is circulated in the maturer embryon. To 
 affirm this postulatum is contrary to analogy (upon which the 
 argument on both sides is founded), for we iind in that stage of 
 Jife in which the necessity of a supply of oxygen is unequivocal 
 that no stationary or fixed quantity is sufficient; it must be per- 
 petually renewed, or its effect ceases. That this is done in the 
 chick, remains to be shewn; and it must first be discovered that 
 the egg possesses a source of air capable of compensating a per- 
 petual exhaustion. 2nd, The same, or a still greater difficulty of 
 the same kind, occurs in the human ovum, where a source of 
 oxygen is not found to have been provided. 3rd (and most con- 
 clusive), Fluids, furnishing all the elements of blood, as those con- 
 tained in the egg, as those supposed to transude through the 
 maternal portion of a placenta, or even as those contained in the 
 lacteals of an adult, may be exposed to oxygen, pure or mixed, 
 to all eternity, and will not become red blood. Oxygen therefore 
 in conjunction with nutritious fluids does not make red blood. 
 
 77. But it is obvious that oxygen is capable of changing the 
 colour of blood; we know that exposure of venous blood to oxy- 
 gen will make it of a bright red colour, and the privation of its 
 vxygen leaves it of a still darker red. From which fact the ab- 
 surdity of imagining oxygen to be the cause of the colour in blood 
 is very manifest. 
 
 78. Neither can we say that iron is the cause of the colorifi- 
 cation of a nutritious fluid, 1st, because there is in the egg no 
 other source of iron than that which is within itself; where, if 
 any, it remains combined with the nutritious fluid, without form- 
 ing blood (as before incubation, &c.); and, 2nd, iron mixed with 
 such nutritious fluid, as chyle, for example, whether sparingly or 
 abundantly, will not make red blood: oxygen also may be added 
 and fifty other fanciful ingredients, but nothing will make the 
 identity of red blood where there is the absence of the efficient 
 properties of the organic spirit, which otherwise, by their relations 
 with the materials, do make red blood. This is too obvious to be 
 further spoken of, though the argument may if required be very 
 much strengthened. 
 
 79. Notwithstanding all that has been just said to detract 
 from the agency of oxygen, which some zealous admirers 
 and bad reasoners have, in a fit of enthusiasm or insanity, cried 
 up as nothing less than omnipotent and universal; notwithstand- 
 ing our restrictions, oxygen is proved, past doubt, to be capable of 
 altering the colour of blood, and of furnishing it with properties 
 which are essential to the maintenance of life. It therefore remains 
 that we should trace more closely its relations with foetal existence. 
 
 80. It is inferred, a priori, that red blood is made by the 
 properties of the organic spirit, iu which chymical agents have no 
 
 
95 
 
 other share than, a mere concurrence which is compelled by the laws 
 of affinity subsisting bet ween those properties and the chymicaland 
 material' constituents. It is inferred, also, that blood being made, 
 oxygen is capable of altering its colour. Dark-coloured blood in 
 the chick is conveyed by the umbilical arteries to the membranes 
 covered by the shell, and it is returned florid blood by the umbili- 
 cal veins; the same thing takes place in the human foetus, with 
 this difference, viz. that the dark-coloured blood is conveyed by 
 tlie umbilical arteries to a thick placentary mass, from whence ft 
 is returned by the veins of a bright vermilion colour, &c. This 
 effect upon the blood, this change, is perpetual. It has been re- 
 marked (at 76), that in the case of the egg there is no source 
 which admits an adequate oxygenation by atmospherical air. To 
 imagine that air passes at all througli the shell is a mere imagina- 
 tion; and to suppose that it passes through the shell so freely as 
 the argument requires that it should, is too absurd to demand a 
 refutation. The want of a source of air in the human placenta 
 has also been remarked in the same place. We find then that 
 oxygen is not only incapable of converting nutritious fluids into 
 red blood, but even that the colour characteristic of venous blood 
 may be changed to that characteristic of arterial blood, without 
 any thing like an atmospherical oxygtnation. 
 
 81. If the blood of the foetus does not undergo this change, 
 which has been attributed to oxygen, the foetus dies. But there 
 is no atmospherical oxygen, or only an inadequate quantity, at the 
 place where this change is accomplished: by what then is this 
 change, viz. the conversion of venous into arterial blood, ac- 
 complished? 
 
 82. The placenta is a production of the ovum, it is governed 
 by its life, are all other growths and structures; its life extinct, 
 its fabric falls to decay; its chymical properties, also, are depen- 
 dent upon its organic spirit. It has properties of life, but no 
 others for which it is not indebted to life. Its properties of life 
 are related with those of the embryon, its function is connected 
 with all the parts of the organic spirit of the foetus; but its rela- 
 tion is not direct but mediate, and not through the medium of the 
 textures, but through that of the blood. 
 
 83. The relations of properties of the spirits in different seats, 
 the effects, &c. of their reciprocal agency, how complicated the 
 concurrence is, &c. have been sufficiently spoken of. This is an 
 instance of that concurrence. The vital properties of the em- 
 bryon are not capable of themselves of maintaining life, or of 
 developing the structures; they want the influence of allied pro- 
 perties: these properties are in the placenta, which are not the 
 identical properties of life, but are made such by their relation 
 with thcs ' of the erabryon. 
 
 84. These properties of the placenta influence those of the 
 embryon by the change they produce in the blood : this change is 
 indicated by an alteration in its colour. The influence which the 
 
96 
 
 blood thus receives perfects the organic spirit, or an essential 
 part of it, residing in some organ of the foetus, further related 
 with its diffused spirit. As oxygen, as is proved, is capable of 
 producing a similar change in the blood, it is to be considered 
 whether these properties, originally conferred in the same manner 
 as the other properties of the ovum, are identical with oxygen. 
 
 85. Oxygen, unassisted by any vital properties resident in 
 the textures, is capable of producing the change of colour men- 
 tioned, but whether it furnishes by itself the properties essential 
 to life, or whether the blood is fitted for this purpose by proper- 
 ties of oxygen, conjoined with those resident in the textures, is a 
 point upon which we have no direct testimony; because, when 
 life is extinct in the lungs it is extinct elsewhere, and therefore 
 its relation with mere oxygen cannot be ascertained. 
 
 86. But that oxygen is the identical influence which is con- 
 ferred on the blood in the placenta appears probable. The evi- 
 dence in its favour is that atmospherical oxygen will produce that 
 change in blood which fits it for the purpose of remote vitality. 
 The truth of this conclusion is to be known only by ascertaining 
 whether the properties productive of change of colour in the 
 blood, and those endowing it with a cause of vitality, belong 
 wholly to oxygen. The affirmative is indicated, and only indi- 
 cated, by the known importance of oxygen in respiration: and as 
 there is not even an indication to the contrary, we may presume 
 that the portion of the ovum which forms the placenta contains 
 oxygen in alliance with other properties of life. 
 
 87. This view of the matter being thus far granted, another, 
 before exhibited, will with propriety be opposed to it. Supposing 
 oxygen to have been originally in alliance with that part or 
 sphere of the organic spirit destined to form the placenta, the 
 quantity of this oxygen must be exceedingly small, not sufficient 
 for one round of circulation, in the latter stages of foetal existence; 
 and as it is confessed that there is no source of oxygen by atmos- 
 pherical communication, in what manner is the oxygen obtained 
 which is said to be possessed by the placenta, or how is this small 
 quantity of oxygen (supposing such original quantity to exist) so 
 greatly increased? This objection is well urged, and the explanation 
 will extend a little our inquiries into these mysterious processes. 
 
 88. It is obviously necessary that t'he increase of oxygen 
 should be in a ratio to the increase of blood. As the source of 
 this oxygen is not from without, it must be internal. The only 
 internal source of oxygen is that which is also the only source of 
 the organic materials, the fluids obtained from the matter. 
 
 89. To imagine that venous foetal blood in the placenta be- 
 comes oxygenated by mixture of fluids derived from the mother 
 would be to suppose, 1st, a readier communication between the 
 foetus and the uterus than we have reason to believe ; and, 2nd, a 
 rapidity of nutrition (or repletion) would thus be occasioned which 
 does not correspond with the ratio of visible growth. 
 
97 
 
 90. It appears then that there must reside a property in the 
 placenta capable of forming oxygen, by an affinity before-mentioned ; 
 a property whose relation with venous blood is to produce an union 
 of its carbon with some oilier constituents of blood, thus yielding 
 eliminated oxygen to the blood, and accomplishing an end which is 
 otherwise brought about by atmospherical communication. This 
 view supposes an antagonist relation between oxygen (derived from, 
 and in proportion to, the maternal nutrient fluid) with the vital pro- 
 perties of the foetal system, and oxygen with the vital properties of 
 the placenta. 
 
 91. In order to satisfy ourselves of the agreement of this 
 solution with the few facts of which we are instructed upon this 
 subject, it is necessary that we should take a view of these facts, so 
 far as they are connected with the question. The fluid imbibed 
 from the mother contains an immense number of constituents which 
 are capable of appearing and acting distinctly, and of being arranged, 
 and of co-existing when subjected to the influence of a mtiteria 
 vitce, or, as we say, an organic spirit resident in the foetus. Before 
 this fluid is subjected to such an influence it appears homogeneous, 
 or at least separable by art into very few constituents (the albumen 
 of an egg, for instance, which in the chick furnishes bones, muscles, 
 arteries, cartilages, nerves, brain, feathers, &c.). This fluid left to 
 itself speedily shews its own tendencies, which may perhaps be 
 called chymical: it soon evaporates or putrifies, and disappears. If 
 the changes which take place in it, in order to accomplish the effects 
 just enumerated, may be called chymical changes (which will here- 
 after be considered), then it is the influence of the principle of life 
 which determines these changes or functions to take place. It is 
 this which changes the relations between the parts of the fluid; it 
 is this, as before explained, possessing different properties in various 
 parts, which acts variously upon the fluid, decomposing and uniting 
 the secret causes of our apparently homogeneous fluid, and alterna- 
 ting these operations, in infinitum. The properties of life are thus 
 related with the parts of the fluid, and these effects are accomplished 
 conformably with the relations in the way of causation before de- 
 scribed. The placenta, it appears, must be a source of oxygen ; it 
 can be a source in no other way than that mentioned at 90. 
 
 92. It will next be inquired how the properties thus related 
 with the venous blood in the placenta come to have so extensive an 
 agency as that which they exert in the maturer periods of foetal 
 existence, when they prepare oxygen for so large a quantity of 
 blood, seeing too how small a sphere they occupied in the original 
 ovum? In answer to this question, it must be seen what is said 
 hereafter under the title of continuance of life, &c. which also exhi- 
 bits processes of growth. 
 
 93. The concurrence necessary to the formation of the tex- 
 tures is, 1st, spiritual properties of the maternal ovum; 2nd, pro- 
 perties of the fecundating principle (these two obey the relations 
 expressed at 16); 3rd, heat; 4th, a nutritious fluid, 
 p 
 
98 
 
 94. The processes of life having been commenced by fecunda- 
 tion, this entire concurrence is necessary to their support. 
 
 95. The fecundated ovum, without heat, remains inactive, a 
 mere pre-disposition to embryonic existence ; its combined spirit is 
 not developed, and its properties do not assume their spheres, but 
 by the aid of progressive nutrition. 
 
 96. The spirit, as is proved by the subsequent organization, 
 the general resemblance to its originals, is perfect in its possession 
 of constituents in its first condition. It depends for the maintain- 
 ance of its identities &c. upon heat, and the material of growth, 
 
 97. The tendency of the spirit, when its properties have 
 begun to be active, is again to return to its state of rest; its activity 
 is maintained by the perpetual supply of its properties, which 
 expire, or change their form if deprived of the source of assimilation. 
 
 98. The changes of the combinations of the properties of the 
 spirit are numerous: they are strikingly preparatory up to the 
 period of foetal maturation, and less conspicuously so throughout 
 the stages of after-life. 
 
 99. As the combinations are changed, or as the properties of 
 the spirit are altered in their respective spheies, so the effects im- 
 putable to them are modified. The peculiarities of combination 
 give rise to the distinction of active and latent properties. 
 
 100. The materials of nutrition furnish common constituents : 
 the properties of the spirit render them peculiar; by them they are 
 appropriated, and made conformable with final purposes. 
 
 101. The material of nutrition possesses all the properties of 
 every kind, and of every stage, of organic spirits. The spirit of 
 the fecundated ovuin assimilates from this material, and the visible 
 constituents with which it is allied are separated from an apparently 
 homogeneous fluid, and are aggregated in the several seats. 
 
 102. The textures are according to the spiritual properties of the 
 fecundated ovum, with the aid of the concurrence before-mentioned, 
 which latter is according to the spiritual properties first conferred 
 on the radicles, viz. on the maternal ovum and the seminal fluid. 
 It is by this law that the resemblance of every kind is perpetuated in 
 the succession. Thus all the varieties of oviparous animals are 
 preserved by their eggs, though the vital processes are maintained 
 in them by a common cause, viz. heat; thus, also, all the species of 
 viviparous animals are perpetuated with a minute resemblance to 
 their originals, though they should all feed on roots or flesh, or both. 
 
 103. According to the changes of the active properties of the 
 spirit, the visible materials of the embryon are laid down: this is 
 done by a natural and common affinity, without any sort of mystery 
 in the business. The textures are conformable with the spiritual 
 properties ; the former exist where the latter are, the former are 
 changed as the latter are modified. 
 
 104. From the views which have hitherto been exhibited, it 
 appears that the government of all the embryonic processes is 
 assignable to the spiritual properties of the ovum; that these pro- 
 
99 
 
 perties are those which are conferred by a function of the generative 
 organs in the two sexes; that in the fecundated ovum the proper- 
 ties of the two sexes, which have a general resemblance to their 
 originals, are mixed. The question then arises, by what mode of 
 causation do parts and properties perfectly resemble those either of 
 the father or of the mother, exclusively; when parts and pro- 
 pensities, the first subservient to a similar function, and the second 
 operating with an opposite tendency, are proper to both? Thus, if 
 the maternal ovum is a resemblance in pre-disposition to the mother, 
 it must have, according to our notions, similar sexual organs. The 
 same is to be said of the cause of fecundation. Thus, also, the 
 father's hair may be black and the mother's white ; and the offspring, 
 though possessing the radicles of both these peculiarites, shall per- 
 haps manifest only one of them, and that unmodified; shall be 
 either perfect male or perfect female; or shall have hair either 
 black or white, and not of a mixed colour. 
 
 105. This apparent difficulty is to be solved only by the rela- 
 tions of properties expressed at 15; a complicated process of 
 causation takes place between the spirit of the maternal ovum and 
 that of the cause of fecundation; some properties unite and modify 
 each other, and their modification is subsequently denoted by a cor- 
 responding state of the textures; others (the third class at 15) 
 preserve unchanged their own natures. If we ask how these things 
 are settled ? it must be replied, we only define a relation subsisting 
 between existences, and we may reduce this example to the level of 
 common examples, and say that the relation here is determined in 
 the same way as that by which an acid and an alkali will unite and 
 form a neutral salt, or as oil and water will not unite; existence 
 forcing existence, c. But to consider more particularly our 
 present example. 
 
 106. It is first to be shewn that the principle, viz. the posses- 
 sion by the seminal radicles (c&teris paribus) of all the properties 
 of the originals is not invalidated by the facts, which is indicated 
 with some force by the following circumstances: 1st, A woman, the 
 offspring of one of an hemorrhagic idiosyncracy, shall attain old age 
 without the slightest apparent tendency to hemorrhage, while in her 
 children, or in some of them, and not in others, the hemorrhagic 
 idiosyncracy shall be so prevailing that profuse bleedings will occur 
 on the slightest occasions, and sometimes without any assignable 
 cause. The next generation of those who bleed shall manifest no 
 such disposition, while the children of those who did not bleed 
 shall preserve the strength of the tendency in the originals, and even 
 transmit it with many irregularities to posterity. 2nd, The same is 
 to be said of scrophula, of consumption, and of most or all here- 
 ditary diseases. 3rd, The same is to be said of the colour of the 
 hair, the development of the textures, the formation or absence of 
 fat, the peculiarities of features, of the peculiarities of the moral 
 character, of the peculiar strength of certain persons, of insanity, 
 &c. In all instances spiritual properties are conferred on the 
 
100 
 
 offspring by progenitors, which properties are variously active or 
 latent according to relations which are so far beyond the scope of 
 our experience, that it looks almost like temerity to hazard another 
 conjecture on the subject. We will not however absolutely leave 
 off here : conjecture is a sort of pioneer, whose business it is to force 
 a road of some kind: if the track can afterwards be followed with 
 advantage, so much the better; and if it cannot, why even then 
 conjecture, the pioneer, only takes a pleasant walk by himself in a 
 shady avenue of his own making. 
 
 107. It is to be inquired, what is the causation in this particu- 
 lar instance? It is to be asked, 1st, why hermaphrodites are not 
 produced by generative processes? 2nd, what becomes of the super- 
 fluous sexual pre-disposition in the offspring? 3rd, what are the 
 causes prevailing sub coitu, if any? We will repeat these questions 
 iii their order, and answer them so far as our evidences will permit. 
 1st. Hermaphrodites are not produced by generative processes, 
 because the relation of the sexual pre-dispositions is not to unite and 
 modify each other, but to preserve their own identities. 2nd, What 
 becomes of the superfluous sexual pre-disposition we cannot say, 
 but the alternatives are, that it is in alliance with the active sexual 
 pre-disposition, or with the organic spirit in some other sphere; the 
 former appears not improbable, and is consistent with a similar 
 predicament of two causes, capable of exerting themselves in the 
 whole system, and producing each its peculiar effects. Thus a child 
 may one day be exposed to the contagion of measles, two days 
 afterwards to that of small pox; the causes of those two diseases 
 will exist in the body at the same time, and it is most probable that 
 they hold the same seats, yet the child may first have the small pox, 
 and, though not subsequently exposed to the contagion of measles, 
 may afterwards have this latter disease when the former have run 
 its course: this I have witnessed, and there are a hundred similar 
 facts. Now, in explanation of this circumstance, it will be said the 
 poisons were inconsistent with each other, and therefore could not 
 run their course together. This however is only another mode of 
 stating the fact, it is no explanation; to discover the explanation, 
 we must ascertain the relation of the other properties of the organic 
 spirit with these causes respectively. However, such as the ex- 
 planation is, transfer it to the sexual organs, and it will appear in 
 this form: the sexual radicles in the uterine foetus are inconsistent, 
 and cannot both have sway together; neither can one modify the 
 other; what happens then? Why, either sexual pre-disposition is 
 not like the contagion of fever, it is not evanescent, nor does it ter- 
 minate in mere actions; its tendency is to live permanently, by 
 assimilation, and the force of its influence is to govern the textures 
 which are conformable with its prevalence, In this way the 
 maternal ovum may furnish the male organs; in what riay? it will 
 be asked, Thus: the female possesses the inactive sexual pre-dis- 
 disposition of the male; and this, in her a latent cause, might beau 
 active oue in the ovum, which is formed by derivations from her 
 
101 
 
 organic properties, and vice versa. We have experience of this 
 relation; we know that these sexual differences are bo h possessed 
 where one only acts. Now the next question is, what determines 
 one to act or to be latent, in preference to the other? 3rd. This 
 is a point which others have in effect conjectured upon ; it has been 
 attributed to imagination, operating sub coitu, as whether the idea 
 of man or woman was most prevalent, in a kind of contest which 
 took place between them. It has also been said that there are pre- 
 formed male and female ova, and the development of either deter- 
 mined the sex; and there are the conjectures of some microscopic 
 observers, which are reducible to the latter class. 
 
 The former of these conjectures, viz. the prevalence of an in- 
 tellectual imago, or any other cause prevailing, strictly nub coitu, 
 is superfluous and inconsistent with analogy, for the sexual diffe- 
 rences take place in offsprings produced without coitus, by mere 
 impregnation of female ova, deposited in sand, or in the beds of 
 waters, as among fishes; besides which, the sexual differences are 
 preserved in animals which have no imaginations (at least we rind 
 no parts among them). The first fact, while it sufficiently refutes 
 the first conjecture, appears to indicate the truth of the second, viz. 
 that maternal ova are of two kinds, male and female; that which- 
 ever of these are impregnated, such is the sex. 
 
 But this conjecture involves the suppositions, 1st, that the whole 
 business of determining the sex rests with the female; and, 2nd, 
 that the original can confer that of which itself has no prototype or 
 resemblance. Without stating the objections to these suppositions, 
 and without shewing how irreconcilable the first is with a whole 
 class of facts, and among others with those expressed at 104; we 
 will make shorter work of it by refuting at once the conjecture 
 itself, which is this, that the organic spirit of the organs of genera- 
 tion is furnished by the female universally, and that the male fur- 
 nishes no spiritual properties of this kind. Now the refutation of 
 this conjecture, and the establishment of its converse, which has 
 been all along supposed, also upon different grounds, are found in 
 this fact, that the generative organs, like all other parts, are modi- 
 fied by differences existing in both parents: thus the generative 
 organs of the products of a variety of the species are modified in 
 their development, as in the mule, &c. and do not resemble those 
 where the species is unmixed, as in the horse or the ass. And the 
 colour of the skin too is found to participate here in the general 
 deviation from that of either parent, as in the mulatto, with many 
 other facts of the same kind. 
 
 Thus we see that notwithstanding the inconsistency of the sway 
 of both the sexual pre-dispositious, there are yet, even here, some 
 properties which do unite and modify each other, while others act 
 with an unchanged identity, and others remain latent, preserving 
 also, in a state of rest, their own nature. 
 
 To return to the question, if we would know by what laws this 
 relation is governed, or what the variety of cause is which deter- 
 
102 
 
 mines these different effects, we must first obtain some additional 
 inlets of experience, by which we may get acquainted with the pro- 
 perties in question, and by which we may be enabled to distinguish 
 their modifications from their regularities; we must even go further 
 or we shall yet be but imperfectly taught, we must have a perception 
 of the tendencies, or a familiarity in the history of the causation of 
 the regular and the occasional. And until we have obtained these 
 additional inlets of experience we must be contended to define rela- 
 tions in a more limited way, in conformity, as has been done in the 
 present case, with the largest class of facts and the most general 
 indications. 
 
 I conclude this chapter on the fecundated ovum with observing 
 that many of the processes which are discussed in it belong also to 
 the subsequent conditions of life, and that therefore the more ample 
 consideration of some points already touched upon will be reserved 
 to a future part of the subject, when the illustration will be less 
 abstruse, because the facts are more familiar. 
 
103 
 
 CHAP. III. The Origin of Man by Constitution. 
 
 1. WE have seen that the existence of man is perpetu- 
 ated by derivation. This appears too to be the general mode in 
 which the whole animal creation is perpetuated. We cannot how- 
 ever affirm that this origin, by derivation, is universal. The pre- 
 vailing form, the general rudiment of future being, appears to be 
 furnished by ova, evolved from the females of the respective species; 
 but that this form of origin is not universal, appears from the 
 examples of constitutions, which are admitted to belong to the 
 animal creation, among which, our experience does not inform us of 
 the existence of ova. 
 
 2. The microscopic observers have detected animals of this 
 kind in vinegar and other fluids, in a mixture of flour and water, 
 &c. In these instances it is by no means ascertained that animal 
 existence is produced from a parental rudiment; on the contrary, it 
 appears to be produced by a change, the obvious part of which is 
 of a chymical kind, as one of fermentation. Myriads of animals 
 appear to start into being in the short space of a few hours, without 
 being preceded by those formal processes which constitute the 
 terms of the existence of man, and of the general tribes of animals. 
 It has been suggested that the fluids in these cases may obtain the 
 ova of the animals they contain from the atmosphere. Such a sup- 
 position is contrary to analogy, for the known ova of animals are 
 specifically heavier than atmospherical air; and if they should, in 
 compliance with an unsupported supposition, be allowed in these 
 instances to be lighter than air, very little is gained by the postula- 
 tum; for if they are so much lighter as to rise out of the element in 
 which their progenitors must have deposited them, the same cause 
 should certainly secure them against the possibility of gravitating 
 into the same situation again. 
 
 3. These examples of apparently spontaneous life, as well as 
 some principles before sketched, suggest to us a consideration of the 
 origin of man which is more remote than that by derivation, which 
 is, unfortunately, prior to any possible records of experience, and on 
 which we are therefore but indifferently prepared to inquire with 
 success. However, we will hazard a few thoughts even on this 
 doubtful topic, which, it must be premised, makes no part, or but 
 an unimportant one, of the general design of this work. 
 
104 
 
 4. All mankind, it is said, have had one common origin in first 
 parents: by which is meant that from two individuals existing as the 
 only examples of the species, ova were furnished by derivation, 
 which produced others of the same kind; to these last succeeded 
 another generation, to this another, proceeding on to such a multi- 
 plication of individuals as maybe said now to constitute the whole 
 of the human race; and the' same is said of other animals. Mere 
 unassisted reason, working with the materials which are supplied by 
 observation of the order of nature, her capacities, &c. if compelled 
 to say something upon the subject, would propose two modes of 
 the multiplication of the species, viz. either by an origin in two com- 
 mon parents, or by a derivation from numerous parental stocks : 
 the latter mode pre-supposing that the causes which formed man 
 and woman in one place might have formed them in many others, 
 perhaps about the same time. As we profess here to pay some re- 
 spect to this same unaided reason, however little it might be en- 
 titled to it, it is necessary that we should take these alternatives 
 into consideration. 
 
 5. We perceive, upon the first view, that a peremptory de- 
 cision is in this case quite impossible, and that to conjecture with 
 any sort of probability is, to say the least of it, very difficult. It is 
 proper to inquire, in the first place, how far history can assist us in 
 the determination? 
 
 6. It appears that history has but a very weak voice, when the 
 business to be spoken of is one so remote as that we are considering; 
 because, at the first periods of human testimony, written or traditional, 
 the earth was found to be already peopled in many places, and 
 though one tribe might so far simplify its ancestry as to reduce it to 
 an origin in one father and one mother, yet it could not be ascer- 
 tained that people existing elsewhere owed their birth to the same 
 originals; there may be even no testimony that these first parents 
 were at all related with a neighbouring tribe, much less with the 
 inhabitants of distant nations. 
 
 7. But the proof of the origin of the human species in two first 
 parents has never been rested upon human record, because it is 
 obvious that none of such antiquity can exist; and even if it did 
 exist, the question would occur whether such record did not apply 
 to one tribe or to one nation, rather than to those others which are 
 scattered over the earth. But such a proof has been grounded upon 
 a revealed account, which assigns one origin of mankind, &c. in first 
 parents, viz. in Adam and Eve, who were created (furnishing an 
 illustration of the origin by constitution) and another origin (by 
 derivation) in the family of Noah. The descendants of the first 
 were destroyed by a deluge, those of the second exist now, and have 
 been multiplying ever siuce the subsidence of the waters. 
 
 8. This account is not traditional, or preserved in manuscript, 
 but rests upon the credit of an inspired writer. This authority will 
 be respected on the one hand by those who acquiesce in the full 
 scope of inspiration, as it is represented to us ; or, on the other, it 
 
105 
 
 will be rejected by those who are not disposed to yield to the doc- 
 trines of inspiration an assent equally implicit, or who may per- 
 haps regard inspiration as the assertion of probable conjectures. 
 
 9. But as this doctrine of inspiration stands, as it were, 
 contra-distinguished to mere rational deduction ; as it is adopted 
 upon faith principally, though perhaps supported in some measure 
 by collateral testimonies of another kind ; it is obvious that our 
 inquiry, which professes to be an examination of the results of 
 unaided reason, must proceed upon other grounds: we therefore 
 take leave of the authority of inspiration here, leaving it to be 
 received upon the terms on which it is proposed, viz. upon faith. 
 
 10. That the whole of the existing human race had their 
 origin in two first parents, cannot become a matter of inference, 
 from any ancient testimonies or recorded facts; because such re- 
 ports must necessarily be partial: they may relate to one or two 
 nations, but not to all the places upon the globe. 
 
 11. Neither can the universality of a deluge be proved by 
 such ancient testimonies, for precisely the same reason, viz. that 
 if only one family should survive a great inundation, this family 
 can afterwards testify no more than that it alone, of all the people 
 of a district or a country, escaped such an inundation; and that 
 this family began anew to people the land upon which it was left 
 by the retiring of the waters. This family, without the aid of 
 inspiration, being necessarily precluded a knowledge of the inhabi- 
 tants or occurrences, belonging to a distant soil, is, from this limited 
 information, qualified to speak only of its own. Thus, if our own 
 island should by a sudden subsidence become covered by the sea, 
 to the destruction of all its inhabitants, save one; that one, if he 
 transmitted the account to posterity, would affirm that the deluge 
 was universal, provided he was unacquainted with any country 
 beyond his own ; and if he should have been acquainted with some 
 neighbouring countries, as Scotland, Ireland, France, Holland, &c. 
 and if these should have participated in the general wreck, he 
 would still be unqualified to give an universal record, since the 
 inhabitants of America, and of the East-Indies, during this great 
 European inundation, might be quietly cultivating the soil, or fol- 
 lowing their habitual pursuits, without the slightest knowledge of 
 this formidable catastrophe. In fewer words, no man can attest 
 the fate of a country which he does not know to exist; acd the 
 earliest inhabitants of the globe are not likely to be acquainted 
 with any other country than their own, because a facility of inter- 
 course, or even a possible intercourse, between distant countries 
 is a result of the arts, and belongs to a later period of civilization. 
 We are therefore to seek for other proofs (of the natural kind) of 
 an origin of the human race in two first parents. 
 
 12. It will be said, by way of furnishing these proofs, that 
 
 every part of the earth, so far as it is known, bears traces of H 
 
 deluge, in the formation of rocks, in the stratafication of materials, 
 
 in alluvial soils, &c. Now if it be granted that the things just 
 
 9 
 
106 
 
 quoted are proofs indubitable of the operation of waters, who shall 
 say whether these several effects, which we allow to exist every 
 where, occurred every where at the same time, or by partial and 
 successive acts, or changes, which have been wrought in an 
 infinity of ages? It is obvious that, up to this point, proofs are 
 entirely wanting ; and though I am aware that a great deal has 
 been said with something like a design of fixing the antiquity of 
 the earth, and that a great deal more might, in the way of dis- 
 cussion, be said on both sides upon the same subject; yet all that 
 has been said, or may be said, is so entirely conjectural and con- 
 tradictory, that I chuse to say nothing more about it. Let us en- 
 deavour to find some better security for our proceedings; a 
 sanction which shall be founded on some part of our own experience. 
 
 13. As, by the order of procreation, the species is multi- 
 plied, so by inverting this order it is diminished ; arid by continu- 
 ing to trace succession from children to parents, it appears that 
 we should at last arrive at such a simplification as that which is 
 denominated one common origin in first parents. Thus much. we 
 may affirm, so far as respects our general experience in population; 
 but we are not to concede the universality of such a result with- 
 out a little further examination. 
 
 14. The animal creation exist on so large a scale, that it is 
 difficult to illustrate the question clearly, by a reference to the 
 aggregate of species. We will then make an imaginary reduction 
 of their numbers, and suppose the condition of mankind, for 
 example, to be this, viz. there are one hundred inhabitants in each 
 of the quarters of the earth. We will suppose these, as we may, 
 without affecting the argument, to be divided into families consist- 
 ing often in each, viz. two parents and eight children; it is then 
 obvious that eighty drew their origin from twenty. If we inquire 
 the origin of these twenty? the answer will involve alternatives 
 which we should not at first sight suspect. 1st, These twenty 
 might have derived their existence from forty parents, viz. a father 
 and mother to each one, and these forty from eighty; or, 2nd, 
 they might have originated from four parents, and these four from 
 two, &c. So that we cannot, by the inverse succession of the 
 general tendency of procreation, arrive necessarily at that simpli- 
 fication which it appears at first sight to promise, for the rate of 
 population is liable to fluctuate from many causes. To state this 
 matter more plainly : 
 
 15. It is possible, from a gradual decline of population, that 
 a thousand inhabitants of any part of the earth may, by many 
 fluctuations, be reduced to a hundred; that this number might be 
 doubled, and then reduced to fifty, to four; or the race might 
 become extinct. Hence, if any people should have preserved a 
 record of two or four or twenty ancestors furnishing the originals 
 often tribes, it does not absolutely follow that these first were in- 
 stances of the origin by formation or constitution, or but that many 
 generations might have preceded those who are regarded as originals. 
 
107 
 
 16. Now that such a reduction of the numbers of a people 
 as from a thousand to a hundred, or even to the extinction of the 
 race, should happen, does not seem in any degree probable, ac- 
 cording to our own experience of the tendency of population, 
 which, without specifying proportions which cannot be ascertained, 
 we know to be generally towards a rapid increase. But the state 
 of things, the causes which prevail in our days, may not have pre- 
 vailed in ages past. This, it will be said, is urging a mere possi- 
 bility without data ; but the supposition is not so absurd as to 
 some it might appear. 
 
 1st, We know that the business of population requires the 
 possession of certain faculties allied with the procreative organs. 
 
 2nd, These organs, like all others, are liable to spontaneous 
 disease, by which a function might be impaired, while even the 
 structure is preserved. 
 
 3rd, We know that many (perhaps we may affirm of the pre- 
 disposition, the great bulk) of the diseases to which our organs 
 are liable, are hereditary. In this way, or from these causes, the 
 tendency of population would be to the extinction of the race. 
 
 4th, Independently of spontaneous disease or disorder, to which 
 the organs in question, in common with the rest, are liable, they 
 are exposed to the influence of moral habits, which may be of 
 such a nature and so prevalent at particular periods of the world, 
 as to frustrate that design which nature never appears to have lost 
 sight of, viz. the perpetuation of the species.* It is unnecessary 
 to cite examples here; we may advert, as to a class, to the in- 
 effectual commerce between the dissolute of either sex. A period 
 of the world, the moral condition of which would render prevalent 
 the relations just cited, would tend to a reduction of its inhabi- 
 tants; and a period of the world in which such a relation was 
 universal, would lead to their entire extinction. 
 
 5th, And that the conjecture of these possibilities is not with- 
 out the support of actual experience, appears to be indicated by 
 the facts that there have been found the remains of men, of a size 
 which has given rise to the inference that the existing inhabitants 
 of the earth are no descendants of their's, but belong to another 
 ancestry, and that their race, there being no living remains of it, 
 has become extinct. The same has been observed of other ani- 
 mals, as of the Mamoth, and many strange things exhibited in 
 museums, bearing the traces of animal remains, but of which we 
 have no known examples in the living state. But all the causes 
 above-mentioned cannot well apply to these latter instances; that 
 is, they must be exempt from the influence of moral depravity, but 
 they are not exempt from the influence of physical change. 
 
 17. We find in some districts a peculiar conformation of the 
 thyroid gland, associated with the other phenomena of cretinism. 
 
 * It is said that population in New South-Wales is now (1816) on the 
 decline, owing to the abuse of European habits. 
 
108 
 
 We find in others a prevailing tendency to calculous disorders : 
 now the same mode of causation as may render prevalent a de- 
 pravity of function or conformation in one structure, may produce 
 a similar change in another. We have even the record of a negro 
 whose skin has spontaneously become white. Here the de- 
 scendants of such a one would most probably be modified in a 
 particular which has been a characteristic of their progenitors. The 
 histories of epidemics both in men and brutes tend to the same 
 evidence. In a race which is not numerous, whether of men or 
 animals, we are supported by our present experience in the sup- 
 position that a prevalent depravity of function in the generative 
 organs might arise, and that, being continued, under many of the 
 modifications which would result from sexual intercourse, it might 
 by many approximations eventually lead to the extinction of the 
 race. But this mode of explaining a circumstance, which has 
 excited little more than the curiosity and astonishment of natu- 
 ralists, is rather foreign to my present purpose; it is sufficient for 
 this to shew, as has been done, that the rate and order of popula- 
 tion among the human species is liable to be retrograde or pro- 
 gressive, according to the operation or absence of the causes 
 enumerated; and that therefore, and for the reasons which precede 
 this enumeration, and for many other reasons, if they are required, 
 an origin of man by constitution can never be authenticated by any 
 records which a people might have preserved of the first founders of 
 their race; and it seems the less worth while to bestow more words, 
 upon this point, as no such records are even said to exist, which 
 affirm an absolute beginning in two first parents. 
 
 18. If then neither record nor tradition can furnish us with 
 examples of the origin of man by constitution, it remains to inquire 
 whether by the laws of constitution itself we are led to such an 
 Inference? Viewed upon this ground, the question resolves itself 
 into the two following alternatives: 1st, has man existed for ever 
 or from eternity? or, 2nd, has there been a period when he began 
 to exist? 
 
 1. It has been before said that nothing can exist without a 
 cause : how far this principle is to be admitted may be seen at 8, 
 9, 10, &c. Book I. Chap, ii.; at 2, Book I. Chap. iii. where the 
 grounds of it are stated. Now if nothing can exist without a 
 cause, it follows that the existence of every thing began at some 
 period, for the time of its causation was that at which it began to 
 exist. It will be inquired if this conclusion applies to forms 
 where there is a provision for endless perpetuity? it will be in- 
 quired whether the principle proves a first origin of the human 
 species? These questions relate to an apparent distinction be- 
 tween those parts of nature whose similitudes are propagated by 
 derivation, and those which being once formed are liable only to 
 re-combination or analysis, and which have no succession of 
 resemblances. 
 
109 
 
 $ 19. It seems scarcely necessary to examine in detail these 
 questions, which are excepted against the principle : for it appears 
 to follow, demonstratively, that if there is no possible example of 
 existence which is not dependent for such existence upon a pro- 
 cess of causation, there can be no example of an existence 
 which has not at some period begun to be. But, if the topic 
 should be resolutely pursued, the substance of the investigation 
 would be thus comprised. Although we have seen that the pheno- 
 mena of nature are in many acts which are visible, and in many 
 more which are inferred, accomplished by a process of causation, 
 which fixes the era of their being; is it not possible that there 
 may be some eternal monuments, which have preserved through 
 numberless ages the characters by which they are now recognized 1 
 
 20. To suppose that any such monument existed would in- 
 volve the following objections, the last of which is not easily 
 obviated: 1st, it would leave its existence unaccounted for; and, 
 2nd, it would imply an existence according to some other mode 
 than by a combination of its constituents. Thus, the peculiar 
 instance in question is shewn to rest upon the same grounds as 
 those general ones which have been before spoken of: and the 
 truth of the general principle referred to in the chapter on Causa- 
 tion will give precisely its own credit alike to general instances 
 and to every particular application. Upon this authority, then, 
 the proof of the origin of man by constitution is rested ; but 
 whether this origin took place only once and in one place, from 
 which single act of primitive causation the present aggregate of 
 the species have proceeded, or whether the same constituent 
 powers have been at various times and in various places exerted, 
 giving rise to many primo-genitors, it has been seen that neither 
 record nor physical testimony, so far as we have examined it, has 
 been adequate to determine. 
 
 21. In a matter so intricate, it is no mean acquisition with 
 respect to a general design, to have come thus near to a settle- 
 ment of one leading point: and having by the help of our notions 
 on causation advanced one step, it remains for us, availing our- 
 selves if we can of the same help, to consider what other condi- 
 tions are implied by this origin of man by constitution. It is once 
 more to be premised that our present occupation consists in 
 making an experiment, the design of which is to ascertain how far, 
 and to what results, mere unaided reason is disposed to carry us. 
 
 22. Here again our choice of the mode of the first formation 
 of man seems to lie between the two following alternatives: 1st, 
 whether he was at once formed and perfected in this state; or, 
 2nd, whether he arrived at it by numerous changes, which would 
 furnish the materials of a long history of approximations? 
 
 1. That the entire man* was at once formed by a congregation 
 
 * Man is taken here merely as a specimen of the animal creation, the 
 Other parU of which are to a considerable extent governed by the same laws. 
 
110 
 
 of his materials, is a supposition little better than absurd; our ex- 
 perience of his growth from the stale of the ovum refutes such a 
 notion, for we observe that his internal functions mutt subserve 
 to his formation and development in every stage. Thus we have 
 dismissed the first alternative very briefly, our business now is 
 with the second. 
 
 2. Recurring to our doctrines of the ovum, we have seen that 
 the formation of an organic spirit must precede that of the textures. 
 As this has been shewn to be 'a. necessary relation, equal to that of 
 cause and effect, it is obvious that our examination of the mode of 
 a qalural origin of man must begin at this point. 
 
 23. We find, variously scattered in the immense extent of 
 being, a principle which has in many respects a resemblance to 
 the organic spirit of man. We find it throughout the animal and 
 vegetable creation, fulfilling (modified indeed in the several forms) 
 a similar function, that is, it governs their textures, and prevents 
 their decomposition. In tracing the sources of this principle we 
 shall find it to exist in substances which are not organic: we per- 
 ceive that the earth contains it; that from the state in which it 
 exists in the earth it is convertible into that in which it exists in 
 plants and animals; and that, finally, by a few transmutations it 
 assumes another place, and constitutes the living principle of man. 
 
 24. This principle is not only or wholly derived from the 
 earth : it floats in the wind, the air breathes life, the waters yield 
 their vital principle, all abound with the spirit of animation, and 
 furnish it to myriads of tribes; some of these, again yielding, 
 others adopting it: by a few simple changes it is identified 
 with each, and something like a common principle may be dis- 
 covered in aU its modifications. We cannot call this principle 
 universal: but we cannot limit its extent; it is widely prevailing, 
 its alliances are without end, and it will be considered more 
 closely when we speak of its particular relations. 
 
 25. We stand in need of no other facts than those just men- 
 tioned to shew the liability of this principle to a change of form, 
 or rather to a modification of properties. These facts, also, inde- 
 pendent of our general doctrines of causation, shew if tp be no 
 simple principle, but an example of being, which, like aH others, 
 js made by its constituents. We infer too from the same facts 
 how endless are the relations of the principle with earth, air, 
 water, and even fire, with organic forms, with its own constituents, 
 these decomposable, part related with some substances, and again 
 its remaining properties with others; finally, throughout nature 
 it has its alliances; and its connections and its possibilities are 
 infinite. It is governed by its constituents, it is modified by these 
 relations and these alliances; it furnishes integral parts of their 
 being, or it receives from them permanent or evanespent qualities, 
 which, by force of all prevailing affinity, are detached from, or 
 endure with, their original receptacles. This series is endless: 
 identities preserved, or changes wrought, all governed by causes, 
 
Ill 
 
 fixing, and in turn obeying relations. Who shall limit the execu- 
 tion of such grand alliances'? who shall say what cannot result 1 
 Let us however descend to the more humble employment of 
 tracing faintly what might result, or what has been done. 
 
 26. Beginning then with almost perceptible effects, that 
 spirit of man whose influence has been before partially developed, 
 we find, is identified. It is identified by what? Our doctrines 
 tell us, by its causes; these working, through all that complexity 
 of relation above sketched, imperfectly. Thus much in a general 
 way: but is not the manner to be traced more closely] Let us 
 examine what those processes of causation might be to which 
 such rare phenomena have been ascribed. 
 
 27. Of the particular causation of the organic spirit of man 
 it is impossible to speak with precision in the limited state of our 
 experience ; many questions must arise to which no answers of the 
 satisfactory kind can be given. These questions may serve to 
 exercise the ingenuity of those who chuse to exercise their in- 
 genuity upon them; and if they would attain an absoluse success, 
 they must first discover some new laws and principles to work with. 
 Some of these questions are the following: 1st, Where was the 
 organic spirit of man first constituted] 2nd, By what previous 
 acts of causation were its elements associated? 3rd, At what 
 period were they combined 1 4th, Was this spirit identified at 
 once, or was it a nucleus, which received many accessions until its 
 perfection was accomplished? 5th, What are the elements, or 
 what are the causes, on a gross analysis, which compose it? &c. 
 
 28. Then, considering it in its union with the material organs, 
 it is to be asked, 1st, What was the primitive state of the spirit 
 in regard to them? 2nd, What were the circumstances necessary 
 to its forming the corporeal alliances which it has now attained? 
 3rd, Was the present formation of the textures at once produced, 
 or by many preparatory changes? These and many more ques- 
 tions must arise upon this intricacy : our unaided reason shall 
 shew to what extent she dares proceed towards their settlement 
 respectively. 
 
 1. It is totally beyond the scope of the wildest conjecture, 
 founded on any thing like natural evidence, to say where the or- 
 ganic spirit was first produced, there being no more reason for 
 preferring one place than another. Nor is it possible to say 
 \vhether it was formed by constitution in one place, or in many, 
 seeing that we have no grounds for supposing that the agents by 
 which such a process was accomplished, existed in one place and 
 not in another. 
 
 2. In order to determine by what previous acts of causation 
 the elements of this spirit were associated, it will be necessary, 
 first, to ascertain the agents engaged in the work, and, second, 
 what the relations of these agents were with each other, together 
 with a history of the influences and mutations which they had 
 themselves suffered, It is obvious that nature has never been 
 
112 
 
 examined with this view. The most that has been done is to have 
 remarked some few effects which belong to the origin by deriva- 
 tion, and to have theorized a little upon these topics; we have no 
 experience to help us in this decision, not having known an origin 
 of the human organic spirit but by derivation. Facts also, which 
 ivould afford the evidence even of a weak analogy, seem to be 
 wanting, because such a drift of inquiry has never been indicated, 
 without which previous step it is scarcely to be expected that in 
 a matter so remote and intricate any data should be attained. As 
 it is now less my business to discover new facts than to reason 
 upon those which we have, so for the present these questions must 
 be dismissed. 
 
 3. It is equally impossible to pronounce at what period these 
 elements were combined, since traditional evidence has been found 
 defective, and since too, in the immensity of duration without 
 beginning which has belonged to the world, the same changes 
 might have recurred many times; it might have been peopled by 
 the causes which have made our generation what it is; destruction 
 might have succeeded, partial or total, in regard to human forms, 
 and myriads of ages might have elapsed before the materials 
 of the universe were disposed to repeat their former processes of 
 causation. 
 
 4. Whether or not this spirit was formed at once or by many 
 approximations, we are equally unqualified to pronounce upon, by 
 reason of the absence of direct proofs. It appears that it would 
 be supposing a concurrence too complicated for one single act : 
 on the other hand, it appears that if the state of life is not directly 
 established, that combination which belongs to it would tend 
 rather to decomposition than to a gradual perfection of its nature. 
 This consideration, however, belongs not to evidence of the de- 
 cisive kind. 
 
 5. Lastly, that we are ignorant of the elements of this organic 
 spirit will not be doubted. It is true we have a satisfactory infor- 
 mation by inference of many things which its properties are capa- 
 ble of accomplishing; we may acquire no despicable instruction 
 on its laws ; but to say what these properties are, that is, to dis- 
 cover that they resemble precisely, or are a part of, any thing of 
 which we have experience, is beyond our warrant, because its pro- 
 perties have no perceptive relation with our senses. Not to ex- 
 tend any further an examination which must be futile, we will 
 merely say that the obstacles to a decisive apprehension of the 
 mode of the origin of the spirit by constitution will interfere gene- 
 rally, to prevent our understanding of the modes of its alliances, 
 &c. with the grosser materials. We have therefore done with a 
 fruitless search after evidence of the first or second order upon 
 these points, and will next proceed to indicate the force and ten- 
 dency of evidence of another description. 
 
 29. The elements of life being furnished from their proper 
 sources, our choice of these sources must be directed by our 
 
113 
 
 nearest experience. Now we find that the earth and the air are 
 commonly related in the causation of life. We find in them the 
 materials of life, and of every species and form of life. These then, 
 from which life is perpetuated, we may most reasonably conclude 
 to be the sources which originally furnished life. 
 
 30. Whether the life of man was at once formed from this in- 
 tercourse of earth and air, we would not attempt to determine when, 
 before submitting to conjecture, we were looking about for proofs. 
 But now, having confessed a weakness in the argument, we may 
 venture to string up a few reasonings. We find then that the diffe- 
 rent specimens of life are to a great extent, if not altogether, pre- 
 paratory. Thus, in the sources which we have named it exists in 
 no specific form. But it is disposed for spontaneous changes, by 
 which some of the most simple forms are produced or have an ori- 
 gin by constitution; among these we have some instances in vegeta- 
 tion, as in the growths of mosses, mucor, fungi, some aquatic weeds, 
 &c. which originate, as is believed, without seeds. The form of 
 life in these examples is one modification of that informal state in 
 which it exists in its sources. As every change of form is a change 
 of relation by which the way is prepared to another change of 
 form, so the first spontaneous formal condition of life, which arises 
 out of its elements in earth and air, is a pre-disposition to another. 
 What that other will be depends upon existing relations, upon the 
 state of causes. The possibility of the materials of life existing in- 
 formally in its sources, assuming a defined form, will not be denied 
 because we ourselves have experience of the fact. 
 
 31. One form of life having arisen from its sources, what is its 
 next fate? Perhaps it sheds seeds and is thus perpetuated, or else 
 it dies; and what then] Simply this, that its life is preserved in 
 death, that its death is only another condition of its life. How is 
 this proved? it will be asked. The proof I shall give at length in 
 another place, suffice at present to say that it is proved in two ways: 
 first, that every change happens by causation, which implies addition 
 or diminution of properties, so that life in death is modified only, 
 and in one of these ways; and, second, that those materials with 
 which an organic life once inhered are found to furnish an organic 
 life to others of the same or of a different species. Thus much being 
 granted (and all its evidence shewn, we may be bold to say it can- 
 not be denied), this point being granted then, we find that this first 
 form of life is changed in death, and has relations which in that state, 
 which for distinction we call life, it had not. In death it exists, and 
 is operated on by the causes related witii it; and it requires no more 
 than the same kind of concurrence among causes as that which first 
 made it a specimen of formal life, again to become life in n second form. 
 
 32. But how, it will be asked (supposing that this explanation 
 of a spiritual origin may be admitted), how does this form of a 
 principle possess itself of a corresponding material form ? This ques- 
 tion has been already answered, or nearly so, in speaking of the rela- 
 tions between the spirit and the structures, in our doctrines of tl"* 
 
114 
 
 ovum. We will however repeat here (referring to these doctrines 
 for the grounds of the assumption), that this spirit has a relation 
 which has been called one of affinity with the materials; that its 
 place (determined by previous acts of causation), being where these 
 materials are subjected to the spiritual affinity, they are aggregated 
 or arranged according to its agency. 
 
 33. Thus then we perceive that an apparent distinction or 
 subdivision arises in the modes of origin by constitution, viz. one 
 which is primitive, resulting from relations between the elements of 
 informal life, contained in its sources; and another which is secon- 
 dary, or arising from a former condition of life, which has been 
 jnodified by death, and is consequently prepared for further modi- 
 fication by a necessary change in its relations. 
 
 34. Now although this distinction appears to be not weakly 
 sanctioned, yet in the real nature of the processes there is no diffe- 
 rence; both these modes of origin being resolvable into those uni- 
 versal ones of causation, viz. by addition or subtraction of proper- 
 ties. In this way that which is called informal has been shewn to 
 become formal life; and in the same manner one spiritual form is 
 by death rendered different from the last; and when again it ap- 
 pears inhabiting a material fabric, it then is that which it is made 
 by a repetition of these same processes; modes of causation, com- 
 mon both to the primitive and secondary forms of life. The dis- 
 tinction may however be admitted, principally for verbal con- 
 veniences, having defined with what limitations if is to be received. 
 Thus much may be said of spiritual origins in a general way: let us 
 return however to that particular one whose history we have more 
 especially undertaken to trace. 
 
 35. We have discovered the complexity o^ the human organic 
 spirit by considering its properties in their effects upon the struc- 
 tures, &c. From this complexity we are inclined to infer that such 
 a spiritual condition is not at once attained. It appears contrary to 
 the little experience we have in the origins of some of the meanest 
 and most simple forms of lift 1 , to imagine that by any single change 
 in the relations of informal life such a state of the principle could 
 at once result. 
 
 3ti. If then this argument (which is of the presumptive kind), 
 supported as it is by all the experience we have on the point, which 
 is little enough, should be allowed to deserve consideration, we 
 should conclude that many forms of organic life preceded the in- 
 tegrity of a human spirit. We should, in conformity with such a 
 view, conceive that its first production from the sources of its ele- 
 ments constituted the simplest state of formal life; that this state 
 of life gradually became more complicated, 1st, by its modification 
 in death, and, 2nd, by a subsequent change of relations and pro- 
 perties which caused it again to be exhibited as a specimen of 
 formal life. 
 
 37. By a repetition of such processes it is impossible to limit 
 the forms of life which may thus be produced. The near relations 
 
115 
 
 aubsisting between the different forms, the facility of their conver- 
 sions from one state to another, we have before been reminded of, 
 and shall hereafter more fully apprehend, when our business is to 
 speak of the maintenance o/ life and the manner of assimilation. 
 
 38. Thus then we have faintly sketched, we may perhaps say, 
 the probable modes of spiritual formation. There are involved in 
 the sketch many objections of a minor sort, which I have not 
 thought proper to notice; and, on the other hand, many collateral 
 circumstances of equal force may be adduced in support of these 
 views. Among the objections which might be urged I shall notice 
 only this one, viz. if man was once formed in this spontaneous way, 
 merely by a train of causation (wrought, it must be remembered, in 
 an infinity of ages) and by a concurrence of elements, how comes it 
 that we have now no examples of such an origin? 
 
 39. To this objection, the force of which is not very great, it 
 may be answered, generally, that all the parts of the universe are in 
 action, undergoing perpetually changes among themselves, changes 
 of combinations resulting from the particular states of causes, fixing 
 particular and present relations; that therefore we are not to expect 
 at this period, or at this stage of change, the same results as occurred 
 perhaps at times incalculably remote. This remark is sanctioned 
 by experience as well as induction. History has preserved many 
 solitary facts in almost every department of * creation; facts which 
 have occurred at one period of causation, effects for which there has 
 been since no relation prepared, no concurrence to give them birth. 
 But I propose to treat the objection a little more respectfully. 
 
 40. Supposing the inference, that the complicated have arisen 
 from the simple forms of life, to be correct ; to descend a little more 
 particularly into the subject, the question is, how it happens, seeing 
 that the first and simple forms of life are now produced from their 
 elements, that they do not in time become converted into the com- 
 plicated forms, thus extending our experience of origin by constitu- 
 tion? This question is replied to in a general way above, and now 
 more particularly as follows: 1st, The state of the elements of life 
 (their relations, &c.) existing in their sources is necessarily very differ- 
 ent, before these elements have been disturbed, before they have 
 established the complicated forms, from the condition of them when 
 their processes have been vastly interchanged, and when, finally, all 
 the effects of their causation are accomplished. 2nd, The conver- 
 sion of the simple into the complicated forms is shewn to be de- 
 pendent upon the condition of the elements. 3rd, There being now 
 no examples of the spontaneous origin of the complicated forms of 
 life, indicates only, agreeably to the argument, that the series of 
 causation which produced these forms has long since been at an 
 end, and that the aggregate condition of life, being now different 
 from its primordial condition, is established in other relations, is 
 governed by another causation, which, among its other results, has 
 prepared the means of identical perpetuity rather than of further 
 change. Consistently with this last observation (which is indeed a 
 
116 
 
 part of our experience), I am disposed to impute very little of the 
 variety of animal forms to the casualties of sexual intercourse and 
 to the peculiarities of nutrition ; for, in the first, we find that the 
 offspring of these casualties of intercourse are incapable of perpetu- 
 ating their kind (this at least holds good generally of the varieties of 
 species), and, with regard to the second, we are assured by experience 
 from the earliest recorded time to the present, that animals and 
 vegetables have preserved characteristic marks of their primitive 
 identity. This is a strong tendency in nature: it is exemplified in 
 the results of grafting, in the varieties of animal and vegetable forms 
 which aie preserved respectively under common means of nutrition, 
 &c. ; at tiie same time it is not to be expected, as will hereafter be 
 more fully remarked, but that the means of nutrition may to a cer- 
 tain extent modify or influence the form of life, these two constituting 
 a relation. And some strange products may occasionally result 
 from a commerce which may be said to be unnatural between 
 animals; of which products there may now exist some solitary 
 remains : the Marnoth however is not to be reckoned of this number 
 since its remains prove it to have been largtr than any known 
 animal; whereas if it were a product of the above description, it 
 would be less than the largest known animal, partaking in this 
 respect of the difference of properties between the parents. It is 
 to be inferred for this reason (if the specimens are not artificial and 
 the accounts fabulous) that this animal at least belonged to a race 
 which, owing to some of the causes before enumerated, has become 
 extinct. 
 
 41. Having once come to a conclusion of an origin of man by 
 constitution, whether called a creation or however denominated, in 
 conformity with our principles of causation, we are compelled to 
 make the following acknowledgment, viz. 
 
 That at a remote period of the world the constituents in it from 
 which such an organic spirit as that we are considering would result 
 as an effect, were disposed to unite and produce as a separate com- 
 bination in nature the spirit in question. The concurrence of con- 
 stituents at this period was determined by one of two modes of 
 causation, or by both, viz. the constituents previously disguised in 
 another constitution, were suffered to form the identical spirit by an 
 agency which detached them from their former alliances; or by an 
 agency which furnished additional properties to constituents which 
 were not otherwise identical; these agree with the only possible modes 
 of causation, by subtraction or by addition of properties, or both. 
 
 42. After all, we are, by candour and a just regard to truth, 
 obliged to confess, that the most plausible conjectures on this remote 
 business of the origin of vital forms by constitution are, in their ap- 
 plication to particular processes, to be very scrupulously received. 
 
BOOK THIRD. OF POST-FOETAL LIFE. 
 
SECTION I. 
 
 GENERAL RELATIONS. 
 CHAP. I. Condition of the Spirit, fyc. 
 
 1. 1 HE organic spirit is liable to the application of 
 all those laws which have been noticed in the chapter on Causation: 
 the proof of which is that those laws are universal, and the grounds 
 of this last assumption are stated in the chapter just referred to. 
 
 2. By these laws of causation we are taught to regard this 
 spirit as no simple elementary principle, but as containing an infinite 
 number of properties by which altogether it is constituted. 
 
 3. The spirit itself is not an object of sense, but its existence 
 is interred from its operation. The effects of its operation are so 
 numerous and the instances so familiar, that the supposition of it 
 acquires a currency and credit in our reasonings equal almost to 
 perceptive knowledge. The existence of this spirit being once in- 
 ferred from its effects, we next begin to class those effects, giving 
 corresponding denominations to the properties of the spirit by 
 which these effects are accomplished. 
 
 4. The progress which has been made in this work of analysis 
 and classification is not much to be boasted of; the most that has 
 been done is to designate three or four species of contractility, from 
 which has originated a vast deal of erroneous and absurd reasoning. 
 The spiritual phenomena have never been considered in their true 
 mode: I shall proceed merely to shew in this place that a proper 
 foundation for reasoning about these processes has not yet been 
 indicated. 
 
 5. The phenomena of life, it has been said, are produced by 
 the operation of stimuli on that which has been called " excitability." 
 By the proportions, &c. of these two the state of excitement or of 
 
120 
 
 life is regulated. Tlje varieties of life or excitement are also said to 
 be two, viz. a state which is above and a state which is below a 
 given standard; all this may be very true, and yet we are very little 
 the wiser for it; it is equally true that life is life, that life is either 
 good or bad, and that when life ceases death begins. 
 
 6. And with respect to our contractilities: their enumeration is 
 very correct, but they lead to the mistake of considering phenomena 
 in relation only to quantities and degrees where an altered consti- 
 tution has taken place. 
 
 7. Thus supposing the action of the heart to furnish the 
 criterion of the proper state of health, and that the precise standard 
 of it, estimated by the frequency of its movements, consists within 
 the range of from 60 to 80 beats in a minute. Now the heart 
 might assume an action of the following kind: the first day of 
 change it may beat at the rate of 96 in a minute, the second at the 
 rate of 110, the third at the rate of 100, the fourth at the rate of 90, 
 the fifth at 72, and the sixth at 60. We see these fluctuations, and 
 our experience allows us to be capricious in assigning the order of 
 variation. At another time the action of the heart shall on the first, 
 second, ( or third day also reach 110; but instead of being reduced 
 by the sixth day to 60, it shall for monlhs fluctuate between 90 and 
 120, and may even reach 160; and whereas the accession of disease 
 in the first case terminated in recovery in six days, the termination of 
 the second may be at the end of six months in death. In these two 
 cases the rate of pulsation, the degree of action, was at some times 
 precisely similar. Why, when in the latter, as in the former case the 
 pulsations were at 90, did not the same termination ensue? The 
 answer is very obvious: it is because the heart was affected by 
 two different diseases, by which we imply, that the principle 
 which governs the action of the heart had assumed two different 
 conditions. 
 
 8. We have the same testimony from the actions which we 
 observe in any particular structure, in diseases whether purely local 
 or conjoined with an altered constitutional diathesis. Thus two 
 cases of pneumonia shall be equally violent, one shall have termi- 
 nated in resolution in twelve or fourteen days, the other in the for- 
 mation of an abscess; in one the heart shall have regained, in less 
 than a fortnight, its healthy rate of action, in the other this action 
 shall never be restored. Why was pus formed in one case and 
 not in the other! We have just grounds for believing that the rate 
 of pulsation, &c. in the affected vessels was the same; further, 
 vessels will sustain any degree of circulation without forming pus; 
 we must therefore say that some other cause, some other condi- 
 tion of disease operated in one case and not in the other, which 
 governed the termination respectively. 
 
 9. Thus, also, in some persons (those of a nervous tempera- 
 ment) the pulse shall be raised at one time to 100 in a minute, while 
 the subject is conscious of the possession of perfect health; at 
 another time iu the same subject the pulse shall not exceed 90 or DO, 
 
121 
 
 and shall be accompanied with other characteristics of fever con- 
 stituting a state of disease. 
 
 10. Thus also it may happen to the same person at different 
 periods of his life: at an early period, to sustain an inflammation of 
 the toe or foot which will proceed to suppuration and finally to 
 recovery, embracing in its course the whole range or every degree of 
 action ; at a late period of life in the same seat and in the same indi- 
 vidual there might occur an inflammation exhibiting a perceptible 
 action or circulation, similar to that which had been formerly ex- 
 perienced; this last diathesis, instead of suppurating, instead of the 
 termination in recovery, may end in mortification, and perhaps death, 
 within 48 hours. Here, as in the other cases, there might be iden- 
 tity of degree (and if such identity is allowed on a comparison at 
 any period respectively of the two cases it is sufficient for the argu- 
 ment), but difference in the state of the governing principle. The 
 same might be observed of vitiated secretions; and indeed the same 
 results of comparison might be deduced in every instance of disease, 
 whether the comparison is made between similar conditions in 
 respect to degrees of action, &c. of the same person at different 
 times, or of others. If there is a single instance in which the degree 
 of excitement, which shall be estimated according to any standard 
 that might be proposed, will account for all the phenomena of 
 disease, I will never urge another objection against its sufficiency. 
 
 11. If I were disposed to pursue this subject to greater length 
 I should shew the fallacy of some arguments which have beeu 
 urged in favour of the doctrine alluded to, as well as bestow a notice 
 on some others which might be made in reply to the preceding 
 objections; but this would be to anticipate a part of the subject 
 which will hereafter be distinctly spoken of. I shall here therefore 
 merely remark in addition, that the state which agrees with the pre- 
 cise though arbitrary condition of health, may obtain many times 
 in the course of disease, and yet under the use of ordinary diet or 
 of medicines, with whatever view directed, the constitution shall 
 digress repeatedly into the former state of disease which may ter- 
 minate either in death or recovery. Thus an intermittent pulse 
 might become regular, and in less than an hour may intermit again ; 
 thus a person shall be wholly freed from a collection of water, and 
 under the prevalence of habits which were previously compatible 
 with health shall again become anasarcous. These events depend 
 upon pre-disposition, or a state of the principle, the peculiarities of 
 which can neither be specified nor even conjectured. 
 
 12. As much as has been said in regard to a pathology which 
 looks only to the degrees of excitement, &c. (which by the way can 
 never be ascertained by any single criterion) is generally applicable 
 to the doctrines which have been founded on the contractilities 
 before spoken of. 
 
 13. Thus we say that such a one is a disease of excessive 
 irritability : we will take for example, as being familiar, an ulcer, 
 the indisposition of which to a healing process is attributed to 
 
122 
 
 excessive irritability. We will suppose it to be ascertained that the 
 property denominated sensible organic contractility, or that which is 
 more immediately connected with the circulation, is alone interested 
 in this disease; the disease is said to Consist in an excess of irrita- 
 bility. Thus far we have stated a case which we must next examine. 
 
 14. The word " excess" is applicable only to the sum or 
 quantity of that which is excessive. How, I would ask, is it ascer- 
 tained that the natural irritability is increased in quantity? I may 
 take it for granted, without presuming too much, that \ve have no 
 measure of the quantity of the principle of irritability. If it be 
 said that the effects of irritability furnish this criterion and this 
 proof; then I reply that it is in order to shew them to be the effects, 
 that the criterion and the proofs are wanting. If then we are unable 
 to estimate the quantity of irritability, why introduce it into our 
 reasonings] Why presume to explain phenomena by that which 
 itself stands equally in need of explanation? It may further be 
 urged, there is in the case supposed an excess of intensity or of de- 
 gree, rather than in the quantity of the principle resident in the 
 fteat of the disease. This may be compatibly with the application 
 allowed above to the word excess; of this " degree" we shall have 
 occasion to say a few words hereafter. 
 
 15. But, to go further, let us allow that irritabilitv either in 
 quantity or degree can be measured in some way or other, loosely 
 or accurately, no matter which; let us allow this, and then examine 
 whether all those phenomena of the irritable ulcer are referable 
 to the quantity or the degree of the sensible organic contractile 
 power. 
 
 1st, The discharge may be sanious and offensive : in what man- 
 ner does the degree of irritability regulate this particular? The only 
 function which is attributed to this contractility is to govern the 
 action of vessels: what rate of pulsation then, or if this objected to, 
 what modification of caliber is required to produce a sanious dis- 
 charge? Such a question, involving so much improbability, was 
 perhaps never thought of, it is therefore no wonder that it is not 
 answered. But that the secretion is not produced by any rate of action, 
 by any degree of the principle alone, seems to be proved by the fact 
 that an ordinary specimen of phlegmonous inflammation in some or 
 other of its periods embraces every rate of action, every condition 
 of an inflammatory diathesis; at least, if we cannot discriminate a 
 difference in favour of that connected with our sanious discharge, 
 we have no right to presume it. But suppose even that a difference 
 of action in the vessels were perceptible, suppose also that a suitable 
 caliber of the vessels were assumed (which last is supposing a pro- 
 perty superadded to that which merely governs the rate of pulsa- 
 tion), suppose all this and every other convenience, the effect would 
 then be that the fluids contained in the vessels would be circulated 
 or poured out either faster or slower than in an ulcer of a different 
 description. Now we know that simple pulsating tubes of a certain 
 area, a mere hydraulic process, can never give a product of secretion; 
 
123 
 
 for every variety therefore in the quality of the secretion we must 
 infer a corresponding condition of the nature or constitution of the 
 cause upon which it depends. 
 
 2nd, With regard to the disposition of our ulcer in other re- 
 spects, instead of healing it becomes more extensive ; these diffe- 
 rences are not dependent merely upon a power whose only property 
 is to make tubes contract faster or slower, to render them larger or 
 smaller, to make them pour out their contents or not pour out their 
 contents. The disposition of the ulcer must be regulated by causes 
 capable of producing more than the effects of hydraulic agency, 
 seeing that its disposition is expressed by processes and varieties in 
 which hydraulic agency can take but a subordinate part. 
 
 3rd, The condition of the ulcer gradually changes, and new 
 organic substance is produced from it. What degree of a principle 
 capable of exerting only the single property of regulating the action 
 or caliber of vessels is capable of forming an animal structure? of 
 endowing that which it has formed with life? of rendering it capa- 
 ble of more phenomena than can be enumerated? I shall pursue 
 this topic no further at present: I will merely remark that these 
 proofs are also applicable against the sufficiency of the other con- 
 tractilities. Without therefore continuing my objections to the 
 doctrines of life and disease, which have prevailed, and do prevail, 
 J shall proceed to state what appears to me the true mode of con- 
 sidering these subjects, the latter of which, viz. disease, being here 
 cited only in the way of illustration, will hereafter be distinctly 
 spoken of. 
 
 16. It has been shewn, in treating of the conditions of the 
 ovum, that the organic spirit is vastly compounded; that it has 
 many properties has been there demonstrated by tracing their par- 
 ticular acts, and that its properties are infinite is shewn by the gene- 
 ral principles of causation. 
 
 17. Hence its general condition is this: it is one whole, the 
 parts of which (to render the division comprehensible) exist in 
 several spheres, which agree with the portions, whether large or 
 minute, of the organized fabric. 
 
 18. This spirit shews itself to be possessed of a great diversity 
 of properties in the different material systems; it has in every seat 
 numerous relations: by these relations it is either preserved identi- 
 cally, or modified and by them its identity or its modifications are 
 expressed. 
 
 19. The effects of the combinations of the properties consti- 
 tuting the spirit may, to a certain extent, be said to agree with the 
 contractilities before referred to. But it must be remembered that 
 these are only certain effects of properties which are latent and 
 which have an internal causation, and alliances both regular and 
 occasional by which phenomena are produced and diversified. 
 Whether a better classification of these effects may be adopted will 
 be considered hereafter. 
 
124 
 
 CHAP. 11. Of the Mode in which Life it maintained. 
 
 1. IN a case of death, while the blood is yet fluid, life is 
 not to be renewed by any means: we may inflate the lungs, or 
 restore the temperature, or stimulate, as it is called, the internal 
 organs, as the stomach and bowels; we may electrify or galvanize 
 the body ; but we shall not re-produce the phenomena of the living 
 state : or, lest some objection should be conceived to this example on 
 the supposition of an injury of the textures or a change of the fluids, 
 
 2. We may amputate a limb, and inject or transfuse blood, 
 which is fit for nutrition, blood which is impregnated with air, 
 arterial blood into its vessels ; but the phenomena of life will not ensue. 
 
 3. It is proved by these facts (and indeed by many others 
 which, with the inference, are sufficiently familiar) that life is not to 
 fa conferred by the only externals which support it, viz. by food, 
 the appropriate parts of which are contained in blood, and by air, 
 of which in its animal relations blood also appears to be the medium. 
 
 4. But we find, that in cases of asphyxia, where life is not 
 extinct, the means above mentioned will succeed in restoring its 
 phenomena; and, what is still more unequivocal and pertinent to 
 our present purpose, we find that the means above mentioned do 
 support life, and that the defect of either is followed by death. 
 
 5. Hence it appears that life is supported by the conjoined 
 influence of ail and food; and that neither, singly, can support it. 
 It is also to be inferred from these facts, that life itself operates 
 upon air and food to the end of its own perpetuation. 
 
 6. This last inference is further proved by the fact that those 
 elements in air and food, which to the living principle furnish life, 
 have no natural affinity; that is, they are not found to unite and 
 produce the | henomena of the living principle spontaneously, how r 
 ever effectual their mutual exposure might be, but are always ready 
 to yield the principle when subjected to its own influence. But as 
 these materials, viz. those derived from earth and air, are found to 
 possess the elements, it is not, as hinted in the article on the Origin of 
 Man by Constitution, an extravagant conjecture to imagine that an 
 accidental union of the elements might, under peculiar circum- 
 stances, take place, though contrary to our experience of their regu- 
 lar tendencies. 
 
125 
 
 7. As we see that life would become extinct but for the sup- 
 port and renovation of its elements, and as we see that these ele- 
 ments require the presence of life, in order that they also might 
 become life; we must infer that the influence of life, in regard to 
 the substances which contain its elements, is to unite these ele- 
 ments, by which they in turn become life, and an uniting principle 
 in regard to other materials. 
 
 8. It is proved by the necessity of the frequent renewal, or 
 rather the constant supply of its materials, that a given quantity 
 of life is no sooner formed than it passes away ; that is, this portion 
 dies, or changes its forra and relations: what becomes of it will 
 be considered hereafter. 
 
 9. Hence it follows, that the duration of life is not dependent 
 upon the sum of the principle, whether conferred on the ovum or 
 collected in the stages of growth, for then it would not stand in, 
 need of the support of external causes. 
 
 10. Nor is it to be imagined that life is maintained by a pro- 
 cess of constitution of the following kind, viz. that a principle 
 which is a mere pre-disposition to life is originally conferred, 
 which is permanent, and the portions of which are made life by 
 the combination with an influence from the externals, air and food. 
 This is not to be imagined: 1st, because there is an entire want of 
 evidence for the truth of such a conjecture; 2nd, if a durable 
 quantity of such a principle were conferred, an animal that died 
 from privation of the mere auxiliaries of this principle, viz. from 
 the privation of air and food (or blood), should be revived by a 
 restoration of these only concurrent means, which a permanent 
 principle of pre-disposition wanted only to become life. But we 
 find, on the contrary, that to preserve life, requires the presence of 
 no single properly of life, but of the living state; and this living 
 state ceases altogether upon the privation of the means before- 
 mentioned. Such a doctrine as expressed in the above conjecture 
 is by these facts irrefragably confuted; and by them it is proved 
 with equal force and clearness, that the following is the true pro- 
 cess of the maintenance of life. 
 
 11. Thf- piincip/e of life, or, as we have hitherto expressed it, 
 the organic spirit, exisls in every part of the textures. Blood, con- 
 taining the elements of life, which are furnished by its two sources 
 before named, viz. air and food, is every where diffused among the 
 textures. The exposure of that which contains the elements of life, 
 to life itself, is in this way complete. The next operation is simply 
 this: that life, by an affinity subsisting between itself and its ele- 
 ments, separates them from a common material, and unites them. 
 
 12. In this manner the life contained in the blood, in the 
 condition of latent properties, becomes by a common act of causation 
 the form of life, resembling that which produces it. As every 
 quantum of the principle is produced, it operates upon the ele- 
 ments (or unites them) for its renewal and it vanishes, successive 
 quantities in this way perpetuating the existence of the living spirit. 
 
126 
 
 13. If proofs should be required of the truth of this account, 
 I say they are already given; but if a repetition should be de- 
 manded for the purpose of a stricter comparison with the doctrine, 
 they are as follow : 
 
 1st, The condition of the support of life is an adequate sup^ 
 ply of the two externals. 
 
 2nd, Life immediately ceases when either is withheld. 
 
 3rd, The two externals are incapable of maintaining life, 
 unless fife is present. 
 
 4th, Life is maintained by this threefold relation. 
 
 As the identity of life would cease but for the influence of 
 these externals, so its identity being preserved by their influence, 
 the operation of life on them is not to produce any thing foreign, 
 but to assimilate its identity; and as the externals before men- 
 tioned are the sources from which life is assimilated, and as in 
 them it exists informally, that is, in the state of its elements or 
 constituents, so the process of assimilation is to unite the elements 
 by which an identity of life is preserved. 
 
 14. This reasoning admits of being placed in many other 
 points of view; but to me, by the combination of the facts, the in- 
 ference is so clearly demonstrated that any additional illustration 
 seems superfluous. The blood is no animal, nor vegetable neither, 
 but it is the material containing the elements of life : it is a further 
 preparation of the informal life which exists in earth and air. 
 
 15. In conformity with our general principles of causation, 
 life has been before said to contain an infinity of properties: it is 
 not here necessary to give so much latitude, we will merely say 
 that it is identified by many properties. These properties cor- 
 respond in their variety, to say the least of it, with the varieties of 
 the whole animal and vegetable creations; different properties 
 of life are not merely exhibited in the different classes of animals, 
 but also in those of the same species. Hence the various forms 
 of bodies, hence the several configurations of organs subserving to 
 the same purposes, hence all the varieties of size and growth, 
 hence the varieties of pre-dispositions, with many other hences. 
 
 16. The general law with respect to the generation of life, 
 appears to be that every specimen of it assimilates from the com- 
 mon elements its own precise identity; this is determined by an 
 affinity or relation which is settled by the causes involved in life 
 itself, in a way before explained. Thus, every animal and every 
 tree maintains in perpetuity its own characteristics: and thus every 
 body preserves for the future a conformity or resemblance with 
 the past; all obeying the common relation of cause and effect: 
 existence forcing existence. 
 
 17. But although this law may in the gross with correctness 
 be said to be general, yet it is liable to many interruptions, still 
 however in obedience to the universal laws. The preservation of 
 a species is interrupted by various accidents before enumerated, 
 and the perpetuation of the past ideality of aa individual is inter* 
 
127 
 
 rupted, 1st, by the development of latent causes, which are inter- 
 nal, and, 2nd, by varieties in the nature and operation of externals. 
 
 18. Both these distinctions are highly important, but the 
 first is more particularly so, from its application to many pro. 
 cesses otherwise obscured in mystery. It is by this law that the 
 organic changes take place which are conspicuous in the several 
 stages of life; and by it the order of disease is for the most part 
 regulated. 
 
 "\ 19. In treating of the ovunv we have found that the differen- 
 tials, whether active or pre-disponent, which serve to distinguish 
 one specimen of organic existence from another, are possessed in 
 the ovum by derivation, and are not attributable to the influence 
 of externals. The proofs of this are variously scattered in the 
 article alluded to; 1 shall not therefore refer precisely to them, 
 but merely recapitulate the two following: 1st, that with oviparous 
 animals all the ibetal processes by which the animal is identified 
 are conducted without any external material of nutrition ; and, 
 2nd, that with all viviparous animals (as well as among vegetables) 
 the characteristics of the respective species are preserved, and 
 even tendencies expressed which are peculiar to the parental stock, 
 under the influence of externals which are common to them all. 
 These proofs may also be strengthened by recurring to our princi- 
 ple of causation; but as the subject is already separately spoken 
 of, such a recapitulation seems superfluous. 
 
 20. Every property of life which acts requires to be renewed, 
 and for its maintenance must therefore require, and find, a simili- 
 tude in the material of nutrition. 
 
 21. But as life appears in every sphere to possess an integrity 
 by which no property has an independent fate; that is, when the 
 whole exists the whole assimilates; and when the whole has ceased 
 to be a whole no single properties are indicated to remain ; and 
 more especially as we observe that when the latent causes from 
 parental pre-disposition become active, they also are renewed 
 from a source: on these accounts it is probable that the whole life, 
 such as it is constituted by its sum of properties, passes away and 
 is renewed by assimilation : and if this is the case it follows that 
 its latent or passive properties are supported, as well as the active 
 ones, by this same process of assimilation. The argument derives 
 additional credit from the following considerations, namely, 
 
 22. That properties of pre-disposition conferred on the 
 ovum, and which for years have remained latent, do when they 
 are become active find their similitudes in the common material of 
 nutrition, and are perpetuated by assimilation: such is the case at 
 the period of puberty, when a peculiar secretion is produced by 
 the agency of life from glands which never secreted before; and 
 the faculty t)f this secretion, obeying all the other laws to which 
 life is subjected, acts and is renewed with considerable duration. 
 
 23. Hence the terms of the continuance of a pre-disposing 
 property with the general constitution of the principle of life, 
 
128 
 
 must depend upon its tendency to assimilate, under all its circum- 
 stances, and this latter will be fixed by its relations with the other 
 properties of the spirit. Enough is here indicated of this relation: 
 it remains to be pursued under the title of disease. 
 
 24. But this spiritual assimilation does not comprehend the 
 entire relation between life, and the medium or material of its 
 elements. At the same time, as life is maintained in every seat in 
 the way described, it separates from the material of its own ele- 
 ments also the materials of the textures. The manner in which 
 this is accomplished has before been said to be by affinity ; but 
 this is a word expressing only the name of the relation. If it 
 were possible to make a more minute analysis of the relation we 
 should be furnished with some very important knowledge of the 
 agents engaged in the relation, and might still reserve the term 
 affinity, to designate the modes of indivisible processes. Let us 
 attempt something in the way of illustrating such an analysis. 
 
 25. As every organic particle composing the structures is 
 first formed, and its cohesion with the rest afterwards maintained, 
 by the organic spirit, so every organic particle is a seat of the 
 spiritual properties. 
 
 26. As the blood (which will be shewn more particularly 
 hereafter), or the fluids separated from it, is the material of nutri- 
 tion, so one condition of the agency between life and the fluids is 
 that the latter should permeate the organic particles. Thus the 
 material is exposed to the agency of life, the results of which are, 
 
 1st, That life produces itself from the material in the way 
 described. 
 
 2nd, That it produces the organic particles, determining their 
 arrangement, &c. as before proved; and, 
 
 3rd, That, having produced the structures, it preserves their 
 coherence: our present business is with the two last. 
 
 27. 1st, The alternatives with regard to the formation of the 
 structures are, 1st, whether they are necessarily attached to the 
 formation of life itself; or, 2nd, whether their formation is the 
 result of a distinct agency of the spirit upon the material. 
 
 28. 1st, That the aggregation of the particles of the textures 
 is attached to the formation of the spirit, requires to be further 
 explained. The proposition supposes that the elements of life in 
 the material are allied with those grosser parts which become the 
 organic particles; that various forms or combinations of the pro- 
 perties of life (as has been shewn) are contained in the same ma- 
 terial; that every form of life existing in a texture assimilates its 
 own form; and that as the properties constituting this form are 
 separated from the blood, the peculiar material particles with 
 which they inhered in the blood are separated also, thus at once 
 perpetuating the living principle and aggregating the structures. 
 
 29. Now this theory seems to agree very well with that unity 
 of operation which we perceive in every other animal process, of 
 which we have a tolerably clear understanding ; but it is irrecou- 
 
129 
 
 cilable with the following facts: 1st, the process of spiritual 
 assimilation is unremitting: and if, with every new portion of the 
 spiritual elements, an accession of new organic particles were also 
 to take place, these having a permanent place, the increase ef 
 the structures may proceed ad infinitum. 2nd, As the spiritual 
 assimilation goes on under all circumstances of disease, &c. as long 
 as life lasts; so there would, according to this notion, he no 
 possibility of a waste of the structures, unless the quantum 
 of life were diminished, for the spiritual and organic forma- 
 tions must proceed together, they being inseparable; a result 
 which is contrary to facts, as is exemplified in fevers, atrophy, 
 &c. 3rd, The basis of the theory stands in need of support 
 equally with the theory itself: for, in the first place, it re- 
 quires to be proved on its behalf that the elements of the spirit 
 are united with any order of particles, independently of some in- 
 termediate bond, as by chymical or other properties; in the 
 second, it requires to be shewn, supposing that the spiritual pro- 
 perties are thus allied with material particles, that this alliance is 
 not divorced by the process of the spiritual assimilation; and in 
 the third, it must be shewn likewise that these material particles, 
 and no others, existing in the blood, are those which are found in 
 the respective structures. This theory, therefore, from the force 
 of the facts just mentioned, I cannot help rejecting; though if it 
 had been allowable to have passed oft' a theory as a true explana- 
 tion, merely because a beautiful harmony would have been exhi- 
 bited by it, the one in question might "have been extended to 
 many other points, and raised with an agreeable construction. 
 
 30. The second alternative is whether the formation of the 
 structures results from a distinct agency of the spirit upon the 
 material? The conclusion of the affirmative is established by a 
 combination of the proofs before cited, which shew the indispensa- 
 bility of the spirit to the formation of the structures, and those 
 other proofs just mentioned, which are meant to refute the 
 alternative above discussed. But to recapitulate some of these 
 proofs : if life (as has been shewn) operates to the formation of 
 the structures, then the structures must be formed by it, either 
 during its own assimilation in the way described, or as a subse- 
 quent act of life. As the state of the textures conforms not with 
 the assimilation of life, which is perpetual, but with the dispositions 
 of it, natural or diseased, so it must be inferred that the textures 
 are affected and governed by the constitution of the spirit. 
 
 31. Thus, then, life existing in the several seats forms the 
 structures which constitute those seats. This process requires 
 not an elementary condition of life, but the living state of it ; we 
 cannot therefore say whether all the constituent properties concur 
 to this end, or whether the organic particles of the material are 
 related in such a way with only some of them. From our igno- 
 rance of the constituent properties, our analysis of the operations 
 of life are likely to be very deficient; for we are compelled, on 
 
 T 
 
130 
 
 almost all occasions, to designate the influence of spiritual pro 
 perties by the term "life," which includes them all; we should 
 therefore* describe, as nearly as we can conjecture, the process of 
 organization in the following way. 
 
 32. The organic spirit in its several spheres has a relation 
 with its own elements in the blood by which it lives; and another 
 with the organic particles existing in the same fluid, by which 
 they are separated from the blood, and deposited in places agree- 
 ing with the continuous spheres of the spiritual properties, by 
 which they were decomposed from their alliances in the state of 
 blood. The particles, thus formed by life, afterwards become 
 inhabited by life, as is proved by their resisting the tendency to 
 putrefaction, which otherwise belongs to them. This leads to the 
 other result, which has been left for consideration, viz. 
 
 33. 2. That life, having formed, continues to preserve the 
 structures. In order to preserve that which the spirit has pro- 
 duced, it is necessary that the spirit should reside in the organic 
 particles; it then maintains their coherence by a continued opera- 
 tion of that same affinity which ivas before competent to dissolve 
 former connections and assign them a separate place. The mode 
 therefore in which the structures are preserved during life, is one 
 which is simple and in strict harmony with the preceding acts. 
 
 34. But this union between life and the organic particles is 
 not permanently maintained during the living state ; for the old 
 particles are perpetually passing as excrementitious into the cir- 
 culation. When, therefore, life ceases to preserve the place of a 
 particle which it has once assigned, it must arise from a change 
 which the particle has undergone, or else from another complex 
 relation, or antagonist process of the spirit, by which the former 
 relation between it and the organic particle is made to cease: then 
 life, in this minute sphere, being free or unengaged, if such is its 
 disposition (as it commonly is, except under disease), produces a 
 new particle, by which the old one is in effect replaced, the con- 
 tinuous spheres of the spirit compelling a corresponding continuity 
 of the particles composing the organized fabric. These latter 
 particulars will be hereafter more fully considered. 
 
 35. Thus much for the present of the mode in which life is 
 maintained. Many other considerations belong to the same sub- 
 ject: but these, together with, I fear, some other unavoidable repe- 
 titious, will fall under more particular heads. 
 
131 
 
 CHAP. lll.Grawlk. 
 
 1. AS it is a property which belongs to the spirit in 
 the several minute spheres, to withdraw from the material the 
 organic particles which agree with these spheres; so, cteteris 
 paribus, the quantity of organic matter thus withdrawn must de- 
 pend upon the quantity of the spirit, or of those properties of the 
 spirit by which the organic particles are separated. 
 
 2. But the assimilation of the spirit may proceed while the 
 organic substances are wasting. This disposition therefore to 
 aggregate the textures is no necessary condition of the existence 
 of the spirit, unless we suppose that under these circumstances 
 the quantum of the spirit itself is first diminished; a supposition 
 which cannot, without further evidence, be indulged, because it 
 is contrary to what happens in spiritual assimilation, where the 
 original quantity tends to increase, as is exemplified by recovery 
 in cases of asphyxia, in limbs which are almost dead from privation 
 of blood, as by a ligature around an arterial trunk, and the 
 vitality of which is rapidly restored in all their parts as soon as 
 the circulation is established by the collateral channels. 
 
 3. The aggregation of the organic particles will depend, as 
 before shewn, upon the disposition of the spirit; and will proceed, 
 not in a ratio to the quantum of a living principle, but in a ratio 
 to the quantum of the spirit disposed for such a relation with the 
 material. 
 
 4. This spiritual disposition cannot operate alone, but re- 
 quires also the presence of organic particles in the material; by 
 the relation subsisting between these two growth is regulated. 
 
 5. A deficiency of growth can seldom arise from a deficiency 
 of organic particles in the material, except under disease; if the 
 sum of the ingesta might be taken as a criterion of the sum of 
 organic particles in the blood, for people of the greatest bulk 
 often eat the least. 
 
 6. But this criterion is not unexceptionable, for the aptitude 
 of organic particles for aggregation will depend upon the offices 
 of the preparatory organs. But we are, nevertheless, not without 
 some testimony in favour of this point, and it is found in the fact 
 that the blood will continue to support the fabric for a considera- 
 
132 
 
 ble time without the renovation of ingesta, with no greater diminu- 
 tion of bulk than that which may result from frequent or continued 
 excretion. But the waste which succeeds to a long privation of 
 food, or an habitual scantiness of it, shews that the facts alluded 
 to will not sanction a very general or positive conclusion. 
 
 7. We may therefore designate the relation we are consider- 
 ing more correctly, by extending a little the chain of dependences. 
 Thus, the process of growth depends, 1st, on the disposition and 
 quantum of the diffused spirit; and, 2nd, upon the presence of 
 organic particles in the material: both these depend, in different 
 ways, upon preparatory functions, to be spoken of hereafter: but 
 when the effects of the relation take place, they prove the agree- 
 ment of the agents, the tendencies of which we are further to 
 consider. 
 
 8. It is sufficient for our present purpose to insist upon the 
 balance hinted at in the last paragraph, for there are no circum- 
 stances of health or disease which will enable us to decide 
 peremptorily when defective nutrition is attributable to the state 
 of the spirit, or when to deficiency of organic particles in the 
 material; thus, leanness might succeed to disorder of the abdomi- 
 nal viscera, or to continued fever of the low kind, while the usual 
 quantity of food is taken: shall we say that under this state the 
 defective nutrition arises in consequence of a disorder of the 
 stomach, &c. which impedes its function of preparing organic 
 particles for aggregation? We can scarcely affirm this, in the first 
 case, because the state of the diffused spirit is liable at all times, 
 directly or indirectly, to participate in its apparently local changes; 
 and in the second case, the same is to be observed of the state of 
 the preparatory organs in respect to a febrile diathesis. Owing 
 therefore to this reciprocation, we must be content to reason upon 
 the facts we have, rather than assume those which we desire. 
 
 9. We are then justified in assigning only thus much as a 
 basis of this relation, namely, that growth or increase requires the 
 concurrence of an adequate quantum both of the disposed spirit 
 and of the organic particles; and that decrease, or the reverse of 
 growth, might result from defect of either.* 
 
 10. The processes of growth are continued from the exis- 
 tence of the fecundated ovum to the period of adult age. Growth, 
 especially in the uterine stage, is not a mere increase of bulk; but 
 many new parts are formed and many conversions occur in those 
 already produced. The examples of the former are found in the 
 formation of organs and structures, of which in the ovum no simili- 
 tude could be detected; and the composition of which could 
 neither be discovered in the primitive radicle, nor in the nutritious 
 fluid which assists its development; the examples of the latter 
 are found by a comparison of the adult fabric with the state of 
 
 * I am sufficiently aware of a function of the absorbents which relates to 
 the same end ; but this will be subsequently spoken ef. 
 
133 
 
 organization in the different stages of foetal growth, as jelly with 
 cartilage, cartilage with bone, membrane with bone, &c. These 
 conversions have been already considered, and they have been 
 attributed to a progressive causation in the spirit, by which the pro- 
 perties which compose it are variously wrought into action at diffe- 
 rent times. 
 
 11. But the accumulation of similar substances, or increase, 
 is our present topic. Now as this process is preceded by an increase 
 both of the particles in the material, and of the aggregating pro- 
 perties of the spirit, it is necessary that we should inquire how these 
 take place. 
 
 12. In order to produce an excess of organic particles, it is 
 required that the blood should contain more than are necessary to 
 supply the waste of organic particles, which is supposed to be unre- 
 mitting, the terms of which will be spoken of hereafter; and on the 
 part of the spirit, it requires that the blood should contain more of 
 its elements than are sufficient to maintain its present sum: the 
 terms of this also will be spoken of under the functions of the pre- 
 paratory organs. But something more is required on the part of the 
 spirit. By what law of assimilation is the sum of the spirit regulated? 
 
 13. This question suggests the following deduction, viz. that 
 the tendency of the spirit, at least during the periods of growth, is 
 to unite a greater sum of its elements in the material than its own 
 original sum. 
 
 14. The manner in which this is done is as follows: a fluid, 
 containing the elements, passes in the way of circulation the several 
 minute spheres of the spirit; as much of the elements as is submitted 
 to the operation of life, by its agency becomes life. Thus, if the 
 quantum of the organic spirit in the material is greater than that 
 which is necessary to support the quantum of that which actually 
 lives, then the latter will be increased. 
 
 15. But this point is one the difficulties of which can be ex- 
 plained only by recurring to our preliminary doctrines on causation. 
 First, to state the difficulty: the argument supposes the living 
 spirit to be a lesser sum of its identity than that with which it is 
 related in the elementary state; in what waj is the lesser capable of 
 affecting (as in this instance it must do) the whole of the greater 
 quantity? * 
 
 16. This is a question which has been already ansj^red gene- 
 rally, when considering the laws of proportion. To apply these 
 laws to this particular instance: the relation of the living spirit is 
 with its own sum of the elements, and the process arising out of the 
 relation is of that kind which has been before designated " simple 
 increase by affinity." The living spirit is related with its own sura 
 of that in the elementary state; the operation of the former on the 
 latter is to separate it from its elementary combinations: thus the 
 same identity being augmented, is capable of extending the influence 
 which is peculiar to it; and in this way the elements submitted to 
 its agency cease to be the elementary and become the living spirit. 
 
134 
 
 17. But it has been already shewn that the spirit changes its 
 form nearly in a ratio to its elimination from the elementary com- 
 binations. The manner in which this tendency affects the process 
 of assimilation is as follows: the spirit endures a sufficient time to 
 produce, in the way described, a repetition of itself, or, if the ele- 
 ments furnish a larger quantity, to increase itself; in other words, 
 the union of the spiritual elements is more rapid than the extinction, 
 or the change of form, which happens to the living principle. The 
 proofs of this tendency are, 1st, that the sum of the living spirit is 
 increased during growth in the several spheres; 2nd, that if its en- 
 durance were not sufficient for such an operation on the elements, 
 the sum would not only be not augmented, but it would not even 
 be preserved, for extinction then would be synchronous with pro- 
 duction. Having settled thus much with respect to the growth of 
 the spirit, we must now return to the increase of the structures. 
 
 18. One proof of the dependence of the aggregation of the 
 solid particles upon the living principle may be here recapitulated, 
 viz. that this living state having ceased, the textures (and the par- 
 ticles composing them) left to the force of their own constitution, 
 which is both mechanical and chymical, tend, not to aggregation, 
 nor even to the preservation of their present state, but to separate 
 from each other and return to another alliance with elementary 
 combinations. 
 
 19. Thus, then, the living principle has in this respect a double 
 operation upon a material containing many constituents: one is to 
 renew, and increase perhaps, itself; and the other, to renew or in- 
 crease the solid particles which are conjoined with it in the agency 
 of function. The, following conclusions are in consonance with 
 these views. 
 
 1. The quantum of the spirit depends upon the quantum of the 
 elements exposed to it, which are contained in, the blood. 
 
 2. The quantum of the elements depends upon the preparatory 
 functions. 
 
 3. The disposition of the spirit, in regard to the structures, is 
 regulated by latent causes which belong to it. 
 
 4. The quantum of the textures depends, 1st, upon the quantum 
 of the disposed spirit, and, 2nd, upon the quantum of the organic 
 particles in the material. 
 
 5. The quan! um of the organic particles in the material, depends 
 also upon the function of the preparatory organs. 
 
 20. It is almost superfluous to make the application of this 
 reasoning: to save, however, the reader the trouble of doing it for 
 himself, it is as follows: both in embryonic and post-foetal growth 
 the identity of the spirit (or its properties in the several spheres) 
 determines its affinity with the organic particles; the particles laid 
 down in the several seats are according to this affinity; and the 
 mutations of the properties constituting the affinity, are followed by 
 corresponding changes of the structures. These mutations are 
 illustrated in every stage of foetal growth ; and afterwards in all 
 
135 
 
 diseases followed by change of structure. As growth is progressive 
 from the state of the ovum to adult age, so, during the whole of 
 this period, the concurrence of disposition and quantum of the 
 spirit, of spiritual elements, and of organic particles, operates. The 
 ratio of growth is settled by this concurrence, or by the agents 
 severally or collectively engaged in it. The varieties of growth are 
 dependent upon the modification of this concurrence, the share of 
 the absorbent function being included in that which has been 
 designated the " disposition of the spirit," considered in its integrity 
 in regard to the organic particles* 
 
 21. Life, producing the structures by its affinity, &c. holds 
 the same affinity as long as it is preserved ; and life, inhering in 
 those materials which it has aggregated, would without some further 
 process of causation maintain the coherence of the identical par- 
 ticles which it had once laid down. We are now conducted to a 
 more particular consideration of the force of the absorbent Junction. 
 
 22. The question first to be settled is, whether any such waste, 
 any such perpetual absorption, as that which has been current 
 among physiologists, actually takes place 7 ? The admitted proofs of 
 the absorption of the solids are as follow: 1st, the osseous particles 
 being dyed with a colouring matter received in the way of food by 
 an animal will be found, it is said, to have been removed in a certain 
 time after this peculiar food has been discontinued ; 2nd, the bulk 
 of the solids is reduced by fever, and the pressure of morbid growths 
 upon the bones will make them disappear. The first has been con- 
 sidered as furnishing the strongest proof of this perpetual absorption 
 of the impacted solid particles; let us therefore examine it. 
 
 23. As the osseous particles are made red by madder, and as 
 this redness afterwards disappears, it has .been inferred that the 
 osseous particles are also removed, in order to account for the dis- 
 appearance of the redness. This, it must be confessed, is very close 
 reasoning. However, close as it is, it does not appear quite impossi- 
 ble but that the bony particles might remain when the colouring 
 matter has disappeared; for wherever the colouring matter can be 
 deposited, there the fluids which are its medium must penetrate. 
 As long as the animal is fed with madder, the bones will continue 
 to be tinged by it: but when this feeding is discontinued, then the 
 dye is very naturally washed off by the fluids which are constantly 
 permeating the places where they before reached, in order to impart 
 the colouring matter. There is no great difficulty supposed in this 
 process. 
 
 24. But in less than a week after this peculiar feeding is left off 
 the osseous particles will have assumed their natural colour: hence 
 it follows, if the cessation of the colour is produced by the removal 
 of the bony particles, that all the osseous matter existing in the 
 body, at any given time is removed in a few days. Now as the 
 bones are not better supplied with absorbents, or certainly more 
 liable to absorption, than other parts ; it follows, further, that not 
 only all the bones, but the whole mass of solids, are removed and 
 
136 
 
 renewed in the course of a few days : and all this latter process from 
 no olher imputed source than what a man eats and drinks, which is 
 not a little wonderful, considering that it is not the custom for men 
 to eat their own weight of food in five or six days, to say nothing 
 about those considerable portions of it which are known to be 
 excrementitious. 
 
 25. With regard to the second proof, viz. that bones, &c. will 
 disappear under disease, this might be accomplished without any 
 vessels distinct from those which are continuous with the arterial 
 system; for by disease the life of a bone, &c. may be destroyed to 
 a certain extent, and its particles, being comminuted and their union 
 dissolved, may be received into and propagated along vessels whose 
 extremities are patent from a partial destruction. Without insisting 
 upon this matter, as I do not mean to question the existence of 
 absorbent vessels, it is sufficient to remark, that though a part may 
 be absorbed under a state of disease, or though an absorption of 
 the fluids, extravasated into the cavities, may be perpetually going 
 on, we are not therefore to infer that the absorption of the solid 
 particles, those which are impacted and coherent, is unremitting in 
 health. Is there then, I would ask, any proof that the particles now 
 identically constituting the solid fabrics of the body, do not remain 
 or preserve their places as long as life lasts, unless disturbed by pro- 
 cesses of disease? 
 
 2G. To this question it may perhaps be replied, the incessant 
 attrition between the fluids and the solids in the work of circulation 
 roust necessarily produce the decomposition of the solid panicles. 
 If this is necessary, then there is no more to be said about it; but 
 that it is necessary, I am inclined to question on the following 
 grounds: 
 
 27. 1st, That our experience of the effects of attrition, in 
 decomposing solid particles, is only among such as cohere by a com- 
 mon property of matter; whereas, in the animal structures the bond 
 of union is of a different kind, it is by the force of the organic spirit, 
 which we know to be so far efficient, that it resists the chymical 
 tendency to decomposition, which, as it prevails after death in a 
 shorter time than that in which a mechanical agency, as by tire 
 attrition of the fluids, would accomplish the same total waste; we 
 must on this account conceive the spiritual power of aggregation to 
 be equal to counteract the weaker, if it is sufficient to counteract 
 the stronger, tendency. The case is different in disease, where the 
 bond of union is perhaps the first to be affected, and then follows, 
 very naturally, such a change in the cohesion of the textures as is 
 agreeable with the change of the medium which unites them. 
 
 *28. 2nd, That the power of mere attrition is not sufficient to 
 decompose the solid particles seems to be further indicated by the 
 following consideration, viz. during the periods of growth solid par- 
 ticles are actually laid down and cohere with the rest; now these 
 particles existed in that fluid which afterwards performs the attrition 
 upon them. If the affinity which aggregates these particles is 
 
137 
 
 sufficient to fix their place, when they are already in motion, we can 
 scarcely conceive it possible that the fluid which could not keep 
 them against this affinity before they were fixed should be capable 
 of unsettling them against the force of the same affinity when their 
 coherence has been established : on these accounts, and in this view 
 of the subject, I reject also this testimony. Is there any other 
 proof of the unremitting absorption of the solids? 
 
 29. It may be replied, the rapid diminution of bulk by fever, 
 by violent and continued labour, by purgatives, &c. proves the 
 facility with which the solids are removed. Granting these circum- 
 stances to be true, they do not prove even that the waste in these 
 instances is occasioned by a function of the absorbents to that end; 
 for the examples are those of disease, of conditions when the princi- 
 ple of life is under preternatural affection, the influence of which, as 
 may be expected, is expressed in the changes of the textures which 
 are governed by it. 
 
 30. In addition to the previous observations upon this subject, 
 it may be remarked, that if an absorbent is capable of removing a 
 solid particle, that is, if it is capable of overcoming the affinity 
 which maintains its place when it is once established in its place, it 
 appears unaccountable how the same antagonist function of the 
 absorbent did not resist effectually the deposition of the particle. 
 I shall pursue the general indications on growth by applying the 
 doctrines to alternatives. 
 
 31. Now if the two processes of deposition and removal of 
 particles are unremitting, it is obvious that the respective powers 
 must, in regard to the same particles, prevail in succession. From 
 whence it would follow that the relation between the agents is of 
 the following kind. While the organic particles are yet combined 
 in the blood, they are related with the affinity of aggregation ; after 
 their separation from the blood they lose their relation with the last- 
 mentioned affinity, and become subject to an agency of decomposi- 
 tion belonging to the absorbents: as all the functions which have 
 ever been demonstrated or fancied to belong to this system (with 
 the exception of a capillary attraction, if any such exists) take place 
 only as the phenomena of the living state, so a relation of the above 
 supposed kind, between the absorbents and the aggregated particles, 
 is directly or indirectly with the organic spirit of the former. 
 
 32. Still treating the perpetual absorption of the solids as a 
 supposed fact, the organic spirit residing in different structures has 
 properties which appear to be antagonist: but as it is contrary to 
 every analogy that each should in turn prevail, during an opposition 
 of their agencies, and the more especially as the weaker (the absor- 
 bent) prevails after the fixture of the particle, when the common 
 cohesion of matter acts as an auxiliary to the force which before 
 prevailed : as this cannot be supposed in consonance with the nearest 
 analogies (facts being almost entirely wanting), so it is necessary te 
 conclude, that when the absorbent function prevails, the relation of 
 the solid particles with the affinity or spirit of aggregation has 
 
138 
 
 ceased. This conclusion nearly frees our topic from the embarrass^ 
 meut of the alternatives; it almost reduces our question to one con- 
 cerning the continuance of the relation between the vital property 
 of aggregation and the solid particles. 
 
 33. As the spirit assimilates, although its nature is preserved, 
 yet its present quantum is perpetually passing away. The relation 
 of the solid particles being with the nature of the spirit, and with no 
 identical quantum of it, it again suggests itself iu this place that 
 every successive quantum of it is related with its own organic par- 
 ticles; and that therefore aggregation keeps pace with assimilation, 
 which also accounts for the uniformity with which bodies, in a gene- 
 ral way, preserve their bulk or change it slowly; which, in regard to 
 the spirit, has been before spoken of. 
 
 34. If then the new quantum of spirit operates upon particles 
 of its own, that quantum which has passed away has left the organic 
 particles whose place it was its function to determine, without that 
 aggregating affinity which first laid them down, and which if it con- 
 tinued with, would afterwards preserve, them; and consequently 
 these particles can offer no other opposition to an antagonist agent 
 than that which results from the cohesion common to matter. Thus 
 these particles are submitted to the controul of an absorbent 
 function, or they are separated by a chymical process, being deprived 
 of life : one of these appears inevitable ; and as that chymical pro- 
 cess which would take place in the absence of any other means of 
 decomposition is one which is never recognized in a living body, 
 during health, so it seems probable that the agency on the particle, 
 begun by the aggregating spirit, this having ceased, is taken up by 
 that of the absorbent. 
 
 35. That such a cessation of intercourse between the aggre- 
 gating spirit and the organic particle does occur, seems probable 
 from the circumstances 1st, of growth, or regular increase, which 
 proves a relation between the spirit and new organic materials, the 
 operation of which we have no reason to think is suspended during 
 health; and, 2nd, from the rapidity with which the bulk of the 
 body is restored after having been reduced by disease. 
 
 36. This latter view furnishes an indication that the processes 
 of aggregation and absorption are unremitting; and according to 
 this mode they are not incompatible; and it furnishes also an indica- 
 tion that the spirit belonging to the absorbents is the agent by 
 which the waste of particles is accomplished and the material co- 
 hesion overcome. But, as remarked before in the discussion, we 
 have no facts on this subject which amount to proof; and in a for- 
 mer view of a similar question (in the chapter on Assimilation), some 
 objections were cited against the harmony thus exhibited, the force 
 of which was there allowed to prevail. 
 
 37. There are many other points belonging to this relation, 
 such as the period of the continuance of life with the particle it has 
 laid down? It is not improbable but this might be regulated by a 
 relation of the following kind : every organic particle laid down is 
 
139 
 
 in alliance with a certain quantum of the spiritual elements, and 
 life continues to reside in the particle until its spiritual elements 
 have changed their form by assimilation. The other questions 
 hinted at are, how long may the organic particle be preserved by 
 material cohesion, supposing that the affinity of the spirit with it by 
 change of relation has ceased, and supposing no chymical processes 
 of decomposition (which are not recognized) to interfere? Is the 
 separation of the organic particle accomplished wholly by an absor- 
 bent function, or in part, or sometimes by attrition of the fluids, the 
 spiritual affinity having ceased ? or do other properties of the spirit 
 contribute to detach that which is no longer possessed of life? &c. 
 
 38. These considerations are rather intricate ; and unless they 
 are made points of a specific inquiry, in which the recollection 
 would concentrate its efforts upon the facts referring to single par* 
 ticulars, there is no great chance of succeeding with them more 
 minutely, 
 
 39, It is therefore best to say, with the degree of assurance 
 which corresponds with the testimony, that the aggregating and 
 absorbent spirits are antagonist; that the one prevails upon a particle 
 as long as the particle is subjected to it ; that the particle, by change 
 of its relations, being free, is then submitted to the laws and influ- 
 ence of the other, 
 
 40, The growth of the absorbent vessels, as they are called, is 
 in a ratio to that of the other structures. It appears therefore that 
 this structure must be furnished with vital properties of opposite 
 tendencies; that is, while their vital properties are engaged in a pro- 
 cess of destruction, in removing the particles composing the textures, 
 they are at the same time occupied in laying down and accumu- 
 lating (during growth at least) the organic particles which compose 
 themselves. 
 
 41. The only intelligible theory of the manner of absorption 
 is that which supposes these vessels to commence with open mouths 
 at every point (so minutely mixed) of the structures. The relation 
 which enforces the function is between the mouths only of these 
 vessels, and the contiguous organic particles. As absorption (with 
 some equivocal and unimportant exceptions) is a process belonging 
 only to the living subject, it is to be inquired what share the organic 
 spirit has in it ? The alternatives are two : 1st, it may operate on 
 the organic particle to be absorbed mediately; or, 2nd, it may 
 influence it directly. In the former case it may give the vessel an 
 undulating contractile motion, the direction of which being from the 
 origin of the tube to a centre of connection wifh others, the effect 
 would be to produce a vacuum agreeing with this course. This in 
 effect is tantamount to a power of attraction, by which loose par- 
 ticles may be received into and propagated along the absorbent 
 vessel. In the latter case the direct influence of vital properties 
 may be an imitation of the mode, to a certain extent, which is ob- 
 served of the stomach, namely, that its vital properties are capable 
 of decomposing organic particles which have lost their aggregating 
 
140 
 
 aftinify, although they have no influence on those of their own tex- 
 tures, where this affinity is preserved. 
 
 42. That one of the above modes, or both of them, comprise 
 the manner of absorption seems probable from these further con* 
 siderations: 1st, that absorption is peculiar to the living subject ; 
 and, 2nd, that with life none of the secondary agencies cease but 
 those mechanical ones which arise from it, the influence of chymical 
 means or the force of capillary attraction being thus in this process 
 of absorption apparently precluded. To pursue this topic any 
 further not being consistent with a design of mere general indication, I 
 shall return to the considerations more especially belonging to growth. 
 
 43. While the several orders of the structures increase in a 
 regular manner, the arrangement which they preserve during such a, 
 complication of agencies is not the least striking or important cir* 
 cumstance. This arrangement, as well as the election of the ma<- 
 terials, has been assigned in a general way to the influence of the 
 organic spirit. As this much has been established in the articles on 
 the ovum, we shall reserve the more precise examination of the in- 
 fluence which belongs to the vital, chymical, and mechanical depart- 
 ments, as a preliminary to the application of the doctrines, to the 
 structures respectively. 
 
 44. We have seen how the mutations of the nature of the spirit 
 in the several spheres govern the selection of the organic particles ; 
 we have glanced at the laws of spiritual assimilation and endea- 
 voured to connect this process with the formation of the solid 
 fabrics. We are now to consider another act of growth illustrated 
 in the instances of regeneration. 
 
 45, We find that the regenerative powers are liable to con- 
 siderable variety. In the higher order of animals they are exerted 
 comparatively but to a trifling extent; in them the most remarkable 
 specimens are exhibited in the union of divided parts, in the exten- 
 sion of bone, by which an interspace, probably of two, three, or 
 four inches may be filled up, and in the healing of extensive ulcers, 
 &c. We have also illustrations of a faculty of growth, not yet con- 
 sidered in the occurrence of tumors, &c. But among the lower 
 tribes the industry of naturalists has discovered specimens of the 
 following description; if the leg of a lizard be cut off, an entire 
 leg will be re-produced ; if the head of a snail be cut off, the entire 
 bead will be re-produced, furnished with the same organs as the 
 original one, as eyes, mouth, &c. The former fact I have witnessed 
 to a considerable extent; that is, I have seen as much as half the 
 leg of a newt, which was amputated close to the body, re-produced : 
 the whole would most probably have been regenerated, but the 
 animal, from some foreign causes, at this time died. The latter ac- 
 count I take upoiv trust; and, upon the same authority, a class of 
 animals may be adverted to which are said to be propagated by 
 cuttings. In vegetables a power of production, in effect similar, is 
 still more extensively exercised : thus, a tree, in its general character, 
 and in all the complexity of arrangement, resembling the original 
 
141 
 
 one, is produced from a slip. These instances are the facts upon 
 which our considerations ase now to be raised. 
 
 46. The examples may be arranged briefly under the four fol- 
 lowing classes : 1st, instances of increase of parts not wholly removed ; 
 2nd, instances of the regeneration of parts once existing, but now 
 totally removed; 3rd, instances of disproportionate increase of struc- 
 tures which have sustained no loss; 4th, instances of production of 
 structures which did not before exist. The two last relate exclusively 
 to spontaneous disease : in all four there is an alliance in the laws by 
 which they are governed. The two last, for purposes of distinction, 
 may be called examples of formation ; the two first, examples of 
 regeneration. 
 
 47* We will define our specimen of increase of parts not 
 wholly removed to be a fractured bone, from which a portion has 
 been sawed off. The interspace is filled up by a substance, in a 
 general way, resembling the bone from which it is produced. By 
 what processes, according to our preceding notions, is this result 
 accomplished ? As spiritual phenomena precede the deposition of 
 osseous particles, so these phenomena are first to be inquired after. 
 
 48. As we have no means of judging of spiritual identities 
 except by their material connections, so it is necessary in this case 
 to infer, in agreement with a simple extension of structure, a simple 
 increase of the spirit which produces it. The solution so far is 
 easy. The spiritual elements existing in the blood are capable of 
 supporting the quantum of the spirit attained; if the quantum of 
 the spirit is diminished by removing it, along with a portion of a 
 fabric, which it before inhabited, or by abridging its sphere, the 
 elements in the material being capable of supporting the original 
 quantum, will actually attain to it, by the assimilating process, on 
 that which remains; and the same is to be said of the organic par- 
 ticles. Supposing therefore, as in our present example, that there 
 is 1 1 inch in the os brachii to be filled up, there is in the material 
 brought to the repairing extremities an excess of the elements by so 
 much as the support of the lost portion would have required. 
 These then are made life by that process of assimilation which has 
 been before said to result from the relation between the elementary 
 and the living spirit; as this is a mere act of growth, the spirit re- 
 generated by assimilation has the same dispositions, the same affinity 
 with the solid particles as that belonging to the rest of the bone and 
 which originally formed it. Hence (liable indeed to some modifica- 
 tions) the regenerated portion resembles that which was lost. 
 
 49. But although the law just mentioned may be true to a 
 certain extent, yet as a general one it is not in agreement with facts; 
 for if the remaining agents of a structure are capable of assimilating 
 and of re-producing the same extent of structure as was originally 
 maintained by the material with which it was supplied, then should 
 three fourths of a femur, removed, be re-produced, and grow from the 
 remaining fourth ; for the material was adequate to maintain such 
 an extent of bone. Nay, further, in agreement with such rules, a 
 
142 
 
 thigh which is amputated three or four inches below the hip, should 
 be re-produced, bone, muscle, and skin ; for an original or a nucleus 
 of all its parts being left, the whole should be regenerated, if re- 
 production were commensurate with the elements. 
 
 50. Although therefore the preceding account may shew how 
 some of the necessities of growth are supplied, it by no means de- 
 clares the laws by which the whole process, its varieties, &c. are 
 governed. The interspace of a fractured bone may be filled up, 
 yet the bone after amputation does not grow. The interspace 
 occasioned by the removal of a portion of a nerve, or even of an. 
 artery, may be rilled up; a certain extent of breach might be re- 
 paired, but not any extent. Then again, although there might be 
 supernumerary elements in the material, corresponding with the 
 amount of the textures which originally existed, yet it does not fol- 
 low, except from laws not adverted to, that the increase of assimila- 
 tion and of organization should take place where the chasm is to bt 
 Jilled up, rather than in any other place, seeing that the blood 
 which circulates in the vessels of the repairing surfaces is common 
 to all other parts. 
 
 51. These facts suggest the theory that the constitution of the 
 life of respective parts tends to preserve a continuity, that if this 
 continuity ^of life is interrupted by the removal of a portion of 
 - structure in which it resided, then the continuity is restored 
 from the repairing surfaces; that this tendency to the establishment 
 of a continuity results from an affinity between a similar constitu- 
 tion of vital properties, which belong to the same structure, by the 
 force of which, an interrupted principle tends to coalesce; that this 
 affinity has certain limits, or that the affinity does not obtain if the 
 interrupted portions are too distantly removed. Thus, to illustrate 
 this theory by an example, suppose four inches of a nerve to be 
 removed, if the principle residing in the divided extremities is too 
 widely interrupted to admit the operation of the affinity, by which 
 these properties were in the ovum first assembled together, the 
 breach of continuity remains ; but if one inch of a nerve were re- 
 moved, the affinity then operating, the continuity of the principle, 
 or of the organic life of the nerve, would be restored ; and in this 
 process either the two portions or extremities must suffer a diminu- 
 tion of the quantum of the principle, corresponding with its exten- 
 sion, or their assimilation must be increased. The continuity of 
 the principle, however, under these circumstances, being from the 
 power of this affinity restored, the aggregation of a corresponding 
 structure must proceed in consequence in a ratio to the assimilation 
 of the disposed spirit in this seat, and to the organic particles sup- 
 plied, from whence the slow process of growth or regeneration. 
 
 52. There is another remarkable property in this affinity of the 
 life of a structure, viz. that where a chasm is to be repaired, it super- 
 sedes a spiritual constitution of another kind, and destroys its cor* 
 responding organization. Thus, though the interspace of a nerve 
 be closed by the union of surfaces, or by granulation*, yet t-bt 
 
143 
 
 portions of nerve will approximate and finally unite, while the 
 foreign substance which impeded this union i's absorbed in their 
 progress towards this end. It is impossible to develop these 
 mysterious relations: it may however be suggested, either that 
 the precise living principle of the nerve has a power of conversion 
 with respect to that of the intervening texture ; or, that as the 
 former increases by assimilation, it engages, from the superior 
 affinity which may belong to it, as its proper sphere, all the ele- 
 mentary properties which can subserve to assimilation in this seat; 
 thus, of course, compelling the extinction of any other assimilating 
 form of life. This suggestion gives rise to another alternative 
 with respect to the time in which the continuity of the principle 
 of an interrupted nerve (or other structure) is restored, viz. that it 
 is only in a ratio to the increase of the principle from the ex- 
 tremities, and a corresponding or synchronous formation of the 
 structures. 
 
 53. Our plainest inference therefore seems to be, the re- 
 generation of lost parts being limited in its extent; being also 
 subject to much variety, and each view involving some difficulties, 
 uot to say contradictions; that processes occur in growth, which 
 are distinct from mere assimilation and its consequences, or which 
 give additional complexity to this process and these effects. 
 
 54. The subject of organization, or re-production, is one 
 upon which much vanity has been expended. Every one can ex- 
 plain it, and yet no one has even conceived a difficulty belonging 
 to it which would puzzle a mere simpleton. It is amazing how 
 men can flourish, and strut, and talk, and write, pompously and 
 dogmatically, upon subjects about which they know nothing; 
 when at the same time an assumption of knowledge is made the 
 basis of their impudence and importance. But as the world is 
 civil enough to allow men to pass only for what they assume, it is no 
 wonder that those who know the least, should find it necessary to 
 assume the most. Those which are called the doctrines of ad- 
 hesion, re-production, &c. are boasted doctrines; it happens how- 
 ever that they are no doctrines at all, or else the doctrinal parts 
 are of a new and curious kind : union by the first intention, &c. 
 the healing of an ulcer, &c. this is how they are spoken of; a 
 medium of coagulable lymph is thrown out, and vessels shoot into 
 it ; or granulations are thrown out, the ulcer is filled up, and then 
 skins over. I can discover no doctrine here, except it is designated 
 by the words marked in italics, to wit, the throwing of lymph and 
 granulations, and the shooting of vessels; the detail is simply one 
 of sensible effects which are different from doctrines. This detail 
 is short, simple, easily come at, and, above all, for practical uses, 
 highly valuable; but if we would have some doctrines upon the 
 subject, we must consider the throwings and shootings only as short, 
 convenient expressions, and seek deeper for a clue to the explanation. 
 
 55. In conformity with the preceding views (upon which I 
 presume no further than an evidence, at best doubtful, warrants) 
 
144 
 
 the following appears to be the mode of re-production: by a 
 function (or by certain properties) of life a secretion is produced 
 from the surface, or the place whence the new organization com- 
 mences: this secretion is lymph; by assimilation life is increased 
 in this place, and its sphere is extended ; but for the lymph pre- 
 viously effused, life, wanting an alliance with the material, would 
 be dissipated, but the lymph being effused, life as it increases, 
 occupies a determinate sphere, allying itself with matter, which is 
 done by an affinity before mentioned. The life produced is con- 
 formable with that which produces it; thus, the life of a tube 
 occupies, or by progressive change assumes, a tubular sphere (this 
 is settled by relations mentioned in the article on the ovum), and 
 by its tendency, whether as to place or properties, the organic par- 
 ticles which it claims, or separates from the material, are laid 
 down: in this case it may possibly have a double source of the 
 organic particles, as well as of spiritual elements; for we have 
 reason to think that both are possessed, as well by the lymph 
 already effused, as by the blood or circulating fluids, each alike 
 wanting the influence of life for the consummation of a final 
 purpose. 
 
 56. That the lymph is prepared previous to organization, 
 seems to reflect some light upon a former question, viz. whether 
 particles are separated from the blood during assimilation or after- 
 wards 1 The fact just mentioned indicates the latter, which has 
 been before thought the most probable : for if life aggregated par- 
 ticles at the time of assimilation there would be no need of a 
 medium for its reception, seeing that it and the particles might 
 grow together from the surface whence the organization begins. 
 We next come to consider the second class of the instances of 
 regeneration, viz. of parts once existing, but now totally removed. 
 57. We have found but little difficulty in getting a concep- 
 on of some sort of the mode of regeneration in structures but 
 partially destroyed, our notions of growth have helped us nearly 
 to a solution in this case; but by what processes of the agents of 
 growth are parts, wholly destroyed, re-produced, as from a nucleus 
 in a distinct texture? Thus, in the regeneration of a limb, a 
 muscle is begun and developed to its proper extent, or a bone 
 grows in a cylindrical form, and at a certain point osseous growth 
 ceases, and cartilage is produced, and then proceeding on from 
 this texture, or by mediate connections, bone is again generated, 
 as in the entire formation of a new limb; or, in the case of a snail 
 which has suffered decollation, from the trunk proceeds the neck, 
 the head formed from the neck: in the progress of organization, 
 the mouth, the lips, &c. are developed; or, in vegetable re-pro- 
 duction, a slip puts forth shoots, these at one period smooth and 
 similar throughout, at anotherat certain places forming branches,&c. 
 58. As the regeneration before described refers to the pro- 
 duction of resemblances, so its processes of vital properties are 
 chiefly those of assimilation; as in the latter cases the production 
 
 a * 
 
 ,i 
 
145 
 
 is that of dissimilars, so this work is conducted by laws of consti- 
 tution. We have hitherto considered the spiritual changes to 
 precede and govern those of the organic materials ; the former 
 therefore are to be considered first. 
 
 59. The identity of the spirit is determined by its properties : 
 some of these properties are latent and others active. The pro- 
 perties composing the spirit in any sphere are liable to spontaneous 
 change, or that which has been before designated in this depart- 
 ment progressive causation. It is by the occurrence of these 
 acts that properties before latent are often made manifest, while 
 those before existing are no longer recognized by their effects. 
 This law is illustrated in the instances of conversion, which are 
 endless. Now these latent properties produce that which is called 
 pre-disposition : the conversion of latent into active properties 
 happens in the same way as all other changes, that is, there exist 
 in this case many related agents, making collectively the entire 
 spirit. These agents, not agreeing in a permanent combination, 
 are liable to become variously combined and modified at various 
 times, producing at these times varieties in the phenomena which 
 result from them: thus the testes at the period of puberty begin 
 to secrete; thus cartilage is converted into bone, or an attack of 
 gout occurs, or an artery is ossified, or a membrane, as the dura 
 mater, is converted into bone, &c.; thus also, and more allied 
 with our topic, a fractured patella produces ligament. These things 
 arise from latent causes, furnishing pre-disposilion, and becoming 
 active from change of relation between constituents, determined 
 by the force of causes. So much by way of recapitulation. 
 
 60. The difficulty then in regard to our present question is 
 not to conceive why dissimilars are produced from established 
 textures, but by what law these dissimilars should assume the form 
 of parts which are removed? We have no hesitation in referring 
 the former to an act of constitution among the spiritual properties, 
 which will be sufficiently intelligible from what has been already 
 said about it: but the latter we must trace more minutely. 
 
 61. The difference in these three cases of growth is this: 
 the first is simple increase by assimilation, the second is increase 
 accompanied with change, the third is increase accompanied with 
 change, tending to produce the resemblances of parts totally re- 
 moved. Now these three follow one law of causation, that is, the 
 processes are according to the relations between the spiritual pro- 
 perties among themselves and the allied materials. As these 
 agents determine the process, so the consequence is that which it 
 is determined by properties possessed already, and by no new 
 accessions. 
 
 62. Hence it appears to follow, as the spiritual properties of 
 an existing texture are capable of forming a different texture 
 which is removed, that the spirit possesses properties in its diffe- 
 rent seats which are common to all or to many, or, relying on our 
 present data, to some others. From whence it will follow, further, 
 x 
 
146 
 
 that the tendency of the internal causation of the spirit is, work- 
 ing with common properties, to produce diffe rent forms of it in 
 different spheres, by which changes of forms, properties, in regard 
 to the textures, become either active or latent. 
 
 63. Thus, if a lost muscle were regenerated, the processes 
 from the surfaces whence it proceeds would be of the following 
 kind: properties capable of forming the muscle are possessed in 
 a latent form by surfaces from whence it grows ; by the relation 
 between properties, life is increased by assimilation from the 
 material in the way described: but the life thus increased, instead 
 of being identical with that inhabiting the textures which originate 
 the new growth, is according to that modification of the spirit 
 which, from the force of internal relations, it has in this place 
 assumed. The production will depend upon these internal rela- 
 tions, and by them, according to preceding data, it will be bone, 
 muscle, ligament, lips, eyes, or any thing else. It is however 
 proper to observe, that where the regenerative processes take 
 place to the greatest extent, as in the lowest tribes of animals, 
 and in vegetables, the new production often differs but very little 
 in the character of its organization from that whence it proceeded, 
 or indeed from the entire mass. 
 
 64. In the examples of morbid growths, as of tumors, con- 
 versions of structures, &c. a similar proceeding is observed: the 
 organic spirit assumes a change in its properties, by this change 
 the condition of the textures is affected; perhaps the seat of the 
 disease might be a small congeries of capillary tubes, from them 
 processes of growth originate, and the character of this growth is 
 determined by the disposition of the spirit which inheres with it. 
 Thus we might have a small sarcoma with no tendency to increase, 
 or .the spiritual properties may dispose it to a rapid increase; 
 having attained a certain bulk, a new spirit may appear to actuate 
 the mass; from a tendency to regular increase, partial acts of de- 
 struction may take place, it may slough, it may suppurate, it 
 may throw out a fungus, its vessels might give way, &c. 
 
 65. Now with respect to this change which has taken place 
 in the tumor, the common phrase is, it has assumed a new action; 
 and if on a sudden it mortified, would this be a new action too? 
 Let, however, the term pass, as it is one of easy and established 
 use. For my own part, a word will not in such cases content me. 
 But, according to this term, the fate of the tumor is allowed to 
 be determined by a government of a vital kind. What then is the 
 law by which this new action (I have a great antipathy to the 
 *word) takes place? Previous to its occurrence, the tumor was 
 tranquil, and it maintained the cohesion of its structure; this 
 must be imputed to the condition of the spirit: the structure is 
 afterwards modified or destroyed; this also must be attributed to 
 the condition of the spirit. 
 
 66. Now the tumor being at the time of change, as before, 
 supplied with blood made by unaffected organs, the change can 
 
147 
 
 arise only from that tendency to progressive causation between 
 the spiritual properties, which when the change is related with, 
 is followed by corresponding changes of the structures. 
 
 67. If, without making any reference to the spiritual agency, 
 we should say that one modification of the structure succeeds to 
 another, until some final state was accomplished, we should then 
 express no more than we see; but our inferences teach us to 
 make this reference. We say in the gross, the tumor has a cer- 
 tain predisposition; analytically, we say the spirit which precedes 
 and governs the textures, has a certain predisposition; pursuing 
 the analysis further, we say this predisposition is constituted by 
 latent causes, by spiritual properties, possessed, but, in respect of 
 their relation with the structures, informal. 
 
 
148 
 
 CHAP. IV. Animal Heat. 
 
 1. ANIMAL heat is distinguished from every other 
 example of heat by the circumstance, that it is maintained only 
 during the living state. 
 
 2. The term animal heat is perhaps not altogether unob- 
 jectionable: because we find that the living structures possess an 
 elevation of temperature, where the characteristics of animal life, 
 namely, sense and voluntary motion, are wanting; while, on the 
 other hand, the generation of this heat does not proceed after the 
 extinction of the organic life. The term vital heat would perhaps 
 be therefore more correct; but as this is a matter of very little 
 consequence, I shall not affect peculiarity by insisting upon the 
 distinction. 
 
 3. Animal heat being produced only so long as life continues, 
 and the chymical and mechanical agents in the structure, shewing 
 of themselves no disposition or ability to produce it ; we must infer, 
 from these facts, that that principle of life, we may according to 
 the last paragraph recur to our old phrase, and say, that organic 
 spirit hitherto spoken of, is in some way or other concerned in the 
 process of generating animal heat; and that heat so far acknow- 
 ledges a dependence upon this spirit. 
 
 4. The formation of animal heat results either from the 
 function of some particular organ or organs; or the process is a 
 diffused one, as universal in the structures as the existence of the 
 spirit itself: the settlement of this point is one of importance. 
 
 5. Now that heat is not produced especially or exclusively in 
 any one place, and from thence diffused all over the body, ap- 
 pears to be satisfactorily proved by the following circumstances: 
 1st, the medium of such diffusion must be either by the continuity 
 of the solid structures, either single or mixed, or by the circula- 
 tion of the blood. In either case, supposing, in illustration of the 
 first, that the central organs of the nerves are the source of Jieat, 
 and their branches the medium of its diffusion; or, in illustration 
 of the second case, that the lungs are the* source of heat, which is 
 in them imparted to the blood, and by it to the textures; I say, in, 
 either case, the temperature of the place, or source, where heat is 
 generated, should be considerably higher than in the places of its 
 remotest distribution. Thus, supposing heat to be generated only 
 in the lungs, these organs bear perhaps in regard to the whole. 
 
149 
 
 the proportion of one to forty: now the perpetual tendency of 
 thirty-nine parts in forty is to become cold; the blood therefore in 
 the lungs should be at least many degrees hotter than that which 
 has reached the extremities, and which has imparted heat in its 
 course to structures so much more considerable than the organs 
 by which the heat was produced: and the same is to be said on 
 the supposition of any other source of heat; whereas there is in 
 fact no regular and assignable difference in the temperature of 
 blood at different places.* This fact seems a sufficient refutation 
 of a local source of caloric, while, if the fact were otherwise, it 
 would prove only a variety of temperature at different places; but 
 not that the seat of the highest temperature was the source of 
 caloric to all the rest; unless it were first shewn that the increase 
 of temperature in this seat was adequate to such a purpose, and 
 unless there was no reason to suppose that the faculty of producing 
 heat was elsewhere possessed. 
 
 6 That heat is not conferred upon the structures by any 
 medium, as from a source, seems also to follow from the irregulari- 
 ties of temperature of different surfaces, either spontaneous or 
 producible by artificial means: thus I have known the temperature 
 of a paralytic arm generally, I believe always, lower than that of 
 the sound arm in the same subject; thus, aho, a division of nerves 
 will reduce the temperature of a limb, perhaps permanently, or at 
 least until re-union of the nerves has taken place, or their function 
 is otherwise supplied. The same consequence has succeeded to 
 the ligature on the arterial trunk of an extremity. Both these 
 instances conjoined prove that heat has a diffused, and not a 
 precise or exclusive, source; and that the degree of it is liable to 
 be affected by an agency upon parts which are intimately con- 
 nected with the vitality of the structures. Conceding then that 
 heat is formed in no single organ, but is a function common to all 
 structures (or some of their components), it is next to be inquired, 
 by what process this evolution of heat takes place, or what rela- 
 tions are engaged in the process] 
 
 7. In speaking of the fecundated ovum, we have seen that 
 the ovum of viviparous animals commences immediately after 
 fecundation, the processes which establish fetal existence; while 
 in oviparous animals the ovum may wait a considerable time after 
 fecundation, and the same processes are never commenced in it 
 until it has acquired a temperature which it afterwards maintains. 
 
 8. It appears therefore that heat is essential to. life, that the 
 ovum of viviparous animals, suffering no interval between fecun- 
 dation and the acquirement of heat, immediately begins the 
 characteristic acts oj lijc; while the ovum of birds, &c. do not 
 begin these acts until their life is adapted for the purpose by ex- 
 
 * It is said that the temperature of blood is raised two decrees by the 
 conversion of venous into arterial blood: this increase of temperature, how- 
 ever, if true, may be easily shewn to be inadequate. 
 
150 
 
 ternal warmth. Hence it is to be inferred, that the identity of a 
 living principle, at least among the animals which afterwards dis- 
 play the possession of vital heat, is not perfected but by the in- 
 fluence of heat.* 
 
 9. As processes of life are commenced by the influence of 
 heat, as heat and life are invariable accompaniments, the one not 
 ceasing as long as the other continues; but more especially as the 
 vitality of the egg is no more than a predisposition to the living 
 state, and as heat perfects it in this state and afterwards remains 
 with it; we must infer from these facts, as well by general consent in 
 matters of reasoning as in consonance with the laws of causation, 
 that heat is an essential property belonging to the common living 
 principle; that heat unites with the other properties of life, which, 
 in the egg, were before only predisponent, and that the identity 
 of life is thus conjointly produced. 
 
 10. It has been shewn that life is so related with its elements 
 in the material, as to be able by uniting them to produce its own 
 resemblance, which has been called assimilation. Now if life has 
 an assimilative relation with the elements, heat being a part of life, 
 is also maintained in the same way; that original heat which was 
 Conferred on, or belonged to, the life of the ovum, is that which, 
 continuing with it and growing with it, afterwards maintains, in 
 conjunction with it, the phenomena of animal heat; no circum- 
 stances of which are not explicable by a reference to this union in 
 its regular or modified conditions. 
 
 11. That heat, like the other properties of life, is maintained 
 by assimilation, is shewn by the same proofs as those which esta- 
 blish this mode, as belonging to the general principle. The proofs 
 may be enumerated as follows: 1st, the chymical and mechanical 
 parts of an animal, life being extinct, become rapidly cold ; they 
 therefore have no relation among their agents, which will produce 
 heat; 2nd, life exempt from heat (as in the ovum, &c.) cannot 
 produce heat, though subjected to the same substances in other 
 respects; 3rd, heat united to the living principle produces heat. 
 The first proves that the composition of the structures cannot 
 produce heat; the second, that the other properties of life cannot 
 produce it; the third, that it is instrumental to its own production. 
 This seems tolerably clear. 
 
 12. But the relation of the heat forming a part of the spirit, 
 is not simply with its own elements, for heat conferred artificially 
 upon dead textures, although the same elements be exposed to it, 
 will not be produced, any more than life will be produced without 
 heat. 
 
 13. Hence it follows, that the relation between heat and the 
 other properties of life is this, namely, there is an affinity between 
 
 * That certain forms of life operate without heat, or but an inconsiderable 
 decree of it, as among cold-blooded animals, and vegetables, proves only that 
 life, existing in different forma, has its peculiar efficacy, dependencies, and 
 relations, respectively in each. 
 
151 
 
 them, by which they originally unite, to form the identical living 
 principle; this affinity afterwards preserves their union. In the 
 material which is subjected to the agency of life are the uncoin- 
 bined elements of life, otherwise said to be latent: there are also 
 the elements of heat which are latent. Now the affinity of life with 
 the materials is with its resemblance or its constituents ; heat is in- 
 cluded in this affinity, and is assimilated as a part of an identity, 
 the force of which is to produce itself, by an operation upon a 
 material which contains its elements. On this point I have scarcely 
 asserted more than the order of occurrence, which is almost sub- 
 jected to our observation. 
 
 14. There is a close resemblance between the manner in which 
 life and the highest degrees of heat are maintained: in both the 
 process is one of assimilation, ind consists respectively in the union 
 of its elements. Ignition does not take place from the contact or 
 mutual exposure of that which contains the elements of fire. Thus, 
 wood or coals existing in oxygen would never inflame; but fire 
 assimilates itself from both, and, like life, is perpetuated by the 
 union of its elements, before separately existing, or otherwise 
 combined. 
 
 15. Fire has another agreement with life, namely, that in each 
 the elements are combined from the two sources of earth and air. 
 
 16. But with respect to the generation of animal heat there is 
 a difference between this process and the ordinary one of its ignition. 
 In general, the elements are assimilated only by that which is 
 actually ignited: a heated substance of 98 degrees is not capable of 
 assimilation. But this animal process can scarcely be expected to 
 be of the common kind, when it can take place only by so peculiar 
 an associate as that of a vital principle. 
 
 17. That elements of this heat are contained in the blood can- 
 not be doubted, because we find that the blood is inflammable, and 
 also, that by the blood the animal heat is supported; not by blood 
 itself simply, nor by the other properties of life as related with 
 blood, nor by heat, as related either simply with blood, or the other 
 properties of life, but by a relation which involves them all. 
 
 18. To say precisely the share which each of these has, or to 
 trace the mode which the relation observes, more minutely, would 
 be at least difficult, or perhaps, without a progressive refinement 
 upon these views, impossible. So much however has been said as 
 appears to be sanctioned by facts. 
 
 19. As animal heat cannot be produced by the other spiritual 
 properties, heat being absent, so heat precedes and governs its own 
 production, and is not, as has been supposed by the chymists, a mere 
 effect of other agents, a product altogether independent of itself.* 
 
 * Spontaneous ignition sometimes occurs: this is a point of analogy with 
 the origin of life by constitution; as the ordinary instances of ignition are 
 analogous with the perpetHation of life by derivation. In the animalization 
 of crnstaceous ova, the origin of life by constitution, or its creation, is partially 
 repeated. 
 
152 
 
 Indeed the subject of animal heat, as is well known, never has been 
 and never can be explained by chymical analogies; for the agents of 
 chymistry, though necessary, are rather of a secondary and subordi- 
 nate kind. Not but that chymical changes and processes must 
 happen in the performance of the function we are considering, but 
 the true ones remain to be investigated, and require that the more 
 essential agencies should be taken into the account. Blood, in 
 parting with the principles which are required or compelled by the 
 other properties of life, cannot in this way yield heat ; or extraneous 
 heat would be unnecessary to begin processes of life, in a body 
 which possesses within itself a capacity to produce it. 
 
 20. There is also another point of analogy between the 
 functions of calorification in animals and vital assimilation: they are 
 each supportable only by arterial blood. Here again we are re- 
 minded of the elementary sources: blood made from food, food 
 from earth; arterial blood, made by food and air; arterial blood 
 supporting life and heat, or we may say only life, as heat is an 
 essential or constituent part of the common forms of life; arterial 
 blood, having supported life and heat, has lost its elements, or at 
 least those from air, and becoming venous blood, requires a new 
 constitution to become again the supporter of the organic spirit. 
 Some further considerations connected with this topic will fall under 
 the titles of " preparatory functions, blood, &c." What is here 
 said will not be properly estimated unless it is connected with every 
 peculiar view of relations before expressed. 
 
153 
 
 CHAP. V. 
 
 General Relations of Vital, Chymical, and Mechanical Agenciet. 
 
 1. THE relation of the spirit with the chymical sub- 
 stances has been hitherto described as one of affinity. That it is 
 not one of constitution, or that the organic chyraicals are not made 
 by union with spiritual properties in the way of constitution, is 
 proved, 1st, by the fact that the spirit preserves its own identity, and 
 is not lost in combination; and, 2nd, because the structures, &c. re- 
 main, when the identity of the spirit has ceased ; which would not 
 be the case, if this precise identity were an essential Constituent. 
 
 2. The chymical alliance with the spirit begins in the ovum : 
 this substance is selected by the properties of the spirit which reside 
 in it, and but for the influence of the properties by which it was 
 formed it would not be maintained. Hence, a form of life, which is 
 only a predisposition to that which exhibits the living phenomena, 
 is capable of maintaining the coherence of organic particles; and it 
 is this property which establishes its character as a form of life. 
 
 3. The chymicals with which the spirit was from the beginning 
 allied, or rather the repetitions of similitudes, perpetuating the rela^ 
 tion, concur as long as life lasts to preserve the liviog principle, by 
 assimilation, &c. 
 
 4. The relation of the spirit with the mechanical department 
 in all the processes of formation and growth is mediate, that is, the 
 alliance of the spirit is with substances composed of certain chymi- 
 cal properties; these properties form the material substances/ and 
 as the relation of the spirit is with these precise propertied, so those 
 precise substances which they compose are the result of its agency. 
 The proof of this is the necessity of precise chymical materials which 
 would not exist if the spirit were directly related with properties 
 common to all matter. 
 
 5. Foreign chymical properties influence the spirit both 
 directly and indirectly* This, however, is rather inferred as proba- 
 ble modes of its influence than proved by any example, because we 
 have not the means of discriminating the instances, supposing there 
 to be many of both kinds. It is therefore inferred, as the spirit is 
 related with the agents of cbymistry, that it might become affected 
 v 
 
154 
 
 by external or foreign ones of the same class 1st, by a direct rela- 
 tion which the spirit might have with these foreign properties; and, 
 2nd, by a relation which the foreign have with the natural chymical 
 properties; an established relation between these latter and the 
 spirit already existing, the spirit may be modified or influenced by 
 the disturbance of the chymical agents which help to form this 
 established relation. 
 
 6. As the chymicals are selected by the properties of the 
 spirit, and as in the living body no chymical process (unless one to 
 be mentioned hereafter in the lungs, &c. be an exception) takes 
 place which is not under the government and direction of the spirit, 
 so it follows that no primitive spontaneous change can take place in 
 the chymicals, but that such change must happen by a previous one 
 of the spirit. Thus, the ehymical nature of the urine may be very 
 different at various times; it may sometimes contain substances of 
 which at others it is entirely destitute, or the proportions of sub- 
 stances usually belonging to it may be variously altered. Thus, 
 also, calcareous depositions may be formed in the coats of the 
 arteries, or about joints, in parts which have been the seat of gout; 
 thus, also, exostoses may be produced, or mucus secreted, or mat- 
 ter secreted, or gelatine secreted: all these may exemplify chymieal 
 changes, but the chymical change in either is not primitive; for, 
 withdraw the influence of the spirit, let this principle be extinct, 
 and they none of them take place. Whatever may be the disposi- 
 tion of the chymicals at the time of its extinction, they are from 
 that period inactive : they form neither urine, nor chalk-stones, nor 
 bone, nor mucus, nor pus, nor gelatine; but they agree in one com- 
 mon tendency, to separate from each other by putrefaction. Hence 
 they are held in a forced allegiance, and the spirit is the bond of 
 their union. And as the identity of the spirit produces and main- 
 tains a corresponding identity among the chymicals, so the devia- 
 tions of the one are productive of corresponding changes in the other. 
 
 7. If there are any exceptions to the truth of this remark, as 
 hinted above, they will be found in the phenomena of the prepara- 
 tory orgaus > where substances foreign to the animal economy are 
 liable to be received, and from the circumstance of their having no 
 relation with the spirit by which they are placed under its eontroul, 
 run into processes agreeing with the relations subsisting between 
 themselves, and by the results of these processes may possibly find 
 a relation with the spirit, so as to place it in the situation only of a 
 re-agent. 
 
 8. But the agents of chymistry may be primitive in affection, 
 when they are introduced from without; in this case these agents 
 are foreign, and their phenomena are not to be enumerated under 
 the title of spontaneous change. 
 
 9. Consistently with the laws of causation, there, might be 
 predisposition to change in the chymical constituents, and this pre- 
 disposition might be excited under the continuance of an unchanged 
 state of the spirit. But, io this instance, the change in the chymicate 
 
155 
 
 is not primitive, for the predisposition which leads to the change 
 is preceded and produced by one of the spirit. 
 
 10. The spirit has also the additional indirect relation with 
 the chemical through the mechanical department. This relation is 
 exemplified in all cases in which the natural relation between the 
 spirit and the mechanicals is disturbed; and the effects of which are 
 afterwards communicated to the chymical connections. In this way 
 it is exemplified in wounds, and in all mechanical injuries in conse- 
 quence of which the spirit is affected, and then modifies the struc- 
 tures or the secretions, 
 
 11. The relation between the spiritual and mechanical, as be- 
 fore remarked, cannot be distinguished from that between the 
 former and the chymical department, in processes of growth; 
 because the particles which compose the structures are constituted 
 by chymical properties. 
 
 12. But this relation, namely, that between the spirit and the 
 mechanicals, may be considered according to the folio wing division: 
 1st, the spirit with the material particles, as a power by which their 
 place is assigned; 2nd, as a power by which they are moved; 3rd, 
 as the spirit is influenced by their place; 4th, as the spirit is influ- 
 enced by their motion. These four divisions include the modes by 
 which the properties of matter are acted upon and operate in the 
 constitution of animal bodies. 
 
 13. 1. The first has been already sufficiently remarked upon : 
 the chymical constitution of the particles interfere to prevent a 
 precise distinction. 
 
 14. 2. The power which the spirit possesses of giving motion 
 to the material parts is copiously exemplified. This power is exerted 
 in the motion of the solids belonging both to the organic and the 
 animal departments, and in the motions of the fluids. The relation 
 of the spirit in producing motion is with the structures, by which 
 latter, motion is communicated to the fluids; in some instances 
 the affinity of certain fluids with the spirit may be a cause of their 
 motion, but to what extent is not ascertained. The properties of 
 the spirit have their seat in the minutest spheres of the textures; 
 their alliance is not simply with particles possessing the common 
 properties of matter, but those precisely formed, as we find them, 
 by chymical constituents. It is therefore probable that the relation 
 of the spirit with the textures, by which the motions of the latter 
 are occasioned, is not directly with the common properties of mat- 
 ter, but through the medium of peculiar constituents belonging to 
 the matter, and which, as they are found united with chymical 
 materials, can scarcely be separated from this class. 
 
 15. We find that mechanical agents, which produce sensible 
 effects upon the principle of life, belonging to either system, produce 
 these effects through the medium of the established textures. This 
 relation between organic and foreign matter is one which requires 
 contact; and by contact the influence of foreign matter is comprised 
 in the modifications of pressure, which pressure, so far as the 
 
156 
 
 mechanical structures are concerned, is to produce merely a change 
 of place, some modification of continuity. 
 
 16. In order to be satisfied of the truth of this principle, we 
 have only to consider what would be the effects of mechanical 
 agencies upon the textures, whether internal or external, under a 
 privation of the spirit which is allied with them. A needle thrust 
 into the flesh during life produces pain; life extinct, its effect upon 
 the textures is to displace coherent particles: a piece of glass buried 
 in a living muscle produces pain and all the phenomena of inflam- 
 mation; in a dead muscle, it merely separates fibres which were 
 before attached : a stone in the living bladder occasions excruciating 
 and complicated disease; in the dead bladder, the stone rests upoi 
 its coats, producing a pressure according to its weight, modified by 
 its shape and asperities. 
 
 17. If we would understand how the spiritual properties are 
 affected by these mechanical agencies, we must ascertain what is the 
 nature of the relation between these properties aad the place of the 
 organic particles. 
 
 18, Now it is obvious that an organic particle, being merely 
 the seaj: of a principle of life, can in this relation impart no influence 
 to the principle which it contains ; by which is further meant that 
 without the intervention of some other agency, provided the particle 
 continues to retain its portion of the principle, the latter cannot be 
 affected by any change which the former might undergo. Thus, to 
 return to one of our examples, if a needle should be thrust into the 
 flesh, its effect upon the mechanism is to separate particles which 
 before cohered \ the particles separated being still possessed of their 
 vital properties, possess them in one place instead of another, and In 
 this simple mechanical relation no further change can happen in 
 them. But in the living state further changes do happen in them: 
 pain, inflammation, &c. result in structures where these did not 
 before exist. But, as just shewn, these phenomena cannot arise 
 from the mere mechanical relation; it is then to be investigated by 
 what laws they do occur. 
 
 lp f 4 s ^e solid particles are the respective seats of cor- 
 responding spheres of the spirit, so by a change in the relative 
 situation of the particles a similar change is produced in the relative 
 minute spheres pf the spirit. 
 
 20. If it cap be shewn that the spirit in the minutest spheres 
 is essentially related with contiguous or distant spheres of the spirit, 
 we shall readily conceive how the condition of the spirit njaj be 
 locally disturbed by an operation upon the textures. 
 
 21. The truth of this spiritual relation is confirmed by the 
 following facts: 1st, the function of a nerve, for example, is modi- 
 fied or lost by mechanical injury, or mechanical interposition, 
 proving that a faculty residing in a particular seat is not perfected 
 in that seat, but has a remoter dependence ; 2nd, the influence of a 
 mechanical injury is not confined to tlip beat of such injury, but is 
 participated in both by contiguous and distant spheres of the spirit ; 
 
157 
 
 3rd, that the life residing in a minute sphere is related even to a 
 limited or circumstantial dependence with that of adjoining spheres, 
 is also proved by the circumstance that although the mechanic ar- 
 rangement of the textures might be preserved, and its chymical 
 qualities also either preserved or conferred by imitation, yet the life 
 of this piece of structure will immediately become extinct on its 
 being removed from its connexions. Indeed that the properties of 
 life existing in any seat are perfected by and related variously with 
 the vital properties of other seats, is perfectly allowed, and the 
 modes of the relation will be hereafter considered. 
 
 22. This truth being established, viz. that the relation between 
 vital properties is according to their states in respective spheres, it 
 follows that the spheres of properties cannot undergo a change 
 without a corresponding derangement of the phenomena which 
 result from their natural relation. 
 
 23. As these phenomena, in the natural condition of the 
 structures and their alliances, constitute the state of health, so 
 those which result from an unnatural condition, whether primitively 
 of the mechanical, of the chymical, or of the spiritual agents, com- 
 prise the state of disease. 
 
 24. But although the relation just mentioned should be freely 
 conceded, it will be inquired whether the influence of external 
 mechanical agents upon the spirit may not be of the direct kind? 
 To this question it can only be replied, that it disagrees with our 
 nearest analogies to suppose that mechanical bodies can affect 
 spiritual properties in the way of constitution, that is, by imparting 
 constituents, or in any other way than by producing indirectly new 
 relations, or destroying those which are established. 
 
 25. The examples of our nearest analogies may be drawn from 
 among invisible flqids (or those even of a grosser kind). Thus, a 
 solid body placed in air or water has no quality to change the fluid 
 which surrounds it : it is only an interposition which interrupts the 
 continuity of the medium it exists in. The same thing happens 
 with any of the gases, the nature of which is not changed by any 
 mechanical agency, though it may be possible that it should be 
 changed by the chymical properties existing in the mechanical agent, 
 provided there is a relation subsisting between them. 
 
 26. But the case is different where the relation of mechanical 
 agents is with others of the same kind, with which latter, properties 
 reside whose natural identity is dependent upon a state of continuity 
 and a free communication with related properties. In this case 
 (which is the case we are considering) an external mechanical agent 
 operates in the following order : the foreign mechanical, related with 
 its resemblance in the textures, produces a corresponding effect, 
 which is comprised in change of place, either simply affecting the 
 line, or the existence, of continuity ; the particles of the textures, 
 thus Displaced, containing chymical properties ; , these following the 
 fate of the substances in which they are embodied; the chymical 
 properties having in alliance with them spiritual ones, these latte? 
 
158 
 
 holding a relation liable to catenate changes with contiguous or dis- 
 tant ones of the same kind ; and being in this manner united with 
 the textures, participate, according to their own relations, in the 
 changes which the textures might be made to undergo. 
 
 27. 4th, The motions of the mechanical alliances can affect 
 the spirit only in the way of re-agency; and the supposed instances 
 of this are rather of a doubtful nature. Thus it is one of the effects 
 of that state of the spirit constituting fever, to accelerate the move- 
 ments of the heart, and to produce a rapid circulation. The fluids, 
 in this case, having an increased impetus, may pass into channels 
 which before received those only of another kind, and in this way, 
 from the relation spoken of between the spirit and the chymical 
 nature of the fluids, the former in these places may be affected ; or 
 the process of the material aggregation mentioned in the article ou 
 Growth, may be impeded by destroying a balance which we have 
 supposed to exist between the motion of particles destined for aggre- 
 gation, and that power of the spirit by which the place of particles 
 is fixed and their impulse of motion counteracted (which agrees 
 with the reduction of bulk consequent upon fevers, though I will 
 hardly call it an explanation of this circumstance). 
 
 28. It has been common to consider this rapidity of circulation 
 as the cause, rather than the effect of the febrile state; and in this 
 view the cure is designed by diminishing the action of the heart ; 
 and this design succeeds because the action of the heart is diminished 
 by means which first influence the state of its moving powers, re- 
 storing them from the modified to their natural state. But how far 
 the rapid or slow motions of the fluids may be capable of influencing 
 the state of the spirit it may be difficult to decide. Indeed the 
 most that we can do with the facts which we possess is to allow that 
 some sort of relation of this kind might subsist; though I see many 
 indications by which even the existence, to say nothing about the 
 assigned phenomena, of the relation, may be brought under doubts. 
 The leading particulars of the relation comprehended in the pre- 
 ceding discussions may be summed up as follows : 
 
 1. The spirit produces the chymical materials both of the fluids 
 and of the solids ; by which is meant that materials are combined or 
 aggregated by the agency of the spirit, which, without this agency, 
 would be neither combined nor aggregated. 
 
 2. The spirit is directly related with the chymicals, both as the 
 spirit is liable to influence and to be influenced by the chymicals. 
 
 3. The influence of the spirit on the chymicals secures their 
 conformity to it, so that, by a natural and healthy condition of the 
 spirit, the chymicals concur for the well-being of the animal; and 
 theirs is a forced concurrence, since no animal condition of them 
 would take place but for the agency of the spirit upon them; and 
 in: the spontaneous changes of the chymicals, as these changes are 
 peculiar to the living state, so it is to be inferred that they would 
 not fake place but for a previous modification of the spirit in some 
 or other of its seats, the dmuicub of themselves tending invariably 
 
to dissolution. The government of the chymicals, their conformity 
 &c. to the spirit, is rested upon proofs before frequently mentioned, 
 which shew that there exists no true causation, such as identifies the 
 spirit with the structures. 
 
 4. But the chymicals are liable to become re-agents in spon- 
 taneous processes: thus the products of disease, morbid poisons, 
 (which, consisting of chymical materials, and displaying no charac- 
 teristic phenomena of life, may be enumerated among the class of 
 chymicals,) being produced by processes peculiar to the living body, 
 are capable of affecting the spirit by absorption, &c. 
 
 5. Chymical agency, producing animal changes, may be primitive 
 when the agents are introduced from without. In this way poisons 
 kill by inoculation, by being taken into the stomach or into the 
 lungs, &c. In these cases the relation of such foreign chymicals 
 may be direct or mediate in regard to the spirit, as before explained. 
 
 (>. It cannot be proved that the relation between the spirit and 
 the mechanicals is ever direct. If the spirit is influenced by 
 mechanical injury, it is because the relation between the parts of the 
 spirit itself in respective spheres suffers a disturbance, correspondent 
 with the mechanical disturbance; and when the spirit acts upon the 
 mechanical arrangements, it is by its relation with the chymical 
 materials by which these arrangements are composed. 
 
 7. The mechanicals may be directly influenced by the chymicals: 
 thus, a nerve or any other part may be destroyed by caustic, or its 
 organization impaired. The mechanicals are influenced by the 
 chymicals, not by a direct relation which external chymicals have 
 with the mechanicals, but by one which the external have with the 
 animal chymicals; these last composing the animal mechanicals, the 
 latter suffer by the influence of a cause, whose relation is with the 
 former. 
 
 8. We distinguish in the ordinary substances of nature proper- 
 ties of two kinds: 1st, those which belong to matter, and which 
 together with their agencies are called mechanical: these properties 
 are distinguished by reason of their being common to, or con- 
 stituting all matter; 2nd, properties which are peculiar to respective 
 substances, and which in each act and are acted upon in a way 
 which is not common to all matter: this difference gives rise to the 
 distinctive appellation of chymical properties or chymical substances. 
 But although there is some sort of difference between these two 
 classes, yet are the relations of each extended by their union ; the 
 reason of which is, that a certain alliance or affinity subsists between 
 the common and the chymical properties of matter, so that when 
 either is influenced, the effect of it upon the other will be according 
 to the established relation between them ; which relation appears to 
 be very capricious, inasmuch as it is almost infinitely varied in the 
 several examples. 
 
 29. It is scarcely possible to give a closer reason for the in- 
 variable union of chymical properties with those of matter than 
 this general one, deduced in conformity with the laws of causation, 
 
160 
 
 viz. that all the phenomena which we can contemplate are as they 
 are determined by their proper causes: thus, there are some causes 
 which, uniting in combination, form certain chymical properties ; 
 there are other causes which determine the alliance between these 
 chymical, and the mechanical properties of matter. But this ap- 
 pears to be a mere, though perhaps an invariable association ; for if 
 chymical properties produced in the way of true constitution the com- 
 mon ones of matter, then should the uniformity of the latter require 
 uniformity of the former, which is not the fact; and if the common 
 produced the chymical properties of matter, then as the former are 
 common so also should be the latter, which again is not the fact. 
 Hence we may say safely, that these sets of properties are conjoined 
 in their respective specimens ; and proceed to indicate a little further 
 some results of this union. 
 
 10. The chymical properties of substances are not capable of 
 being directly altered by mechanical agency ; this latter may give 
 motion, or it may compress or separate the parts of the former: but 
 if, after a mechanical agency upon the substance, its chymical proper- 
 ties are changed, it will be by a new relation which is opened be- 
 tween them and others of the same class. As when a solid body is 
 extenuated to a mere surface, its atmospherical exposure is more 
 complete, and changes may then occur in it which would not have 
 taken place before, at least, in the same time. 
 
 11. But the common appear liable to be directly changed by 
 an influence on the peculiar properties of substances. Thus a solid 
 body by chymical relations may be rendered fluid, or converted 
 into gas ; and although in this case the properties of matter would 
 not be lost, but would still be associated with the chymical proper- 
 ties, yet it cannot be denied but, as mechanical agents, the common 
 properties of matter are very different in the two states : in the one 
 it resists the impulse of other substances, or is itself put in motion, 
 and again communicates the impulse of a solid body to others of 
 its own kind; but, after its conversion, it yields to the substances 
 which it would before have resisted, and neither takes nor communi- 
 cates motion, &c. It may be contended, as 1 am aware, that all 
 these varieties are only modifications of matter, or of extension ; 
 but this doctrine is completely refuted (which is saying a great deal) 
 in the chapter on Causation. 
 
 12. The common substances of nature, being provided with these 
 two sets of properties, we find these in animal bodies still more 
 complicated by another class of properties, which are not common 
 to substances considered either in their mechanical or chymical 
 nature, or in both. Sufficient has been said of these properties : it 
 remains only to add, 1st, that spiritual properties are related with. 
 others of their own kind ; 2nd, that as the cbymical are allied with 
 common properties of matter, so the spiritual are allied with both ; 
 3rd, that whereas the common cannot change the chymical proper- 
 ties of matter, neither can they the spiritual; but the class of chy- 
 mical agents, having in alliance spiritual properties (for they maintain 
 
161 
 
 the spirit), so to this class belongs, with the spiritual, a relation 
 of re-agency. 
 
 13. Spiritual properties are directly related with those of 
 their own kind ; chymical and mechanical properties, respectively, 
 are related with those of their own kind. Spiritual and chymicai 
 properties are united by a natural alliance : hence the relation be- 
 tween them is always direct; chymical and mechanical properties 
 are united, with the exceptions mentioned, by a similar natural 
 alliance ; hence they are liable to influence each other, though not 
 reciprocally in a direct manner. These three sets of properties 
 are united in an animal body; hence, mediately or directly, the 
 properties of each are liable to modification from the changes 
 which either might undergo. 
 
162 
 
 CHAP. VI. 
 
 Gtneral Relation of the Spirit with itself in different Seat$. 
 
 1. IT has been fully exhibited in the preceding pages 
 that the organic spirit in its different seats exercises various pro- 
 perties. The varieties of texture invariably denote variety in the 
 properties of the principle which belong to the textures respec- 
 tively. These modifications of properties, may be inferred as be- 
 fore shewn, merely from the varieties of the textures; but there 
 are, also, other differences of vital properties in the respective 
 seats which a 7 re not indicated by corresponding differences in the 
 composition of the texture, and which shew themselves by other 
 products, as those of secretion, &c. Properties also are frequently 
 manifested under disease, when their existence is not to be de- 
 tected in the condition of health. 
 
 2. These properties, or, as we say, the spirit, existing in the 
 several seats, is liable in each to a relation with that existing else- 
 where. It is the design of this section to indicate generally the 
 nature of this relation. 
 
 3. The relation of vital properties in one with those in another 
 seat, may be said to be, 1st, direct; and, 2nd, indirect: direct, as 
 when the spirit being affected in one seat, the influence of this 
 affection is communicated to that in another seat, without the in- 
 tervention of any change in the alliances of the latter, whether 
 chymical or mechanical ; indirect, as when the function of an 
 organ whose office it is to prepare the chymicals for the use of the 
 spirit in other seats, becomes impaired, in consequence of which 
 the spirit is affected elsewhere, by a disturbance of the relation 
 which subsists between it and the chymical or other products of 
 the organ, and not with the spirit belonging to the organ. The 
 more evident examples of the latter are furnished in the prepara- 
 tory organs, to be spoken of hereafter. 
 
 * 4. The instances of direct relation are some of them furnished 
 by physiology, and others by disease. The former are exemplified 
 in the cases where a dependence of the function of one part ap- 
 pears to exist upon that of another. Some obscurity and doubt 
 must rest upon these examples; some of them may, however, be 
 
163 
 
 enumerated as follows. In the organic system, the action of the 
 heart ceases by the destruction of the spinal marrow j all the 
 powers of motion existing elsewhere are destroyed in the same 
 way : some secretions are modified or suspended by a division of 
 nerves supplying the secreting organs ; the function of the organs of 
 respiration is made to cease in the same way, &c. In the animal 
 system, the action of a voluntary muscle is destroyed by a similar 
 division of nerves, or by compression or laceration of their centres* 
 Sensation in all its seats acknowledges a similar dependence. 
 
 5. The latter instances, viz. those illustrating dependence in 
 disease (or preternatural condition), are exemplified in the cases 
 denominated those of sympathy. These, also, are in some respects 
 liable to doubts: they are enumerated as follows: a fractured bone 
 disorders the action of the heart, quickens the pulse, &c.; the 
 stomach becomes disordered from the same cause, there is loss of 
 appetite, furred tongue, &c.; the brain is affected from the same 
 cause, and delirium may occur; the secretion of the kidneys is 
 scanty or almost suspended, and the urine is changed in other 
 respects, &c. These consequences appear to indicate an exten- 
 sive chain of dependence: thus, inflammation arises in the fra,c- 
 tured limb, with other local peculiarities which need not be men- 
 tioned ; the whole constitution sympathises t or the whole of the 
 organic spirit in its several seats becomes affected by a communi- 
 cation with that which is locally changed; or, to pursue the in- 
 stances, pain arises in the shoulder when the liver is influenced, 
 or a testicle may swell from strictures in the urethra, &c. These 
 examples are numerous and familiar, and need be no further 
 particularized. 
 
 6. It may be objected that these latter examples are not un- 
 equivocally illustrative of the direct relation, as, in the case of 
 inflammation, the fluids may be changed by the altered condition 
 of the spirit in one seat, and the influence thus mediately com- 
 municated to other parts. But this would be to lay an undue 
 stress upon a mere possibility, which there is the less reason to 
 do as the objection can scarcely be imagined to apply to some of 
 the other examples, which for the sake of a more complete illus- 
 tration I shall still further extend. 
 
 7. If a considerable injury is inflicted upon one part of the 
 spinal marrow, the functions of the whole (indeed of the whole 
 body) cease. If one part of the brain be injured, the function of 
 the whole are either modified or cease. I have seen also, in an 
 experiment, the action of the heart immediately destroyed by 
 passing a lancet through one ventricle. If a muscle be half 
 divided in a transverse direction, the power of contraction in the 
 uninjured portion will be either impaired or destroyed. The 
 injuries of nerves also exhibit many curious connections of the 
 same kind. All these instances are sufficient to prove a direct 
 relation of some kind : the kind or mode of the relation remains 
 to be investigated. 
 
,164 
 
 8. The place of injury, or that which appears to- give origin 
 to the series, may be called the primary seat; that place, or those 
 spheres, where the distant or contiguous effects of the injury are 
 contemplated, may be called the secondary seat, which may also 
 be the primary in relation to a further seat of affection, and so on 
 to an undefined extent. 
 
 9. In our doctrines of causation we have assigned only two 
 modes of influence producing change, viz. by adding to or taking 
 away from the properties which constitute the subject of the 
 influence, or the subject of the change. When the function of 
 uninjured parts of the brain cease (as they will) from an injury of 
 the spinal marrow, what, according to the investigation just pro- 
 posed, is the process of this consequence! The brain was in 
 possession of certain faculties, which were manifested by their 
 operation: the spinal marrow is injured, and those faculties of the 
 brain cease,' or reverse the order, and suppose the function of the 
 spinal marrow to cease from an injury of the brain; this case is 
 not so liable to objection, by reason that though an universal 
 paralysis may have occurred in the system of voluntary motion, &c. 
 yet the action of the heart may be but slightly interrupted. A 
 change has taken place in a secondary seat: has it arisen from a 
 communication of properties to it from the primary, or seat of the 
 injury? or, is it that the natural functions of the secondary, was 
 before dependent upon properties imparted to it from the primary, 
 eat, which communication of properties ceasing in consequence of 
 the injury, the dependent function of the secondary seat ceases 
 from their privation? This question, which is in every respect a 
 legitimate one, shakes some received doctrines of physiology to 
 their foundation. 
 
 10. There are many parallel cases where the question is also, 
 though perhaps not equally, applicable. A nerve is intercepted 
 and the functions of the inferior parts cease. Hence it is inferred 
 that the inferior parts were in a sort of habitual receipt of proper- 
 ties or faculties from the superior parts. This inference is made 
 upon an analogy which must not be universally admitted: it must 
 not be admitted (unless it should be found to agree with a criterion 
 which remains to be discovered), because in the instance of a nerve 
 the properties of it might be, in a way before explained, related 
 with the foreign agency. Not so with the blood in an artery, 
 which is a specimen or the analogy : here the communication is 
 merely cut off; out in a nerve the properties of inferior parts may 
 be modified or destroyed by an influence conferred. I would ask, 
 theft, as the effects of injuries of this kind may happen in two ways, 
 what known criterion have we by which to ascertain from such ex- 
 periments the true relation between connected parts? 
 
 11. This criterion can neither be deduced from succession 
 nor from the existence or want of reciprocation; to exemplify, it 
 may be said the destruction of the function of the lower portion of 
 a nerve always succeeds to its division, while the superior portion? 
 
165 
 
 continue their functions unimpaired, though the inferior portions 
 may be removed. Such, I say, may be the result of a relation be- 
 tween the injury and the properties of the inferior portion without 
 giving occasion to infer from such facts that the inferior is con- 
 tinually deriving properties from the superior parts of nerves. 
 But if the inference is questionable in this example, what shall we 
 say of it in others? Without pushing this point any further at 
 present, let us see the amount of that which is absolutely proved 
 by these facts, which is simply this: 
 
 12. That there subsists a relation between the properties of 
 different seats; that, by an influence upon, or destruction of, those 
 in one seat, those of another will either be modified or made to 
 cease. If we would have unquestionable proofs of a perpetual 
 communication among the vital properties (similar to that of the 
 blood, which is perpetually passing from one set of vessels into 
 another), we must derive them from some other source. 
 
 13. Although I have objected to some inferences, as necessa- 
 rily true, which have been made from the effects of the division 
 of nerves, yet I would not be understood to deny their probability 
 in general instances. I have mentioned that which might be 
 urged as a refinement upon scepticism, merely to furnish an indi- 
 cation for an inquiry of the strictest possible kind. Meantime, in 
 addition to the evidence which is afforded by the consequences of 
 the division of nerves, we possess also that afforded by the general 
 fact, that no insulated portion of an animal structure can live. 
 Hence it may be presumed (but how fairly we shall presently 
 examine) that the life of no part is perfect of itself, or that it is a 
 specimen of independent life. If however this conclusion were 
 granted, it would follow further that the life existing in one sphere 
 is invariably dependent upon a supply of properties which it re- 
 ceives from some other, which, as will presently appear, is not 
 agreeable with truth, 
 
 14. But, it will be asked of this additional proof, whether the 
 life that ceases in an insulated sphere may not be destroyed by an 
 agency conferred by the means which separated this portion from, 
 the rest? To this I reply that the supposition is not in agreement 
 wilh fact. If a muscle be cut transversely, half through the 
 divided fibres both above and below will live while there is com- 
 munication with living parts; but if the limb be amputated at the 
 same point, then the life of the same identical fibres, which have 
 sustained the very same operation, will become extinct, that is, a 
 portion of structure will live while connected with the rest, under 
 precisely that agency which would occasion its death when separa- 
 ted from its living connections. 
 
 15. This last observation appears to give additional validity 
 to the inference before said to be liable to some sceptical doubts, 
 It is to be inquired what sort of criterion we possess, for dis- 
 tinguishing between changes produced by accession, and those 
 Arising from privation iu general instances. The subject is full of 
 
166 
 
 difficulties: much error and confusion have arisen from these 
 difficulties, yet the source of perpetual blunders and of the greatest 
 confusion has never in this instance been even suspected. It is my 
 present business to indicate some points which belong to the topic. 
 
 16. Perhaps it may be said that all the phenomena of life 
 which can become the subjects of investigation are matters of in- 
 ference; hence the great uncertainty which must attach to them, 
 and the more especially as the few facts upon which the inferences 
 are grounded are not those of every-day experience, so that their 
 force and connexions are known but partially. In agencies of 
 which the senses can take account, it is easy to discriminate be- 
 tween a phenomenon which results from a cause conferred and 
 one taken away. I need only advert to the operations of chymis- 
 try: though here a great deal of the subtler business is matter of 
 inference; and therefore this science is not certain to the full ex- 
 tent to which it is investigated, or to the extent for which it has 
 obtained credit. To return to the inquiry respecting our 
 criterion, &c. 
 
 17. If the connection between two continuous parts may be 
 separated, and each part preserve unchanged the properties which 
 belonged to it, it may be inferred that the properties existing in 
 each of these parts have no essential dependence upon those 
 existing in the other. 
 
 18. A primary, producing a secondary affection in a different 
 seat, proves of itself only that the properties of the two seats are 
 liable to communicate. 
 
 19. In order to determine the mode of the secondary affec- 
 tion, it must first be ascertained what are the effects of a separa- 
 tion of the two continuous seats? If such a separation might be 
 made, and each seat preserve unchanged the character and pro- 
 perties which before belonged to them, then it might be inferred 
 that the secondary affection does not arise from the privation of 
 properties naturally and regularly imparted to its seat, but that 
 the secondary affection results from a foreign influence, conferred 
 in consequence of the preternatural condition which the properties 
 pf the primary seat bad assumed. 
 
 20. If in consequence of the separation of connected parts 
 the characteristic properties pf one should be rendered extinct, 
 the alternatives to be inferred are, eitjier that the injury involved 
 in the separation has produced the extinction of these properties 
 by an influence conferred, or that their extinction happens in con- 
 sequence of an habitual source of the properties in question being 
 simply intercepted. 
 
 21. In order to decide this matter in a way which is the least 
 likely to mislead us, we must recur to our nearest analogies. In 
 a general way, then, in consideration of these analogies, we are 
 warranted to infer that a simple division of continuous parts does 
 not operate to the destruction of properties independently main- 
 tained; one iottaope pf this has been cited i" the division pf 
 
167 
 
 muscular fibres: this is unequivocal in regard to the organic life, 
 which we are now considering, and is borne out by a similar testi- 
 mony in the animal department Which we shall presently mention. 
 22. But some injuries of connected parts, where there is no 
 dependence, as on properties received, may destroy the health, or 
 render extinct the living properties of a secondary seat. As an 
 example of this law, a ligature on one or more of the brachial 
 nerves may in a rabbit destroy the vitality of the foot, occasion- 
 ing the sloughing of the skin, muscles, &c. below the place of 
 injury; but the same nerves may be divided at the place where 
 the ligature might have been applied, and the vitality of the skin, 
 muscles, c. of the foot and leg will continue. The former is a 
 clear case of influence by communication, assumed in consequence 
 of the injury; and not of influence by privation, because the 
 division of the nerves, with the preservation of vitality in the in- 
 ferior seats, proved that the vitality in these seats was independent 
 of that superior seat, by a preternatural condition, of which the 
 vitality of the former may be modified or destroyed. 
 
 23. There appear to be cases in which parts may be naturally 
 dependent by communication, and yet preserve an unimpaired 
 condition under a separation; but these cases are equivocal, by 
 reason that the continuity of vessels may perform the relative 
 ottice otherwise imputed to spiritual continuity. Thus, to exem- 
 plify such a case, suppose such a defined spot 
 of a nerve in an extremity as 7 communicating 675 
 with 6 and 5. If the communication with 6 I " I ' : 
 
 be cut off at the line 8, then the properties 
 will be maintained at 7 by communicating 8 9 
 
 with 5. If cut oflfby the line 9, the properties 
 at 7 will be maintained by communicating with 6; and that the 
 dependence of the properties at 7 is by communicating either with 
 5 or 6, or with both, is proved by the fact that if the two sections 
 8 and 9 are made at the same time, and the portion of nerve 7 
 thus separated totally from its connections, it will die and its struc- 
 ture fall to decay. 
 
 24. These laws apply to, and are deduced in conformity with 
 the modes of change in general instances. They are also by their 
 illustration shewn to belong to animal bodies. It remains to in- 
 vestigate the agents concerned in the dependence spoken of; and 
 this must be done by a retrospect of some former doctrines, con- 
 necting them closely with the business of this section. 
 
 25. It cannot be proved that the life or the organic spirit of 
 any seat is essentially dependent upon that formed or existing 
 elsewhere: for though it is admitted that a portion of a structure 
 when separated from the rest cannot live, yet there is in such por- 
 tion not only a separation from a contiguous living principle, but 
 its sources of blood are also cut off. It is shewn in a former article 
 that the terms of the maintenance of life are comprised in the 
 existence of an organic spirit properly identified, and in the sub- 
 
168 
 
 jfction of arterial blood to the influence of this spirit: from the 
 former, the latter assimilates itself. The truth of this account 
 must be rested on the proofs cited in the chapter on the Condition 
 of the Spirit. 
 
 26. Now if life is maintained by a reciprocation between the 
 properties of blood and the organic spirit in every sphere, in the 
 way of assimilation described, it follows that the existence of the 
 organic spirit is in no sphere dependent upon an habitual receipt 
 of properties from another seat, for if life were diffused to all seats 
 as from a centre, there would be no need of the presence of blood 
 to maintain the life of respective seats. But the processes are 
 incompatible upon the supposition even that the spirit in distant 
 seats is identified by certain auxiliary properties derived from a 
 centre ; for that which is maintained by assimilation being once 
 formed ,depends upon its pabulum (the blood), and is independent 
 of a source, supposing it } to have been originally derived from one. 
 
 27. If it be said that a limb will not preserve its life though 
 arterial blood be injected into it, I reply, that it is very certain 
 that it will not after the principle of life has become extinct: but 
 I am inclined to think that if a transfusion of arterial blood into 
 the amputated limb could be made before its life had become 
 extinct, from stoppage of the circulation, or conversion of arterial 
 into venous blood, its life would be preserved in a ratio to the 
 truth of the imitation. We have no direct fact upon this point, 
 and the experiment, though difficult, would require attention to 
 many more particulars than are here suggested. We find, however, 
 that by oxygenating the blood (or inflating the lungs) after decapi- 
 tation, the organic life may for a considerable time be maintained, 
 notwithstanding the separation of that which was considered a 
 source of spiritual properties: thus far the analogy; but as this 
 fact, to the extent to which it is assumed, is undecided, we must 
 rest our proofs upon the doctrines and connections just referred 
 to. We may, if we please, multiply our analogies, tending to the 
 same conclusion; we may advert to some animals, among whom, as 
 is well known, a detached portion will not only live, but originate 
 growths. This must happen from some laws of conversion be- 
 tween their life and their structures which are not common to the 
 Mammalia, which we profess to be considering. 
 
 28. The phenomena of the ovum not only agree with, but 
 help to confirm this supposed independence of the existence of 
 the organic spirit of one sphere of that existing in any other. The 
 development of the growths is preceded by an unfolding, or a 
 series of changes in the combinations of the integral properties of 
 life. The forms of life separate and assimilate : their first separa- 
 tion is no weak proof of their independence respectively ; it proves, 
 and the results of the several combinations prove, a difference 
 which precludes the supposition of a common source. Thus, then, 
 the properties of the spirit in the ovum, having relations among 
 themselves, afterwards preserve certain relations; the respectife 
 
169 
 
 combinations of properties constituting the life of the respective 
 seats are capable of assimilating and maintaining themselves by their 
 relation with the blood, independently of other spiritual properties. 
 29. But although an organic spirit may exist and assimilate 
 independently, yet the spirit in every sphere cannot always be said 
 to be perfect in that sphere; that is, although, independently of the 
 spirit of any other sphere, an organic life, according to our defini- 
 tion, would be maintained, yet the attributes of this life may be 
 modified or suspended by an interruption which relates only to 
 spiritual communication, and which is no interruption to the blood. 
 Some powers of muscles (which will hereafter be appropriately 
 designated) we know to depend upon a communication with the 
 brain; yet the organic life of those muscles may be preserved under 
 a total division of the nerves. So the secretion of the stomach is 
 said to be prevented by a division of the eighth pair of nerves, &c. 
 But in these cases, and especially in the latter, it is not to be inferred 
 that the life, or even the power of secretion, is wholly dependent 
 upon a nervous centre; for we Hnd that where there is already the 
 predisposition, the effect of it does not take place for want of a mere 
 stimulus,* and this might be furnished by a hundred things indiffe- 
 rently. As when the mouth is, dry, saliva might be made to flow by 
 sugar, salt, tobacco, by chewing a stick, &c. Hence it has been, 
 absurdly perhaps, inferred, that agents, capable of re-producing a 
 secretion suspended in consequence of a division of nerves, have 
 been the full and total identity of the cause of the secretion, as 
 electricity, &c. We find, however, from these views, that the sub- 
 ject is liable to be considered in the modes before proposed, viz. 
 influence of spiritual properties of seats by privation and by com- 
 munication. It remains that we should sum up the criteria deduced 
 from some of the illustrations of the present article by which the 
 inquiry is to be conducted. 
 
 1. A simple division of a structure may destroy the life of an 
 inferior part of the same structure; but if a connection with living 
 structures is preserved by blood-vessels, this rarely happens except 
 by processes of disease. 
 
 2. When a secondary, happens in consequence of a primary, 
 injury or affection, if it is ascertained that the life of the secondary 
 seat may preserve its identity, &c. when separated from the primary, 
 it is to be inferred that there is no dependence between them, and 
 
 * The word " stimulus" is employed to denote a cause capable of producing 
 certain effects upou a certain predisposition, by properties common to it, and 
 many other substances which are made to appear different by their combina. 
 tions; thus, brandy, ather, laudanum, blisters, spurs, whips, &c. are all 
 stimuli, that is, these substances, though different, have, so far as the effect is 
 common, a property in common which produces it. This matter has beeu 
 explained in the chapter on Causation, where, treating on the various associa- 
 tions to which similar properties are liable, it is also explained, that notwith- 
 standing these different associations, the properties in question may produce 
 their proper effects upon their other relations, unless the associated properties 
 are so related also as to counteract tins end. 
 A A 
 
170 
 
 consequently that the secondary change must happen by communica- 
 tion, and not by privation of properties. 
 
 3. As the cases just referred to are among the commonest we 
 are called upon to witness, it is to be inferred that the communion 
 between parts may subsist without dependence, so that an injury in 
 one seat may destroy in another, by the derangement imparted from 
 the tirst to the second : thus a ligature on a superior part of a 
 nerve may produce a sloughing of the inferior, while no such effect 
 will follow a simple division. Hence injuries are no proofs of de- 
 pendence, although they have been confounded with others as such. 
 
 4. But the results of simple division in general will indicate a 
 dependence, because it is not the common effect of division to im- 
 pair the properties of remote parts by communication of influence. 
 Not but this may happen, and the cases have been adverted to in 
 which it does happen; but, weighing the larger portion of our ex- 
 perience against the smaller, we are, according to the right of 
 inference, justified in thinking, when certain properties, making its 
 function in an inferior part, as of a nerve, cease in consequence of a 
 simple division, that then the inferior part is dependent upon 
 the superior for those properties. But of what kind, or how far 
 they may be possessed in common |>y other substances, entitling 
 them merely to the appellation of stimuli, is neither discovered nor 
 sought for. A determined scepticism may oppose both the above 
 conclusions and the general sense of mankind, upon the same cases; 
 it may urge, that under the change which a portion of a nerve un- 
 dergoes by an injury, &c. this local state of the nerve may open a 
 relation with the brain, by which the latter acquires or derives pro- 
 perties from the former, thus identifying or constituting pain, and 
 other phenomena of such injuries, by the properties of a nerve, 
 which remain after some are taken away. 
 
 5. As the mere existence of organic life is not directly dependent 
 upon any other seat than that in which it assimilates; so if the 
 organic life is modified or ceases in a secondary seat, as a conse- 
 quence of a primary injury, it is by a communication of propertiet 
 through connected tpheres. 
 
171 
 
 SECTION II. 
 
 ON THE PREPARATORY ORGANS. 
 CHAP. I. General Relation* of Preparatory Organs. 
 
 1. BY the preparatory organs are meant those whose 
 business it is to make biood: they are well known as consisting of 
 tlie abdominal viscera and the lungs. But of the share taken by 
 each in this process we are but indifferently informed. I shall, in 
 their proper place, offer a few indications upon them respectively. 
 
 2. By the function of the stomach, food is made chyle: this is 
 the effect of the function ; but of the function itself, docs it reside 
 wholly, or partially, in the stomach? if partially, on what other 
 seats has it a dependence? and what is that in which its own 
 principle is deficient? These questions certainly cannot be all 
 answered at once, and some of them perhaps not at all. 
 
 3. The life of perhaps every part, but certainly of most parts, 
 is of two kinds, viz. regular or independent, and occasional or de^ 
 pendent. That which I call regular is made up of those properties 
 which, separated originally from the entire spirit of the ovum, and 
 becoming diffused according to the laws of properties (elaborately 
 spoken of in the chapters on the Ovum), develop, or form, or per- 
 manently influence, those which become their respective seats. The 
 occasional life is that to which properties are communicated from 
 another seat, modifying the regular life. The regular life is capa- 
 ble of maintaining itself by assimilation, and of preserving also the 
 existence of the textures which it before formed. The occasional 
 is not an assimilating life, because the properties which make it 
 occasional endure no longer than a communication is preserved with 
 their source. 
 
 4. These two spirits just mentioned (c&teris paribus) act when 
 they are present ; the regular is always present, and always main- 
 
tiinn il-i idrnhly. .HI. I |i. rrvi ' h. Ir^t.iMs, ,\ t . Thr o annual 
 innninn .!<!. .HI I i lit . I , it, puiposr, :tii(l <;!,. iti tin- KIIM.I. 
 orgim. milr v, tin- omnium, ahon r, in idr m xoinr dr/nrr |M i m.im nl 
 to fulfil llir ohp-rls of finrh .1 dm.ilion. 
 
 '-.'.. I lii- M "idai .r. .iimhlni" .pint mpnrrs only lo hr Mlpplird 
 Wllh ai l.-lial I.|.M| 'I lir, rs supplied lo Mir lolnshya pirpaiallon 
 xvlnrh liiltcH plarr III foirii.Mi ol^ans. llrmr llir lo-lin in .ill it , pio 
 greiliVQ ^lovvlli. \,.|)| m (In- l.itl.i JMIKMI.. ji.iHsrssrK in lls 
 urv< tal sral-i only lln % Mfimllllting lilc; wlin h, rr<|iinni;' only to In- 
 ,ii|'|>hr.| vvilli Mood, in onlt-i lo he in. mil. lined, d,,. not i.md in 
 nrrd of tin .,<., i, ,n.il Id- . .nid i-vlii|iils lioiii- hill llir f nurl nun .n 
 lirrlnl u.lli lis aHHiiiiilalliMi: iV.s //// /s pTOgttnitt l!<< fmnhnn^ 
 tO aid iti dmloptnml . ll,, only rondilion is llir supply ,| 
 hlood. \\lmli il olil.un. hoin ;i lonifii <MII<< Tin. -.oiiirr 
 prrvrnlrd, an il in in tin* Muf* of indrpnidn.l lifr, tl i, 
 
 neceiwry thHtunoccmioriid hi.- .i.onid !,< .-..lahh h. d, pidu. in;- .|>. 
 
 < ill. l-ni. linns. MM pnni i|):il ohp-. I (.1 wlin II, III |i-;ul to llir OIM .1,1, 
 lift, ft 10 muK< lli.it hlood loi llir animal ivlnrli was hrfotr in;id< 
 lot linn. 
 
 I II. AltlMn;di, Mini, llir Irndrnry of llir vpinl of llir ovum i . In 
 ICpai.ihon ol llir pipi i lies \vlii< li roinjio,. it, lo a diflu in in 
 irhprrtivr nplu-ic't, yrt llir roinirrlion o( a \vliolr i pK-srtvrd; and 
 wlnlr IIM ,r\<i ii > onihin.itioir. of pioprilirs I. Il \,, ihrinsrlv 
 -ipaldr r,f luihillial or ir-nlai fl - I . yi I lliry air Ir.ddr |o hr in 
 HIM n. rd hy < liall^rn ill linn di.l.inl n-l.ilion... 'Ilir . i li;in < miv 
 hr ofjill oidrily 01 of .in arrldnit.il Kind. \vr liavr rxainplr-. of in. Id . 
 hnt Ihr fiiin IIOIP. wlin Ii an.r al'ln llir hnlliof llir annual, and 
 who Ii lo In. pn nvafion, IH lon^ lo llir In .1 
 
 ^7. I.llr, Hi Ihr Id-lal shl^r . ciprialrM Ilidrprndrnl I y of MM) 
 i -xiilin;' in othri sral',. Tin- all M na 1 1 vr>. afln hnl Ii ;u c. thai lln> 
 ifldrprndriMr .lionld hr (onlnnird, and tlir animal dir fioni drfr I 
 Of llir hlood whn h w. is hrfotr pnpaird foi il. 01 lli.il < liiinrr-. 
 dionld ir.snll, m roidoiinily xvilli a nr\v rondilion, whirl) r|ian^r 
 air in a;'irrmrnt with irlutions hrfoir nol rallrd into a lion, and 
 \vlinh allriu.iMl. Irnd lo prrprlnalr llir r\i ,|<-nrr <d llir animal. 
 Tim:, llir drprndrnl fun- lion, l, ;MII ly < lian;;r of n-lalioiiM, and Ilir 
 <|rprnd IK r i, .d|([W.ild, Kept n|> hy llir opriahon ol lit. .mi. 
 air%r-. o| < li.ci ;-. Tin- .< ( li.iii . ii, jy .ui,c m p. nt 01 \vliolly, 
 Uponlanroii'.lv, dunn;' llir la .1 .l.i,"< , ,,f fo-tal fioulli. 01 lliry limy 
 hrrsMlrd m pa I I hy Ion l/;il < air.r ., nnidrnl lo llir slalr o| mdr- 
 |M-|l(!rnl llir. 
 
 :;. II is a-u.rilainrd Ilia! llir inrdnmiral pouris of ir'.pnalioil 
 air drprndrnl Upon llir hiam o| r-| viral IlirdllHa. 'I'ln-.r |)o\\n i 
 ill |||. nr not p", ...d hrran.i llir nlalion hy ulnrli lliry 
 
 airohlanird i^ nol llim r<.lahlnlicd. T/nl In.w, if may hr asKrd, i. 
 it piovrd Ilial Ilirponn, |lnni;;linol r\tni,rd. dors nol rr.snlr willi 
 lln i< ,pn aloi y mns< Ir . ' If l!ir pnwri ol merit, HIM .1! iripnahon 
 dor, at ih.it Imir rxi.tt in Ihr . nm < Ics, il |||||<il hr ohtainrd Jioin 
 
 (In- hiam, MIILC this po\v.i ceases when the coniinuiiiuiUoii wilh Ihu 
 
173 
 
 i. in!rM-|i1fl. II tin. IM ;illow-i|, il followi, MUM: Hi' pown 
 i . !-|n n!i Hi upon li I'l-iin, that 'A relation MuhninU h tw--n l)n 
 
 ! (fa " !"' ''"/ '-"'-"i-;. l.y whuh tl,. l.,n< ,.r in il,. 
 
 ii:ilntii;il <"i|>l of |io|,i-ri--. l>v vvhi.li ll,y -,)< ;inirn;tlrf| from UK- 
 
 loriiM-r (/r.irilm;' tin . Hi' fli-.lirif tion of I >n<\ 
 
 jjrnricrit fpmliiiil |>roj>. r tn -. r. r,',l in v:ilil;i l. I'.ul whrlftcr 
 
 rebtiOtl CXI -., W- niil<--f nflll fnrll, r /.n,, 
 
 '>. It rrr.iy > '.))" l 'I H^.iiir I li I. .1 
 
 tii;i ii r. contrary " iii.it oin of prorrwwri wini ;iio.- 
 
 'Il.i |, '-'//. r Vrhich |.rforiir: n," M.IMM .! 
 
 . ..lion r: oiu- wln h i -illy i-xp'-no 1 ' 'I . it i . (.r vi 'I tin r 
 
 lor liy thin cm urn. ./ tin- f.it tl..i ll, l,r.)/.i l-n 
 
 in I,'--, it no longer tli.ui tlux vr.r lit i. .IJ,|.|M <l hv.uUri.il IJ',,f, 
 llj.it tln>. |,',y/ r Pt r'TM-wi-o 1 I h- rii'lif l *J |hr 
 
 1 ii, ll,< -, 
 
 ,ui'l tli- :-.!; '.i llu |. irilu.il ' '<inhirr.it K)fl Will, 
 
 ;illow"l. fix"l. lil:- lli.it of '-V-ryotlMr -.pirilu.il r otrihit,.-! ,-.i,. o y 
 
 win* Ii ohhtirM-o* 0*1- rioU of f 
 
 'I IK- t'ri'J'ii'y of lli- M-|:ih,rr- win' ft //// 
 
 ,1 il-. -. p. ,,,-, n from tlif n't t 
 II v/i! - :put"l. h I'. J.f','1 
 
 .h'/ri //In' Ii 'li'l i.- /(, < ( , 1(4 felt WMf (I' 
 
 With-. ,/,'l'j' f'.rfit, W Hi;- 
 
 i analogy: Jirroro'in;/ il,. to it, tin- ^.|,; 
 rntl '/vlii Ii '-. jir it'- ffrr. i}.' 
 
 .r.r,- I") :in t ll t^Xtllf 
 
 '. and pf 
 j.li-r*r of on tpint irr ifa that of notbffy 
 
 vl.K Ii [,. -.f tin ir *<-ll|rmor,t 
 
 .'ufnrl*rrj f;y r,l'/ifi; > mo t 
 
 ' ))!, '.ir,r| it r. r/lnhit-'l l,y v< ;" taM'-* an'l by 
 
 aniniJiU v\> -I v/hi'li, po--. . 
 
 i-r th;n, lit' ;f- , iiiM>t. h'- rtfptdtA tWI nKMml 
 
 whir Ii our <l I 
 
 i'/ . ! tK" .i,f,por of fftnffil an- 
 
 JklialHirjrJ ' / th;it tlx- r hitiom of proj,' 
 
 hv whu h th<-y i.orni. irjH)(M >. '/f f, 
 
 -il th- r I, 
 iriMr|-i,t tr, inO-|*-rid ot li/ l^rc takrn \t\'A<#; w*- thai I fi;. 
 
 ,., jf not t'miuiin-'. 
 analo^ir* and -x/irnpk. 
 
 II. We will begia with rl't/lutihori the ffMMdt* "' " ""' "i 
 
 rocew, ami thovr -A //i <oim*etiWu with tiW> 
 
 - /o:t/l lif 
 
 ftft; they firt act oy v. 
 
 -, 
 tbeaa; ttii> 
 
174 
 
 pendent life, which the animal at the first periods, of nutrition from 
 externals has begun to assume. This then is one illustration of out 
 argument: muscles of deglutition, &c. possessing their own proper- 
 ties in utero and at rest; a volition originates from the brain, the 
 assimilating life of the muscles in question receives properties by 
 communication; to trace this series 
 
 12. The function of digestion, not manifested during foetal 
 development, is formed by the life which afterwards preserves it; 
 this being made up of properties settled by the relations between 
 spiritual properties, and their subsequent material of nutrition, in 
 the ovum, food enters the stomach by the preceding acts of degluti- 
 tion, &c. ; the properties of the stomach have a relation with food 
 and sustain corresponding change; properties of the stomach con- 
 nected and related with those of the brain ; change in the proper- 
 ties of the stomach, producing correspondent change in those of the 
 brain: the end of this relation is, that properties, quitting their 
 native sphere, pass and re-pass between the stomach and the brain, 
 producing their specific effects, that is, complying with the relations 
 of the properties engaged, and contribute to accomplish the pheno- 
 mena of digestion. Whether this is a true account of this particular 
 example, or a mere illustration of a mode, we shall hereafter 
 consider. 
 
 13. To recur to the instance of change preceding communica- 
 tion before mentioned, which is exemplified in respiration. The 
 organs in the fcetal state, quiescent and independent ; their inde- 
 pendence first disturbed by a cause of change; that cause, the 
 admission of air into the lungs ; properties of the respiratory organs 
 affected in consequence, according to their relation with air, these 
 properties related with the brain or cervical medulla; properties 
 pass and re-pass from the organs of respiration to the brain, a per- 
 petual re-agency occurs, settled by predisposition, or the pre-existent 
 relations of properties; the end, the establishment of the function of 
 respiration. 
 
 14. To anticipate a little our subject, we may borrow an illus- 
 tration still more conspicuous from the system of animal muscularity 
 which is subservient to loco-motion. The muscles of the leg (for 
 the sake of precision) have their assimilating life, which first formed 
 and is afterwards capable of preserving them; the nerves which 
 upply them are formed and preserved in the same manner; this is 
 their organic existence, and thus far they are independent of other 
 seats; but they have a function capable of originating loco-motion, 
 and for this they are dependent upon a nervous centre. But the 
 exercise of this function arises not from a natural communication 
 of properties from the nervous centre, but from a disturbance of 
 the natural disposition (meaning that disposition which occurs 
 during fcetal growth), from a change of the properties of the nervous 
 centre, which results from the influence of causes to which in its 
 new condition it is exposed. To exemplify still further the origin 
 of a relation by disturbance of the properties of a seat, 
 
175 
 
 15. We will suppose a time when the animal system is at rest* 
 possessed and actuated only by the organic life: the senses also may 
 not just then be taking cognizance of the objects which surround 
 them; but the mind might be associating, or engaged on past im- 
 pressions, as in a reverie : on a sudden the report of a pistol is heard, 
 the man starts up; what is this process] Properties Constituting 
 the sense of hearing are changed, modified, or affected, According 
 to their relation with the report of the pistol. The brain, Before 
 independent of the properties of the auditory sense, is now affecied 
 by them ; that is, a relation is opened or exhibited which is de- 
 pendent upon the change (or disturbance) produced in one sphere of 
 connected properties. To proceed: the muscles of the .leg, before 
 quiescent, and their state independent of the brain, now assume 
 actions corresponding with the relations of their properties with the 
 present, the changed, condition of the brain. The man starts on his 
 feet, rushes into an adjoining room, and, by a similar series to that 
 just described, engages in all the complicated re-agencies of proper- 
 ties incident perhaps to a contest for life. These illustrations are 
 sufficiently numerous: to subjoin then the principle, the proofs of 
 which are before stated, and these examples are not designed as 
 proofs, but are introduced chiefly for the purpose of illustration, 
 and in order to shew their conformity. 
 
 16. The organic life is every where an assemblage or combina- 
 tion of properties, making an assimilating principle, the identity of 
 which is the result, or settlement of that progressive causation which 
 takes place among the vital properties of the ovum, and is matured 
 in the periods of uterine growth. In almost every seat, the proper- 
 ties of the organic life are different and peculiar; their differences 
 may arise from the relations engaged in the progressive causation 
 just spoken of, and these differences, respecting only the assimilating 
 principle, are independent of any other seat; or difference, or pecu- 
 liarity, of the spirit in any seat, may arise from communications with 
 organic properties assimilated in another seat. Hence the organic 
 properties (or life) of seats, may be classed under these three divisions 
 viz. the regular assimilating, the regular dependent, and the oc- 
 casional dependent properties. The first assumed their place in the 
 processes of the development of the ovum, and they maintain them- 
 selves in their place by assimilating their own identity from arterial 
 blood ; the second do not originate in the place where their action 
 is observed, and they are not maintained in this place by assimila- 
 tion, because they are dependent upon a source; but they originate 
 in some other sphere, with which that where their action might be 
 observed is naturally and spontaneously related; the third, or oc- 
 casional dependent life, is so produced that by an influence, oc- 
 casioning change in the properties of one seat, the distant related 
 ones may be also changed, arid re-act upon the properties of the 
 seat where the affection or impression (if it is more intelligible) com- 
 menced. The first is displayed in all the stages of foptal growth ; 
 of the second there are many examples iu the latter stages of foetal 
 
176 
 
 growth; the third is chiefly produced by the influence of the exter- 
 nals to which the condition of post-foetal or independent life is 
 exposed. 
 
 17. How far properties may communicate during all the 
 periods of foetal growth, for the purposes of that progressive causa- 
 tion which M proved by the development and conversions of the 
 structures cannot be affirmed. Properties may, during these pro- 
 cesses, assume their spheres by abstraction or separation from that 
 nucleus in which they were first combined ; or they may be identi- 
 fied in their respective spheres by subsequent communications. 
 These are relations not easily analyzed : but presuming that an in- 
 tercourse of properties does not take place without an object .or a 
 result, it may be conjectured that the communications between vital 
 properties which subserve to the establishment of functions and the 
 maintenance of independent life, either commence when the maternal 
 alliances cease, or else are preparatory to this period. The animal 
 being then exposed to the operation of new causes, these causes 
 produce other changes in his spiritual properties, which changes are 
 again influential upon connected properties. The final result of this 
 disturbance of primordial relations in the department which we are 
 considering, is to produce that blood which was before supplied by 
 the mother: this is the physical effect of the causes concerned ; and 
 the organs by which this end is accomplished are called, in reference 
 to the blood which they prepare for purposes of life, preparatory 
 organs, concerning which, respectively, some indications for inquiry 
 are now to be suggested. 
 
CHAP. II. The Stomach. 
 
 1. THE object of investigating the function of this 
 viscus is to understand by what agents, and according to what laws 
 its purposes are accomplished. The most familiar and obvious use 
 of the stomach is the conversion of food into chyme. 
 
 2. We are taught by our doctrines of causation, that every 
 change is produced by something added, or by something taken 
 away; accordingly an investigation, for the purpose of ascertaining 
 in what the above change consists, must be of the analytical kind. 
 
 3. There is no such thing as a perfect or complete analysis. 
 To follow distantly the design of a perfect analysis in the present 
 instance would require that we should be so far informed of the 
 constituents of food, as to be enabled, by a comparison of food with 
 chyme, to say what the former has lost or what acquired by its con- 
 version into the latter. So perfect a knowledge is hopeless: we 
 have not even ascertained the relation of the constituents of food 
 with each other, so as to be enabled to say, how much in a conver- 
 sion is to be attributed to a change in the combination of its own 
 constituents, and how much to foreign ones. 
 
 4. A few of the chymical differences might be enumerated : is 
 is then to be asked, what are the properties, or where are the pro- 
 perties which produced these changes, seeing that nothing like a 
 similar conversion will result from an imitative employment of the 
 same alleged agents? Let us, however, make a more precise indica- 
 tion upon this matter: he who profits by it must be a shrewd 
 inquirer. 
 
 5. The relation subsisting between food and the function of 
 the stomach is to be considered (conformably with the general 
 division before expressed). 
 
 1st, According to the mechanical relation subsisting between 
 food and the structure of the stomach. 
 
 2nd, According to the relations between the chymical consti- 
 tuents of food and those supplied by the stomach. 
 
 3rd, According to the relations between the vital properties of 
 the stomach and the properties of the same kind in food: thus far 
 they may be considered separately. They are also to be considered 
 reciprocally, that is, as the stomach acts upon food, and the con- 
 
 8 
 
178 
 
 verse. They are also to be considered a* regular ami occasional. 
 Lastly, their mutual or conjoint agencies are to be considered ac- 
 cording to the following order. 
 
 1. MECHANICAL RELATION: 
 
 1st, As mechanical phenomena in food are directly produced by 
 the mechanical agency of the stomach. 
 
 2nd, As mechanical changes in food are produced by relations 
 of the chymical agents furnished by the stomach, with those of the 
 same kind in food, with which the mechanical are in alliance. 
 
 3rd, As mechanical phenomena in food are produced directly by 
 the agency of vital properties of the stomach, or as mechanical 
 phenomena in food are produced by vital properties of the stomach 
 through the medium of the chymicals and their relation with the 
 mechanicals. It is also a matter to be decided, whether this latter 
 (the mediate agency) is not invariable, or in other words whether 
 the direct ever takes place. 
 
 2. CHYMICAL RELATION. 
 
 1st, As chymical changes in food are produced by the chymical 
 matters supplied by the stomach. The changes attributable to this 
 agency are to be specified. 
 
 2nd, As chymical changes in food (if any) are produced by 
 mechanical action of the stomach (this action may perhaps contri- 
 bute towards the process of digestion in birds, by a mechanical 
 mixture of the chymicals of the stomach with those of the food). 
 But the effect of such a relation, if any take place in the human 
 stomach, can be scarcely worth inquiring after. 
 
 3rd, As chymical changes in food are produced by a relation 
 ubsisting between its constituents and the vital properties of the 
 stomach, these changes are to be inquired after and specified. 
 
 3. SPIRITUAL RELATION. 
 
 6. To propose an investigation of the precise relations between 
 vital properties, pre-suppose at least that these properties are known. 
 The investigation would require that the varieties of vital properties 
 contained in food, as well as those belonging to the stomach, should 
 be specified. The question, whether the effects result from priva- 
 tion or addition of properties, in agreement with our doctrines of 
 causation, will require in every topic of these relations to be deter- 
 mined. The relations between individual properties on either side 
 can be known only by distinct experimental combinations: and the 
 integral relation of the spiritual properties belonging to the stomach 
 and those of food, can be known only by a separation of these pro- 
 perties from their alliances, and by rendering them objects of the 
 senses, which we may venture to say will not be done until a method 
 shall be discovered for performing impossibilities. Thus much, 
 however, by way of indicating those points, the possession of which 
 would leave us as well instructed respecting one great operation of the 
 animal economy, as we are of the relation which the parts bear with 
 ach other in the simplest piece of machinery. We must be con* 
 tent for the present with a looser method, which aspires only to 
 
179 
 
 furnish a few hints upon the objects of the investigation, or to ex- 
 hibit another example of the general conformity and subordination 
 which we have hitherto traced. 
 
 7. If food is put into the stomach of an animal some hours 
 after death it will not be reduced to chyme. The stomach may 
 contain those secretions which are formed preparatory to a meal, and 
 which furuish the chymicals produced by the stomach: our regard 
 also may be had to temperature ; yet this food will not be digested 
 as in the living stomach, but, if of the animal kind, will follow the 
 fate of the animal structures, it will be decomposed by putrefaction. 
 
 8. As food will not be digested unless life is present, it i 
 necessary to infer that life is essential to digestion. 
 
 9. But it is not a mere principle of life of any sort that will 
 accomplish this end. How, it will be asked, is this ascertained! 
 A digestible substance may be well impregnated with gastric secre- 
 tion, and in this state sewed under the skin of an animal, by which 
 it will be as effectually surrounded by a principle of life as in the 
 stomach; yet, without making the experiment, it may be almost 
 affirmed that this substance will not be reduced to chyme. That it 
 should is contrary to analogy; for, in the experiments and operations 
 of grafting animal substances, we find that the foreign ones are 
 never made chyme, but that they are dissolved by putrefaction, 
 except in cases where an union takes place between them. 
 
 10. The organic spirit of the stomach, then, is one which has 
 peculiar properties, in addition to those (many times specified) which 
 are sufficient to characterize a vital principle. The relation, or 9 
 relation, of these properties with food is to assist in its digestion. 
 
 11. The secretions of the stomach furnishing on the part of 
 the animal, as has been said, the chymicals which are related with 
 food, it is supposed, contribute towards digestion; but their share 
 in this process is not ascertained, although experiments have been 
 instituted with something like this view. 
 
 12. The general history of these secretions, made up of consti- 
 tuents, which chymistry to a certain extent can analyze, is this: 
 Tubes, variously connected, continuous with the blood-vessels, 
 called their secerning extremities, open into the stomach. These 
 tubes separate, and then excrete into the stomach peculiar fluids. 
 The fluids which it is their function to form, cannot be produced by 
 any known hydraulic imitation; they are never known to be pro- 
 duced but whilst life is present. It is hence to be inferred, that 
 blood supplies a material, certain parts of which are so related 
 with the vital properties, inhering with a certain order of vessels, 
 that the end of their relaiion is to produce the secretions in question. 
 
 13. Thus the participation of chymical agents in the process 
 of digestion may be said to be the effect of a previous operation of 
 certain properties of life. The history of this life is to be a little 
 further traced. 
 
 14. It has been before said thai our means of analysis are too 
 imperfect to admit a specification of the share which the agent* 
 
180 
 
 concerned, respectively, have in the process we are considering. 
 But the final purpose of their concurrence is sufficiently clear. 
 
 $ 15. The substances which support life, when submitted to the 
 functions of the preparatory organs, not only will not support, but 
 actually destroy it, if introduced into the circulation in their crude 
 state. * Hence it is obvious that the final purpose of the function of 
 the stomach is to produce in food a change which constitutes the 
 second stage (mastication and deglutition comprising the first) of 
 preparation, for such a relation with the other seats of life and 
 organization as will concur towards their support. 
 
 16. The life of the stomach has been divided into the regular 
 assimilating, and the dependent functionary. The former is that 
 properly belonging to the texture, and is independent of all other 
 seats, being dependent only upon the properties of arterial blood : 
 the latter is so far dependent upon another seat, that a division 
 (which we have admitted as a test of influence by privation) of the 
 nerves which supply the stomach will impair, or perhaps incapacitate 
 the organ for its digestive function. 
 
 17. The laws which govern the functionary life are perhaps in 
 many circumstances irregular. In the instances quoted from the 
 animal system, we have observed that the influence communicated 
 to a distant seat is traceable to a foreign cause, which disturbs the 
 natural state of quiescence, and in some measure of independence. 
 Thus the muscles of the legs may act in consequence of an operation 
 upon the auditory or optic nerves, &c. In other words, an influ- 
 ence is communicated to the brain, of the occasional sort, which if 
 the muscles of the legs before possessed, independently of the 
 brain, they would move, whether a train of actions were laid or not, 
 by an operation upon the auditory or optic nerves. 
 
 18. But, although communication of influence making function 
 is clearly shewn to take place in many instances, as the result of a 
 relation which is manifested under preternatural circumstances; as 
 in the examples just quoted, by foreign excitation; yet it does not 
 foljow but communications for the same end, viz. that of perfecting 
 functions, may be perpetually taking place under the operations of 
 causes, which are so far natural, that they may even be possessed 
 by the foetus. Such a perpetual communication may take place 
 without invalidating our distinction of the assimilating and de- 
 pendent or occasional life; and whether the communication does 
 take place in the subject of our present consideration, we are to 
 examine. The question relates to the organic system. 
 
 19. The proper secretion of the stomach is formed when this 
 organ is under no foreign excitement by food, or, in other words, 
 when it is empty. If the properties necessary to the secretion do 
 not wholly belong to the stomach, but are in part derived from 
 another seat, then this example furnishes a proof of a spontaneous 
 diffusion of vital properties, and an alliance of them with the in- 
 herent life of the seat to which they are conveyed, for the purpose 
 of establishing a function. It bag been assumed, upon tbe credit of 
 
181 
 
 experiments which are uot wholly unobjectionable, that the secrer 
 tion of the stomach is no longer formed when its communication 
 with the brain is intercepted. Hence, if the secretion cannot be 
 produced by the regular and assimilating life of the stomach 
 singly, and if properties from the brai.n singly (as may be proved) 
 cannot produce the secretion, it follows that both are necessary 
 to this result; and if the result takes place, as it is said and known 
 to do, when the organs are under no preternatural influence, it 
 follows that the properties by which the function is constituted 
 unite for this end, in conformity with a natural and habitual rela- 
 Jion. It is probable that, in the progress of experiment, many 
 instances of spontaneous habitual diffusion of properties from one 
 seat allying themselves with those of another, for the objects of a 
 function, will be discovered. It is probable also, that instances of 
 the same kind might with truth be quoted from the animal system, 
 as the possession of a faculty of sensation, which is manifested in 
 all sentient points and derived from the brain, &c. But the in r 
 stance already mentioned is sufficient to sanction an indication. 
 In the mean time it is not proposed as the proof (any further than 
 the fact asserted in the experiment may be admitted) of a spon- 
 taneous disturbance of the assimilating spirits of independent 
 spheres. All that I would insist upon is the probability that the 
 vital properties of one seat pass spontaneously to another, for the 
 purpose of perfecting a function; and that they are sometimes 
 derived in the secondary seat by the presence of foreign agents, 
 which have a primary operation upon the properties of this seat. 
 Of the latter, or occasional properties, we have spoken fully: of 
 the former it is necessary still further to inquire, keeping in view 
 as much as possible a line of investigation which is applicable 
 to both. 
 
 20. Now if it shall be confirmed by the increase ot facts, as 
 it is more than indicated by those above mentioned, that spiritual 
 properties, which live in one seat by assimilation, pass from thence 
 to another; it is to be inquired why they leave their original seat: 
 and if they do not assimilate with the vital properties with which 
 they enter into alliance (as it is plain they do not, because the 
 function would then be independent of a source), it is to be asked, 
 what is the mode of this union? 
 
 21. Before it can be asserted why properties leave the seat 
 in which they are assimilated, it seems proper that we should 
 understand what becomes of the properties which appear to be 
 unremittingly consumed 1 ? This is not an easy speculation, nor is 
 it perhaps likely to be a very satisfactory one. However, difficult 
 as it is, and although it is likely to prove unsatisfactory, the ques- 
 tion belongs rather to the subject of death than that of life; and 
 the consideration must be deferred till we speak of that subject. 
 
 22. Thus much for the present may be observed, viz. that 
 we do not find it indicated by the most distant connexion with 
 our experience, that the properties which assimilate in one seat 
 
182 
 
 universally pass to another; or, in other words, that they do not 
 expire, as we must say, for want of a better word, in the' seat io 
 which they assimilate and live. Thus we have no reason to sup- 
 pose that the function of any seat is influenced by the properties 
 of that life which assimilates in the muscles of the foot, the skin 
 of the forehead, in the os calcis, the olecranon, or the alae of the 
 nose, &c. 
 
 23. If then, as it appears from this view, it is not an universal 
 or even a general tendency in the properties of the organic spirit 
 to pass from one seat to another (under natural circumstances), it 
 is to be asked, why they do so in those few instances in which 
 such a communication has been reasonably supposed! We cannot 
 reply to this question: a real answer to it would comprise, 1st, a 
 specification of the properties which pass (for example) from the 
 brain to the stomach; and, 2nd, a citation of the properties with 
 which the latter are related, and by which their migration from 
 one seat to another is determined. This necessity is founded 
 upon principles of causation already sufficiently explained. 
 
 24. Here then again we are brought to a recollection of that 
 which we want for a satisfactory information on subtilties which 
 we aspire to understand. The deficiency I allude to is an addi- 
 tional sense, which would enable us to /enow properties, whose 
 existence and laws we can now only infer, from particular analogies, 
 or in conformity with general principles. 
 
 25. Hence we cannot pretend to say what causes sometimes 
 determine vital properties, to leave their native sphere, and some- 
 times not. We can merely remark, that the vital properties of 
 respective spheres are of various kinds; that various relations ob- 
 tain among them; and that the phenomenon in question is one 
 among the results of particular relations, which we must be con- 
 tent to enumerate, and that imperfectly. 
 
 26. Concerning the mode of the union of properties which 
 do not assimilate, to understand this process requires that we 
 should be informed what becomes of the properties which do 
 assimilate; or what is meant by their being consumed. This con- 
 sideration we have said is to be deferred to the subject of death. 
 
 27. But, in order to make our present question dependent 
 only upon the result of that inquiry, it is to be observed, 1st, that 
 the properties communicated modify only the life of the seat 
 which receives them; and, 
 
 2nd, That they endure no longer than the communication with 
 their source is preserved ; and that therefore they, uniting with 
 the assimilating life (when their communication is unremitting) as 
 fast as it is formed, follow the fate of that life, or they expire; a 
 process which we shall hereafter consider. 
 
 28. Although it is rendered probable that some part of the 
 organic function of the stomach is dependent upon the connection 
 of this seat with the brain, yet it has not been attempted to 
 Ascertain how much. The experiments before alluded to refer 
 
principally to the secretion of the stomach. Whether the digestive 
 faculty depends upon communication with the brain, any furthet 
 than the secretions of the stomach are necessary to digestion, 
 remains to be determined. 
 
 29. It is necessary further to inquire what other relations 
 the stomach has with contiguous or distant parts. It is to be 
 examined whether its function is in any way dependent upon the 
 the liver, the spleen, the pancreas, &c. In this examination the 
 division of the living fabric is to be observed. Of each severally 
 it is to be asked, does the stomach obtain vital properties from the 
 liver, the spleen, the pancreas, &c. ? or has it with either a chyuii- 
 cal, a mechanical, or a mixed relation 1 ? 
 
 30. A perfect physiology of the stomach would instruct us 
 of its relations as an agent, with respect to other organs, as well 
 as concerning its own dependences. 
 
 31. It has been indicated in the beginning of this article 
 that in this way it is related with the brain. It has been remarked 
 that the function of digestion is neither required nor manifested 
 during ftetal life; that it takes place afterwards under circum- 
 stances (those of ingeslion) in which the primary operation of an 
 occasional cause must be upon the stomach and its properties. 
 We have therefore to decide whether the stomach derives proper- 
 ties from the brain directly necessary to digestion, of an habitual 
 or occasional kind; whether such an habitual communication 
 takes place as that which has been almost proved with regard to 
 the cerebral properties which concur in gastric secretion ; or 
 whether the function, being occasional, the brain furnishes pro- 
 perties for the purpose of digestion in consequence only of an 
 operation of properties of the stomach upon those of the brain, 
 the series of which might be expressed in this order, 1st, inherent 
 properties of the stomach, produced by its assimilating life, affected 
 by the presence of food; 2nd, properties of the brain, affected by 
 relation with those of the stomach; 3rd, the result of this latter 
 affection, a re-action of properties of the brain upon those of the 
 stomach, contributing towards the process of digestion. This 
 point cannot at present be decided, because we stand in need of 
 facts to prove eveu that the digestive function is dependent upon 
 the brain. 
 
 32. But we are not without examples that a series of opera- 
 tions of the above kind does occur in other cases, where the oc- 
 casional relation is exhibited. Thus a substance violently emetic 
 produces vomiting so speedily as to preclude the supposition of 
 its having reached the brain by the tedious course of absorption: 
 properties either of this substance, or properties of the stomach 
 modified by those of this substance, are propagated to the brain; 
 a re -agency of the properties of the brain occurs, the secretions of 
 the stomach, which arc traced to a dependence upon the brain, are 
 increased or modified, or both; the sensations of the stomach are 
 also produced, and, finally, vomiting happens, by a participation 
 iu the disturbance on the part of the diaphragm and abdominal 
 
184 
 
 muscles, which participation also is dependent upon the integrity 
 of the nerves which supply these seats. 
 
 33. Hence we perceive that the stomach is liable (agreeably 
 with a general division) to the operation of three sets of proper- 
 ties; or is to be considered in respect of them, viz. the assimi- 
 lating, the spontaneous communicating (or the habitual), and the 
 occasional, or excited, comrnqnicating, properties. The first is 
 distinguished by its having no dependence, except upon arterial 
 blood; the second is inferred from the necessity which exists (for 
 the purpose of certain phenomena resulting from its function) of 
 a communication with another seat, and from the habitual or 
 regular occurrence of the phenomena dependent upon this com- 
 munication, when their seat is under no preternatural influence. 
 The inference of the third must always be dubious: for, although 
 the phenomena (as, for example, the digestion of food) are of an 
 occasional kind, and never take place but under the presence of 
 foreign substances, yet it does not follow, because the subject of 
 the operation of a power is sometimes present and sometimes 
 absent, that therefore the power itself is not always present. Yet 
 this seems the only criterion: and if it be allowed to furnish evi- 
 dence of any kind, it must be rated (in this example at least) at 
 that which is weakly presumptive. 
 
 34. There are many other instances of affection and re-agency 
 which would illustrate our present topic, but they are well known, 
 at least the facts are well known: they are enumerated under the 
 head of sympathy, and belong less to physiology than to disease. 
 My business is not to detail particulars, but to seek after and 
 arrange those facts only which are important because they sub- 
 serve to the establishment of principles. It is here sufficient to 
 advert to the class of facts; merely observing, that affection 
 might commence in any part of a related circle; that the order 
 might proceed irregularly ; and that the complication is difficult to 
 be traced, because the natural order of affection, if any, may be 
 inverted, and if no natural one existed, the unnatural is not at 
 once recognized. But, granting the order of the affection of seats 
 to be made out, there is still the most difficult part of the process 
 to be analyzed, viz. the share in effects to be assigned respectively 
 to vital, chymical, and mechanical, means; the agencies of which 
 are rendered still more complex by their being liable to be con- 
 sidered, 1st, as results by addition and by privation; and, 2nd, 
 according to the two modes of operation between them, viz. the 
 direct and the mediate, of which we shall say more hereafter. 
 
 35. There remains then, in viewing the stomach as an agent 
 with respect to other seats, to inquire with what other seats it may 
 be in this manner related: considering first the contiguous ones, 
 as the spleen, liver, pancreas, intestines, &c.; and then those 
 remote, if any. This examination, proposed rather in conformity 
 with a systematic design than with any expectation of useful re- 
 sults, belongs to the detail of physiology, and not to the indica- 
 tion of its topics. 
 
185 
 
 CHAP. III. The Intestines. 
 
 1. THE perceptible changes which food undergoes in 
 these organs need not be enumerated. It is designed only to 
 point out briefly the objects of investigating their function; and to 
 exhibit their relations as a part of those general ones, making a 
 system, to which they belong. 
 
 2. It is the business of analysis to specify in what consists 
 the difference between chyle and chyme. The changes which 
 food sustains in its conversion into chyme are supposed to some 
 extent to have been ascertained. A similar investigation belongs 
 to every portion of the intestinal canal, the effect of the function 
 of which is to produce new changes. Thus, it is to be asked 
 severally of the chymical changes sustained by that which was 
 originally food, in the duodenum, the jejunum, the ileum, the 
 cecum, the colon, the rectum; and perhaps the same question may 
 apply to the several parts of each. 
 
 3. The chyraical differences assigned, as they may be to some 
 extent (the mechanical scarcely furnishing a topic of inquiry), it is 
 the further business of analysis to specify the vital changes which 
 are also produced in the same seats. 
 
 4. The spiritual changes are in truth the principal objects of 
 the several functions : for the final purpose of every stage of the pre- 
 paration which food sustains is that it may become a material, the 
 elementary life of which may be so related with the diffused formal, 
 that the former may be capable of supporting the latter, and of 
 contributing towards those phenomena of the structures which are 
 connected with, or dependent upon, spiritual assimilation. 
 
 5. I say then that it is the business of analysis, no less to 
 settle these spiritual changes than to remark the grosser cbymical 
 differences ; which latter will never be in any great degree explana- 
 tory of an animal process. But to specify these subtile changes 
 would require that other sense, of which we have before regretted 
 the want. Since then in this case, as in that of the stomach, we 
 can only particularize that which we desire, rather than that which 
 we are at present qualified to attain, we must \)p content with in- 
 quiring more generally and distantly into these processes, 
 
 6. The intestinal material of nutrition is mixed with the 
 secretions of the structure, and with those of adjoining glands. 
 The chymical differences (or at least some of them) produced on 
 c c 
 
186 
 
 chyme by a mixture with the fluids added in the duodenum, may 
 be known by synthesis, that is, by mixing chyme with the biliary, 
 pancreatic, and mucous secretions, contributed by this part. 
 This may be done in the laboratory. The artificial product may 
 then ,be compared with the natural: some differences may be 
 found to depend upon temperature. Under an imitation of the 
 natural temperature, the chymical analysis, if it were sufficiently 
 perfect, would detect the presence or absence of combinations in 
 the artificial compound when compared with the natural product 
 of the intestine which are attributable to the want of that spiritual 
 agency, which will have a share in every process belonging to a 
 living body. 
 
 7. This chymical investigation in the present state of our 
 information would most probably serve but to illustrate the ne- 
 cessity of the operation of that principle which has no substitute 
 in the laboratory, or, by shewing us how much may take place 
 without spiritual properties, to indicate what, or how much is ac- 
 complished by them. But as all this belongs to particular inquiry 
 with which I do not now profess to be engaged, I shall state the 
 history of the function in that imperfect way which will at least 
 render it conformable with the preceding views. 
 
 8. In the progress of experiment, it may perhaps be decided 
 that the chymical changes which chyme undergoes, in order to 
 become chyle, may result from the combination of the former 
 with the intestinal fluids, &c.; or, it may be discovered, that an 
 approximation only to a similitude takes place between the natu- 
 ral chyle and that produced by an artificial mixture of the duo- 
 denal fluids with chyme. But, in a general view of the subject, it 
 does not appear necessary to decide upon this matter, since, by 
 tracing the agency a little higher, we shall find that both the al- 
 ternatives resolve themselves into one common inquiry. 
 
 9. If the processes of the conversion we are considering are 
 but partially accomplished by the mixture of intestinal fluids with 
 chyme; or if this conversion takes place but imperfectly, under 
 circumstances similar to the latter, save that the principle of life 
 is extinct; then, that, the absence of which renders the conversion 
 imperfect, may be considered, when it exists, as a product of the 
 direct operation of vital properties upon the constituents of the 
 material with which they are related. But if the intestinal fluids 
 should be found capable, without the presence of a principle of 
 life, of accomplishing a perfect conversion (which is perhaps 
 scarcely to be, known), then the relation of the principle of life 
 with the constituents of chyme is mediate. The difference is, that 
 in the one case, (the direct) life produces changes in chyme, in 
 which the fluids do not co-operate; and in the other, that life pro- 
 duces fluids which accomplish the changes which chyme undergoes 
 in its conversion into chyle. I will not with our present facts 
 decide whether either of the relations just mentioned is exclusive, 
 or, if mixed, how much is assignable to each ; but after bestowing 
 
187 
 
 a few words upon the last (supposing it in conformity with general 
 opinion to obtain at least to some extent), I shall proceed to in- 
 quire into the laws of that which we perceive to be mutually 
 essential, viz. the spirit which presides in the seat of these operations, 
 
 10. The chymical constitution of chyle being determined by 
 appropriate analysis, it is to be asked whether such a chymical 
 production necessarily involves that state of the elements of infor- 
 mal life which is essential in this stage of preparation for the 
 maintenance of the living principle/ or, whether latent spiritual 
 changes do not take place in this conversion, to which the chymi- 
 cal are, so far as regards subsequent relations with life, mere 
 accompaniments? 
 
 11. To ascertain this point is perhaps beyond the scope of 
 experiment. The constituents of chyle, such as they are men- 
 tioned by chymists, may be easily drawn from foreign sources, 
 and put together. But we cannot thus ascertain whether this 
 artificial combination involves the prepared state of the spiritual 
 elements, unless it were possible to keep an animal alive, by filling 
 his lacteals with this production of the laboratory, without sub- 
 jecting it to the influence of the stomach or intestines; an experi- 
 ment not likely to be attempted, and still less likely to succeed. 
 
 12. That a process so complex as that of chylification should 
 be performed merely for the purpose of producing a few chymical 
 constituents (such as have been enumerated in books) appears very 
 improbable; and we have the more reason to suspect that the 
 latent are also the most essential changes, when we consider that if 
 an animal were fed with chyle, or substances which approach very 
 near to it, the same conversions, or nearly the same, would take 
 place as when fed with ordinary food. An heterogeneous mass 
 would be produced by the stomach and duodenum, and the agents, 
 so far from availing themselves of a chyle ready made at their 
 hands, would still go through the regular business of preparing a 
 part for the purposes of the animal, and another part which is 
 termed excrementitious. 
 
 13. Indeed, whether the chymical involves all the changes 
 which occur in the formation of chyle, or whether others exist, of 
 the spiritual kind, which are superadded to the chymical (chyle 
 being made a medium for their circulation), it seems scarcely worth 
 while to inquire; since it is clear, 1st, that chyle possesses pro- 
 perties which concur to maintain the assimilating spirit; 2nd, that 
 the fluid, or medium of these properties, will not support the 
 assimilating spirit, if the changes which are produced in it in any 
 stage of its passage through the preparatory organs be. omitted; 
 and, 3rd, that therefore, the function of every seat of these organs 
 is to produce changes, which, among other purposes, refer to the 
 aptitude which must subsist between the elementary and the for- 
 mal life. 
 
 14. This business, this progressi/e adaptation, may take place 
 in two ways, or by a complication of them : 1st, it may be, that 
 
188 
 
 the principle belonging to the preparatory structures may be con- 
 sumed in separating from the fluid destined for nutrition hetero- 
 geneous substances or properties; or, 2nd, that the living properties 
 of the textures passing into the fluids destined for nutrition, and 
 becoming again informal life, may determine the due relation be- 
 tween the nutrient material and the peculiar nature which it is 
 destined to support. 
 
 15. Whatever the precise nature of these curious processes 
 may be (and which, for want of the sense which we have so often 
 alluded to, we shall never understand) this law appears common and 
 universal to the living specimens of both kingdoms, viz. that though 
 an immense variety of animals (and vegetables) of the same genus 
 may derive their support from the same aliment, yet the condition 
 upon which the life and corporeal character of each are maintained 
 is, that the aliment for such purposes should undergo a preparation 
 by the organs of the living form which it is destined to nourish; 
 nay, so essentially and peculiarly is the function of the preparatory 
 organs related with the diffused life and textures, that blood itself, 
 from an animal of the same species, thrown into the system of the 
 circulation, will not prove a substitute for that fluid whose proper- 
 ties are endowed by organs, in conformity with a natural and 
 specific relation.* To this general view we shall perhaps have oc- 
 casion to return. Having shewn the necessity of the operation of 
 the living principle belonging to these organs, we are next to con- 
 sider the laws which belong to the principle itself, or at least to 
 exhibit some alternatives respecting it. 
 
 16. We have seen that the operation of the organic spirit be- 
 longing to the structure of the intestines is either direct or through 
 the medium of the fluids supplied to the chyme. There is a de- 
 ficiency of facts to prove whether indeed the former mode occurs 
 at all, though, for the reasons stated, it appears probable. It is now 
 to be inquired, 1st, whether those spiritual properties which are 
 engaged in the conversion are those of the assimilating life; or, 
 2nd, whether they are that conjoined result which we have ex- 
 pressed " the regular dependent;" or, whether they are of the 
 
 * The only instances of nutrition by a material prepared by foreign 
 organs are those exemplified in the engrafting of animal and vegetable sub- 
 stances. In these cases, the life of the foreign substance mnst in its proper- 
 ties and constitution so far resemble that of the substance with which it is 
 united, that the material which is prepared for one agrees with common pro- 
 perties of both. When substances are in this way united, the foreign or 
 additional one commonly preserves its own character, or takes only itself out 
 of a material which possesses its properties as well as those of the organiza- 
 tion with which it is allied. In such cases, the affinity betweeu the substances 
 is only of resembling properties, without constitution or the production of a 
 differential. In other cases which are perhaps exceptious, the growth and 
 product of the foreign substance is modified by its new connexion. In this 
 case there is not only an union of common properties, but communion of other 
 related ones giving rise to change, or constitution: as in generation, some 
 properties of the parents mix and modify each other, and some preserve their 
 separate and original character. 
 
189 
 
 occasional kind. So far as these questions can be decided will 
 occupy but a short discussion. 
 
 17. It matters but little which of the agencies we have sup- 
 posed to occur in this conversion is chosen as an example ; whether 
 the direct spiritual, or that through the medium of the secretions; 
 the latter is the more probable. As the effects of the functions of 
 the intestines have never been observed except during the integrity 
 of the organs, and whilst their connexions were preserved; we can- 
 not, in the present state of the facts, pronounce that they derive 
 properties from any distant source necessary to their function. 
 Hence, we cannot, from any evidence which has been attained re- 
 specting these parts, affirm that their function, or any part of it, is 
 produced by that life which we have called the regular dependent. 
 
 18. As the secreting function of the intestines (or the superior 
 ones of which we are chiefly speaking) is unremitting, so in deciding 
 by what form of life it is accomplished, our choice lies only between 
 the assimilating and the regular dependent. But, as the conversion 
 of chyme into chyle is not equally unremitting (seeing that there 
 are times when the duodenum may be supposed, if not empty, to 
 have accomplished the end of its function upon the chyme dis- 
 charged into it), so we cannot affirm but some part of the process 
 may be dependent upon the occasional life. In other words, it is 
 to be inquired, if it should be found that the operation of the vital 
 properties is not wholly through the medium of the secretions, 
 whether those properties operating directly which are engaged in 
 the conversion, are latent in the structure of the intestines, or 
 whether their presence is excited or derived by a disturbance of 
 natural or quiescent relations, which might occur upon the intro- 
 duction of a substance foreign to the foetal condition. My mean- 
 ing will be found more fully expressed in the beginning of the 
 article on the stomach. 
 
 19. In the case of the stomach, the operation of the regular 
 dependent life has been assumed, 1st, because the secretion is un- 
 remitting, which decides it, if dependent, to be regular; and, 2nd, 
 because the secretions have not been found to take place, when the 
 communication of the stomach with a nervous centre has been in- 
 tercepted, which last, if the experiments may be relied on, proves 
 the dependence. 
 
 20. But, in the case of the stomach, as in that of the intestines, 
 it would be difficult to decide on the question of an occasional 
 dependent life; seeing that the dependence of processes which 
 might involve the direct operation of spiritual properties, in diges- 
 tion on the one hand, and in chylification on the other, can- 
 not be known but by a division of nerves, which might prevent or 
 impair those secretions from defect of which all the other agents of 
 the function may be rendered inefficient. 
 
 21. In order to decide whether the conversion of chyme into 
 chyle is attributable in any way to properties derived from a 
 foreign source, the faint success which has been obtained in some 
 
190 
 
 such inquiry indicates, for the purpose of confirmation, that it 
 should be observed, whether the conversion takes place under a 
 division of the nerves which supply the intestines, or any sufficient 
 portion of them, to constitute an adequate field for the observation. 
 If the conversion did take place, the independence of the functionary 
 properties of this, on any other, seat is proved: if it did not take 
 place, it decides that the unremitting processes require properties 
 of the regular dependent kind; but the experiment is not decisive in 
 regard to the share of the occasional properties. 
 
 22. If we were to yield our assent to the indication of a partial 
 analogy, we should say, that as the secretion of the stomach seems 
 to depend regularly upon the communication of properties from a 
 distant seat, so it is probable that secretion in the intestines ac- 
 knowledges a similar dependence; and extending the argument of 
 analogy, which is indeed here very weak, we should say, as in the 
 animal system, properties which act occasionally are found to be 
 obtained in the seats where they act, only by the presence of some- 
 thing foreign to the state of life during the earlier periods of foetal 
 growth: so, applying this fact to the present purpose, we should con- 
 jecture that the modes of the operation of life in chylification were 
 mixed, and that the direct was also that which we have distinguished 
 as the occasional. Both these analogies are, however, too imperfect 
 to justify any certain conclusion. 
 
 23. There are those who would reason on the supposed de- 
 pendence of digestion, &c. upon a distant source, by citing those 
 well known examples of the suspension of the process of digestion, 
 together with the disorder producible in the bowels by passions and 
 emotions of the mind. They would argue, Is it not clear that 
 digestion depends upon the brain, when we have all had experience 
 that anxiety will destroy appetite, that sudden anger or sudden grief 
 will suspend the digestion of food already taken ; and that these 
 things occur by affection of the brain, as is proved by their taking 
 place through the medium of a sense, as when a person reads a 
 letter, or hears an oral account, &c.? 
 
 24. The persons who argue thus do it upon a ground the 
 fallacy of which we have sufficiently exposed, but which may here 
 be in part repeated. If one seat is influenced by a process of 
 change which commences in another, the influence takes place in 
 one of two ways, either by conferring upon the secondary seat new 
 properties, or by suspending the communication of habitual ones. 
 Seeing that secondary change is liable to these alternatives, we are 
 to consider the mode of discriminating between them. The mode 
 of discrimination has been already stated: it is by ascertaining by 
 the test of intercepting the medium of intercourse, without com- 
 municating a foreign influence, whether the effect (digestion, or any 
 thing else) will take place under such circumstances. If it does take 
 place, the independence is proved : if it does not take place, it will 
 afterwards remain to be decided whether a secondary affection, 
 which takes place from an occasional disturbance of a primary seat 
 
191 
 
 by a foreign cause, involves the natural or regular dependent com- 
 municated properties ; or whether it is produced by others, arising 
 out of a new condition, so far distinct from the natural, that the 
 medium of communication subsisting, the secondary affection may 
 occur where there was no natural communication of properties of 
 the regular kind. 
 
 25. In addition to the analysis of chyle, which has been sug- 
 gested for the purpose of enabling us by an artificial combination of 
 the constituents detected to decide whether even all the perceptible 
 phenomena of the conversion are dependent upon chymical agents, 
 there remains to be remarked, in the chymical department, the pre- 
 cise share or import which each secretion has in the common result. 
 Thus, it is to be inquired, how much of the conversion is performed 
 by the constituents of intestinal mucus; how much by the biliary; 
 and how much by the pancreatic secretions. This investigation is 
 to be prosecuted not merely with a view to the general result of 
 the combination of one or more of these fluids with chyme, but 
 relations of constituents are to be sought after, and the combina- 
 tions and changes among them to be specified, and this respectively 
 according to the threefold division of the spiritual, chymical, and 
 mechanical departments. Such an inquiry, to the extent permitted 
 by the imperfect means of analysis which we possess, is not difficult; 
 but this same imperfection in the means of analysis would most pro- 
 bably render it of no value. 
 
 
192 
 
 CHAP. IV.~The liver. 
 
 1. THE function of the liver is said to consist in the 
 secretion of bile. Is this the only way in which it is related with 
 the animal economy? As the function of this viscus has never been 
 investigated with minuteness, we are destitute of the facts which 
 would enable us to decide satisfactorily upon this question. It is, 
 however, to be presumed that the separation of bile from the blood 
 in some way or other makes a part of the general concurrence of 
 processes for the maintenance of life and health; and that in this 
 way the function of the liver may not be without its use, inde- 
 pendently of any further purposes to which its product might be 
 applied. 
 
 2. I am not aware that we possess any direct facts which 
 prove a relation with the animal economy of the kind just sug- 
 gested. And indeed it seems almost impossible to attain such facts; 
 for the only mode of ascertaining that the separation of bile from 
 blood is salutary, or fulfils an important end, is by witnessing the 
 event of the suspension of this secretion: and here we have to dis- 
 criminate in the subsequent derangement (if any) whether such de- 
 rangement is to be imputed in part, or wholly, to the presence of 
 bile in the blood, or the want of it in the intestines; or, if to both 
 these causes, the share is to be decided which is attributable 
 to each. 
 
 3. But that the mere separation of bile from the blood con- 
 tributes towards the well-being of the animal is to be presumed 
 from the analogy of this, to the secretions, which are also excreted, 
 serving no ulterior purpose, and therefore not liable to the confusion 
 above noticed ; as in the case of the urinary secretion, the suspen- 
 sion of which is known to be productive of disease, and its restora- 
 tion to be followed by a return to health. The use of the mere 
 separation of bile from the blood is rather to be supposed upon this 
 ground than from the phenomena of jaundice, which are liable to 
 happen in two ways, between which we have no unequivocal criterion 
 for the purpose of discrimination. To which may be added, that 
 supposing the disordered functions of distant seats, which usually 
 take place in jaundice, to be clearly imputable to the presence of 
 bile in the sanguiferous system, this would prove only that bile 
 
193 
 
 in the blood, which has never been separated from it. That such 
 an absorption takes place it appears reasonable to infer from the 
 circumstance that, in jaundice, bile may be copiously secreted with 
 the urine, and if this bile had not been previously separated by 
 the liver, there is no reason why the kidneys should not at other 
 times produce bile, seeing that the blood cannot be at all other 
 times free from the materials of bile, because its secretion by the 
 liver is unremitting. Leaving this, then, as a matter which would 
 not be the worse for some additional illustration, we shall proceed 
 to consider some particulars belonging to the liver as one of the 
 preparatory organs. 
 
 4. As bile is mixed with the chyme discharged by the sto- 
 mach into the duodenum, it is to be inquired what share has bile 
 in the conversion of chyme into chyle? This inquiry proceeds 
 upon the supposition that the liver is not directly related with the 
 preparatory processes, but through the medium of the fluid it 
 produces. 
 
 5. An opportunity is afforded for a comparison between the 
 chymical differences of chyle with which bile is mixed, and that 
 into the composition of which it does not enter, by a ligature on 
 the bile-ducts. But would a specification of these chymical diffe- 
 rences illustrate or explain the importance of bile in these processes, 
 with regard to the future relations of the common product of 
 these organs? To proceed in the analysis, in the way indicated by 
 our causation, 
 
 6. It is to be asked, with what bile exhibits the first relation! 
 with the contents of the duodenum. Bile is mixed with chyme, 
 and helps to constitute chyle ; this is the first operation in 
 which it is engaged: but its history is to be more minutely traced. 
 Chyle is separated into two parts: one, nutrient, which is taken up 
 by the lacteals; and the other, excrementitious. Concerning this 
 separation, it is to be asked, does it happen from spontaneous 
 processes which chyle undergoes from the force of its constituents! 
 or, is there an additional function, viz. that of the lacteal orifices, 
 by which the separation is performed? This is a matter which 
 will be recurred to hereafter: in the mean time, if the separation 
 is spontaneous, the parts are first to be defined ; it is then to be 
 inquired what those properties are which determine the separation, 
 or without which it would not take place? The agents are to be 
 sought after, distinguishing efficient properties from associated 
 ones (a shrewd work this for analysis) ; and the share which bile 
 has in the operation is to be specified. 
 
 7. But without laying any stress upon the result of an inquiry 
 on the above question, we will proceed only in our examination 
 upon that which is obvious. As the separation of chyle takes 
 place, the constitution of either part is to be sought after, if possi- 
 ble, by analysis. It is to be asked of the lacteal chyle, does bile 
 contribute towards its constitution, or does bile furnish any requi- 
 site constituents? The philosophical mode of answering this 
 
 D D 
 
194 
 
 question would be, 1st, by obtaining; an accurate knowledge of th<?> 
 constituents of bile; 2nd, by an analysis of lacteal chyle, with a 
 view to the detection in it of the constituents of bile ; 3rd, by 
 ascertaining, if any constituent of bile should be found in the lac- 
 teal fluid, that it is furnished by bile, and not by any chymical or 
 animal process elaborated on the common intestinal material. 
 This is to be ascertained by preventing the entrance of bile into 
 the intestines. Here it will be argued that if bile furnishes any- 
 such property, it is not an essential one, seeing that life has been 
 in various cases continued where the secretion of bile is suspended. 
 But as the analysis suggested, even in these cases has never been 
 made, so it cannot be pronounced that here there is not a de- 
 ficiency of properties or substances necessary to healthy lacteal 
 fluid. Besides, this would be arguing from ai/exception, which at 
 most can never reflect but a dubious light, because it pre-supposes 
 that the analogy is imperfect. A person may live for a month with- 
 out taking any thing but gruel or water, and this may be vomited as 
 regularly as it is taken into the stomach (quod vidimus testamur), but 
 it does not follow that a person in a natural or healthy condition 
 can live a month without better nourishment, even though the pro- 
 gress towards death should not be aided by incessant vomiting, &c. 
 
 8. It will be further observed that if bile contribute any thing 
 towards the constitution of lacteal fluid, it is by a decomposition 
 of itself, since the colouring ingredient of bile, whatever it might 
 be, does not, if we may judge from the absence of its usually per- 
 ceptible effect, enter into the composition of lacteal chyle. 
 
 9. Having, by the analyses we have sketched, determined 
 what changes are produced by bile in the material with which it 
 combines, what changes take place in related constituents as well 
 as in the general mass, what decompositions ensue, what new 
 alliances are formed ; having fully ascertained the changes and 
 processes which take place in consequence of the mixture of bile 
 with the intestinal material; it is next to be inquired concerning 
 the other relations, as those subsisting between the chyle of the 
 intestines and the properties of their structures, in the establish- 
 ment of which the constituents of bile might have some share. 
 
 10. The question more simply stated is this, what is the 
 relation of bile with the vital properties of the intestines? Here 
 again we must recur to our analysis: we cannot ascertain what is 
 to be attributed in this way to the operation of bile, unless we 
 know what takes place without it. We should say also in this 
 instance, in order to understand whether bile concurs with the 
 vital properties of the intestines to produce phenomena, we must 
 first be able to take cognizance of the class or kind of phenomena 
 to which our conjectures relate: having attained this faculty, we 
 have then only to inspect the phenomena which take place under 
 the usual and natural influence of the bile, and afterwards, having 
 tied the bile-ducts, to observe what changes occur upon its priva- 
 tion; and if we wish for further satisfaction, we might repeat the 
 
195 
 
 synthetical process, and, removing the ligature from the bile-ducts, 
 observe whether those first phenomena recur which were remarked 
 under the natural condition, and found to cease upon the preven- 
 tion of the presence of bile. However impossible or even absurd 
 all this may seem, until it is fairly and fully accomplished, I shall 
 take the liberty of saying, that the offices of the bile, the results 
 of the function of the liver, have never been successfully investi- 
 gated. Let others be bold in professing knowledge: for my own 
 part, I find that the profession of ignorance is much more be- 
 coming, and am apt to believe that there would not be half so 
 many puppies in the world if men were as honest in confessing 
 their real deficiencies, as they are ingenious in gaining credit for 
 better qualifications than they possess. Let us, however, bestow 
 a few words upon the popular notions on this subject. 
 
 11. There are those who pretend to know all about it. The 
 use of bile 7 why, say they, is it not the natural stimulus to the 
 intestines? does it not help to produce their peristaltic motions! 
 would the bowels act without the presence of bile? Such is the 
 explanation which some men, who pass for shrewd ones too, will 
 offer. Bile, then, say they, is the natural stimulus to the bowels. 
 I would ask what is meant by a natural stimulus? I presume that 
 as a stimulus is a something which produces an. effect, it is another 
 name for a cause, which is the ordinary term by which we express 
 those things upon operations of which changes or results depend. 
 But the word stimulus, it will be said, does not imply the cause of 
 the motions of the bowels, seeing that these motions may take 
 place without it; but it designates an adjunct to the other powers, 
 a something that gives energy to the other powers, tending to the 
 same end. Then the stimulus of bile, instead of being the cause, 
 is a cause of the motions of the bowels. Is there, I would ask, any 
 proof that the bile is either the cause or a cause of those motions 
 of the bowels by which the faeces are expelled? This is a matter 
 which may be argued at some length. It may be said by those 
 who assign the above office to bile, that diarrhoea always happens 
 when the intestines contain a preternatural quantity of bile. It may 
 be said, in reply, that it is not proved that the bowels contain, in the 
 cases alluded to, a preternatural quantity of bile ; for the bile which 
 is vomited in cholera may be no more than a misplaced portion of 
 the natural quantity, and that which is evacuated from the rectum 
 may also belong to the natural quantity of bile, which appears to 
 be increased by a mixture with a large and preternatural proportion 
 of the visceral secretions. Besides, granting in this disease the 
 quantity of bile to be increased, the action of vomiting and the 
 supposed quickened, or inverted peristaltic motions of the bowels, 
 as at other times they all take place when there is no reason to 
 suppose a preternatural quantity of bile, and, as in cholera, the 
 sickness, &c. often continues when bile ceases to be discharged, 
 so these actions may be concomitant only with an increased secre- 
 tiou of bile, or the unconnected particulars of a general affection. 
 
196 
 
 Then, *ay the gentlemen, who will have bile to be a stimulus, 
 what gives origin to that commotion which takes place in cholera, 
 if it is not the presence of such an additional stimulus? This is a 
 ridiculous question, replies the opposite party ; it may be just as 
 well asked what gives origin to the increased secretion of bile, or 
 liow disease of any kind ever happens spontaneously? It is then 
 urged by the stimulators that the bowels are most regular when 
 the secretion of bile is the most natural. Aye, say the others; but 
 the bowels are sometimes the most active when there is no evi- 
 dence of the presence of any bile, as we have witnessed in those 
 who have had frequent and loose evacuations almost white, and 
 accompanied with much griping and tenesmus. It may be further 
 urged, on the same side, that the stools of those of the most 
 costive habits appear, so far as may be inferred from their colour, 
 to contain the largest proportion of bile: it may be noticed too 
 that persons may have stools of the usual appearance or even 
 lighter for some time, when, upon the the exhibition of a purgative, 
 dark scybala may be discharged, which, so far as may be judged 
 a priori, and from appearances, had lain a long time in the intes- 
 tines. Now if these scybala are made dark or black by the bile 
 they contain, how comes it that portions of faeces, apparently con- 
 taining the most bile, are not discharged so soon as portions con- 
 taining less, if the action of the intestines is stimulated by bile? 
 These and such like witticisms may be pursued on both sides, at 
 great length, but it is a subject on which little or nothing is 
 proved; I shall therefore hasten to take leave of it, merely sug- 
 gesting to the stimulators, that if the functions of animal bodies 
 are to be explained by a reference to efficient causes, precise rela- 
 tions, and real agency, it must be done without calling in the aid 
 either of whips or spurs. 
 
 12. But it will be asked seriously, does not then the bile con^ 
 tribute towards those actions of the bowels by which the faeces are 
 expelled? To this I reply, the inquiry is analytical, it has never 
 been attempted: and, unless we should gain some unexpected 
 lights from collateral knowledge, it never will be attempted with 
 success, until we have acquired that other sense of which we have 
 Before spoken. 
 
 13. There are others (I rejoice to say, very few) of those bold 
 theorists, men of some place too, who will tell us the use of bile as 
 easily as they can reckon their fingers. And of what use do they 
 say it is? Why, truly, to make fat: so weak, so silly and extra- 
 vagant a notion is very much below scrutiny. Let it suffice to say 
 that a child of ten years old would discriminate that such an in- 
 ference was not warranted, if the shallow grounds of it were clearly 
 stated to him. Suppose I were to assert the use of bile to be, 
 that the souls of elephants, formed in the air, imbibed by the 
 earth, taken into the stomach, and embodied with our food, should, 
 by its operation, be freed from purgatory, where they had been 
 confined for their sins, passing away into their native air, in a 
 
197 
 
 smoke, fitted for Elysium, &c. Suppose I were to assert this, no 
 one could prove that it was not so: the most that they could say is 
 that there is no proof of the existence of the souls of elephants in 
 the bowels. Just so with the assertion about the fat : I will main- 
 tain that there are the souls of elephants in the bowels, with just 
 as correct a reasoning as that which has been cited to prove that 
 the use of bile is to form fat. Quitting these puerile pretensions 
 to ingenuity, let us return to our indications of an analysis. 
 
 14. It has been stated in the preceding pages of this article, in 
 conformity with the prevailing opinion, that the principal end of the 
 function of the liver is to secrete bile : that it does this there can be 
 no doubt; and that the result has a reference to certain purposes in 
 the animal economy, or at least that it produces certain effects, is 
 equally clear. The object of investigation is to shew what these 
 effects are, and the strict mode of analysis, by which this object may 
 be attained, has been imperfectly pointed out. Having said thus 
 much concerning the uses or the effects of bile, it remains that we 
 should inquire a little into the history of its own formation. 
 
 15. The structure of the liver has been minutely examined by 
 anatomists, and is well known to every student, so far as it has been 
 described. The anatomists inform us that bile is produced in 
 minute tubes, expressed as the acini, pori biliarii, &c. or secreting 
 structure. The processes, or manner of secretion in general, will 
 hereafter be more particularly considered under that title. 
 
 16. As the secretion of bile has never been found, to take place 
 in the dead subject, and as this secretion, unless prevented by disease 
 or malformation, is found regularly to take place when life is present; 
 and as the only variety in tubes must consist of their comparative 
 size or shape, and as no specimen can be supposed to exist in one 
 place, which has, among myriads of tubes existing in every struc- 
 ture, no parallel elsewhere; so it is to be inferred from these data, 
 1st, that the organic spirit, or the living principle belonging to the 
 secreting structure of the liver, is necessary to its product; and, 2nd, 
 that as the same secretion does not take place elsewhere, although a 
 similitude in mere structure and material is assumed to obtain, so 
 the spirit, which is said to be essential to the secretion of bile, is a 
 peculiar one, or a modification of that general one which is identified 
 in all seats by the exhibition of common properties. 
 
 17. The peculiarity of the spirit in this seat is for the present 
 rested upon the above grounds, which are confessedly assumed. The 
 questions which might arise upon it have been in part discussed 
 in the chapter, " General Relations of Spiritual, Chymical, and 
 Mechanical Agents," and what remains to be said upon it will belong 
 to the article on Disease. For the present, the settlement of the 
 difficulties involved in the proposition is unimportant, and would 
 therefore be misplaced here. 
 
 18. Whatever the nature of the spirit which resides in the 
 secerning tubes of the liver might be, whether peculiar or common, 
 the dependencies of the spiritual formations of one part upou the 
 
198 
 
 relation subsisting between these and others belonging to a diffe- 
 rent seat, suggest, on the ground of analogy, that the existence of a 
 similar dependence should be investigated in this instance. It is to 
 be asked, 
 
 1st, Is the spirit, which by its relation with venous blood forms 
 bile, the regular assimilating life of the structure? or, 
 
 2nd, Is it dependent upon the vital properties of another seat? 
 and, if dependent, 
 
 3rd, Is the dependence regular? or is the communication constant, 
 by the force of a natural relation? or is it of the occasional kind? 
 19. In this case also, in inquiring into a dependence, it is our 
 first suggestion from analogy to intercept the communication of the 
 hepatic nerves with their centres. This should be done so near to 
 their entrance into the liver as to obviate any confusion which might 
 arise from considering the communication with their ganglia as 
 equivalent to a connexion with the brain or spinal marrow. The 
 result of this experiment would be, either that the secretion of bile 
 proceeded as usual, or that it was suspended. If the former, the 
 independence of the functional spirit of the liver of properties exist- 
 ing in the seats of the nervous centres would be shewn; if the latter, 
 viz. that the secretion of bile was suspended, then it would be in- 
 ferred that the functional life of the liver acknowledged a dependence 
 upon a distant seat. This inference would be sanctioned by certain 
 analogies, proving that where there is no dependence the injury in- 
 flicted by simple division does not tend to suspend or impair organic 
 processes. The dependence in this case, as before suggested, would 
 be one of two kinds, either for the receipt or the privation of certain 
 properties, by the force of a distant relation ; which of these remains 
 to be discriminated, for which purpose we are not without some 
 analogies. 
 
 20. With respect to the third question, viz. whether, -the de- 
 pendence being proved, it is of the regular or occasional kind, this 
 is to be determined only by observing the conformity of the result 
 of the function with these alternatives respectively. It will be 
 asserted that the secretion of bile is unremitting, and that therefore 
 the communication which makes the dependence, if any, must be so 
 too. That bile is unremittingly secreted is probable, and if it is not, 
 I do not perceive to what occasional cause an irregular communica- 
 tion can be ascribed in this instance. If a summary of the function 
 of the liver were to be attempted upon an imperfect evidence on 
 many points, furnished by loose and distant analogies, it would be 
 of the following kind. 
 
 '21. Bile is produced by the secerning structure of the liver. 
 It is produced by a relation which subsists betxveen the functional 
 life of this structure and venous blood. The functional life of the 
 liver is of the regular dependent kind : that is, the assimilating life 
 of the structure is so related with arterial blood as to produce itself, 
 or to separate and unite its elements; properties communicated 
 from another seat unite with the assimilating life of .the secerning 
 
199 
 
 structure of the liver, and constitute the functional life : such a 
 relation subsists between these two sets of properties, in the assimi- 
 lating and the acquired ; while the latter, or the properties obtained 
 from the distant seat, being only certain properties of life, and not 
 an assimilating principle, do not produce themselves from the blood 
 of the structure to which they are transposed, but merely unite with 
 the assimilating spirit of this seat and expire with it, requiring to be 
 renewed from their own source. These united properties, the 
 identified functional life, by its relation with venous blood, separates 
 bile; the laws of which separation will be hereafter spoken of under 
 the head of secretion. The bile thus produced is mixed with chyme, 
 and assists in those changes by which it is converted into chyle. 
 The use of bile is either wholly confined to the processes of the ali- 
 mentary canal, or else it gives some properties, independent of its 
 colouring principle, which being combined in the lacteal fluid have 
 a reference to some future offices in the animal economy, which 
 arise out of the relations of blood. The kind of investigation (ana- 
 lytical or synthetical, or both) which would enable us to decide upon 
 these present difficulties, is imperfectly sketched in the preceding 
 pages. Chymistry has detected certain substances, belonging to 
 bile, in its department : the chymical investigation, so far as it has 
 been honestly conducted, is no doubt laudable, as is every sincere 
 attempt to augment the sum of our intellectual wealth; but as the 
 chymical investigation has not yet elucidated a single question upon 
 which we have any interest in being informed, the exhibition of its 
 results may here be dispensed with. 
 
 . 
 
200 
 
 CHAP. V. The Spleen. 
 
 
 1. THE spleen i enumerated among the preparatory 
 organs, because from its situation and connexions it appears to be- 
 long to the system of the chylopoietic viscera. It is supposed that 
 its use, if it has any, is one subservient to the preparation of food. 
 but there is no absolute proof that it contributes any thing to this 
 purpose. The same might be said of the liver; at least, as remarked 
 in the last article, it is not ascertained what share bile has in those 
 intestinal conversions which are necessary to the maintenance of life. 
 The analogy holds good no farther than that there is mutually an 
 absence of demonstrative proof: but, in the case of the liver, a 
 product of its function is perceived, the destination of this product 
 may to some extent be traced: it is seen to mix with food, &c. and 
 that it tends to accomplish some useful purpose in the system, is 
 believed, agreeably with an extensive experience, that no regular 
 operations of this kind, which we have been enabled to understand, 
 take place in animal bodies without a reference to such future 
 purpose. The spleen furnishes no product: and as we are not ac- 
 quainted with the manner in which any similar viscus extends its 
 function beyond itself, we are left to conjecture concerning the mode 
 in this instance, without the support of any, or but a distant, analogy, 
 deduced from the phenomena of animal life. 
 
 2. We are nevertheless disposed to assign some use to the 
 spleen, on a ground which differs from that on which we assign an 
 use to the liver in these respects, viz. that the use of the former is 
 supposed from a general analogy, and that of the latter from the 
 particular analogy which obtains between it and other secreting 
 organs. We observe in a general way, that there is no part of an 
 animal body without its use, and when an apparent exception occurs, 
 in agreement with our general experience, we presume that our 
 ingenuity has been insufficient to discover the designs of Nature, 
 rather than that she has made the object of our suspicions in vain. 
 Let us, however, having stated the grounds by which we are induced 
 to seek a function of the spleen, take a short view of the more par- 
 ticular manner in which the inquiry respecting it has been conducted. 
 
 $ 3. The spleen, as is well known, has been removed from dogs, 
 and the animals have not only survived but have appeared to suffer 
 
1201 
 
 no inconvenience in some instances from its loss. This fact 
 proves that the use of the spleen, if it has any, is but of trivial 
 importance; accordingly, a function of the hydraulic kind only 
 has been supposed to belong to it. It has been considered, in- 
 geniously, as a mere reservoir of blood, subservient to the function 
 of the stomach. The theory alluded to is this : when the stomach 
 is distended by food, it compresses the soft texture of the spleen, 
 diminishing the quantity of blood which would otherwise pas* to 
 the splenic arterial ramifications, and thereby determining a 
 greater quantity to the stomach, through the vasa brevia and 
 gastro-epiploica sinistra, branches given oft* ^o the stomach, 
 HI the course of the spleuic artery to the spleen. The theory 
 further assumes, that the stomach receives an augmented supply 
 of blood, at the times when it is most required, for the purposes 
 of digestion. 
 
 4. That such an effect may take place from this arrangement, 
 in some degree cannot be denied; at the same time it may be 
 suggested that the pressure which the stomach may, under any 
 circumstances, be supposed to exert, is scarcely sufficient to 
 diminish the area of an artery of the smallest size, when blood is 
 forcibly impelled through it with the usual velocity of the circula- 
 tion. It may be suggested, that the momentum of the blood, cir- 
 culating in the spleen, presents a considerable resistance to any 
 cause of compression, and that the resistance is likely to be the 
 more effectual, when the compressing substance is from its texture 
 and configuration (that of a membranous cavity partially occupied 
 byjhtid contents) even more easily compressible than the spleen 
 itself. Some truth however may be allowed to this theory; and 
 the trifling degree in which the spleen, according to it, can be 
 conducive towards any useful purpose, agrees very well with the 
 slight derangement which has been observed to follow its entire 
 removal. It may be observed further, in the way of objection to this 
 theory, that determination of blood to particular seats takes place 
 either regularly, or at intervals in many, perhaps in most, diseases ; 
 and that such determination is produced without any such arrange- 
 ment as that which is here supposed to be merely subservient to 
 it. But, without drawing our examples from the phenomena of 
 disease, we may quote one instance in which the occasional in- 
 crease of the quantity of blood, circulating in an organ, takes 
 place indispensably for the purpose of an occasional function. In 
 this instance (furnished by the phenomena of the pudic artery) 
 nature is seen to accomplish the increased determination of blood 
 to a part with no other mechanism or contrivance than that which 
 belongs to its own vessels, which are made liable to a general, and 
 an occasional state of dilatation. It must be observed iu regard 
 to the spleen, that the fact just quoted furnishes an analogy 
 against the theory proposed respecting it; and further, that we 
 perhaps ought scarcely to conjecture that complicated means are 
 at one time instituted by nature, for a purpose which is in other 
 E 
 
202 
 
 instances observed to be accomplished by the most simple. 
 Enough, however, of this. 
 
 5. Another theory which has been proposed in explanation 
 of the use of the spleen is, that it is a viscus to which a large 
 volume of arterial blood is sent, for the purpose merely of its con- 
 version into venous blood; that the object of this conversion is to 
 supply to the liver an adequate quantity of that blood from which 
 bile is secreted. This theory is perhaps ^better supported by per- 
 ceptible occurrence than the last j the blood from the splenic vein 
 certainly goes to the liver, and if bile is secreted, as is from other 
 circumstances made probable, from venous blood, then the spleen 
 must have a function of this kind by which it is related with the 
 office of the liver. These theories, perhaps, may, either singly 
 or both together, make up the tru account of the use of the 
 spleen. That it is not a secretory organ is obvious: we have 
 therefore, in considering its vital properties, to determine only 
 concerning the laws of those which belong to a structure made up 
 of arteries, veins, nerves, membrane, &c.; exhibiting, either in- 
 dividually or collectively, no function which is not every where 
 common to these components of the textures. 
 
 6. According then to the analogy of the mixed structures, 
 and according to the test of division, which has already been 
 sufficiently spoken of, we should at once decide that the life of the 
 spleen is simply of the assimilating kind. The only manifest con- 
 version of fluid which .takes place in it is that of arterial into 
 venous blood; a process/which goes on alike in the paralytic 
 limb, or in one, the nerves of which havse been divided, and in 
 that whose animal character is entire. 
 
 7. If, then, the spleen can scarcely be suspected to be related 
 with the preparatory processes, in- any except the subordinate way 
 suggested by the preceding theories; if such is the only way in 
 which it concurs mediately with the digestive organs ; it is next to 
 be inquired, if it contributes directly, by a relation with the 
 spiritual properties of adjoining structures, to the common end? 
 In answer to this question, it need only be reoiarked that we are 
 precluded the precise analytical and synthetical tests in examining 
 relations of this kind. We can merely ascertain the existence of 
 such .a relation, and we infer it when regular phenomena are modi- 
 fied, or made to cease by intercepting communications between 
 parts, and when there is no reason to suspect a mediate relation, 
 established by the intercourse of fluids. Hence, as the spleen has 
 been removed, with no other eiFect or influence of. the direct kind 
 than that which might be supposed to arise .rather from the in- 
 fliction of an injury than from the privation of accustomed pro- 
 perties, we possess no evidence by which a relation of this sort 
 may be established in the present instance.; .Indeed the fact just 
 cited proves, that if the spleen, has any use. at all, it is not worth 
 inquiring after; a sufficient ground for dismissing it from: our 
 present consideration. 
 
203 
 
 CHAP. VI.- The Pancreas. 
 
 1. OF this viscus it is sufficient to say, that it is liable 
 to the same order, and furnishes nearly the same objects, of inves- 
 tigation, as those which have been suggested with respect to 
 the liver. 
 
 2. The end accomplished by the function of the pancreas is 
 first to be inquired after. Its structure is glandular, and it pours 
 a fluid into the duodenum. What is the importance of this fluid? 
 This question is to be answered by an analysis, many times indi- 
 cated, and therefore requiring here no repetition. Is it useful 
 only in the processes which are conducted in the intestines? or 
 does it furnish properties which constitute a part of lacteal chyle, 
 and have a relation with the animal economy, through the medium 
 of the circulation? 
 
 3. Having determined the importance or objects of the pan- 
 creatic secretion, it is next to be inquired whether it has any other 
 mediate relations? The one suggested as comprising the function 
 of the spleen, vii. the deterioration of arterial blood, will occur as 
 one other mediate relation; and in this respect the pancreas, in 
 common with the other abdominal viscera, appears subservient to 
 the purposes of the liver. 
 
 4. The direct relation, if any, of the pancreas with adjoining 
 organs, is next to be sought after. The mode of conducting such 
 an inquiry has been pointed out, so far as is compatible with our 
 limited means of cognizance. But as there is no reason to suspect 
 the existence of any relation of the direct kind between the pan- 
 creas and the other preparatory organs, so it is superfluous to be 
 more minute in our indications respecting it. 
 
 5. The chief use of the pancreas appears to be that of pro- 
 ducing a fluid which mixes with the common material of the in- 
 testines. It remains only to inquire into the history of this secre- 
 tion. The dependences of it are to be sought after; as whether it 
 is a product of the assimilating, the regular dependent, or the oc- 
 casional life: with the investigation which has been proposed as 
 appropriate to these respectively. 
 
204 
 
 CHAP. Wl.Mesenteric Absorbents. 
 
 1. DO these vessels merely serve the purposes of tubes, or 
 have they a function superadded to their mechanical construction? 
 
 2. if the absorbents of the mesentery had a relation of the 
 mechanical kind, and no other, with the contents of the intestines, 
 there appears no reason why the peculiar fluid . which is found in 
 them should be taken up, rather than some others which also make 
 a part of the intestinal contents. There are sufficient grounds for 
 supposing that bile is poured into the bowels, sometimes, in con- 
 siderable quantities; yet it does not appear that bile is taken into 
 the lacteals, or any of those almost aqueous fluids which exist in 
 the intestines, and are tinged with bile. If it be said that bile is 
 too thick a fluid to enter the orifices of the absorbents, the same 
 cannot be said of these aqueous fluids: nor, indeed, is the objec- 
 tion with respect to bile itself founded on analogy. To put this 
 discussion into a briefer form, 
 
 3. Fluids existing in the intestines, and of a tenuity which 
 renders them capable of permeating the lacteals, are not taken up 
 by these vessels. Certain other fluids, constituting one of a pretty 
 uniform character, are taken up by the lacteals. The inference from 
 these facts is, that the lacteal orifices exercise a function of the 
 elective kind, by which some fluids are taken into them and others 
 rejected. 
 
 4. The great proportion of watery liquors taken into the 
 stomach pass off by the kidneys or skin: as when a person drinks 
 two quarts per diem, and has a costive stool once in two or three 
 days. It matters but little how the qualities of these riquid ingesta 
 are varied; whether cyder, beer, lemonade, water, wine, tea, 
 coffee, gruel, or medicated drinks, or these mixed, they all enter 
 the lacteals to pass off by urine or sweat. From this fact we 
 should be disposed to infer that fluids pass from the intestines into 
 the lacteals merely according to hydraulic laws. But this in- 
 ference cannot be made positively, because the feet is liable to 
 another explanation; and we require some further facts to decide 
 whieh is true. A function of the above elective kind might be 
 exercised by thelacteal orifices on all these fluids; that is, they 
 may possess some properties in common with which tjiose of the 
 absorbents are related. 
 
205 
 
 5. Hence the alternatives to be decided upon in this stage of 
 the inquiry arc, whether the entrance of fluids from the intestines 
 into the mesenteric absorbents is a process wholly hydraulic or 
 wholly functional, or whether not exclusively either, but of the 
 mixed kind? These alternatives may be discussed by consulting 
 analogies, &c. to some length ; but as we do not possess the facts 
 which will justify any very positive conclusion, I shall leave them as 
 alternatives on which our decision is suspended. 
 
 6. Although we cannot determine whether the hydraulic pro- 
 cesses have any, or how great, a share in the entrance of fluids into 
 the lacteals, it will scarcely be doubted that the orifices of these 
 vessels operate processes upon the intestinal material of the functional 
 kind. We know that the fluids of the intestines are mixed, and that 
 it is inconsistent with analogy (as well, perhaps, as verifiable by 
 direct experiment) that the separation of lacteal fluid from this mass 
 should be performed by a mere mechanical filtration, or a mere 
 capillary absorption. If then the separation is an animal process, 
 in some respects resembling secretion, it is to be investigated rather 
 according to the laws of life than of inanimate matter. 
 
 7. Does any lacteal absorption go on after death? An animal 
 may be killed a few hours after a full meal, at a time when it might 
 be presumed the nutrient fluids exist copiously in the bowels : it is 
 possible that, under these circumstances, by examining with a magni- 
 fier one or more lacteal trunks, the contents of which are compressed 
 out, it may be ascertained, either by their filling again or remaining 
 empty, whether lacteal chyle is separated and absorbed from among 
 the general contents of the intestines after life is extinct. The 
 peristaltic movements may be imitated, or the contents of the small 
 intestines agitated, with a view to facilitate mechanical separations; 
 and under the experiment the animal temperature may also be pre- 
 served. If no absorption took place, as from analogy seems most 
 probable, it would then be decided that this instance of absorption 
 is wholly an animal process. Presuming that it is an animal process 
 from the analogies hinted at (which may be adverted to in the gross, 
 by saying that none of the processes which take place during life 
 happen in the same way after death), presuming upon these analo- 
 gies, it is to be inquired in what way, or what are the agents mutually 
 concerned in the separation and absorption of chyle from the intes- 
 tines by the operation or concurrence of the properties of life? 
 
 8. It may here be urged against the conclusiveness of the 
 above experiment, that after death the area of the absorbents is 
 different from that which obtained during life; and hence a separa- 
 tion of an hydraulic kind may not take place from an altered diame- 
 ter of the tubes which should perform it. This objection, however, 
 is of no great weight; for we can conceive a fault in the diameter of 
 the tubes to be one of only two kinds, they are either too large or 
 too small. Now it is ascertained in the sanguiferous system, and it 
 is here in consonance with every analogy which can be cited, that 
 the area of vessels is greater during life than after death ; that is, both 
 
206 
 
 their powers of contraction are, during life, to a -certain degree, over- 
 come by the distending force of the fluids they convey; hence the 
 separation and absorption of chyle proceed under, their greatest possi- 
 ble area. And as there are tinu:s and cases of inanition, in which ab- 
 sorption does not proceed at all, or but dubiously, so at these times the 
 vessels being left to the operation of their tonic contractile power, will 
 be reduced to a less diameter Jhan after death. Yet will the process 
 of lacteal absorption be resumed, when the material (as in those nearly 
 starved^ is again furnished, although their area be reduced to a size 
 less than that to which they would be brought by their elastic power, 
 the only one which operates after death. Hence, if lacteal absorption 
 proceed under the extremes and intermediate degrees of area of 
 which these tubes are capable, and after death does not proceed under 
 a degree which during life was shewn to be compatible with the pro- 
 cess, the want of absorption in the former case, and the occurence of 
 it in the latter, must be attributable to something more than a de- 
 pendence upon the caliber of the vessels. This reasoning in part 
 proceeds upon the assumption of an analogy between the contrac- 
 tilities of the mesenteric absorbents and those of the arteries. 
 
 9. The question would be in a great measure decided by the 
 result of such an investigation. But presuming upon the analogies 
 before mentioned, that the absorption of fluids by the lacteals is a 
 process in great measure, if not wholly, functional, the laws of the 
 function are to be investigated principally with a view to the settle- 
 ment of the following points: 
 
 1st, By what is the function of the lacteal orifices constituted? 
 This question must be answered (if the function is one belonging 
 necessarily to a living structure) by properties of life, with the con- 
 currence of a structure of certain mechanical arrangement, and made 
 up of chymical constituents. 
 
 2nd, What are the properties of life engaged in this function? 
 We cannot define them: we may say that they are peculiar, or in- 
 volve, or are connected with the common ones, viz. with those which 
 prevent decomposition of the textures; but how they are connected 
 with these we are not yet to consider. 
 
 3rd, What share in the function is to be attributed to the vital 
 properties, and what to the mechanical and chymical constitution? 
 This is an inquiry into dependences on which a short sketch must 
 suffice. If the absorption does not take place without life, then it 
 is dependent upon life; but there is no example of a process of any 
 kind which is confessedly dependent upon life, taking place without 
 also the aid of the textures. Here, in perhaps most other instances, 
 analysis must stop; but in this we may proceed a little further: as 
 observed in the article " Relations of Vital, Chymical, and Mechani- 
 cal Properties," mechanical construction is directly related only with 
 mechanical phenomena. The spiritual and chymical agencies have 
 been said to be directly related with each other, and to be inter- 
 mixed. We are under the necessity of supposing this, because we 
 remark the perpetual changes which are mutually operated in these 
 
207 
 
 departments ; we find that the most powerful agents which affect 
 the spirit are of the chymical kind; we know how life and its pro- 
 cesses are modified by them ; and we see them, as in the cases of 
 poisons, producing its extinction, &c. But although from their 
 alliance we consider these properties as chymical, yet may they (the 
 efficient ones) be wholly vital, and not those by which the pheno- 
 mena of the laboratory are accomplished. My meaning may be 
 illustrated by a supposed example. Thus, death may be occasioned 
 by one of the metallic oxyds: with respect to its chyraical nature, it 
 is an oxygenated metal which kills ; but it may possess properties 
 related with life, which do not belong to the metal or to the oxygen, 
 but which are allied or associated with them, and having their rela- 
 tion only with vital properties, are inefficient in regard to the 
 chymical ones: that is, the chymical substances may be related with 
 those of their own kind, which are met with in the laboratory; and 
 their vital associated properties also with those of their own kind, 
 which are met with in living bodies, and perhaps in spontaneous 
 formations approaching to life. This, however, is a refinement 
 merely consistent with the doctrines of causation, and not worthy of 
 attention in the present state of analytical research, which is yet to 
 be employed upon grosser matters. To return from this digression: 
 the supposition of a mechanical agency in this business of lacteal 
 separation and absorption is, on the grounds referred to, dismissed. 
 With regard to the chymical, we observe that the agents of chymis- 
 try are generally of the material kind; hence we have difficulty in 
 distinguishing their share in phenomena occurring by means of the 
 secretions, but not in places where secretions do not take place; and 
 as the absorbent, in some respects stands contra-distinguished to the 
 secerning, extremities, so on this ground the supposition of a chymi- 
 cal agency can scarcely be indulged. According then to this view, 
 at least the principal agency in the business we are considering ap- 
 pears of the spiritual kind. 
 
 4th, Are the separation of lacteal fluid from intestinal chyle and 
 its absorption to be considered as the result of one process, or are 
 they accomplished by the same properties? We can answer this 
 question only by remarking, that the absorbents elsewhere shew a 
 capability of absorbing almost any substances which are fairly sub- 
 mitted to their action ; and that when, as in the present case, they 
 take only, from among many, one fluid, which rarely digresses from 
 a pretty uniform character, the exception must be attributed to some 
 peculiarity, to the operation of properties which do not obtain gene- 
 rally in the absorbent system. Whether these modifying properties^ 
 those which make this example of absorption peculiar, are those 
 upon which also depend the separation of lacteal fluid from the in- 
 testinal material, is more than can be decided, or even conjectured 
 upon with any great shew of truth, in the present state of our 
 evidences. 
 
 5th, Is lacteal fluid a mere separation? or is it a new constitution 
 made up by a combination of properties from absorbent orifices 
 
208 
 
 with related properties, and, conjoined with them, mediately-re- 
 lated substances, belonging to intestinal chyle? As the properties 
 referred to are of the spiritual kind, analysis cannot reply to this 
 question; which must therefore remain a question, on which perhaps 
 a few words might be said when we speak of secretion and absorp- 
 tion in general. 
 
 6th, Do any changes happen to the lacteal fluid, in the course of 
 its transmission from the lacteal orifices to the left subclavian vein? 
 Do any changes occur in consequence of a function possessed, by the 
 tubes themselves, or by their glands? There is, I believe, no proof 
 of such changes. The sensible appearance of the fluid is throughout 
 pretty nearly the same. With respect to a supposed function be- 
 longing to the mesenteric glands, some remarks might be cited from 
 our pathological experience; these however will have but little 
 weight. It may be said, that if these glands are obstructed, nutri- 
 tion will be impeded : this proves only that a mechanical fitness of 
 the structure, a pervious state of the vessels, is necessary for the 
 transmission of their contents. It will be said, too, that in old age 
 the glands of the mesentery are almost entirely removed : old age is 
 sometimes attended with a diminution, and sometimes with an 
 increase of bulk.* These facts, therefore, so far as they may be 
 allowed to favour any conclusion, seem to indicate that the tubes 
 and glands of the lacteal system have no function or use, in addition 
 to that which they possess as a mechanical structure. This opinion 
 derives its principal credit from the circumstance that whatever 
 variety the tubes and glands of the mesentery might suffer from 
 disease, the variety affects only the quantity of fluid transmitted to 
 the sanguiferous system, while the quality and appearance of the 
 fluid have not been observed to suffer any alteration which might 
 be imputed to a disordered function. If I were inclined to con- 
 jecture upon the use of absorbent glands, as one might conjecture, 
 in infinitum, upon things where the evidence is of the most dubious 
 and insignificant kind, I say if I were disposed to do this, I could 
 add but very few conjectures to those worthless ones which have 
 been already proposed upon this subject which is as well left alone. 
 
 7th, As it may be said to have been shewn that the separation 
 and absorption of lacteal fluid is probably accomplished by the 
 spiritual properties of the structure, or by its life; the nature of this 
 life, or the history of these properties, is next to be inquired after: 
 here there is little to be done but to recur to a leading division 
 which has been proposed with respect to the other organs. It is to 
 be inquired, is the assimilating, also the functional life of the lacteals? 
 or, is the latter of the regular dependent, or of the occasional kind? 
 The choice lies between the two former, and the only clue for the 
 investigation is that before mentioned to have been adopted in some 
 
 * Is such spontaneous removfcl of the glandular structure of the absor- 
 bents attended with an obliteration of the absorbent vessels, which before 
 passed through it, or is the continuity of permeable absorbent tubes pre- 
 served amidst the absorption of connected structure? 
 
209 
 
 other instances with success, consisting in a division of the nerves 
 which supply this structure, and an observation of the results 
 of this division, in regard to the separation and absorption of 
 lacteal chyle. 
 
 10. The processes by which the ends of this function are ac- 
 complished may be inquired into with much greater minuteness. 
 There is hope, however, of adding but little that is valuable, by 
 such inquiry, to the information which is already attained upon 
 the subject. This information respects the final purpose of the 
 function. It may be said, in the way of a summary, that the vital 
 properties of the lacteal orifices are, with the concurrence of their 
 structure, so related with the contents of the intestines, that a 
 fluid of a certain character is separated, or formed from the gene- 
 ral mass: that this fluid is conveyed in a way, of which we shall 
 hereafter say a few words, through the absorbent vessels and 
 glands into the sanguiferous system; that the fluid thus conveyed 
 is necessary to nutrition ; and that the function of the lacteals is 
 thus mediately related with the diffused life and textures, there being 
 no evidence of a relation of the direct kind, or one by which the 
 results of a functional life, or occasional phenomena, are produced, 
 as by a communication of properties with a related seat. The 
 only way in which the lacteal system may be supposed to be 
 directly related with another seat is that of a possible dependence 
 for properties received ; of which enough has been already said. 
 
 11. At this place we may say, that the enumeration of- one 
 system of preparatory organs is ended. It has been sketched 
 what are the principal points of investigation belonging to these 
 organs: these points might have been much more minutely par- 
 ticularized ; but the design of these articles is to exhibit a general 
 view of relations which are to be taken into the account, though 
 most commonly overlooked, in an inquiry concerning the opera- 
 tions which concur to maintain a living body. It is not attempted 
 to give a complete explanation of any single process ; each process 
 must be the object of a specific and undivided investigation. 
 Such particular investigations abound in the records of physiology, 
 but they have not embraced the whole of the topics which belong 
 to them. Some have thought to explain the physiology of these 
 organs by a minute delineation of their anatomical structure; 
 others have applied chymistry to the same end : both have failed 
 totally. Others have considered the principle of life as the secret 
 agent in all these processes. But none have considered these three 
 as they are related with each other; much less has any one at- 
 tempted an analysis of the last, by which any leading laws, or 
 classification, may be assigned to it : and still more remote has it 
 been from the designings of physiologists to evince that life, as an 
 agent, operates, and is acted upon, in a manner which is common to 
 every possible form of existence. This matter will however here- 
 after require a general recapitulation. 
 
 F F 
 
210 
 
 12. The organs enumerated in this section appear to form 
 one system: the division here adopted may be artificial, but 
 it is convenient. It is founded upon an apparent concurrence of 
 their several functions to produce lacteal chyle, and to convey it 
 into the system of the blood-vessels. The accomplishment of this 
 purpose constitutes that which is termed nutrition. The further 
 history of this lacteal fluid will shew that there is no part of the 
 body, no process in it, we may say no property of it, which does 
 not acknowledge a dependence upon this nutrient material. Hence 
 the organs which produce it are thus mediately related with all 
 other parts: the relations subsisting among themselves, and tribu- 
 tary to this one purpose, still afford an ample field for research and 
 discovery. Lacteal chyle being poured into the sanguiferous sys- 
 tem, its future history will commence from this point, and will be 
 involved in the phenomena dependent upon the blood. 
 
 . 
 
211 
 
 SECTION III. 
 
 RELATIONS OF BLOOD, AND ITS PRODUCTS, IN ITS VESSELS, 
 AND IN THE SEVERAL PLACES OF ITS DISTRIBUTION. 
 
 CHAP. I. Formation of Blood. 
 
 1. BLOOD is a conversion of chyle, or another change 
 in the preparation of that fluid furnished originally by food, and 
 traced through the processes of digestion, &c. We have found it 
 no difficult matter to specify the seats of certain conversions which 
 take place in the alimentary canal: it \vill not be found so easy to 
 assign the seat of conversion of lacteal chyle into blood; this, 
 however, is our present business. 
 
 2. To pursue the question analytically, according to rules of 
 causation, would embrace an investigation with respect to the follow- 
 ing objects: 1st, it is to be determined whether blood has proper- 
 ties communicated to it, which properties are not possessed by 
 chyle; or, 2nd, whether chyle is made blood by a separation or 
 abstraction of some of its properties; 3rd, whether these modes 
 of causation both take place; and, 4th, what are those properties 
 which constitute the difference, whether foreign ones superadded 
 to chyle, or deficient ones abstracted from chyle, and by such ab- 
 straction admitting the condition of bloodl 5th, is blood made by 
 a single conversion of chyle in the sanguiferous system, or many 
 conversions? if the latter, the comparative changes are to be in- 
 vestigated with the above objects and the properties engaged, 
 specified ; 6th, the causation is to be proved by the analytical and 
 synthetical tests ; 7th, the seats of individual conversions or changes, 
 with the history belonging to each, are to be respectively developed 
 and assigned. An investigation, according to this method and 
 with these views, is to be hoped for in the progress of science : it 
 
212 
 
 must be specific and undivided ; the several objects and their con- 
 nexions must never be lost sight of; in the conduct of it there must 
 not be one superfluous design, and in the detail of its results not one 
 superfluous sentence. This is a project, I fear, for the next age : we 
 must for the present, at least in this place, be content to proceed 
 more loosely, without however wholly losing sight of these indica- 
 tions for an analysis. 
 
 3. Lacteal chyle being poured into the sanguiferous system, of 
 course becomes red by its mixture with blood ; but a source of its 
 colorification is necessary, 1st, because the present red blood is 
 changed, or other blood substituted for it from the lacteal fluid, in 
 the lapse of time; and, 2nd, because, although a white fluid may 
 have its colour changed by mixture with a red one, this mode could 
 not obtain before the red fluid was formed, viz. in the first periods 
 of the ovum ; or, as best exemplified in the stages of incubation. 
 Some source of the colour therefore is necessary. 
 
 4. The change of colour is the most obvious one which chyle 
 undergoes: perhaps in real utility it might be subordinate, or 
 probably altogether unimportant. Whether this change is only a 
 concomitant with others, and what those others are, can be deter- 
 mined only by our comparative analysis. The seats of those other 
 changes are to be sought after when the changes can be specified ; 
 for the present, we may take the obvious one of colour, as a clue Jo 
 the investigation of the associated changes which we have supposed. 
 
 5. If it is inquired generally what is the seat of the conversion 
 pf chyle into blood? it must be replied, as generally, the seat of it 
 is in (he vascular system, where it is observed to occur; but a more 
 particular question would require us to specify in what blood-vessels, 
 or in what structure of their distribution, or is the faculty of the 
 conversion common to all? 
 
 6. The general opinion seems to tie that arterial blood is made 
 in the lungs; that venous blood is a product connected with a 
 function either of the arterial capillary terminations, or of the 
 minute origin of the veins. 
 
213 
 
 CHAP. II. The Lungs. 
 
 ], THAT the seat of the conversion of venous into 
 arterial blood is in the lungs, is very evident: it is quite another 
 matter to affirm that the lungs constitute the seat of the conversion 
 of chyle into arterial Wood. If we seek here for proofs, we shall 
 not find them. To proceed, however, 
 
 2. Chyle, it is said, or if not said is currently imagined, is made 
 blood in the lungs. What are the grounds of the inference? Why, 
 jt will be observed, we see that the colour of the blood carried into 
 the lungs by the pulmonary artery is different from that which is re- 
 turned to the heart by the pulmonary veins. This fact relates to 
 the changes of blood, not to those of chyle. Is there no better proof! 
 
 3. The function of the lungs, it is said, consists in an exposure 
 of blood to the influence of atmospheric air, by which it becomes 
 oxygenated. Now, then, imitate this function with respect to lacteal 
 chyle, expose it to atmospheric air, and see if it will be converted 
 into blood ; the experiment is easy. It is converted into nothing, in 
 point of colour, like blood, either arterial or venous. The lacteal 
 chyle is nearly white, its colour is not immediately changed by ex- 
 posure to air: by a continued exposure it becomes a little darker; 
 but still its colour cannot, without a great stretch of the imagina- 
 tion, be fancied to resemble distantly that of arterial blood. It re- 
 mains to be known whether any of those differences between chyle 
 and blood, which chymists have either discovered or fancied, occur 
 on the exposure of chyle to atmospherical air. 
 
 4. From the above fact, viz. that lacteal chyle is not made 
 blood by exposure to atmospheric air, one of two inferences must 
 be deduced ; either that the conversion we are considering does not 
 take place in the lungs, or that, if it does take place in the lungs, 
 these organs possess a function independent of, or superadded to, 
 the influence by atmospherical air. These alternatives will require 
 a short discussion. 
 
 5. We are furnished by nature with no proofs derived from the 
 observance of the phenomena of health or of those of disease, that 
 the conversion of chyle into blood takes place in the lungs. If 
 therefore we require proofs upon this point, they must be sought 
 after experimentally. 
 
214 
 
 6. There is only one experiment which can apply to this ques- 
 tion; it is by observing whether chyle, thrown into the vessels of the 
 lungs, is made blood. Thus far the experiment is practicable: but 
 but there would be absurdity in attempting it, 1st, because in the 
 Jiving organs the blood in the pulmonary vessels would be fluid, the 
 chyle would mix with this blood, and the design of the experiment 
 would thus be frustrated; 2nd, because if the blood were not fluid, or 
 if it were in part coagulated, then chyle would in some degree mix 
 with it, and receive a tiage from its colouring matter; and, 3rd, because 
 the lung in this state would be deprived of its life; a circumstance 
 sufficiently important to invalidate any inference which might be 
 founded upon an assumed analogy between the natural and the 
 artificial process. 
 
 7. We are then, it appears, furnished with no proofs, either 
 natural or from the resources of art, by which the seat of the con- 
 version of chyle into blood may be shewn to be in the lungs. As 
 we cannot obtain proofs with respect to this conversion, we must 
 seek for evidence of a weaker kind. 
 
 8. The conversion takes place somewhere in the sanguiferous 
 system : is it by a property possessed by the blood-vessels them- 
 selves? There is, it must be replied again, no proof of the existence 
 of such a property; neither is there any experiment which would 
 decide the question, unless it be one by which the mixture of chyle 
 with ready formed blood would be prevented. This may be done 
 by enclosing a certain space of an artery of a living subject between 
 two ligatures, and injecting this portion with chyle; but if the con- 
 version did not occur in this space, it could scarcely, on this account, 
 be inferred that the arteries do not possess the properties by which 
 the conversion is effected, as the action of the ligatures may intercept 
 a spiritual intercourse, upon which such a function may depend. 
 However, the evidence furnished by the result of such an experi- 
 ment is liable only to the general objection that the natural function 
 of a part is to be inferred suspiciously from experiments which place 
 it in a preternatural condition, and thereby destroy the analogy upon 
 which the inference is founded. This latter is the point to be attend- 
 ed to in experimenting: and, in the present case, to decide whether 
 the operation of the ligatures interfere with those points of analogy 
 which affect the inference, would require another investigation. 
 
 9. There is only one obvious change which takes place in the 
 lungs, and that is the conversion of venous into arterial blood. 
 This change appears to be wholly atmospherical, as a similar one is 
 found to occur in venous blood, when exposed to the air, removed 
 from any influence of the properties of the living structures. This 
 is a change upon which chyraistry has been busily employed ; and, 
 as is usual with chymical investigations, applied to animal pheno- 
 mena, just so much has been ascertained as is not worth knowing. 
 
 . 10. The seats of the other conversions of the circulating fluids 
 may be fixed with some precision, because it may he observed 
 where, in what order of vessels, in what viscus, these changes occur. 
 
215 
 
 With respect to the conversion of chyle into blood, the scope of its 
 seat is no less ample than the whole vascular system. These additional 
 questions arise upon it: 1st, is the conversion produced by a relation 
 which chyle has with the properties of the arteries? or, 2nd, is it by 
 a relation with properties of the veins? or, 3rd, is it by a relation 
 with properties of the lungs, superadded to their atmospherical 
 function? or, 4th, is it by a relation with the secerning extremities 
 of the arteries? or, 5th, if with these extremities, is it common to all, 
 or does it belong only to those of a particular seat? or, 6th, is there 
 any other viscus in which the conversion takes place? or, 7th, is the 
 conversion of chyle into blood an effect produced in no single seat, 
 in no one order of vessels, but a result of all the processes which 
 occur in the vascular system? and, 8th, if not the result of all, but 
 of some or many of the processes, what are the seats of those pro- 
 cesses r and of what kind are they? This latter question will admit 
 the application of the analysis which has been many times ske'tched. 
 
 11. Until it shall be shewn that the conversion of chyle into 
 blood takes place in the lungs, there is nothing more to be said of 
 these organs; there being no proof that they possess any function in 
 addition to that of converting venous into arterial blood. X er > e ven 
 in this simple matter, there is something for the chymists to settle, 
 the minute inquiry into which might furnish those proofs which we 
 have just said were wanting. We require to be informed satisfac- 
 torily, whether the same integral changes occur in blood removed 
 from the body as those which take place in the lungs. To answer 
 this, they must extend their analyses: whether the same gases arc 
 evolved? whether the same are imbibed ? whether the same constitu- 
 tion succeeds among the other components of blood, i.e. whether the 
 constituent properties of blood will preserve in every respect the same 
 relations? whether the exhalations are of a similar quality? From 
 the results of inquiry upon these topics (which may be still further 
 multipled) it is to be inferred whether the relation of blood in the lungs 
 is wholly of the atmospherical kind. If it is not, then the properties 
 of life come to be considered, as whether of the assimilating, or of 
 the regular dependent, or of the occasional kind, in agreement with 
 those indications for an analysis which have been before mentioned. 
 
 12. The mechanical phenomena of respiration have been in- 
 vestigated with more success than those which respect some other 
 relations of life. The lungs are considered as passive in the 
 acts of respiration. Their soft and cellular texture is compressed by 
 the diaphragm, &c. and the air thus forced out of them, the capacity 
 of the thorax being at this time diminished: this is the act of expi- 
 ration. In inspiration, the air enters the cells of the lungs, the 
 diaphragm sinks, and the capacity of the chest is increased : these 
 acts are alternated, and they constitute mechanical respiration. 
 Thus far the matter is very clear. Yet though the supposition is 
 tolerably current that little or nothing remains to be added to our 
 information respecting this process (its dependence upon the brain 
 
216 
 
 through the medium of the nerves having been ascertained), yet I 
 suspect there are some points which have either not been thought 
 upon or are at least not determined, and may therefore be proposed 
 as questions. 
 
 1st, Is the descent of the diaphragm in the first and subsequent 
 inspirations mechanical? that is, does the pressure of the air cause it 
 to descend, or does it descend by an inverted contraction of those 
 fibres which produce its ascent! or, 
 
 2nd, Are these two acts, viz. inspiration and expiration, pro- 
 duced by the contraction of two sets of muscular fibres ? The most 
 obvious solution of this matter seems to be, that the fibres of the 
 diaphragm contract only in the act of expiration, that their power of 
 contraction is spent by each exertion of it, and that having con- 
 tracted their full sphere, the resistance to the pressure of the air 
 ceases, and this medium entering the lungs, distends them and de- 
 presses the passive diaphragm, which having attained a certain 
 point, re-acts and expels the air. Thus far the theory: then, arising 
 out of it, it is to be asked, 
 
 3rd, What share has the pressure of the air or the distension of 
 the lungs in producing a contractile movement of the muscular 
 fibres? It will be pertly answered to this question, the stimulus of 
 pressure or disteution causes the diaphragm to contract. Let it then be 
 called a stimulus, since we must designate the agent by some name. 
 
 4th, What then is the relation of this stimulus with the power of 
 contraction? is there a property belonging to pressure or distention, 
 directly related with the animal properties of the structure ? or is 
 the relation mediate; that is, by the intervention of mechanical 
 properties of the texture, related with the vital ones? These points 
 settled, it remains to be determined concerning the relations by 
 which the act of contraction is constituted ; as, 
 
 5th, Whether the properties related with this stimulus of dis- 
 tention, and concurring with it to produce the contraction, live by 
 assimilation in the structure of the respiratory muscles,? or whether 
 they are obtained from a distant source? The latter appears to 
 have been ascertained by the results of the division of nerves, &c. 
 This conclusion admitted, 
 
 6th, Are those properties of the respiratory muscles derived 
 from a distant source, regularly and unremittingly communicated 
 while the nerves are unimpaired ? or are they of the occasional kind, 
 that is, produced in the muscles by a process of the following order : 
 1. Foreign properties (the stimulus of distention) related with and 
 producing change of the inherent ones of the muscles. 2. This 
 changed condition of the inherent muscular properties related with 
 others belonging to the nervous centres. 3. Effect of this rela- 
 tion, that properties from the centre (under this process) are com- 
 municated to the distant muscles. 4. Conjoint result of all these 
 properties, a contraction of the muscular fibres? These questions 
 belonging to mechanical respiration, are here merely suggested, 
 
217 
 
 their discussion will belong more properly to the subject of 
 animal life, and to that part of it which relates to the laws of 
 muscular motion. 
 
 13. The probable mode in which the oxygenation of blood 
 in the lungs takes place, may be thus briefly described: during 
 expiration^ capillaries which communicate with the air-cells imitate 
 the process of secretion, or else merely exhale an aqueous vapour; 
 during inpiration, these capillary, or exhalent, vessels become 
 filled with air, and by continuity of tubes convey air, or certain 
 properties of it, to the blood. 
 
 G G 
 
218 
 
 CHAP. III. Arterial Blood. 
 
 1. IT has not been presumed to assign the seat of the 
 conversion of chyle into blood: but the conversion of venous into 
 arterial blood takes place in the lungs. It has been suggested, in 
 speaking of these organs, that the obvious changes, as that of 
 colour, &c. may not be the most important ones. Although the 
 exposure of venous blood to the air, by which, as they say, it i* 
 oxygenated, is a thing necessary to the support of life; yet the 
 mode, or process by which it becomes necessary to life has not been 
 minutely investigated. The change which takes place in the 
 blood in its passage through the lungs is one interesting chiefly 
 the vital properties of this fluid, it is a preparation of the blood 
 for future purposes. We know in the gross that the admission of 
 air into the lungs is requisite to this preparation; but that the 
 preparation consists in the mere oxygenation of blood is more than 
 we have a right to conclude. Such an inference can be sanctioned 
 only by facts which shew that blood exposed to air and oxygenated 
 in any other seat is capable of maintaining life. We know no such 
 facts, and until they are attained we have a right to suspect that 
 the vital properties of the structure have a relation with those of 
 the blood and contribute towards its preparation in this stage ; and 
 that the change which blood suffers in the lungs is one produced 
 by the complex relations of blood, air, and the properties of the 
 structure: for it must be remembered that although earth and air 
 have been said to contain informal life, and to furnish the elements 
 of constituted life, yet these sources are modified by the living 
 form in every variety of animal existence, and, so far as we can 
 trace the matter perceptibly, in every stage of their relation with 
 each. If we could not satisfy ourselves by observation to the con- 
 trary, we may as well suppose that food containing its share of the 
 elements of life is diffused among the structures which are the 
 seats of it, without the previous changes elaborated by the vital 
 properties of those which have been termed the preparatory organs, 
 as that air, mixing with blood, is at once fitted for all the future 
 purposes of this fluid, without any concurrence in its adaptation of 
 the vital properties of the organs into which it is first received. 
 At least we are justified by analogy in this suspicion in the absence 
 of proofs on either side, the want of which we are still likely to 
 lament, as our analyses do not reach the order or constitution of 
 spiritual change. 
 
219 
 
 2. It is proved by the results of intercepting the supply of 
 arterial Wood to the structures that the life of these parts can- 
 not be supported without it. In some instances this is shewn by 
 direct experiment, as by ligatures upon the arterial trunks through 
 which blood is conveyed to the seat which might be the subject of 
 the observation. In other instances which have never been sub- 
 jected to this test, the necessity of arterial blood to the support of 
 life is inferred agreeably with the results just hinted at. 
 
 3. Unless the tendons, &c. form exceptions, there is no struc- 
 ture which is not composed of tubuli, communicating with the 
 arteries. But the extremities or minute communications differ in 
 many respects from the trunks : hence, as the continuity of a vascular 
 system is extended, the tubes composing it are arranged into several 
 orders, exercise different functions, hold different relations, and ex- 
 hibit phenomena peculiar to each. That all structures are com- 
 posed of tubuli continuous with the arteries is inferred on these 
 grounds: 1st, that the life of the parts in question would not be 
 preserved if this continuity were interrupted ; 2nd, that all parts dis- 
 play the phenomena of growth, and require the processes of 
 nutrition; 3rd, that all parts are .permeated by fluids, all of which 
 results are dependent upon the supply of blood. If any parts 
 .ire nourished by porous absorption, the argument is not by such 
 fact invalidated, as it is of no consequence whether the fluids pass 
 into such parts through an uninterrupted tube, or whether by 
 proximity of the openings jute vessels,, or by the arrangement of an 
 intervening structure performing the office of an uninterrupted 
 tube, by an intermediate .channel. The communication of the com* 
 ponent tubuli of every structure with the arteries is preserved, and 
 this is all I now stipulate for. 
 
220 
 
 CHAP. IV.- Relation of Blood with the Heart. 
 
 1. THE heart possesses the assimilating and the 
 functional life. In this, as in other instances, the assimilating life 
 maintains itself, and is proper, or belonging to this place or structure : 
 the functional, accomplishes those phenomena which are peculiar to 
 the organ, and superadded to the common properties of life. The 
 objects of a full investigation of the physiology of this organ would 
 be comprised in a history of the chances of its principle and struc- 
 ture, from the state of the maternal ovum till it has attained a fixed 
 and perfect constitution, when its phenomena and relations are to 
 l>e specified, and their dependences inquired into. 
 
 2. The principal questions here to be discussed are, 
 
 1st, Are the assimilating and functional properties of the heart 
 distinct or identical? 
 
 2nd, What are the relations of blood in the cavities of the heart, 
 with respect to the above properties] 
 
 3. 1. The first question is to be determined by facts which 
 prove whether any of the properties concerned in the action, &c.of 
 the heart would cease if the connexion of this with other parts were 
 intercepted. It is difficult to experiment upon this subject with 
 satisfactory results: a short view, however, of the state of the ques- 
 tion may here be admitted. 
 
 4. The nerves of the heart, it is said, may be divided, and the 
 heart will continue to contract and dilate: hence it is inferred, that 
 the action of the heart is independent of the nervous centres; or, in 
 other words, that its properties are all inherent, or maintained in its 
 own structure. But the facts are too imperfect to justify this in- 
 ference, as the heart possesses a power of acting/or a time under a 
 privation of an ascertained cause, and a necessary one to the per- 
 manence of its action, viz. after the circulation of blood has ceased. 
 
 5. On the other side of the question, it is urged, the power of 
 action of the heart is destroyed by an injury, or breaking down of 
 the structure of the medulla spinal is. A dependence is inferred from 
 this fact, but with less propriety than from the last; for it has been 
 shewn that the simplest mode of intercepting a communication, as 
 by division, &c. is in some degrf-e liable to the suspicion that the 
 remote change takes place by an influence, or properties, conferred, 
 foreign ones; and cettainly in no case will the injury of one part 
 
221 
 
 prove, by an affection of a distant seat, that the latter ever acknow- 
 ledged, with respect to the former, a dependence as for properties 
 habitually, or even occasionally received in the condition of health. 
 Hence, the facts which have been quoted to prove either the inherent 
 muscular power of the heart, or the remote dependence of this 
 power, are alike inadequate. I say nothing about the idle experi- 
 ments made on the heart by galvanism, electricity, &c. which are 
 scarcely worthy to form an amusement for a school-boy. Those 
 also who have sought for analogical proofs from frogs, toads, 
 and fishes, had very little more wit than the subjects of tlvir ex- 
 periments. The multiplication of useless facts, and of those which 
 are irrelevant to important conclusions, tend rather to impede, than 
 to promote the progress of science. 
 
 6. There are then no facts which prove whether all the pro* 
 perties of the heart are assimilated in this seat, or whether some of 
 them are derived from another, and superadded to the assimilating 
 ones. The voice of analogy must here also be silent. We have 
 ascertained a certain dependence of the voluntary muscles on the 
 nervous centres; but we cannot transfer this fact to the heart. We 
 are told that some secretions, as the gastric, &c. are suspended by a 
 division of the eighth pair of nerves; yet we know that other secre- 
 tions, as those of lymph, pus, &c. will proceed in the arm, which is 
 paralyzed, or in the leg of an animal after a division of the axillary 
 plexus. In short, we cannot decide the point by a just reasoning on 
 the facts we possess; and therefore, as with all other doubtful mat- 
 ters, it is best to acknowledge it undecided. 
 
 7. 2. The relations of blood in the cavities of the heart may 
 be considered, 1st, with respect to the vital properties of the organ*; 
 2nd, with respect to its material structure. 
 
 8. That the motions of the heart are not dependent upon the 
 quality of the blood contained in its cavities appears to be proved 
 by the fact, that either ventricle will contract upon venous or 
 arterial blood. And that the motions of the ventricles are not de- 
 pendent upon the volume of blood, or produced by a repeated dis- 
 tention, appears to be deducible from the fact that the movements 
 of contraction and dilatation continue when the circulation has 
 ceased. Hence, the blood in the ventricles appears to contribute 
 nothing essential to the function of the heart. A strict and minute 
 inquiry may perhaps indicate that the movements of the heart are 
 liable to be affected by varieties in the volume of blood in its 
 cavities: this, indeed, we may pretty reasonably infer from analogy. 
 But the fact, if admitted as one, is very short of proving an habitual 
 dependence of the action of the heart, upon a fluid which is poured 
 into it, rather to suffer, than to act. 
 
 9. If the blood in the cavities of the heart is not necessary to 
 the function of this organ, what are we to say of its relation with its 
 assimilating life? Does the blood in the ventricles maintain this 
 organic spirit, or is it assimilated from the vessels which ramify in 
 its structure] We observe that the functional properties never sur- 
 
222 
 
 me the common or assimilating ones: hence, if the former continue 
 when blood ceases to be poured into the ventricles, we must infer 
 that the latter also are not extinct; and that if it is allowable to con- 
 elude the functional properties independently of the volume, &c. of 
 blood, it is, by parity of reasoning, allowable to infer of ihe com- 
 mon ones a similar independence. But the truth is, that a positive 
 inference is justified in neither case; for, as the heart continues its 
 motions after the circulation has ceased, or after all the blood has 
 been abstracted, so if these motions are admitted to prove that the 
 powers of the heart are independent of the presence of blood in the 
 ventricles, they must also be allowed to prove that its powers are 
 independent of the blood altogether, whether in the ventricles o* 
 in the coronary arteries, which is not the fact. 
 
 10. We are here (as in the case where the independence of the 
 beart of the nervous centres is inferred from the results of the 
 division of its nerves) brought back to the conclusion that the heart 
 retains its life, or is endowed with a certain quantum of it; or rather 
 that its assim latiou is peculiar, by which its phenomena continue to 
 be exhibited under an absence of the regular circumstances which 
 are essential to its permanent action.* 
 
 11. As then there is no small disagreement, or rather confusion, 
 among the facts already noticed; and as the facts, if less confused, 
 are generally of a kind so loose and distant as hardly to apply with 
 correctness to any argument for which they have been cited ; we must 
 on these accounts seek for evidence from some other quarter, and of 
 another kind. 
 
 12. I have seen it somewhere stated that the beart is paralyzed 
 by ligature on the coronaries. This fact, if it is one, appears at first 
 sight to be conclusive in regard to the source of the heart's assimila- 
 tion, &c. It is however liable to these objections: 1st, that the 
 injury inflicted might destroy, by communication, the function of 
 the heart; 2nd, supposing this not to be the case, and that the 
 function depends upon the blood in the coronaries, as upon a source; 
 a similar dependence cannot be inferred with respect to the assimi- 
 lating life, because this latter would cease from a cessation of 
 functional operations, without any dependence upon that cause, the 
 privation of which renders the muscular properties of the heart 
 extinct. This circumstance also remains to be reconciled with the 
 fact that the heart will continue to act after the circulation has 
 ceased, or even when removed from the body. To extend therefore 
 a little further the discussion, 
 
 13. Venous blood, it is pretty well known, will not maintain 
 life; that is, the spirit cannot assimilate or produce itself from venous 
 blood. As none but venous blood circulates through the right 
 cavities of the heart, it is to be inferred, in consonance or analogy 
 
 * It is possible that this peculiarity may consist iti a power of assimilation 
 both of the common and the functional properties, from the blood which 
 pervades the structure of the heart, although it may be in a state of rest ; and 
 that this assimilation proceeds, as long as this blood contains elementary lite. 
 
223 
 
 with the fact just mentioned, that the life of this side of the heart 
 is not maintained by the blood in the ventricle, &c.; and although 
 arterial blood passes through the left cavities of the heart, it is to 
 be inferred, from the resemblance of their structure to that of the 
 right side, that there is another source of the elements of life besides 
 the blood in the ventricles: in other words, that the blood from 
 which the life of the heart is assimilated is not that which is con- 
 tained hi the ventricles, but that which circulates in vessels of another 
 order. It will be suggested that the conclusion is further supported 
 by the fact, that, in asphyxia, the circulation is continued a short 
 time after the office of the lungs is prevented. The evidence how- 
 ever of this fact appears to lose its force when we recollect that the 
 action of the heart will continue for a time, when the circulation 
 (an acknowledged source of its permanent life and action) has ceased. 
 
 14. There are no facts which prove that the pabulum of the 
 structural assimilation of the heart is furnished by the blood in its 
 cavities. The argument of analogy, quoted in the last paragraph, 
 would rather decide against such a supposition ; for, if venous blood 
 will not maintain spiritual assimilation, we can scarcely expect that 
 it should produce the structures, the formation of which we know 
 to be dependent upon the life which precedes their growth and 
 preserves their cohesion. 
 
 15. To repeat: the two questions proposed, as including the 
 physiology of the life of I he heart, and the relation between this 
 organ, and the blood in its cavities, are, 1st, Are the assimilating 
 and functional properties of the heart identical or distinct? 2nd, 
 What are the relations of the blood with the above properties? 
 
 1G. These questions, agreeably with our discussion, are thus 
 answered: 1st, There is an entire absence of proofs whether the 
 heart is directly dependent upon a related seat for the properties 
 which aid or perform its motions. The action of the heart may be 
 influenced, as every one knnws, by affections originating with distant 
 nerves: but this fact proves no regular dependence. 2nd, There are 
 no facts which prove either that the functional or common spiritual 
 properties of the heart are renewed from the blood in its cavities. 
 At the same time there is reason to believe that the action of the 
 heart may be affected by the quantity of the blood in its ventricles, 
 &c.: this will be supposed in agreement with many analogies. We 
 are, in this case, precluded the analytical test of dependence, because 
 the blood cannot be excluded the ventricles without a cessation of 
 the circulation; and any inference which might be made from the 
 observation of phenomena under such circumstances would be 
 equally, and perhaps more justly, attributed to the absence of blood 
 in the coronary arteries. 
 
 17. The strongest facts which relate to the physiology of the 
 heart are, 1st, the heart continues to act after a division of its 
 nerves: this fact suggests the conclusion that the action of the heart 
 is independent of a nervous centre. 2nd, The heart is paralyzed by 
 tying the coronary arteries: this fact suggests that the life and 
 
224 
 
 functional properties of the heart are assimilated from the blood 
 which is distributed by these vessels. 3rd, The action of the heart 
 continues after the blood has been abstracted and the circulation 
 lias apparently ceased, or after the heart is removed from the body. 
 The two last facts can be reconciled only by one of the following 
 alternatives: 1st, that the life of the heart may be assimilated from 
 blood in a state of rest, as long as it contains the elements of life; or, 
 2nd, that, owing to the contiguity of the mouths of the coronaries to 
 the cavities of the heart, blood is forced into these vessels by its 
 contractions; and that a slow or imperfect circulation is locally 
 maintained in the heart, although it has ceased elsewhere, and finally 
 ceases in this place also, either because the blood gradually coagu- 
 lates, or else because the elementary life of a given quantity of blood, 
 which has no source of renovation, becomes exhausted. 
 
 18. Although there is no evidence, even of the weakest kind, 
 to shew that the life of the heart does assimilate from the blood in 
 its cavities, there is the evidence of analogy to indicate that such an 
 assimilation does not take place. This evidence arises from a fact, 
 currently received, that the spirit does not assimilate from venous 
 blood; which exclusively flows through the right side of the heart. 
 This conclusion leads us up to a wider view of the relations of blood. 
 
tti AP. V. Other Relation* of ktoo<t. 
 
 1. THE principal objects of blood are,' 1st, to furnish 
 the elements of the spirit ; and, 2nd, to furnish the elements of the 
 structures. The other relations, as Secretion, &c. being tributary 
 to these ends, are sfo far subordinate, and \vill be afterwards spoken of. 
 
 2. The proof that life is maintained by that which is called 
 arterial blood is, that death quickly follows the interruption of the 
 process by which venous is converted into arterial blood. This 
 fact is sufficiently conclusive upon a question of the necessity of 
 arterial blood to the maintenance of life; but it is not altogether so 
 conclusive, as to the mode by which life becomes generally extinct 
 in consequence of suffocation. The alternatives are, 1st, that ar- 
 terial blood is required every where for the diffused assimilation of 
 the spirit; or, 2nd, that it is required by one organ, upon the 
 function or relations of which the diffused spirit is dependent. But 
 as the diffused spirit has been shewn to live by assimilation, so it is 
 impossible that such a principle should have any regular dependence 
 for assimilating properties, which, if originally derived from a dis- 
 tant source, are, by their capability to assimilate, rendered inde- 
 pendent of that source. Hence, as the second alternative appears to 
 be without foundation, or incompatible with other proofs, and no 
 other suggesting itself, we may venture to admit the first, vii. that 
 the assimilating life, which is the regular organic spirit of every part, 
 preserves itself by uniting its elements, which are informal, in 
 arterial blood. 
 
 3. That the blood circulating in the arteries, although of the 
 kind proper for the purpose, is not that which maintains the life of 
 the artery, seems to be evinced by the fact, that a portion of an 
 artery, intercepted by ligature, through which blood ceases to flow, 
 preserves its life ; it contracts, and finally becomes almost ligamen- 
 tous; but if its life were extinct, its decomposition would ensue. 
 
 4. If, then, the blood in those arteries which have been the 
 subjects of the observation does not maintain their life, it is next to 
 be inquired whether the blood in the smallest arteries is that from 
 which their spirit is renewed] If it were permitted to decide this 
 question by analogy, we should say, that as the texture of these ves- 
 sels is very similar, as the blood moves through them with con- 
 siderable velocity, and as no material difference is remarked between 
 
226 
 
 them, except that of size, on which we can scarcely presume, we 
 should, from these poiuts of similitude, be inclined to reply, that the 
 assimilation of the spirit belonging to the arterial tubes does not 
 take place from the blood which flows through them. But as tlws 
 analogy, confessedly, is not quite perfect, we will attempt to decide 
 the question of the seat of assimilation by viewing the matter on 
 other grounds. 
 
 5. The component structures of the body may be said, in the 
 gross, to be tubular, fibrous, or consisting of particles, held together 
 by some power of cohesion : into this last, perhaps, the fabric of 
 both the others might be ultimately resolved. Of these, the vascu- 
 lar system is an example of the first; the muscular structure, of the 
 second ; the osseous (with some equivocal exception*), of the third^ 
 6. As we found reason to believe that the heart is not 
 nourished by the blood in its cavities, but by that supplied to it by 
 the coronary arteries, so it is currently said that the arteries also 
 have their nutrient vessels, and that they live by the blood furnished 
 to them by the vasa vasorum. The proofs of the existence of these 
 minute vessels are, that the structure of the arteries contains blood, 
 which it can do only by communicating with the arteries; and that 
 their structure may be injected. These proofs, however, are by no 
 means conclusive; though it is scarcely worth while to shew in this 
 place in what they are defective, 
 
 7. If an artery is nourished by a minuter order of vessels*, by 
 what are these vessels nourished? Will it be replied, by vessels still 
 more minute? this would be rather to strain the imagination. But 
 the existence of these still more minute vessels granted, even they, 
 to be identified as vessels, must have their eoats, their internal and 
 their external surfaces, and their intermediate composition of organic 
 particles. Jf the existence of such tubuli is supposed further than 
 it might be demonstrated, wtere is the supposition of them to end? 
 In truth, the supposition of tubuli may proceed in injimtum? but, 
 happily, it is made obvious that the declension of the area of tubuli 
 has some limit, by the fact ttoat when the smallest tubulus is sup- 
 posed, the lines of constituent particles, of which its sides are com- 
 posed, must be less than the tube itself, Hence we come to the 
 inference, that particles are laid down* which are not directly obtained 
 from continuity ef tubular cavities. 
 
 \ 8. But, independent of this limit to the gradual diminution of 
 tubuli, it is sufficient to assign the existence of tubes, continuous 
 with the arteries, so far as there is evidence of their existence; and 
 it may therefore be said, with the anatomists, arteries terminate in 
 secerning extremities, &c. 
 
 9. Now the questions to be decided are, whether nutrition 
 takes place from the blood in any order of vessels? or whether it 
 takes place from exuded fluids? or whether from both these sources? 
 We can scarcely hope to decide these questions by an evidence 
 amounting to proof; the argument may, however, be stated 
 93 follows: 
 
227 
 
 1st, The life of a targe artery is maintained where the circu- 
 lation of blood through its canal is prevented. Hence, from the 
 similitude subsisting between the arteries, so far as their structure, 
 &c. is capable of being ascertained, it is on this ground of analogy 
 indicated, that the life and nutrition of all orders of these vessels 
 are supported by fluids which do not circulate in their canals. 
 
 2nd, Tbata nutrition of vascular structures takes place from 
 fluids not contained in the blood-vessels, may be positively in* 
 ferred from the fact mentioned above, viz. that the nutrition of 
 component particles of the minutest tubuli cannot take place 
 directly without exudation from a vascular tube. 
 
 3rd, That as an extra-tubular source of nutrition may be said 
 to be a necessary one, so any other mode not supported by testi- 
 mony of the slightest kind is to be treated as an unfounded con- 
 jecture, aad in agreement with rules of reasoning rejected; be- 
 cause it is contrary to the analogy furnished by the fact first cited, 
 and because also it differs from the nutrition ascertaiuable ou 
 other grounds, in these respects, 1st, that the blood which circu- 
 lates in the vessels moves rapidly, while extravasated fluids have 
 only a slow motion, or are nearly at rest; and, 2nd, that the fluids 
 having a nutrient relation with minute particles are extensively, 
 if not universally, products from blood, and not red blood. On 
 these data it appears not too much to assume a general, if not 
 an universal, mode of nutrition, from fluids not contained in 
 blood-vessels. 
 
 10. If the material of nutrition is not contained in vessels, 
 identified by their coats, &c. there is only this alternative, viz. 
 that the nutrient fluids are extravasated, or effused from the se- 
 cerning extremities of the arteries, aud that they obtain contact 
 and relation with the particles of the structures by a porous or 
 interstitial absorption. 
 
 11. We have traced some stages of the preparation of a fluid 
 whose end is nutrition, or the maintenance of life, and the struc- 
 tures, from its state of food, to its formation into blood. It seems 
 consonant with analogy to suppose, that the seceruing extremities 
 of arteries exert a function with respect to blood, which is a fur- 
 ther, or an an additional, slage of preparation, for the above 
 object, to those which we have already enumerated. 
 
 12. That a preparation of blood which is connected with the 
 above purpose taJkes place, is proved by the facts before cited ; 
 and which will be spoken of again, shewing that the products of 
 secerning extremities are, perhaps, in no instances mere filiations: 
 but what relations the changes which blood sustains, by the pro- 
 cesses of secerning extremities, may have with the purposes their 
 results are destined to fulfil, is a question of more especial 
 and difficult investigation. 
 
 13. It may here be urged, that if a bone is scraped it bleeds; 
 and that with such an exudation, as to warrant the supposition 
 that red blood is extravasated, which, it may further be conjee- 
 
228 
 
 tured, has that direct nutrient relation with the structure which 
 has just been assigned to the secerned fluids. But the fact proves 
 only that blood-vessels ramify very minutely in the osseous tex- 
 tures, and that blood escapes in consequence of the abrasion of 
 their coats. I would repeat also, in reply, that the relation of 
 the nutrient fluid is with particles composing the minutest 
 cylinders, to which blood cannot pass by vessels, unless it can be 
 shewn that parts less than possible cylinders may be permeated by 
 cylinders. 
 
 14. In agreement with the same views, we find that in the 
 processes of organization, subjected to our inspection, as in the 
 regeneration of parts destroyed by ulceration, or in the union of 
 wounds, the nidus of growth is not blood, but a secretion; that which 
 is called coagulable lymph. Whether this is the common product 
 of secerning extremities for purposes of nutrition, or growth, we 
 can perhaps scarcely affirm ; it appears, however, to be exhibited as 
 such under disease, and to accomplish this end as a product of 
 dissimilar structures. Thus I have witnessed the production of a 
 circumscribed fungus, which has been cut off" and grown rapidly 
 again, and this growth was preceded visibly by a copious deposi- 
 tion of lymph. That a similar lymph is a precursor to organiza- 
 tion in other instances is well known. 
 
 15. Upon the collective strength then of these circumstances 
 we may venture to assume that the nutrient fluid is a product of 
 secerning extremities of arteries; that it is perhaps generally this 
 lymph of which we have just spoken, which, containing infinite 
 properties (as all other things do), is formed into the various struc- 
 tures by finding new relations in the spiritual properties of each. 
 
 16. If it be granted that the nutrient fluid of the body is such 
 a product of arterial blood, the changes which this blood sustains 
 in consequence of the exertion of a process by which the fluid is 
 produced, may be next considered. It is the business of analysis, 
 or of analysis and synthesis conjointly, to specify what is the con- 
 stitution of the separated material, and to demonstrate the precise 
 change which arterial blood has suffered. In other words, sup- 
 pose the fluid separated to be coagulable lymph; this identity of 
 it will be ascertained satisfactorily only by separating coagulated 
 lymph from arterial blood, and observing if the same changes oc- 
 cur as in the separation accomplished by a secerning process; and 
 again, by adding coagulable lymph to the blood, which has 
 suffered secretion, and observing whether its former identity is 
 restored. But these minute acts of the analytical inquiry are much 
 more easily directed than performed. We 'must now, as formerly, 
 be content to consider grosser circumstances. 
 
 17. We observe at about this stage of the circulation, viz. 
 when arterial blood has reached the capillary system, that a great 
 and distinctive change occurs in its appearance and properties: 
 this change is implied in the conversion of arterial into venous 
 blood. The question first to be decided is, where this conversion 
 
229 
 
 occurs, or the seat of it? We can on this question propose only 
 tJae three following alternatives: 1. the conversion is produced 
 by a function of the extreme arteries; 2. it is produced by one 
 belonging to the origins of the veins; or, 3. it is produced by a 
 function of the secerning extremities of the arteries. 
 
 18. 1. That venous blood is not produced from the extreme 
 arteries appears sufficiently obvious from the facts, 1st, that the 
 arteries are no where observed to possess the properties of ac- 
 complishing the conversion in question; and, 2nd, that the ex- 
 treme arteries, so far as they can be traced, contain that blood 
 denominated arterial. 
 
 19. 2. That the change is not accomplished in the beginning 
 of veins, it appears warrantable to infer, 1st, from the analogy of 
 the small to the large veins; and, 2nd, from the fact that veins 
 will circulate florid or arterial blood without changing its dis- 
 tinctive properties and appearance; as in the instance of the 
 pulmonary veins. 
 
 20. 3. That venous blood is produced by a function of the 
 secerning extremities of the arteries, it appears warrantable to con- 
 clude, 1st, from those grounds of rejection of the only other al- 
 ternatives which suggest themselves; and, 2nd, from the agree- 
 ment which this supposed fact has with the process of nutrition 
 before expressed. This agreement will appear from the following 
 exhibition of particulars: 
 
 21. The material of nutrition, separated from blood by the 
 secerning extremities of the arteries. This material, having many 
 constituents, appears to consist of coagulable lymph, possessing this 
 most obviously ; this lymph containing the matters of which the 
 structures are composed; this lymph containing also the oxygen 
 of arterial blood, the relation of which is with the Jiving spirit, or 
 with the process of assimilation; this lymph thus furnishing to the 
 living powers and constitution their elements, said to be contained 
 in, or derived from, earth and air: arterial blood thus deprived of 
 its oxygen which passes with a new medium to the places where 
 its nutrient relations exist,, is converted into venous blood. 
 
 22. Venous blood also contains lymph, most probably in con- 
 siderable abundance, as we are informed by analysis, and as we 
 may guess from the appearance of venous blood abstracted in 
 fever or inflammation: but venous blood will not maintain life; 
 for although it might have lymph and all the other material con- 
 stituents, in being venous blood, it is deprived of its oxygen ; to say 
 nothing of other properties which, though less obvious, may never- 
 theless be supposed. 
 
 23. The preceding theory of the conversion of arterial into 
 venous blood, is in agreement with all that is either perceptible or 
 inferred upon strong grounds in this stage of the circulation ; and, 
 in agreement with the theory itself, it is uecessnry to suppose the 
 arrangement of the circulating organs, &c. in the seat of this con- 
 version, to be such as may be briefly illustrated in the following way : 
 
230 
 
 a an extreme artery, b b secerning ex- a b 
 
 tremities,c the commencementofa vein, \ \ 
 
 which carries on that blood, peculiar i ^ - 
 
 to this order of structure, and which " ' - 
 
 has been subjected to the function of /' 
 
 secerning tubes which immediately 
 
 precede the venous origins. If the 
 
 arterial structure is continued further than this point, before it 
 
 joins a vein, then, to a corresponding extent, the artery carries 
 
 venous blood, as an artery is known to do in the instance of the 
 
 pulmonary artery, &c. Whether therefore the venous structure 
 
 commences immediately where the secerning occurs, or at a short 
 
 space further than this point, is a matter upon which we cannot 
 
 satisfy ourselves by observation, and upon which, as it is totally 
 
 unimportant, we may be allowed to indulge either conjecture. 
 
 24. The history of the secerning function of the extremities 
 of arteries is still further to be traced. It is to be inquired, what 
 is the process by which the nutrient fluid, whether oxygenated 
 lymph or any thing else, is produced from arterial blood? We 
 cannot answer this question: we can attempt it with an eye to 
 truth only in the analytical way; and what sort of an analysis can 
 we make of properties whose existence is only inferred from their 
 effects of those of the spiritual kind, which are not objects of the 
 senses, and which we cannot denominate? We must be satisfied 
 with referring thif separation to a vital process; and if we would 
 push our investigation into its laws, it is to be pursued by that 
 mode of examining dependences many times described, with a 
 view to ascertain whether the life engaged in this process is the 
 assimilating, or the regular dependent, &c. 
 
 25. The fluid produced by the secerning extremities is con- 
 veyed through the extent of their tubes; and then, becoming ex^- 
 travasated, its relation with the maintenance of life and the tex- 
 tures begins. As the minutest particles of the textures cannot be 
 cylindrical, so if it is necessary for their own regeneration that 
 a nutrient fluid should obtain contact with them, this can take 
 place only by interstitial absorption. Such an absorption implies 
 that solid particles do not touch each other, but are separated by 
 the medium of nutrition; or, if their contact is actual, that it sub- 
 sists only as at a mathematical point. To conceive, however, the 
 process in this way, is perhaps but straining the imagination un- 
 necessarily. Rather than these infinitely minute particles, it may 
 be more convenient to conceive them as distinct molecules of visi- 
 ble bulk connected together, but having irregular interstices, by 
 which a fluid is allowed to pervade their aggregate masses. Thus 
 far we have traced, theoretically indeed, the nutrient material 
 through all its several stages, up to that point which may be said 
 to be its scene of action ; or where the ^Maintenance of organic 
 life, &c. begins: our peroration at this stage is thus briefly made; 
 a nutrient fluid slowly pervades the minutest perceptible molecules 
 of the structures* 
 
231 
 
 26. TliHs the fluid which supports life attains the seat of 
 life. This seat we have hitherto spoken of generally : the minuter 
 view which we are now taking requires that it should be con- 
 sidered more particularly. 
 
 27. We have said, generally, that the spirit exists in the tex- 
 tures, and that its distinct constitutions, or those which manifest 
 diversity of properties, have their respective spheres. Is it then, 
 it will be inquired, meant to be affirmed that the properties which 
 we have denominated spiritual (or an aggregate of them which we 
 have called the spirit) occupy space] This question involves the 
 old dispute about materialism. The question whether all things 
 are material, is readily decided, when it shall be understood what 
 we agree to call matter. Matter is commonly agreed to consist of 
 an assemblage of properties ; and this very necessity of an assem- 
 blage of properties, to constitute matter, proves that there are 
 existences which are not material, namely, those identical proper- 
 ties individually, by which, collectively, matter is constituted. 
 But if the question whether all things are material, is so readily got 
 rid of, there h another which might be proposed as allied to it 
 which cannot be decided so promptly, viz. Is there any form of 
 existence which is not extended? and which, though it wants 
 tangibility, and is not an object of any other sense, does not occupy 
 space? If this question cannot be deckled, although I think by 
 a hmg discussion in conformity with our doctrines of causation it 
 raight be decided ; if then, I will say, this question cannot be 
 readily decided, we need not regret the difficulty of its decision, 
 so far as respects its connexion with our present subject, for either 
 of the alternatives into which it might be resolved will alike answer 
 the purpose to which it might here be applied. The alternatives are, 
 
 1st, That constitutions denominated spiritual may pervade 
 substances and exist in solid particles, or have their sphere in a 
 place filled by matter; or, 
 
 2nd, That matter is composed of infinitely divisible particles, 
 which have corresponding infinitely minute interstices; that 
 spiritual properties may occupy partially or wholly the interstices 
 of particles, and thus pervade aggregate masses and become related 
 with every portion of their solid contents without adding any 
 thing to their bulk. It is implied by this supposition that the 
 particles composing solid bodies nre not in actual contact. Now 
 though I have said that one of these two alternatives must be 
 adopted, and that either is good enough for nay purpose, yet I feel 
 inclined to bestow another paragraph or two, in the way of di- 
 gression, upon the choice of alternatives. 
 
 28. The argument against spiritual existence, as meant to 
 imply the existence of something which has no property of matter, 
 and among others does not occupy space, arises from our having 
 so imperfect an experience of such existences; that is, they are 
 not objects which anyone sense is fitted to perceive: such at least 
 is a prevailing atsertkm. But to me it appears that we may quote 
 
232 
 
 , 
 
 the evidence of the senses in proof of the existence of such pro- 
 perties. Thus, those things which are seen and fell are known to 
 be bodies, and to occupy or fill a place in which no other bodies 
 can exist at the same time: of such bodies we have an experience 
 by two senses, but a third sense will afford us just the same evi- 
 dence of properties which do not possess the above characters ; 
 that is, a third sense is related with properties which we can 
 neither see nor feel, and which, admitting the sufficiency of the 
 eye and touch to distinguish all things visible and tangible, must 
 be allowed to have neither bulk nor solidity, nor to fill a space. 
 Thus sound is, according to the test of those senses whose business 
 it is, or which are adapted, to discriminate matter or extended sub- 
 stances; sound, according to this test, must want altogether the 
 characteristics of matter, or extended substance, because it is 
 neither seen nor felt. Thus, also, flavours and odours are proper- 
 ties of which we have an evidence as satisfactory, an experience as 
 unequivocal, as we enjoy with respect to the objects of vision and 
 touch. Yet are flavours and odours not extended, or capable of 
 filling space, according to the testimony of the senses which take 
 account of those things which are extended, and which do 
 fill space. 
 
 29. The chief difficulty of admitting the existence of spiritual 
 or purely immaterial existences proceeds from the limited ac- 
 quaintance we have with them, and from the great familiarity 
 which we hold with their opposites, viz. with matter in all its forms. 
 We have senses which take cognizance of immaterial, as the eye 
 and touch do of material, existences; but the forms which the 
 former are fitted to recognise are those spiritual properties 
 making flavour, odour, sound, &c.; while the two other senses of 
 vision and touch, having a more extensive relation, are fitted to 
 perceive not one or two, but all, the forms of matter, and to witness 
 their operations upon each other. But if we are informed by the 
 senses that there are properties which do not bear the characters 
 of material, we are justified in inferring, when we witness effects 
 produced by causes which are equally destitute of the characters 
 of matter, that the causes producing such effects are of that 
 spiritual kind of which we have some examples furnished by the 
 senses of taste, smell, and hearing; but which are nevertheless not 
 objects of these senses, simply because they constitute neither 
 flavour, odour, nor sound ; but agree with these in not being visible 
 or tangible, and, so far as this analogy goes, must be inferred to 
 be of the same kind. 
 
 30. But it will be urged, there is a still weightier objection 
 than any which has yet been proposed to the belief of spiritual 
 or not extended existences, viz. that these spiritual agents, as they 
 are called, operate upon matter: solid masses are variously affected 
 by them, &c. which it will be said we cannot conceive to happen 
 without contact, and contact implies a junction of surfaces. That 
 one thing cannot move another without contact is true, or appears to 
 
233 
 
 he true, of the objects which we see or feel, or of matter: hut as 
 a difference must he confessed hetween matter and other properties, 
 of whose reality we have also a sensible testimony, so we cannot 
 deduce an inference from analogy, where we have ascertained 
 diversity; on points where matter and spirit agree, we may found an 
 inference: as, in a mere question of existence, which is common to 
 both, from witnessing that no material constitutions arise spon- 
 taneously, without a formation, by the causes of which they consist, 
 we infer that causation is equally necessary to spiritual forms; be- 
 cause as both exist, this point of analogy justifies the inference so 
 far as the analogy goes. 
 
 31. And this reference to causation brings us up to the true 
 solution of the matter. It has been shewn that every identity is 
 made by the combination of differentials, or of causes separately 
 different from the effect. Hence if it be asked whether there is any 
 thing which is not solid? we may ask, what makes that property 
 which we call solidity] to which it must be replied, other properties 
 which are different from that of solidity; for if they are not diffe- 
 rent, then solidity exists per se, or has sprung into existence of its 
 own accord, which is as much as to say that it has capabilities, be- 
 fore it is; and is contrary to the standing axiom of tx nihilo nihil 
 &c. already sufficiently remarked upon. 
 
 32. Some grosser facts might also be urged against this doc- 
 trine of universal materialism, or against our second alternative, viz. 
 that infinitely divisible particles, constituting the subtilest fluids, 
 pervade substances by filling infinitely minute interstices of appa- 
 rently solid masses. Still grosser facts may be urged against this 
 doctrine : as that fluids so subtile as to pass through the most dense, 
 should certainly pass more readily through the more porous sub- 
 stances. Thus, light, which is transmitted through glass, a matter 
 having no perceptible interstices under the most powerful magnifier; 
 light, so readily transmitted by glass, should certainly be transmitted 
 through a stone four inches thick, the texture of which is sufficiently 
 open to permit a filtration of the grosser aqueous fluids. 
 
 33. This digression becomes tedious: the case is, that which it 
 has been stated in our preliminary articles; the various causes which 
 are contained in the world, as well those in the smallest sphere as 
 those of one half of the universe, hold, with respect to each other, 
 certain relations by which they combine and make effects, differing 
 from themselves; these causes respectively, of course, retain their 
 existence in this work of causation; but two are different from one, 
 and it is upon the same principle that an effect is different from its 
 causes. Some causes that are combined in masses preserve their 
 identity; that is, they are recognized or not lost in the combination : 
 this is determined by that further relation, before spoken of, which 
 things have with our faculties. 
 
 34. It will be seen from the general tendency of this, which I 
 have called a digression, that the first alternative is the one which I 
 am disposed to adopt; and which may be re-stated thus: properties 
 I I 
 
234 
 
 not occupying space, are joined in existence with those winch do oc- 
 cupy space, and the place of the latter denotes the sphere of the for- 
 mer. But lest the design of the alternatives should suffer by insist- 
 ing too positively upon either, so far as respects the present 
 application, let them remain as alternatives, either of which is 
 alike convenient. 
 
 35. A nutrient material, of the gross, fluid kind, penetrates the 
 interstices of the component molecules of the structures, and thus 
 obtains a relation with the living spirit, whose sphere is acknowledged 
 in every molecule, and in the conceivable particles composing the 
 molecules, of the fabric of organization. 
 
 36. The nutrient fluid, thus obtaining a relation with the or- 
 ganic spirit, a consequence of this relation is, that the elements of 
 life, or its causes (or the informal life) contained in the nutrient fluid, 
 cease to be elementary and become the identical or living spirit. 
 The mode of this conversion has been already explained ; it may 
 however in this place be re-stated thus: the elements of life are 
 latent in the nutrient material, they are separated from their previous 
 combinations, and united, and thus become life. If it be inquired 
 still more minutely concerning the mode of this instance of causa- 
 tion, it is sufficient to say, such is the relation of the causes con- 
 cerned; but if it should be required to explain it in terms of analogy, 
 we may say that the effect is accomplished by affinity, in the same 
 manner as tire, by an affinity for its own substance, repeats itself, or 
 produces itself, from those sources in which it exists informally, as 
 in coal, wood, &c. and air. That the process is one of assimilation, 
 and not one in which the living spirit operates only as a cause, 
 which is combined with properties in the nutrient material, is proved, 
 as has beeii more elaborately said, 1st, by its preserving its identity; 
 2nd, by the necessity that life should exist in order to its own re- 
 production; 3rd, if life were produced by the union of differentials, 
 one existing in the structures and the other in the material of nutri- 
 tion, the former must fail, as the state of life is perpetually passing 
 away or tending to its extinction, and is continued only by a per- 
 petual renewal of the properties engaged in its support. 
 
 37. It appears then an unobjectionable solution to say, that the 
 living spirit forms itself by an affinity for its elements. This is true 
 of every form of the living spirit. Every organic life belonging to 
 the most simple or the most complex structures affects its own 
 identity; and thus is the uniformity of character of individuals, as 
 well as the general uniformity of species, preserved, alike in the 
 vegetable and in the animal world. 
 
 38. As the living state ceases as soon as the means for its sup- 
 port are withheld, so it is to be concluded that there is no stock of 
 life, that it is not a permanent identity; it lasts as long as the iden- 
 tity of a living or assimilating spirit is preserved, and as long as this 
 spirit is supplied with its constituents. Hence two subjects of in- 
 vestigation are started at this stage, 1st, what effects are produced 
 on related existences, or substances, by the living spirit? 2nd, what 
 
235 
 
 is the nature of the conversion which life suffers in again becoming 
 informal! Our business is with the first, the second question 
 belongs to the consideration of death. 
 
 39. The first question leads us to consider the relation be- 
 tween the spirit and the materials of the structures: this subject 
 has been pretty copiously discussed under the title of Growth; 
 it requires, however, to be touched upon again in this view of the 
 relations of blood. 
 
 40. The particles composing the textures are aggregated in 
 consequence of a relation subsisting between them and the or- 
 ganic spirit. The particles composing the textures tend of them- 
 selves not to aggregation but to separation ; it is therefore indi- 
 cated that the power which first overcomes this, their natural dis- 
 position, is the one which retains them in their aggregated state; 
 and hence the power which produces their aggregation may be 
 inferred from a knowledge of that which preserves their state of 
 cohesion. 
 
 41. The alternatives then, viz. whether aggregation is pro- 
 duced by the living spirit or whether by a causation connected 
 with its return to informal life, may be briefly decided: as the 
 separation of organic particles takes place within a short time 
 after the living spirit has ceased, so their aggregation, upon the 
 grounds here stated, and more fully spoken of in the chapter ou 
 Growth, must be accomplished by the properties of the living 
 spirit, and not by those of informal life, which would remain, and 
 persevere in aggregating force, after the form of the living spirit 
 had passed away. The mode of this aggregation is to be further 
 investigated. 
 
 42. As the spirit is necessarily renovated by assimilation, so 
 additional quantities of the organic particles might be incessantly 
 laid down ; but if these were to remain fixed while the spirit passed 
 away, 1st, they would impede the admission of new quantities of 
 the nutrient material to the minute spheres of life, which would 
 then in such spheres become extinct, which is not the fact; and, 
 2nd, an endless and enormous increase of bulk would be attained, 
 which also is contrary to fact. There must then, in this business 
 of assimilation and aggregation, be some limit of the latter opera- 
 tion, which we are to investigate, or else some countervailing 
 process, by which growth is restricted, and the material admitted 
 to perpetuate life wherever life exists. The following is a theory 
 by which both these objects would be supposed to be accomplished 
 in the most simple way. 
 
 43. It supposes that, as the living spirit is incessantly reno- 
 vated by new quantities of its elements, and aggregates at the 
 same time new quantities of the structures, so as the living spirit 
 becomes informal, the particles which it has laid down or aggre- 
 gated must also be removed. 
 
 44. Such a piece of causation would exhibit an instance of 
 that simplicity which in the operations of nature we so often meet 
 
2SC) 
 
 \vith by chance, ami admire accordingly; and give Nature credit for 
 it in all her works: to explain it further, spiritual assimilation and 
 material aggregation are thus supposed, both, transient acts. The 
 spirit in a sphere has an affinity with its similitude (elementary) in 
 the nutrient material; by this affinity its proper elements are sepa- 
 rated from their fluid medium; these elements, agreeing in 
 peculiarities with the spirit they are to renew, are allied with 
 organic particles; these are such as agree with the elements of the 
 life assimilated, and as life differs almost in every sphere, so a cor- 
 responding diversity of the structures prevails. The living spirit, 
 assimilates or separates spiritual elements; these allied by affinity 
 willi the organic particles; the elements of life no sooner assimilated 
 than they become informal, and the relation between life and the 
 particles allied with the elements ceases, the bond of their relation 
 having ceased. Hence particles in the living state, according to this 
 theory, are not fixed, but withdrawn from the fluid mass in which 
 they are contained, and the power that withdraws, then ceasing to 
 act upon, them, they mix again with the common material, being 
 displaced by new particles which are attached to the sphere of the 
 spirit, or else become the subjects of a new relation, as, with the 
 system of the absorbents. 
 
 45. The truth of the above description of a minute and in- 
 scrutable process is indeed most questionable; it will be argued 
 against, and perhaps justly, thus: it will be urged in the first place 
 that such a perpetual succession of new particles in the spheres 
 occupied by the old ones is not demonstrable; nay, if a raw surface 
 be examined ever so attentively with the microscope, the same sub- 
 stance still appears to the eye, at least nothing like a loco-motion 
 of the minutest spherules of the structure is observable. This is 
 certainly a strong argument. It will be further urged, if the co- 
 hesion of the solid particles is dependent upon that precise quantum 
 of the living spirit by which they were aggregated, how comes it 
 that their cohesion endures days, weeks, and in some of the textures 
 months and years, after the living principle has been extinct] 
 
 4G. These objections, if the argument were strenuously insis- 
 ted upon, would admit the following replies: to the first it would 
 be answered, the successive deposition and removal relate to in- 
 finitely divisible particles, and being thus minute they are not 
 objects of sensible cognizance, even with the aid of a microscope, 
 any more than those interstices or pores in glass through which 
 light passes, &c. To the second it would be answered, that when 
 life becomes extinct, the affinity of aggregation ceases, and the par- 
 ticles already laid down are left to obey the laws of matter, and ure 
 not superseded by other particles, which, from their affinity with the 
 sphere of the spirit, would tend to displace the old ones, and occupy 
 their place. 
 
 47. But as I am not desirous of supporting a theory by 
 argument, where facts are wanting to give it the only sanction 
 which would entitle it to be received; so I shall be content to 
 
237 
 
 state alternatives, to be at a future time decided upon, when 
 minute research shall have become more familiar than it is at 
 present; for which end the summary I propose will serve as 
 indications. 
 
 48. 1. Particles composing the solid structures are withdrawn 
 from the fluid nutrient material, and deposited in the sphere of the 
 spirit, by a property belonging to it, which has been called the 
 affinity of aggregation. 
 
 49. 2. The aggregation of solid matter is connected with the 
 process of spiritual assimilation., The mode in which the formation 
 of the structures is connected with the process by which life itself is 
 preserved, may, \ am aware, admit a diversity of opinions; in the 
 discussion of which, we should perhaps find that the evidence was 
 inadequate to a settlement of either. Premising this doubt, 1 have 
 supposed the elements of life in the nutrient fluid to be in alliance 
 with matter, peculiarized by other properties; that, by the affinity 
 subsisting between the living and the elementary spirit, the latter is 
 converted into the former, and the material particles with which 
 the elements were allied, at the same time separated from their 
 other connexions. But I am aware that the spirit may not operate 
 in this way; that a causation of another kind may take place : as, 
 elementary life constituting the properties of certain substances; 
 these elements of life being withdrawn from their combinations and 
 immediately changing their form, may leave, -as particles composing 
 structures, those substances with which they were before combined, 
 and which they helped to constitute: or, it may be suggested, in 
 addition, the deposition of organic particles may be an act of life 
 distinct from its own assimilation; it may result, and its extent 
 and instances limited; from uninvestigated relations of the functional, 
 or regular dependent life, &c. 
 
 50. 3. The particles laid down and forming tbe structures 
 either remain permanently where they are deposited, or else are 
 removed, within periods, regulated by their proper laws. That they 
 are not permanently fixed, appears to be indicated by the pheno- 
 mena of febrile diseases, wherein the bulk of the body is observed 
 to be speedily and greatly reduced, and afterwards its original size 
 to be rapidly restored. And that the particles are fixed for a time 
 seems to be demonstrated by the locality of the same spherules 
 being preserved, when they are viewed under the microscope. The 
 laws then by which particles change or retain their place are to be 
 still further investigated. 
 
 51. 4. If particles remain fixed for a time during health, al- 
 though they may be removed under disease, and replaced on the 
 return of health, then it is to be inferred that new particles are not 
 produced by the assimilation of every new quantum of the elements 
 of life, but that the quantum of life is related with a quantum of 
 the properties of the structures; that if the quantum of life is 
 diminished, as by disease, the quantum of the structures is also 
 diminished, the proper bond of cohesion having ceased ; that if* 
 
238 
 
 as after disease has ceased, the quantum of life is increased, or its 
 original one restored, that then the new quantum of life is related 
 with new organic particles, which are produced accordingly, and 
 remain as long as this agreement shall subsist. In this alternative, 
 viz. that particles once laid down continue to preserve their place, 
 an operation is attributed to life, or to another process of causation, 
 to which the common cohesion of matter, and the faculty which 
 life has to prevent putrefaction, are both inadequate; for under 
 disease the particles are unsettled, and the textures waste, thus 
 proving the inadequacy of material cohesion to preserve them ; and 
 this takes place without, as we have reason to believe, the occur- 
 rence of putrefactive processes. 
 
 52. 5. As then it appears probable from this view, and also in 
 agreement I believe with general opinion, that the particles com- 
 posing the structures are laid down, occupy their places for a period, 
 and are then removed, it remains to be decided whether their re- 
 moval is permitted, 
 
 1st, In consequence of a change in their relation with life, as 
 by the cessation of intercourse or influence between particles which 
 have been for a while laid down, and the properties by which their 
 place was first assigned; or, 
 
 2nd, Whether their removal is wholly mechanical, as if worn 
 away by a gradual attrition of the fluids moving on their surfaces 
 and in their interstices; or, 
 
 3rd, Whether, after remaining in the places in which they were 
 first deposited, they become subject (by a progressive causation or 
 change in the relations of these complex properties) to another 
 function, viz. to that of the absorbents ? 
 
 As these alternatives respectively will admit of discussion, and 
 as there is a deficiency of facts by which the questions may be 
 settled ; or if such facts exist, the recollection and arrangement of 
 them require that the subject should be made an individual inquiry: 
 on these accounts I leave them as alternatives or views, which, as 
 originally proposed, are designed to serve at best but as indications 
 for the use of those who are inclined to think more minutely and 
 methodically upon the subject. 
 
239 
 
 CHAP. VI. The Absorbent*. 
 
 1. THE office of these vessels has been before discussed 
 under the title of Growth. From what is there said, as well as from 
 the preceding views, it will be perceived that the prevailing doc- 
 trines with respect to the share assigned this system in the organic 
 processes is very questionable. 
 
 2. It appears probable, perhaps it may be said indisputable, 
 that the absorbents remove the particles of the structures, when, 
 from other causes, their cohesion has ceased. But if the vital pro- 
 perties belonging to them have any operation upon the fixed par- 
 ticles of the structures, this operation must be preceded by a change 
 in the relation subsisting between the material particles and the 
 spiritual properties by which they were first aggregated. 
 
 3. If any such vital relation should be discovered, it will then 
 remain to be decided concerning the life of the absorbents, as 
 whether of the assimilating only, the regular dependent, or of the 
 occasional kind. But until a vital function is ascertainable, it is 
 superfluous to inquire into its possible laws. 
 
 4. The strict mode of philosophizing, which has before been 
 sketched, the analytical research, the investigation conformable 
 with doctrines of causation, would proceed upon these objects and 
 these difficulties something in the following way: 
 
 5. Each single effect has a history of causation; each effect 
 may be taken separately and this history traced. Suppose then the 
 question to be by what agents, or by what process, do the particles 
 composing a portion of muscle, a muscular fibre, assume their place? 
 We have already answered this question, by imitating, theoretically, 
 the sensible analytical process ; but the strict account would require, 
 
 1st, That we specify the state of the particles previously to that 
 act, that effect in which it is concerned; which gives rise to 
 our question. 
 
 2nd, To explain the change which it suffers, we must specify 
 whether properties are added to it, or whether its condition is 
 changed by a relation with other properties with which it was before 
 in combination, or from which it before received influence. 
 
 3rd, Having settled whether the change in the condition of the 
 particle is produced by properties directly conferred on the particle 
 itself, or by abstracting other properties (or separating their alliance) 
 
240 
 
 with which it was before connected ; having decided upon this mat- 
 ter, we are next to specify the precise properties which produce the 
 change. Thus a fluid medium contains solid particles, which help 
 to compose its fluid bulk: some of these particles of the fluid leave 
 their fluid state and become solid; why do they leave their fluid 
 state? something produces this change in them: what is it? here 
 we ask for the cause. If the instance of causation were of the sensi- 
 ble kind, we should proceed as above. We should first define the 
 identity of the particle in its original state. We should then exa- 
 mine those substances which were foreign or additional to its original 
 identity; or we should ascertain that it possessed no additional pro- 
 perties, but, on the contrary, that some of its original ones were de- 
 ficient, which, leaving the particle to be identified by its remaining 
 causes, would explain the history of the change, which we should 
 endeavour still further to confirm by the synthetical process, viz. 
 by that of adding to the changed substance the properties in which 
 it differed from the original ones, with a view to restore its identity. 
 
 6. To take another example, supposing it to have been ascer- 
 tained that the particles composing the textures retain their place; 
 but for a time; are particles unsettled from their cohesion, and re- 
 moved by the influence of vital properties, constituting a function of 
 the absorbents? How we are enabled to reason upon this matter 
 has been partly shewn in the aiticle on Growth ; but a perfect ana- 
 lysis would require, 1st, that the constitution of the particles in 
 their fixed state should be ascertained ; thus we should come at the 
 knowledge of the precise properties which held them in cohesion. 
 2nd, The properties by which the particles are identified in their de- 
 composed state must be ascertained; thus, we should understand 
 the precise properties which determined, or were the causes of the 
 change: unless, as is sometimes the case, the properties vanished iii 
 the act, or assumed another form, or another combination, having 
 only a transitory relation with the properties belonging to the or- 
 ganic patricles; in which case, the acting properties, or the cause of 
 the separation of particles from others with which they cohered, 
 would not be discoverable in the particles which would remain 
 identified by their own causes, the subjects of a causation which had 
 passed away, and with which they are no longer related. 3rd, Sup- 
 posing the precise properties concerned in the aggregation to be 
 ascertained, an investigation conducted upon the same principle 
 would then be required to decide whether these were properties 
 which belonged to absorbent vessels, or whether they were obtained 
 from any other source? If an affirmative of the former were upon 
 just grounds to be pronounced, some ingenuity may afterwards be 
 expended in settling the laws by which the interchanges of processes 
 are regulated, between the constitution of the organic particles, the 
 assimilating life with which they are in alliance, the functional pro- 
 perties of the absorbents, their assimilating life, and their structure. 
 
 7. As we have no senses for this work, we must be content 
 with the suggestions offered with a view to the attainment, at some 
 
241 
 
 future time, of a theory which shall not be altogether un- 
 satisfactory. 
 
 8. Among the many real difficulties which impede our un- 
 derstanding of the relations of the absorbent system, physiologists 
 have perplexed themselves chiefly about one, and that one of no 
 great importance. How, it is asked, do these vessels propel their 
 contents? It may be said, briefly, either by capillary attraction or 
 by an operation dependent upon properties of life. With respect 
 to the first, it cannot be asserted that it obtains in no instance, 
 though it appears probable that the laws of matter are in this 
 case, as iu most other animal processes, superseded by the laws of 
 life. There are no proofs of absorption by absorbent vessels after 
 death: cysts, before turgid, may collapse; swellings containing 
 fluids may appear to subside; but these changes may be attributed 
 in part to the difference of position in which such swellings are 
 examined before and after death, and in part to that general 
 flaccidity which ensues from the want of distention by the circula- 
 tion of the blood. Without entering into a full discussion of 
 lesser circumstances, it is sufficient to remark the most important 
 fact which has relation to this subject, viz. that lacteal absorption 
 has never been observed to proceed after death, although the lac- 
 teal system of animals have been examined at times when the 
 intestines have abounded with chyle. If absorption were capillary 
 or mechanical, as fluids exist in the intestines after death up to 
 the period of their decomposition, so an unremitting absorption 
 up to this period should take place; and lacteal fluid should in- 
 variably be found mixed with the blood of the right side of the 
 heart and its contiguous veins. As such is not the fact, we are 
 compelled to acknowledge the dependence also of this process of 
 absorption, upon the agency of properties of life. 
 
 9. With respect to the manner in which an absorbent propels 
 its contents, other theories have been proposed ; they are none of 
 them worth consideration : and, to add to their number another of 
 about the same value, it may be suggested that the contents of an 
 absorbent are propelled by a vig a tergo, and that the origin of 
 this force is not in the heart, as in the case of the circulation of the 
 blood, but in the absorbent orifices; that is, fluids, &c. are in. 
 cessantly drawn into the mouths of the absorbent vessels by the 
 affinity which the life of these spheres has with certain particles: 
 that the vital properties perform this function in connection with 
 their assimilation, and hence these properties have relation with 
 successive quantities of the fluids they affect; which process at the 
 absorbent orifices being unremitting, gives rise to a circulation in 
 the tubes by a vis a tergo. 
 
 10. A process which has been mentioned in the article on 
 Growth may be here again adverted to. If a portion of nerve is 
 removed, the intervening substance by which the interspace is 
 filled up gives place to the progressive growth of the nerve. It 
 may here be said merely, that absorption is subservient, under cer- 
 tain circumstances, to the laws of growth. 
 K K 
 
242 
 
 ' 
 
 CHAP. VII. Secretion. 
 
 1. THE secreted fluids are generally produced from 
 arterial blood : there is one, the biliary, which is said to be formed 
 from venous blood. Again, secretions are the products of glands 
 and of secerning extremities, and of surfaces ; and they are natural, 
 or the result of disease. 
 
 2. It seems proper first to decide from what blood the secre- 
 tions are produced? If it is settled that secerning extremities of 
 arteries are in general given off, before those tubuli communicating 
 with the veins; it may be inferred, on grounds of analogy, that 
 secretions in general (being formed by secerning extremities) are 
 obtained from arterial blood, because they are produced from 
 vessels, the fluid of which has not yet acquired the character of 
 venous blood. Thus far we are furnished with an argument of 
 analogy, if the grounds of the analogy have been sufficiently ascer- 
 tained. I am, however, acquainted with no certain proof that the 
 secerning system of a gland is given off before the terminations 
 of the arteries in veins. 
 
 3. It seems probable (and yet the foundation for the inference 
 is in some respects questionable) that secretion in general takes 
 place from arterial blood. The results of injections, which are 
 known to favour the conclusion to some extent, alone can prove it ; 
 but of these I am not satisfactorily informed. All the other pro- 
 cesses of the living state appear to require the presence of oxy- 
 genated blood ; and upon this general fact we may, nothing appear- 
 ing to the contrary, infer that the relations engaged in secretion, 
 which is an animal process, acknowledge the same law. 
 
 4. It cannot be determined whether the secretion of a gland 
 is produced from arterial or venous blood, by a ligature upon the 
 communicating trunks. If, for example, the renal artery were tied, 
 the secretion of urine might be suspended merely because the part 
 is no longer supplied with blood of any kind ; and if the vein were 
 tied, the ligature would be upon the trunk, while, if there were any 
 venous branches which gave off secerning extremities, less than, 
 themselves, they must, as may be witnessed by observation, be 
 those which are contiguous to the venous origins. 
 
 5. That, however the secretions take place from tubes which 
 are given off previous to the terminations in veins, it seems war- 
 
243 
 
 rantable to conclude from this fact, in addition to the general 
 analogy before spoken of, viz. that the circulation in all the per-f 
 ceptible ramifications of veins tends towards their trunks, while 
 the reverse happens with the arteries. 
 
 6. One exception to this remark occurs in the instance of the 
 vena portae : and here, agreeably with the exception, an office of 
 secretion has been inferred, though how justly is indeed, without 
 the aid of a strong case in point, merely from a priori reasoning, 
 extremely dubious. The branches of the vena portaj, instead 
 of collecting towards a trunk from minute beginnings, as is usual, 
 are distributed from a trunk, and are minutely divided in the 
 structure of a glandular viscus. Unless this exception to the 
 ordinary arrangement be admitted as a testimony, I am acquainted 
 with no other proof that bile is secreted from venous blood. 
 
 7. Moral reasoning on physical subjects is sometimes absurdly 
 proposed, where there is a deficiency of other proofs. In this way 
 we might be asked, why should so unusual a distribution of a vein 
 occur in the liver, unless it is subservient to the peculiar function 
 of the organ, to the secretion of bile I Why, in the way of paral- 
 lel it may be asked, did God make men with any livers at all, 
 seeing that as he is omnipotent he might have made them equally 
 well without them? In the latter case, it will be replied, it was 
 God's will that men should have livers; and in the former it must 
 be answered, nature has determined that the distribution of the 
 ven. port, should be different from that of the other veins: if we 
 would know what end is answered by this peculiarity, it is not the 
 mere confession of a peculiarity that will inform us, but we 
 must trace it by an appropriate inquiry. 
 
 8. If mercury would pass from the trunk of the ven. port, 
 into the secerning structure of the liver, and finally make its escape 
 through the gall-ducts, the evidence of such a continuity of tube 
 would indeed be tolerably conclusive on the question; and, for 
 further satisfaction, the experiment might be repeated on the 
 hepatic artery : but as such a proof, although perfectly practicable, 
 has not to my knowledge been attained, I shall allow the matter to 
 rest with these suggestions, stating the argument upon these points 
 thus: there is reason to believe on certain grounds, partly of per-? 
 ceptible phenomena and partly of analogy, that the secretions in, 
 general are formed from arterial blood; there is however one 
 instance conjectured, on weak or questionable grounds, of a secre- 
 tion produced from venous blood; thus indicating that secretion 
 might be produced from either, by a corresponding modification 
 of the powers engaged in the process. 
 
 9. In agreement with the agencies concerned in the pheno- 
 mena of animal bodies, three modes of the process of secretion 
 might be suggested : 1st, that it is a mechanical operation ; 2nd, 
 that it is a chymical one; 3rd, that it is one governed or per- 
 formed by the properties of life. These modes respectively (each 
 having had its advocates) may be briefly considered. 
 
244 
 
 10. J. That secretion is not a mechanical process is proved 
 by these facts: 1st, that the structure of the secreting organs re- 
 mains after death; and if a.part of the blood were separable by this 
 structure in the way of filtration, the injection of blood into the 
 supplying arteries of the organ should be followed by the separa- 
 tion of that peculiar fluid, which is precisely fitted to transude 
 through such a peculiar structure. Against the force of this argu- 
 ment it might be objected, filtration, or mechanical secretion, sup- 
 poses a precise adaptation of certain particles to tubes of a certain 
 area or figure, and these being left after death with no other 
 power to regulate their area except that of elasticity, a force cor- 
 rectly imitating the natural one of the circulation may impel into 
 these tubuli particles of a different order, thus substituting another 
 for the secretion of the living state. According to this objection, 
 a dependence of secretion upon properties of life is acknowledged ; 
 but the dependence is thus supposed to be upon a vital contrac- 
 tility, which has no other effect than to regulate the capacity of 
 tubuli. But the objection itself (founded indeed only upon a 
 possible fact) assumes that the component particles of different 
 fluids are of different shapes and sizes; some fluids no doubt are 
 capable of a more minute divisibility by the operation of the same 
 agents than others. We find that clear thin fluids will transude 
 readily through substances into which the thick or viscid ones will 
 not pass. Hence the variety of the divisibility of fluids seems to 
 be that rnore numerous particles of some cohere and make up 
 larger molecules, while fewer particles of others cohere and make 
 up lesser molecules; hence the separable masses of some are large, 
 and those of others small; the former fitted to permeate only large 
 interstices or tubuli of large area, and the latter capable of per- 
 meating those of a smaller size. It is hence obvious that the tubes 
 which are large enough to admit (or secrete) fluids composed of 
 the largest molecules, must at least admit at the same time, those 
 composed of the smallest ones, both existing in one common source. 
 Hence urine or sweat should run abundantly through the tubuli 
 testis, which admit the most viscid secretion; and all the mucous 
 and synovial membranes should pour out milk, bile, urine, lymph, 
 \vater, or blood itself, rather than, or at least mixed with, those 
 thick, infiltrable juices which they are found to produce. Such, 
 however, is not the fact; and secretion in this view, as it does also 
 in many others, appears to be governed by laws very different 
 from those of the mechanical process just considered. 
 
 11. That secretions are not produced, or elected, or sepa- 
 rated from the blood by chymical affinity appears satisfactorily 
 proved by the facts before insisted upon, viz. that these secretions 
 do not continue after death, &c. If it should be urged, in objec- 
 tion to this proof, that we do not know but the chyrnical proper- 
 ties may undergo a change at the time of death, I ask what are 
 those properties I The chymical properties of substances remain 
 as long as the substances to which they belong, aud whkh they 
 
245 
 
 help to form, suffer no decomposition If it be urged further, al- 
 though the materials (blood and the structures, or rather the latter, 
 as the former may be supplied, recent, by art) suffer no immediate 
 or sensible decomposition, their latent chymical properties may 
 nevertheless suffer a change, to which the suppression of the pro- 
 cesses of secretion might be imputed. But this evasion will 
 scarcely be admitted unless it be affirmed that all properties which 
 are not mechanical are chymical ; which would leave us still to 
 inquire into the laws of life, only under another title, as, " of the 
 chymical properties which are different from all other chyraical 
 properties, and never met with in the laboratory," &c. For the 
 present, however, it is convenient and methodical to designate 
 these unknown properties by a term expressive of the limitation 
 with which they exist, and we have chosen to consider them, 
 
 1*2. 3. As animal properties, or properties of life, which suffer 
 the conversion from the living to the dead state; in which latter 
 they are no longer capable of producing the secretions, which are 
 to be reckoned only among the phenomena of the former. 
 
 13. If then secretion in general is found to depend upon an 
 assemblage of properties peculiar to the living state, the first 
 question on which we are desirous to be informed is, what are 
 those properties? The answer is, they are not objects of the 
 senses, nor can we even witness their operations; we can infer 
 their existence from results, and we may trace some of their laws 
 by analogy ; but we cannot designate them respectively by appella- 
 tions: or if in some instances, as in those of the powers of con- 
 traction, we do this, our appellations are founded only upon some 
 point of analogy with other more familiar agents; while their real 
 nature, their constitution, their alliances, their relations, are 
 scarcely in the slightest degree indicated by such terms. We will 
 not then pretend to give names to the properties of life engaged 
 in the process of secretion ; but the properties, as a commencement 
 of their investigation, might be inquired into according to those 
 classes of animal properties before suggested, as whether they are 
 of the assimilating, of the regular dependent, or of the oc- 
 casional kind? 
 
 14. In deciding upon these alternatives, the choice appears 
 to lie between the two former; natural secretion being, as we have 
 reason to suppose, unremitting, we cannot attribute the function 
 to properties obtained from another sphere, by the operation of an 
 occasional cause. 
 
 15. But although the natural, unremitting secretions cannot 
 be attributed to those vital properties which we have considered 
 as occasional, yet even these are liable to be modified by coinuiuiii- 
 cation of properties from a distant seat which is primarily affected. 
 Thus, the passions influence in well known instances the functions 
 of the organs of secretion : the first impression is upon the senses, 
 the next upon the brain, and thence the effect may be propagated 
 
246 
 
 to the kidneys, testes, prostate, &c. The natural secretions may 
 be thus affected by properties of the occasional kind ; and by simi- 
 lar occasional causes secretions might be produced, de novo, as 
 exemplified in some forms of disease, as when the fore arm sup- 
 purates from an injury of a finger, &c. 
 
 16. There is no other mode of distinguishing whether 
 functional properties, regularly operating, inhere altogether with 
 the organs, or are habitually derived from another seat, than that 
 division before proposed as a test. We commonly regard the 
 nerves as constituting the medium of intercourse of the vital pro- 
 perties of different seats. We possess a few facts which indicate 
 in the organic system that the nerves are the medium of this in- 
 tercourse: in the animal system these facts are more numerous and 
 less equivocal. Accordingly, an examination instituted to dis- 
 criminate between the assimilating and the regular dependent 
 forms of life would be directed according to the analogy furnished 
 by these facts. 
 
 17. If then the inquiry was concerning the function of the 
 kidneys, we should thus be led to make a division of the renal 
 plexus, or of the contiguous trunks, from which this plexus is 
 formed. Supposing it possible to complete this object in a satis- 
 factory manner; either, 1st, the secretion of urine would proceed; 
 or, 2nd, it would cease. The unconnected inference from the first 
 would be, that the functional properties of the kidneys are inde- 
 pendent on another source ; from the second result, the inference 
 would be that these properties are communicated from a nervous 
 centre. The first inference would be liable to this doubt, viz. that 
 although the organ is independent of any properties communicated 
 through the nervous trunks, yet does it not follow but that pro- 
 perties might be derived from another sphere, by relations with 
 the spirit residing in other, as the mixed, structures, which are 
 also continuous. Thus we find in our experiments upon nerves, 
 that the division of the brachial plexus may produce a sloughing, 
 perhaps followed by suppuration of the extremities; in which case 
 a dependence is exhibited upon related properties, which are not 
 furnished by a centre of nerves. This objection, though proper to 
 qualify the inference, is perhaps not entitled to any great weight, 
 any further than, that it indicates the design of additional inquiry. 
 The inference from the second result, viz. that the secretion ceased 
 upon the division of the nerves, is liable only to this objection, 
 viz. that, from injury of parts, the function might be destroyed by 
 modified communicated properties, and not by an impeded com- 
 munication of habitual ones, necessary to produce it. How far 
 this latter doubt is entitled to consideration it has before been at- 
 tempted to decide. In a general way the cessation of an office in 
 the seat of the inferior distribution of a nerve in consequence of a 
 division of its trunk, has been admitted to prove a dependence, as 
 on properties derived from a source ; but if the nerve is deeply 
 
247 
 
 seated, and its division not to be accomplished without much ex- 
 traneous injury, some suspicions may arise on the truth of the 
 analogy upon which the inference is founded. 
 
 18. We profess not to decide on matters which are necessarily 
 doubtful; on such we state alternatives, which in the present case 
 are, 1st, that secretions in general are produced by spiritual pro- 
 perties which live by assimilation in the organs of secretion; or, 
 2nd, that the secreting function of organs is aided by properties 
 derived from another seat; or, 3rd, that particular examples of 
 both these modes occur among these structures which perform 
 offices of secretion. 
 
 19. Notwithstanding a mechanical secretion or filtration of 
 fluids through tubuli or pores has been rejected, it is necessary 
 that an adaptation should subsist in this respect. There are also 
 instances in which secretion appears to be superseded by a mere 
 hydraulic process, as when blood itself is forced through exhalents, 
 as in the serous membranes, &c. which effect results from, or at 
 least succeeds an increased impetus of the circulation. We find 
 this effect to take place in pneumonia, in nephritis, &c. and effu- 
 sion of blood by transudation is an occurrence which is said to take 
 place not unfrequently in the brain. 
 
 20. Seeing then that this hydraulic process occurs some- 
 times, we are led to a wider consideration of the laws by which 
 in general specific secretions are formed and filtrations prevented. 
 Here we must recur in part to a statement of circumstances 
 already alleged. 
 
 21. The tubuli of secerning structures, which admit without 
 impediment the most viscid fluids, should, according to their 
 mechanical construction, admit still more readily the most subtile. 
 Yet we find that these viscid secretions are even unmixed with the 
 thinner ones. Hence it is necessary to infer that the hydraulic 
 laws are superseded. 
 
 22. If a fluid which is capable of passing freely through 
 tubuli is forcibly impelled against them (as with the impetus of 
 the circulation) and does not enter them, and if at the same time 
 these tubuli admit a grosser fluid, it is necessary to infer that they 
 admit the grosser fluid, by some agency of attraction, or affinity 
 which is more efficient than the force with which the thinner fluids 
 are impelled against their orifices. In this way, becoming filled 
 with the viscid, the more subtile fluids are excluded. 
 
 23. This power of affinity or attraction we need scarcely in- 
 quire after. It is not exerted after death : it is peculiar to, we 
 may say without assuming too much, it is dependent upon, that 
 which distinguishes the living from the dead structure; it is de- 
 pendent upon the living spirit. With what properties or sub- 
 stances, or with what class of properties or substances, then exist- 
 ing in the blood, is this living spirit related? 
 
 24. In answer to this question, it must be remarked, the pro- 
 ducts of the secreting function are found to consist of chymical 
 
248 
 
 substances. It is hence to be inferred that the vital properties, 
 governing the processes of secretion, are related with chymical 
 ones existing in the blood. On this relation it is only further to 
 be observed, that we know not whether vital properties ^are directly 
 related with such chymical substances constituting the secretions 
 as are displayed in our analysis, or whether others, not known as 
 chymical properties, but in alliance with the materials of the 
 secretions, furnish the medium of a relation between the latter and 
 the functional properties of the structure. 
 
 25. But that properties, not known as chymical, are in 
 alliance with those chymical substances exhibited by analysis in 
 the secretions, appears to be propable of them in general, from 
 this fact, that the products of secretion cannot be imitated 
 synthetically; or the result of a synthetical process, or putting to- 
 gether of such constituents as are decomposed chymically, will not 
 agree with the natural secretions in their character and relations. 
 This is true generally ; and in some particular examples the latent, 
 or those properties not known to be chymical, are the most essen- 
 tial, as in the bilious, and more especially the seminal secretions. 
 
 26. Hence then, of secretion in general it may be said, 1. the 
 materials of the secretions are combined in arterial blood, so as 
 to be neither distinguished by the senses in this fluid, nor in gene- 
 ral to be separated from it by any known means of art; 2. the 
 secretions are separable from the blood by the agency of vital pro- 
 perties; 3. vital properties withdraw the chymical constituents of 
 the secretions from their state of combination in blood by a rela- 
 tion of affinity or of attraction, subsisting either directly between 
 the vital properties of the secretory organ and the chymical con- 
 stituents, or by a relation of affinity between the former and latent 
 properties, perhaps vital ones, in alliance with the chymical. In 
 the former case, the chymical constituents of the secretions are 
 separated by a direct relation with the functional properties ; in 
 the latter case, the relation between these is mediate. A more 
 complex mode (which is also a possible one) of the separation of 
 the secretions from the blood is, that vital properties of the 
 secerning organ pass into the blood and decompose (by relations 
 with its constituents, latent or sensible) the fluids which are 
 secreted. This mode supposes two acts of causation, which, 
 without additional evidence, it is unphilosophical to assume, when 
 the end might be accomplished by one. It supposes that one set 
 of properties pass into the blood for the purpose of decomposing 
 the secretion, and that the affinity before mentioned then operates 
 to determine the course of the separated fluid through the 
 secreting tubuli. As, however, positive evidence has been cited 
 of the relation of affinity, it may be perhaps best to adopt this, 
 without supposing additional possible modes, concerning which, 
 if they are admitted, many alternatives might be proposed. 4. The 
 vital properties producing the secretions combine with the secre- 
 tions, and exist in these fluids in the condition of informal life. 
 
249 
 
 5. The secretions are identified by the properties derived or sepa- 
 rated from blood, and by those of secreting organs, which combine 
 with, in order to act upon, to separate, to modify them, and finally 
 to extend their relations. The vital properties themselves of the 
 secreting organs have also a history: we have been content to state 
 that the efficient ones belong either to the assimilating or the regu- 
 lar dependent life. Such is the history of secretion furnished by 
 close analogies with our experience. 
 
 27. The minuter mode of inquiry into these processes would 
 require that, being informed of the general laws of the properties 
 which yet remain to be decided upon, we should then specify the 
 properties themselves; as, What are the properties which hold the 
 affinity with secretions contained in the blood? or, what properties 
 combine with these materials iu blood] what properties are so re- 
 lated with, as to separate the secretions from their alliances? what 
 properties combine with the secretions and help to constitute them, 
 and remaining perhaps latent, multiply their relations? what proper- 
 ties are furnished by the organ, and what from a distant sphere? 
 with many other questions which it will be time enough to propose 
 when our chances of settling them are improved; at present I fear 
 we require additional senses for this work. 
 
 28. The objects to which inquiry might be applied with this 
 view are, secreting surfaces, and glands. The first comprehend the 
 mucous, the serous, and the synovial, membranes, and the surfaces 
 produced by wounds or ulceration ; the second, the cutaneous, the 
 salivary, the mucous, the biliary, the pancreatic, the uriniferous, and 
 the seminal glands. Some of these glands concur with the mem- 
 branes, as the mucous ones of the intestines, and the salivary of the 
 mouth and fauces: perhaps the instances of glandular structure 
 are not to be accurately enumerated or distinguished. The last- 
 mentioned or seminal glands may be taken as an example, and the 
 processes, in agreement with the general view, described thus, or in 
 the following order : 
 
 1. Secreting tubuli, communicating with arterial blood. 
 
 2. Properties of life, belonging to, or conjoined with, the struc- 
 ture of these tubuli, related with a part of the constituents of 
 arterial blood. 
 
 3. History of these properties: they live by assimilation in the 
 glands where their action is exerted ; or they are communicated 
 from other seats. 
 
 4. -Effect of these properties, related with a part of the consti- 
 tuents of blood, to produce the seminal secretion. 
 
 5. The seminal secretion consists either wholly of the substances 
 and properties which before existed in other combination in the 
 blood; or, 2nd, it is made by the combination of the properties of 
 the glandular structure with blood, or with a portion of its consti- 
 tuents. The alternatives differently "stated are, Is the secretion 
 withdrawn by an ageut which does not combine with it ; or, changing 
 its form, only adds to its properties, which are not exhibited in any 
 L L 
 
250 
 
 future relation? or, is the secretion identified, and the peculiar pro- 
 perties which distinguish it conferred, by the union of those vital 
 ones belonging to the structure, with the fluid obtained from blood? 
 The latter appears probable on the following grounds: 
 
 1st, If the secretion is separated by affinity, by the vital proper- 
 ties of the structure, it is consonant with the known laws of affinity, 
 that these properties should combine with the substance which they 
 so far affect as to be capable of detaching it from another state of 
 combination. Thus far that the secretion is formed by a constitu- 
 tion to which the vital properties of the structure contribute, is 
 strongly indicated, if not proved. 
 
 2nd, The secretion is found to possess properties, which may 
 be developed into a similitude of those of the animal in which it is 
 produced. Hence, if those precise vital properties which are after- 
 wards exhibited by the secretion, are not those which before existed 
 in the structures, and are conferred on the secretion; at least, pro- 
 perties agreeing with those diffused ones of the animal in which the 
 secretion takes place, must belong to the glandular structure, and 
 must then operate by a causation more complex than we have 
 hitherto supposed ; this, at least, is to be inferred from the fact that 
 the constitutional peculiarities of various seats are transmitted to 
 the offspring, &c. Upon the ground then of these considerations, 
 which are indeed deserving of some reliance, and to avoid the con- 
 fusion of still greater subtilties, we may thus continue the enumera- 
 tion of processes. 
 
 6. Vital properties of the glandular structure combine with the 
 gross fluid secretion produced from blood, and constitute its latent 
 vital properties, the history of which has been sufficiently discussed 
 in our first chapters. 
 
 7. As in the other instances of secretion there is reason to be* 
 lieve the governing properties are in part obtained from some other 
 seat, so in this it has been inferred in the chapters alluded to, and 
 rested principally on the fact that this secretion contains all the pro- 
 perties of the animal, or those combinations capable of producing 
 all the textures, and of displaying all the phenomena of life: so, in 
 agreement with preceding views, and principally on the strength of 
 this fact it is concluded, that the functional spirit of the testes is 
 formed by a participation of that existing in every sphere. Whether 
 the nerves are the medium of this communication, I neither know 
 nor care. Some may in this case use the word sympathy; be it so, 
 sympathy is a causation among these properties which I have been 
 taking some pains to trace. 
 
 8. The secretion contains the properties conferred by the struc- 
 ture, and those withdrawn from blood ; it is that which it is made by 
 these two; they are related, they modify each other, and final pur- 
 poses are accomplished by them in additional stages of causation. 
 
251 
 
 CHAP. VIII. 
 
 Relations of the Organic Life in the Nervous System. 
 
 1. LIFE, or the organic spirit in the nervous system, 
 maintains its own identity, or assimilates itself from blood, in the 
 same manner as in the other structures. But the properties of life 
 in this system appear to have an intercourse so rapid, so frequent, so 
 important in its results, so subtile, so mysterious, so difficult of in- 
 vestigation, that this system on these accounts deserves rather to be 
 particularized than some others. 
 
 2. The assimilating life in the nervous system is that which 
 belongs to the seat, to every seat in which life is maintained. This is 
 to be inferred on the ground before stated, that properties which 
 maintain themselves by assimilation depend only, 1st, on their own 
 existence, and, 2nd, upon a supply of that material from which their 
 existence is renewed. Hence the assimilating life of the nerves is 
 every where independent of the other parts of the system, at least it 
 has no direct dependence; the indirect will be hereafter spoken of. 
 
 3. Such a conclusion is furnished a priori t and we find it to 
 agree with facts to a considerable extent. The nerves are the 
 organs of the animal functions, or those of sense and motion : a de- 
 pendence is obvious, in the exercise of these functions, upon their 
 centres, as the brain, spinal marrow, &c.; accordingly, we find that 
 if the nerves of a voluntary muscle are divided, that muscle no longer 
 obtains those properties which are derived from the centre of its 
 nerves, and which enable it to perform voluntary motion ; the faculty 
 of sensation is also suspended or destroyed in the inferior distribution 
 of the divided nerves. Not so with the organic assimilating life: 
 the terms of the maintenance of this are not violated, its organic 
 spirit survives the division of the nerves distributed in its seat, it 
 is supplied with blood, and it preserves its identity, maintaining the 
 cohesion of the structure, and exhibiting its usual characteristics. 
 
 4. Thus far the distinction and the independence of the assimi- 
 lating life of nerves is plain to our experience. But we are called 
 upon, in order to extend or correct our view of this same indepen- 
 dence, to consider facts of the following kind. If a sciatic nerve 
 
252 
 
 close to the spine sustain a certain injury, the organic life will cease 
 in the spinal marrow and in the brain, and consequently elsewhere: 
 if the spinal marrow be divided in the middle, the parts below will 
 be paralyzed; they will for a time maintain their organic life, but 
 finally this will cease, as well as the organic life in seats more im- 
 mediately connected with the superior half of the spinal marrow, 
 and with the brain: if the brain be injured in its basis, the life of 
 the spinal marrow will cease, and that of the other parts will die ; 
 if the brain be injured in its superior parts, its entire functions will 
 be impaired, and finally its life, as well as that of the spinal marrow, 
 will probably cease from the same cause. These are the descriptions 
 of facts, which require to be a little further analyzed. 
 
 ' 5. If the medulla spinalis be divided about the middle of the 
 dorsal vertebrae, death is not the immediate consequence; the or- 
 ganic assimilating life is preserved for a time in the nervous structure 
 both above and below, but the general extinction of this principle 
 at no great distance of time will succeed this injury. From the fact 
 that the assimilating life is maintained for a time in this system both 
 above and below the place of division, we are disposed to infer the 
 independence of the inferior on the superior parts, and vice versa. 
 From the fact that death does succeed to such a division of the 
 spinal marrow, though an interval as we have reason to think in some 
 animals of several hours might elapse before this event takes place ; 
 from this latter fact two inferences are suggested, between which it 
 remains for us to choose, 1st, that the assimilating life ceases from 
 privation of properties which are necessary to constitute its identity ; 
 or, 2nd, that it ceases in consequence of disturbed relations, as by 
 foreign properties, or a preternatural condition of local properties, 
 which have a preternatural relation with those in another sphere ; the 
 result of the communication of such properties is the extinction of 
 the assimilating life in the sphere to which they are imparted. To 
 decide upon these inferences, will require but a short discussion. 
 
 6. 1. That the assimilating life does not cease either in the 
 superior or inferior parts of this system by privation of properties, 
 or by interruption of those which we have called the regular de- 
 pendent, is indicated forcibly by the fact, that the life of the parts 
 in question is maintained for many hours after their communication 
 is intercepted ; and the same conclusion is still more satisfactorily 
 proved by the general fact before cited, that assimilating properties 
 roust be independent of every distant sphere. Hence the rejection 
 of this alternative gives room to admit the other, viz. 
 
 7. 2. That if the assimilating life ceases in any part above the 
 place of division of the spinal marrow, the properties directly con- 
 cerned in its extinction can be those only which are foreign; or, to 
 describe the change more particularly, the vital properties interested 
 in the injury assume in consequence (as does the vascularity of the 
 structure also) a preternatural state, and the properties composing 
 this preternatural state have a relation with distant ones which does 
 not belong to the condition of health ; the result of this relation is 
 
253 
 
 the extinction of the assimilating life in a distant seat by properties 
 communicated.* This inference granted, we have to trace still 
 further the process by which according to this method universal 
 death eventually supervenes. 
 
 8. It has been insisted upon that the only conditions of the 
 continuance of life in every seat are the existence of life, fitted for 
 assimilation, and an adequate supply of perfectly formed blood. 
 Hence, according to this view, we are again furnished with two 
 alternatives of the mode in these instances of universal death: 1st, 
 the direct one, implying that foreign properties (or the preternatural 
 state above spoken of) are related, not merely with superior or in- 
 ferior parts of the nervous system to a trifling extent, but with the 
 whole body, producing through the medium of the nervous con- 
 tinuities an'unassimilating state of the diffused principle, according 
 to the process just described, as belonging to the parts above or 
 below the place of the division of the spinal marrow: this is our first 
 alternative; the 2nd is the indirect mode, as when, in consequence 
 of the cessation of the assimilating life in one sphere, a functional 
 one which depends upon it ceases ; which functional life is related 
 with the diffused spirit by its offices, in respect to the formation or 
 the circulation of the blood. 
 
 9. 1. That the injury of the spinal marrow produces universal 
 death by properties communicated every where to the diffused spirit, 
 or that death is produced in the direct way, is an alternative on 
 which we can cite no proofs. At the same time that this mode of 
 death is an improbable one appears from the following considera- 
 tions : 1st, life ceases to assimilate in all the structures, with but 
 few exceptions, and those rather equivocal at the same time; 2nd, 
 If properties originating at the place of the injury should be allowed 
 to possess a relation by which the life of all the structures might in 
 the direct way be rendered extinct, the course of the propagation 
 of these properties (which, as is proved by the succession, is not 
 sudden) must be through the nervous organs, and the contiguous 
 assimilating life must suffer before that which is remote. Hence, 
 although the relation of the properties engaged in the injury 
 should be directly with the spirit in distant seats, life in such seats 
 must otherwise cease, as if no such relation were possible, by the 
 destruction of that existing in the spheres of the nervous organs, 
 upon which functions depend which are necessary to the formation 
 or the circulation of the blood. 
 
 10. 2. On our 2nd alternative, viz. that the diffused life is 
 made by the injury we are considering to cease indirectly or through 
 the medium of the blood; on this alternative it is proper only to 
 remark, that this mode of death must happen from the extension of 
 
 * It is possible, agreeably with the modes of causation, that the new rela- 
 tion may be such as to destroy the assimilating life of another seat, by with- 
 drawing properties necessary to its identity. This, however, cannot be 
 ascertained, and if admitted, does not prove the dependence of the assimi- 
 lating life ot" one seat upon that of another. 
 
254 
 
 the effects of the injury to contiguous parts of the nervous system, 
 upon which the formation of the blood depends, as to those parts 
 at least which are necessary to mechanical respiration. 
 
 11. To define then with greater precision our conclusions 
 upon this subject, 
 
 1. The life which assimilates in the nervous system, as in the 
 mixed structures, is every where independent of spiritual properties 
 which live in distant spheres. 
 
 2. If the assimilating life of one sphere is affected or destroyed 
 by an injury or a cause which operates primarily upon the life of 
 another seat, this happens by a new relation, conformably with a 
 new or foreign state, which has been produced on the spirit by the 
 operation of such cause or injury. 
 
 3. There are two ways in which the preternatural condition of 
 a primary, may influence the secondary seat of change : one is direct, 
 as by communication of foreign spiritual properties ; the other is 
 indirect, as by an influence on the formation or circulation of the 
 blood, with which the spirit in every sphere holds a common relation 
 of dependence. 
 
 4. The assimilating life is always affected in the direct mode 
 by additional or preternatural properties: the functional life may 
 be affected or destroyed by foreign properties conferred, or by pri- 
 vation of natural communicated ones; in either of the latter cases 
 the essential change is of the assimilating life, upon it all phenomena 
 ultimately depend. To extend a little our illustration. 
 
 12. An injury of one part of the spinal marrow, or an injury 
 of one part of the brain, may be directly extended to that cerebral 
 portion, the assimilating life of which furnishes the functional pro- 
 perties of the diaphragm, and are necessary to respiration; the life 
 of this portion being thus modified, respiration ceases, and death is 
 then extended, in the mediate way, to parts which have no relation 
 with the primary seat of the injury. Thus also in an injury of an 
 extremity, as a fracture of the leg, the local state of vital properties 
 is extended to those which govern the movements of the heart, the 
 pulsations of which in the course of a few hours are increased, per- 
 haps from 70 to 130 in a minute : properties which govern the 
 caliber and phenomena of the vessels of the brain, might from the 
 same extension of preternatural influence assume that state which 
 constitutes phrenitis. In short, from the interchange of these two 
 modes of affection, the direct and the mediate, complex changes 
 and relations may be variously exhibited, and they furnish a history 
 in almost every seat, which is to be traced only by a specific investi- 
 gation. This matter might be pursued more minutely: the time 
 which elapses in the succession of these phenomena is a point of 
 important but of difficult explanation, it belongs however more pro- 
 perly to the subject of disease. 
 
 13. It would appear that an inquiry into the physiology of any 
 given portion of the nervous system can scarcely be separately pur- 
 sued- The complexity here hinted at must occur in the investiga- 
 
255 
 
 tion of functions. It remains that the seats of functions should be 
 discriminated: the relations of the properties of different seats with 
 each other will principally comprehend their physiology. I shall 
 take only one or two examples with a view to indicate the objects 
 of inquiry. 
 
 14. The method by which we come at the knowledge of the 
 seats of functions of nerves is of the analytical kind. We take an 
 effect, in which we suspect from analogy the offices of nerves to be 
 engaged, and we trace in this system the laws and processes which 
 are exhibited in the instance under consideration. Thus, for example, 
 let the effect be the movement of the muscles of respiration: does 
 the power which animates the muscles of respiration belong to their 
 structure? is it a property of their assimilating life, or is it dependent 
 upon another seat? We find that it ceases upon the division of the 
 phrenic nerves ; and as it is assumed, on grounds before exposed, 
 that division of a structure is a test of the dependence, or the con- 
 trary, on properties which are propagated only by its continuity, so 
 in this case we infer that the action of the muscles of respiration 
 is a function dependent upon the centre of the phrenic nerves. 
 
 15. The inference thus attained is that some properties, ne- 
 cessary to the action of the diaphragm, are derived from the spinal 
 marrow; the next step in our analysis requires that we should 
 specify what these properties are. Before this question can be 
 answered we must have reduced the whole of the properties con- 
 cerned in the effect to certain classes, that we might say, these are 
 the properties inherent in the structure; these are the properties 
 related with them, which, when united, identify the power of respira- 
 tion ; this is a stimulus merely, or a property which is also common 
 to externals, or to many substances; this property is given off from 
 the assimilating life of such a seat ; this is formed by relation of 
 the assimilating life of such a seat with that of a secondary 
 source ; the relation of these properties is direct ; of those, mediate ; 
 these act by affecting the caliber of vessels, or by an operation upon 
 the blood ; those, by modifying its formation. Such definitions as 
 these we must hope to find accurately applied to their examples in 
 the progress of research: the time however, if ever, is distant. We 
 cannot here pursue to any extent the true analytical method, ac- 
 cording to principles of causation, so as to specify of the properties 
 identifying an effect; this change takes place by the addition, this 
 by the abstraction of such properties, leaving the effect to be identi- 
 fied by remaining causes. 
 
 16. There appears, it might be said, to be an inconsistency, or 
 at least some confusion, in the evidence which has in these views been 
 assigned to the experiments of dividing the nervous structures. The 
 inconsistency alluded to is this, if a function in the seat of the in- 
 ferior distribution of a nerve ceases upon a division of the trunk, we 
 infer the dependence of the function upon the centre of the nerve 
 which supplies its seat. If the functions and life of the superior 
 parts of the medulla spinalis cease, after a division of the spinal 
 
256 
 
 marrow at the lumbar vertebrae, we do not from this instance of 
 division, although followed, as in the former case, by a suspension 
 or cessation of certain phenomena, infer, as in the former case, a 
 relation of dependence. This objection requires a little explanation. 
 
 17. If the results of the division of a structure prove depen- 
 dence in one instance, they must also be allowed to prove it in 
 another, provided the circumstances of the structure furnish no 
 exception, and provided also the results of the division are the same. 
 These then. are the points to be ascertained in cases where the above 
 distinction is attempted. The question only respects functions, the 
 independence of the assimilating life being necessary. 
 
 18. In these cases, in which dependence is inferred from 
 division of nerves, the function supposed to be dependent ceases 
 immediately upon the prevention of intercourse between the seat of 
 the function and the source of its properties. The function must 
 always cease as soon as the nerve is intercepted, because the proper- 
 ties communicated under a continuity of the nerve cannot assimilate ; 
 if they did, there would be an end of the dependence. Hence, when 
 phenomena immediately succeed to division, we must in every case 
 infer the dependence we are considering ; but if an interval of time 
 elapses between the prevention of intercourse and the cessation of 
 phenomena, than the analogy in this essential circumstance is de- 
 stroyed ; and, for the reason just stated, dependence cannot be in- 
 ferred. Thus, for example, 
 
 19. If the sciatic nerve of a rabbit be divided close to the 
 spinal marrow, the animal, as I have found in the experiment, might 
 become convulsed and die within 36 hours. We do not in this case 
 infer a dependence of the functions of the superior parts of the 
 spinal marrow on properties obtained from the inferior portions of 
 the sciatic nerve, because these functions continue for a time, 
 whereas in the case of dependence they would immediately cease. 
 The functions of the spinal marrow are made to cease by a new 
 relation, which is opened between a disordered condition of the 
 nerve at the place of injury, and the functional properties of the 
 superior parts of the system; just as it is rendered more than pro- 
 bable by the same argument, the action of the heart is maintained 
 by its a'ssimilating life, continuing after the division of its nerves, 
 but is destroyed by a new relation which is opened with it by cer- 
 tain injuries of the spinal marrow. 
 
 20. When functions are made to cease, or life is destroyed by 
 this disordered or foreign state of the properties engaged, it happens 
 either directly or indirectly: directly, as in the example of the sciatic 
 nerve just mentioned, that is, a new relation is opened between 
 vital properties without being produced by disorder of the circula- 
 tion; and indirectly, as when the life of that portion of the brain or 
 spinal marrow which furnishes the power of the respiratory muscles 
 dies, from an injury inflicted upon the superior parts of the brain. 
 Thus a wound of the brain may for thirty-six hours appear to pro- 
 duce but little derangement i at this period phrenitis may supervene. 
 
25J 
 
 and the death of the independent functions may succeed to this 
 condition of the blood-vessels. Whether life ceases wholly in this 
 instance from disorder of the circulation, or whether a change which 
 is directly propagated from the place of the injury, to parts other- 
 wise not related, can scarcely be decided ; at least, the precise share 
 of each of these modes of impairing function or destroying life 
 cannot be defined. By these modes aud their complication, functions 
 are modified or destroyed where the relation of regular dependence 
 does not subsist. 
 
 21. The ways in which the effects of causes are extended be* 
 yond the primary seat of their operation appear simple; they are 
 reduced to two, the direct and the mediate ; but their complexity 
 may be greatly increased. As the direct and the indirect might be 
 mixed, or the direct may have complex relations, as when functions 
 cease in a third, by the relation which a primary, has with a 
 secondary seat; or a complication might grow out of the relations 
 between the direct and the indirect modes of influence in different 
 seats; their connexion may be extensive or partial, common or par- 
 ticular; or obtaining in some seats and not in others: these varieties 
 all tend to modify phenomena. Such a tissue of subordination and 
 re-agency can be unravelled only by specific investigation, which 
 must respect some or other of the numerous examples in which it is 
 displayed. 
 
 22. It has been attempted to establish dependence by injury : 
 this mode of experimenting has, in some of our former pages, been 
 rejected, and the grounds of the rejection are there stated. I have 
 only further to remark upon this subject, that when muscular motion 
 is for a few minutes exhibited in dependent seats, under the infliction 
 of an injury which destroys the source of their properties, this hap- 
 pens, not by an assimilation of functional properties in the dependent 
 seat, but by a progressive disorder of their source; the injury of 
 which, though speedily, is not immediately fatal. Thus, an animal 
 will use for a time vehemently the voluntary muscles, after his head 
 is cut oft": the reason is, that the spinal marrow is capable of sup- 
 plying properties for muscular motion, until life is destroyed 
 mediately, as in this case, by the prevention of respiration, or an 
 influence connected with the blood. This circumstance indicates 
 that the voluntary powers of the muscles supplied by spinal nerves 
 is not dependent upon the continuity of the spinal marrow with the 
 brain ; at the same time it must be remarked, that a different con- 
 elusion is indicated by the paralysis of the lower extremities, which 
 is known to succeed certain injuries of the medulla spinalis about 
 the lumbar, or even the dorsal, vertebrae. We find it agreeable 
 with our experience in other respects, that when properties of 
 motion are no longer communicated to the muscles from a true r 
 unequivocal source, the powers of motion cease immediately and 
 entirely in the dependent seat; just as a leg drops, aud is not con- 
 vulsed, the moment that aw axillary plexus is divided with one 
 stroke of the bistoury. . . . . 
 
 w M 
 
23. The relations of properties of nerves may be inquired into 
 upon grounds of analogy, and by the mode of investigation many 
 times repeated in every case in which a function is displayed.* 
 Thus it may be inquired after in the instances of secietion before 
 enumerated, and in the parts of the nervous system, with relation to 
 each other: this latter examination will refer principally to the 
 brain and spinal marrow; and, with but few exceptions, and those 
 almost equivocal, will respect the animal and intellectual pheno- 
 mena, rather than those of the organic life, with which we are at 
 present engaged. 
 
 24. Can we then, it will be asked, define in abstract no cri- 
 terion by which the seats of dependent functions might be assigned, 
 and the functional dependent distinguished in every case from the 
 assimilating properties? No such criterion exists: we may say 
 those phenomena depend only upon the properties which assimilate 
 in their seat, which phenomena take place merely as a result of 
 the relation between blood and the living spirit of the seat. Thus 
 much might be set down as an abstract, general criterion; but the 
 investigation we have indicated must be applied in every instance 
 before we can decide the question of dependence, &c. in the examples 
 in which this question might arise. Thus, it cannot be said either 
 that secretion is pioduced wholly by the assimilating life of its seat, 
 or that secretion is a process dependent upon properties obtained 
 from a distant sphere, because to the former assertion it would be 
 replied, the secretion of gastric fluid ceases upon the division of the 
 eighth pair of nerves; and to the latter it would be objected, that a 
 wound will suppurate below the place of the division of an 
 axillary plexus. 
 
 25. After discussing certain relations subsisting between the 
 properties of the nervous system, the more difficult inquiry must be 
 suggested here, as on former occasions, concerning the identical 
 nature of the properties engaged in these relations. Our causation 
 teaches us that for every diversity of effect a different cause is to be 
 assigned: this axiom is incontrovertible, and therefore the different 
 phenomena of the nervous system are to be referred to so many 
 different agencies. It has long been a favourite design with certain 
 physioligists to evince the identity of electricity with the properties 
 of the nerves; but the inferences deduced from the facts prove such 
 physiologists to be but very indifferent reasoners. Electricity will 
 produce muscular contraction, after certain functions, characteristic 
 of the living state, have ceased : so also will irritation of the muscles 
 of an amputated limb with a scalpel excite their contraction. From 
 these facts, there is as much reason to pronounce life to be a scalpel, 
 as electricity to be life. Electricity will excite powerful actions of 
 the muscles after death ; other substances, perhaps mechanical ones, 
 will excite weaker contractions ; the former is therefore to be con- 
 
 * The functional instances have formed the subjects of preceding pages, 
 fend need not hereto be repeated. 
 
259 
 
 sidered a powerful stimulus, the latter as stimuli of a weaker kind* 
 Certain phenomena of the branches of nerves, dependent upon 
 their connexion with their centres, are said to be producible by 
 electricity, when this connexion is intercepted ; as, if a portion of 
 nerve were removed and an electrical conductor substituted, the 
 phenomena which otherwise occur during the integrity of the 
 nerves may be produced by electricity. This experiment is just 
 as conclusive as former ones; for if electricity is communicated to 
 the muscles, or to the branches of nerves, it matters very little in 
 what way it gets there, whether by means of a conductor or by a 
 common electric shock : here, also, is the parallel of the scalpel ; 
 for the nerves of an amputated limb is totally separated from their 
 centres, yet irritation with a scalpel will produce the contraction 
 of its muscles, &c. But electricity, it is said, will substitute the 
 influence from a centre of nerves in processes of the organic life, 
 as in digestion. Granting the fact (which is, however, extremely 
 questionable), it proves only, as the other facts respecting the same 
 agent prove, that certain properties derived from a nervous centre 
 may be substituted, and consequently that such properties come 
 under the denomination of stimuli. A passion of the mind may 
 produce a temporary diarrhoea; so also may Epsom salts, or 
 rhubarb; yet we should scarcely call rhubarb a human passion. 
 If electricity is life, it should produce the phenomena of life: if it 
 fail of producing one effect of the properties of life, its identity with 
 these properties cannot be admitted, because life in this respect is 
 different from electricity. The most that can be assumed from 
 the facts collected on this subject is, that electricity holds a rela- 
 tion with life; that certain of the properties of life may be substi- 
 tuted by electricity, and in a less degree by other agents, in which 
 cases these properties are regarded as stimuli, or as properties 
 which are common to many substances. 
 
 26. The influence from a centre of nerves produces the con- 
 traction of a muscle; so will electricity: thus far there are proper- 
 ties in common. But the influence from a centre of nerves 
 produces voluntary contraction of a muscle, or modifies its con- 
 traction, in connexion with the mind, and volition: so does not 
 electricity. Life produces secretion, circulation, &c.; electricity 
 will excite life in connexion with the organs of circulation, secre- 
 tion, &c. or it may appear to produce these effects after they 
 have ceased by the first changes incident to death; that is, while 
 certain properties of life remain free to hold a relation with such 
 an external, or such a stimulus: but electricity will not produce 
 these effects when life has entirely ceased, or when all the pro- 
 cesses of the death of the spirit are accomplished, and when those 
 properties forming irritability, and the last to assume their final 
 change, or alliances, have become extinct. Life forms blood from 
 food: so will not electricity in connexion with the same organs, 
 and in the same temperature ; at least this may be presumed* Life 
 maintains itself by assimilation, electricity is produced by different 
 
260 
 
 law*, and in a different manner: life produces' the organization of 
 an animal, electricity has never exhibited the faintest approxima- 
 tion to such a power. Not to be tedious in enumerating diffe- 
 rences, where, in ten thousand phenomena, there are scarcely half 
 a dozen points of resemblance, and those common in a lesser de- 
 gree to other substances, it appears that in the intercourse of vital 
 properties these properties in some instances are to be reckoned 
 as mere stimuli, and produce the phenomena of a distant seat in 
 conjunction with the regular properties of such seat: to what 
 extent they are to be considered in this light, in the examples of 
 dependent life \vhether regular or occasional, is to be determined 
 by the ascertained instances in which these properties may be 
 substituted. That electricity should have an intimate relation 
 with life is not more extraordinary than that grass should furnish 
 the materials of the animal structures; but neither is grass a 
 muscle, nor is electricity life, until by causation they are dis- 
 tinguished from other forms of existence, and identified as these 
 creations. 
 
 This section concludes our physiological sketch. The design 
 hitherto has been to shew distantly how life is maintained, and to 
 point out those particulars for further inquiry, the possession of 
 \vhich would make us almost perfect in this department of science. 
 Physiology has never been investigated with these views: the pur- 
 suit of it has turned principally on mechanical arrangement, which, 
 with respect to function, has no other importance (which indeed 
 is very considerable) than belongs to an instrumental fitness to the 
 powers by which it is actuated. The design has been to incite 
 attention to these powers, to shew that they might be reasoned 
 upon with a probability perhaps equal to that which is boasted in 
 those coarser topics which are commonly received as more level 
 to the faculties with which men are endowed. Many circum- 
 stances or particulars here unnoticed concur also with those 
 which have been spoken of in the business of the formation and 
 support of an animal body: these have their respective histories 
 and relations; to particularize which, would be very little more 
 than to swell by repetition the views, the analyses, the indications, 
 concerning which as much has been already said as is conformable 
 with a general design. The condition of life having been thus 
 faintly exhibited, it remains that we trace it in the two further 
 itages of disease and death. 
 
261 
 
 GENERAL NATURE OF DISEASE. 
 
 CHAP. I. 
 Origin of Disease according to Doctrines of Causation. 
 
 1. THOSE conditions of the body designated by the 
 terras health and disease are fixed by the consent or agreement 
 of mankind ; that is, one state of the body is said to be a healthy, 
 and another a diseased state. To settle these definitions, then, we 
 have only to describe the respective conditions which men have 
 agreed to call by these names. 
 
 2. By the word health is implied a certain condition of all 
 the organs and functions of the organic, the animal, and perhaps 
 we may include the intellectual, systems: the latter, at least, is at 
 present foreign to our purpose. The certain condition, implying 
 that of health, has been said to consist of a natural and easy use 
 of all the functions : this definition, however, is not perfect; for to 
 say that a natural function is a healthy one, is a mere substitution 
 of terms which alike require a definition ; and to say that health 
 is an easy use of the functions, is to say more than is true, for the 
 kidneys may secrete easily, that is, without pain, in diabetes, yet 
 it would be suspected that the state of their function was not a 
 healthy one; or there may be disordered action of the heart with- 
 out pain, or a furred tongue without an uneasy exercise of its 
 function, or a wen upon the shoulder, or on the head, not uneasy 
 in itself, nor at times productive of uneasiness; yet at these times 
 nevertheless a disease. 
 
 3. But although such objections may be raised to the defini- 
 tion of health, which assigns it to consist of an easy use of all the 
 
262 
 
 functions, yet a better definition cannot be given without an 
 elaborate description of that state of all the organs respectively, 
 which may be agreed to constitute a healthy condition. Thus, 
 beginning with the head, it may be said the condition of health 
 requires that the head should have no tumours on it, that the skull 
 be covered by the scalp, that the scalp be supplied with blood, 
 that its structure should be of such a kind that its sensibility and 
 its life should be so and so; and then an average thickness proper 
 for the cranium must be defined; and then of the contents of the 
 cranium, &c. ; all of them endless themes. Let us therefore be 
 content with a looser, with the loosest, definition, rather than 
 incur so tedious a history. Let us say that health is one condition 
 of the body and disease another; and that men are so well agreed 
 about the use of these terms, that they do not require to be any 
 further explained. But, if it should be resolutely insisted that 
 some standard between health and disease should be established, 
 we shall, in the respective instances, readily discover such a 
 criterion, although an universal one cannot be proposed, It has 
 indeed been said, to this effect, that health is such a condition of 
 an animal as is agreeable with all his purposes. It then comes to 
 be asked what are his purposes, as, for example, those of a man 1 is 
 the art of flying one of his purposes'? no: why? because he is 
 not provided with the organs ; in the same manner, walking or 
 running would cease to be among the number of his purposes, if 
 he should happen to have lost his legs. 
 
 4. According then to this common understanding or consent, 
 to which we have referred the definition of health and disease, 
 health is a certain state (settled by this common agreement or 
 understanding), and disease is a. change or modification of the state 
 of health. 
 
 5. Health is the effect of the causes which have to some 
 extent been traced in the preceding sections. These causes con- 
 cur to identify the condition of health. Disease is a modified or 
 altered state of the causes which produce health. 
 
 6. An healthy condition of an animal is the sum of the causes 
 which concur to this end : so, if one only of these causes should be 
 90 modified as to impair this concurrence, the animal may then be 
 said to be unhealthy or diseased. Yet, under a modification so 
 trifling as this, many parts, or many, perhaps by far the largest 
 proportion, of the causes of the animal may not participate in this 
 modification, or may be in a state of health. This distinction 
 indicates the first step of analysis. If the healthy identity of an 
 animal is dependent upon all his parts, a deviation from this con- 
 dition in any will make an unhealthy state of the animal. As 
 then we have analysed his parts,, with a view to come at the 
 minuter knowledge of the conditions of health, so we must descend 
 also to the state of constituents, in tracing the history of disease. 
 
 7. Disease is primary, secondary, or general, aud it is acci- 
 dental or spontaneous: primary, as when it originates in. ojie seat 
 
263 
 
 by a causation peculiar to the properties of this seat; secondary, 
 as when disease is extended from the original, to a related seat; 
 general, as when, in some form, few parts of the system are exempt 
 from it; accidental or foreign, as when disease is produced by 
 external agents, which are related with properties common to the 
 healthy condition of the species, as in the instances of wounds, 
 poisons, &c.; spontaneous, as when disease happens without any 
 external assignable cause, or as when it is excited by a natural 
 cause, as air, food, &c. operating upon a state of constitution 
 which does not belong to the healthy condition of the species. 
 Of these classes, our principal business at present is with spon- 
 taneous disease. 
 
 8. Before we enter upon the discussion of the general origin 
 of spontaneous disease it will be proper to give an instance of it, 
 which will serve the purpose of illustrating our reasonings without 
 the necessity of a frequent appeal to examples. A person attains 
 the age of twenty, enjoying generally good health: at this time a 
 slight cough occurs; the action of the heart becomes a little 
 quickened; the temperature of the skin is irregular, sometimes 
 cold with slight rigours; these succeeded by flushes of heat, and 
 the blood forced into the cutaneous vessels of the face (or rather 
 admitted by their preternatural dilatation) gives a vermilion tint 
 which is, perhaps, supposed by the ignorant an indication of 
 health; this, which is a feverish state, continues a short time; the 
 cough becomes more troublesome, the voluntary muscles are 
 sooner fatigued than usual; this debility is increased by periodical 
 sweats, which are perhaps the spontaneous relief of the febrile 1 
 diathesis. The person observes, perhaps in the morning, after a fit 
 of coughing, that the mucus is tinged with blood ; or a little blood, 
 which has been gradually forced up from the lungs during the 
 night, is expectorated with the first effort, appearing io have 
 lodged on the top of the glottis; the fever is now continued, with 
 evening exacerbations, which perhaps terminate by an expectora- 
 tion, in which more blood is perceived ; a pain is felt in the side, 
 the bulk of the body is rapidly dimished; this state continues, the 
 lungs cannot be inflated without exciting pain or cough; the ex- 
 pectoration becomes purulent; the feet swell ; the powers of loco- 
 motion are almost extinct; respiration becomes quick and labo- 
 rious; the pulse is raised perhaps to 160 in a minute ; it may then 
 sink to 70 or 80; the extremities are cold, and the patient dies. 
 This will be recognized as one form of pulmonary consumption; 
 and this is an example among many of spontaneous disease. 
 
 9. These which have been enumerated are the symptoms of 
 the disease; or they are effects, each of which has an history of 
 its own, which we shall thus trace in our analytical method. We 
 have mentioned the cough as the first symptom: this may not he 
 true; but we must begin at some point. What produces the 
 cough? irritation, it will be said, which has its seat in some part 
 of the membrane which lines the trachea, and is continued into 
 
264 
 
 the bronchial ramifications: this irritation, it will be replied, 
 affects the respiratory muscles sympathetically, and thus the 
 coughing is produced. 
 
 10. Irritation is said to be the cause of our first symptom ; 
 and what produces irritation? it is excited by cold: with what, 
 then, is cold so related as to produce irritation? is it with the or- 
 ganic fibres? no, for cold never makes dead people cough ; is the 
 cold so related with the blood in the vessels of the part? no, for 
 there is always blood in the vessels of the part, and this blood 
 shall many times be surrounded by an atmosphere of the same 
 temperature, &c. yet it Will not produce a cough; or if this 
 answer should be excepted against, as it might, we will add, dead 
 vessels may be filled with blood, but we have no experience of 
 cough having been produced by a simple relation between blood 
 and air. This cough then takes place only during the presence 
 of life, and must therefore be considered as one of the phenomena 
 dependent upon life. 
 
 11. What then shall we say of the state of irritation? merely 
 that it is a disordered or modified condition of life, which produces 
 those effects, those symptoms, which are just referred to it. 
 There are few terms more common in medical subjects than this 
 word irritation. A modified condition of the spirit is meant by it ; 
 it is employed to designate almost any modification, and by no 
 means a particular one: thus we say a part ulcerates because it is 
 irritated, as by a foreign body; or a wound is painful and secretes 
 bad matter, because it is in a state of irritation; or sympathetic 
 disorder of a system, as of the nervous, takes place from irritation 
 of one part; or a membrane, which would not otherwise secrete, 
 throws out mucus because it is irritated, &c. These are all 
 instances of irritation, yet the state which is the cause; the agent 
 producing different phenomena, though related alike with the 
 common material, must on this account consist in each of a diffe- 
 rent combination or assemblage of properties; in other words, the 
 irritation which makes a cancer spread is different from the irrita- 
 tion produced on the schneiderian membrane by a pinch of snuff. 
 If then we retain this word, or in our future use of it, let us under- 
 stand that it is designed to express a modified condition, liable to 
 much variety, of the spirit, and not one precise identity of it. 
 
 12. To return to our symptom. The cough, it is said, is pro- 
 duced by irritation; the state of irritation, by a relation between 
 properties of life, the seat of which is in the membrane lining the 
 trachea, and the properties of the atmosphere. But the same 
 person may, many other times, have been exposed to the same 
 atmosphere, which has not before produced a cough; or many 
 other persons might at the same time have been exposed to the 
 stime atmosphere without such exposure being followed by our 
 symptom. If the atmosphere be the same in these instances of 
 different results, where must we look for the cause of the diversity? 
 We have no choice: we rawst look for the difference where alone 
 
265 
 
 it can exist, viz. in the condition of the part which is the seat of 
 the affection. We have already attempted to settle with what 
 order of the properties of this part the atmosphere in this case 
 holds its relation, and we have found it to be with the pro- 
 perties of life. 
 
 13. Thus it appears necessary that the properties of the seat 
 should have undergone a change, preparatory to that of irritation 
 by atmospherical influence, to which our symptom has been more 
 immediately attributed. This change implies a different form or 
 combination of the properties making the life of the part; the 
 atmosphere is related with this form (which, as it tends to disease, 
 may be called the disordered condition), so as to produce the 
 symptom in question; while it is not related with the healthy state 
 of these properties, so as to produce such an effect in conjunction 
 with them. 
 
 14. This first deviation from a healthy state of the proper- 
 ties, this peculiarity in the constitution of the spirit, this state 
 which precedes the symptoms of disease, by wjiich we judge of 
 its presence, is expressed familiarly by the word predisposition. 
 This predisposition we have shewn to consist of a change of the 
 combination, or assemblage of the properties which constitute a 
 healthy state. 
 
 15. The state of predisposition must precede every spon- 
 taneous disease, at least in its primary seat: this, without recurring 
 to particular examples, is sufficiently obvious from the fact that 
 the same exciting causes, as they are called, do not affect others in 
 the same manner, and perhaps have entered into the habits of the 
 individual who suffers the disease for many years, as in our 
 example, without being attended by preternatural effects. Our 
 next inquiry is into the history of this state of predisposition. 
 
 1(>. Our topic is "otherwise thus expressed: Why does that 
 change take place in the properties of a seat, which disposes them 
 for disease? We infer, in agreement with our general principles, 
 that this change, like every other, is accomplished by an act of 
 causation, of which there are two modes, viz. the addition and the 
 abstraction of constituents. We have many times before led up 
 to that point where analysis ends: here again we must recur to if. 
 It requires, in order to specify what properties are added to, or 
 what taken away from, the healthy, in order to produce the pre- 
 disposed condition; for this purpose it requires that we should 
 know the properties concerned in either case; but as they are 
 not objects of the senses, we cannot pursue the analysis in thit 
 strict way. 
 
 17. Our first change of the healthy state in a particular seat 
 is thus easily reduced to a conformity with our general principles. 
 But, iq admitting the conformity in this instance, the following 
 difficulty occurs. If the predisponent condition is produced, 
 either by properties added or causes taken away, it would appear 
 that they must, in the former., be communicated from some oilier 
 
 N N. 
 
266 
 
 seat; or, in the latter, that some power, as one of affinity, must be 
 exerted by a distant seat, for the purpose of withdrawing proper- 
 ties from that which becomes the seat of disease: in either case, 
 implying a first change to have taken place in a related part, and 
 thus precluding in fact an origin of disease in any part; for the 
 same modes of causation must every where obtain. This view 
 suggests another origin of disease, or of the origin of the change 
 from the healthy to the predisponent state, viz. change happening 
 spontaneously in any given seat, and change happening in one seat 
 from a previous change in a related one: our difficulty belongs to 
 tiie first of these. 
 
 18. The spontaneous change originating in a given seat hap- 
 pens from the operation of some cause which did not before pre- 
 vail. We have assumed that the externals are the same as before: 
 the cause in question, then, not being obtained from without, must 
 belong to the seat in which its effect is contemplated. If this cause 
 before resided in a structure in which it did not display itself by 
 effects, we can express its conditions only by saying that it was 
 latent or passive, and afterwards comes to be inferred from its 
 effect, or is active. We are not yet arrived at the origin of 
 these processes. 
 
 19. By saying that a cause is latent, we intend that it is in a 
 state of combination in which it is not cognizable to our faculties; 
 if a cause is in this state which we call latent, or is better ex- 
 pressed as passive, why, it must be inquired, is this passive con- 
 dition changed? We here perceive the necessity of a causation 
 previous to that by which an effect is produced by a latent cause. 
 
 20. This remoter causation admitted, we are still as far from 
 arriving at an origin of these processes; for every change must be 
 preceded by another, and the series, as well in the limited subject 
 which now occupies our regards, as in the universal scheme, must 
 be infinite. We see a certain state of constitution is preserved for 
 many years; at some period this state is altered, predisposition, 
 changes into disease, disease into death. In our physiology we 
 have remarked an order analogous in its kind, and some examples 
 still more striking may here again be mentioned. We perceive, in 
 the growth of the foetus, how, from a mere speck, bones, muscles, 
 arteries, veins, nerves, &c. are produced. We see the being thus 
 made, afterwards preserving a form, without any striking change, 
 except the gradual increase of the structures: after the lapse of 
 years, the attainment of puberty, glands secrete which never 
 secreted before, and the general changes which happen at this 
 period mark an important era in the history and existence of 
 the person. 
 
 21. These are instances of that complication which has been 
 remarked to arise out of only two modes of causation. Causes are 
 infinite: their modes of producing effects have been said to be 
 only two by addition, &c. ; they may be still further simplified: 
 essentially, the mode of the operation of a cause is, that it exists; 
 
267 
 
 it can do no more, it has no virtue to be what it is not. But 
 causes have relations by which they join their existence, and each 
 being a different form, their distinction is lost in this union, at 
 least to our perception. The study of these relations forms the 
 principal business of philosophy ; and as knowledge of individual 
 causes must precede the steps by which we investigate their rela- 
 tions, hence the complication which in this our present subject 
 belongs to the analysis of the causes upon which phenomena depend. 
 We are professedly ignorant of the most essential of these causes: 
 and where this particular knowledge is denied us, we can only 
 state our difficulty, and, with a view to future progress, shew its 
 conformity with those general principles which must direct our 
 research in this, as well as in all other instances. 
 
 22. If a gelatinous bed is converted into muscular fibres, if 
 cartilage is converted into bone, if the amazing structures of a per- 
 fect animal are developed to this state from a nucleus to all ap- 
 pearances without a character, if in the course of being new 
 functions arise, if the functions which maintain this fabric become 
 disordered and finally cease, and this piece of anatomy fall to 
 decay, we can regard this series as the result only of properties 
 and relations which are disposed/or progressive change. 
 
 23. Progressive change is accomplished by reiterated causa- 
 tion. If a thing preserve an uniform identity, it does so because it 
 is surrounded by no agents which are so related with as to affect 
 it ; if a thing is once changed, and then preserve its new form, it is 
 that it is exposed to the operation of a related agent, and that the 
 form which it assumes in consequence ceases to be related with the 
 existences which surround it ; if a thing suffers one change and 
 then another, and a third, through a lengthened, series* it is because 
 each successive form of existence has a caus,ative relation with 
 Other forms. 
 
 24. To apply these principles first to our physiology. Pro- 
 perties are related with a nutrient material containing infinite con- 
 stituents, so as to separate or produce from it a gelatinous fluid; 
 the properties which produced this fluid belong to the organic 
 spirit, and constitute one state, of it; this state is a form of 
 existence which is related with surrounding agents, so as to suffer 
 a change; this new condition is again related with other constitu- 
 ents of the material, and the end of this new relation, thus esta- 
 blished, is, that the properties producing jelly, having changed 
 their state, cease to separate this fluid, and produce, conformably 
 with their present or new state, the aggregation perhaps of carti- 
 lage. These processes are repeated, and cartilage gives place to 
 bone, and so of all the other structures. 
 
 25. But we observe in.stan.cea wherein thjs progression ap- 
 pears to be interrupted : the subject or t,he particular effect which 
 we contemplate appears for a time to be at rest, and then at per- 
 haps a distant period it assumes a change. We may trace the 
 stages of conversion in the .growth of the fetus, and we can 
 
268 
 
 observe how one form succeeds to another; but in these changes at 
 remote periods (as in the attainment of puberty, or the occurrence 
 of spontaneous disease) a process seems to have commenced, without 
 any preparatory acts or connecting links. What is the explanation 
 of a change of this sort? If this change is not produced by foreign 
 externals, which we have assumed, it can happen only by that pro- 
 gression the nature of which has been just explained. If the precise 
 subject or effect which we regard preserve its identity and then 
 alter it, apparently under habitual circumstances, it is because 
 changes are going on among connected agents which have no rela- 
 tion with the subject of our regards; until they have arrived at a 
 particular state, viz. one in which they hold a causative relation. 
 Thus, it happens that we suppose a process to originate, without 
 the preparatory changes, merely because we are regarding one set 
 of phenomena, while changes which come in time to affect these 
 phenomena (and then it is that change is first perceived) are going 
 on among connected properties. 
 
 26. The growth of the body, and its changes, are similar to 
 those of the mind, and the former may be further illustrated by what 
 is more familiarly observed of the latter. The mind of an infant 
 has been said to be a blank tablet : this is said in the way of meta- 
 phor. The mind in this early stage is a state of properties which 
 has certain relations with the external world : the effect of these 
 relations is, that the mind which was a predisposition is made by a 
 common act of causation another identity, by the introduction or 
 combination of additional causes; or becomes, according to com- 
 mon metaphorical language, stored with ideas, which again are 
 related with each other, and help to accomplish the phenomena of 
 association and inference, &c. Thus much for our present pur- 
 pose: we see this mind by degrees making its acquisition of know- 
 ledge ; as its identity changes new relations are opened, its notices 
 are first on one set of objects, having attained the state which these 
 constitute its notices are extended to another set of objects, these 
 familiarized, its predisposition is again a new one, and it takes cogni- 
 zance of things to which it was before blind or unconscious. By 
 this progression, similar to that which all nature observes, one 
 acquisition disposes to another, materials are accumulated, new 
 associations arise, thought improves, taste is developed, and the 
 interchange of agencies in the constituents of mind itself or its 
 affections, by relation with the external world, are limited or exten- 
 sive; confined to the sober walk of industry, plodding upon a 
 business or upon domestic concerns; or, if it is so prepared, taking 
 a wider range; or soaring perpetually some bold flight of genius. 
 These processes make a growing predisposition, which can never 
 preserve one given state, because the constituents of mind being 
 related, and these relations being further extended to all the variety 
 of externals, progressive changes must succeed; and these are rapid 
 or slow, not necessarily in their own nature, for in this they are 
 perhaps uninterrupted, but in the apparent, and in the imperceptible 
 
conversions of related beings. If, then, it be asked why the testes 
 secrete at J6 and did not secrete before; let it be asked as a paral- 
 lel, why a person understands a certain proposition in Euclid at 16, 
 and did not before? The reason is the same: a progressive change 
 or a series of causation leads up to this effect. The character of the 
 changes of mind, each particular phenomenon which it exhibits, is 
 that which it is made by its own constitution or by an external 
 related agent; each change, each phenomenon, whether belonging 
 to the physiology or disease of the body, is produced from similar 
 sources. We have then to discriminate between those things which 
 proceed from the original constitution, or parental radicle, and 
 those which are to be attributed to the influence of externals. 
 
 27. It is demonstrated by our anatomy, that the first per- 
 ceptible original of an animal (as of a man) is an insignificant aggre- 
 gation of matter, possessing no sensible arrangement, but endowed 
 with certain properties. This radicle suffers or exhibits the nume- 
 rous changes which are just represented; but these changes do not 
 occur among its own inherent properties, but in obedience to a 
 relation which subsists between these and certain external properties 
 and substances. The question here then to be discussed is, what 
 share have the properties of the ovum in the subsequent changes 
 which it undergoes! 
 
 28. There are two modes in which the properties of the ovum 
 may contribute towards the conversions which occur in its develop- 
 ment. 1. The first state of the properties of the ovum may be so 
 related with the external as to produce, m conjunction, one change; 
 this change, or this new state, may open a new relation with exter- 
 nals, and produce another change; and so on through a series: 
 in this way, the properties of the original predisposition, or the 
 ovum, may have with respect to subsequent phenomena the impor- 
 tance only of remote causes, and the series and nature of ensuing 
 changes, though taking their determinate character from this first 
 predisposition, may concern principally the accession of properties 
 and substances obtained from the external world. The 2nd mode 
 in which the original properties of the ovum may operate in regard 
 to ensuing changes is by a direct causation with respective pheno- 
 mena; as if that progressive change which has been described went 
 on in properties originally belonging to the ovum, and as if every 
 new change resulted from the development of a latent property, in 
 the manner explained. The latter of these has been preferred (in 
 the instances there cited) in our section on the constitution of the 
 ovum. As we possess no criterion by which we may discriminate 
 when, in particular instances, either of these modes obtains; as also 
 it is probable that in all instances these orignal and external proper- 
 ties are mixed in causation, and the more especially as in our present 
 state of knowledge we may rest satisfied with a deduction from 
 alternatives; on these accounts it appears superfluous to state the 
 objects with which an inquiry for such a criterion might be con- 
 
270 
 
 ducted. Let us therefore, as such is the highest success to which 
 we might aspire at this time, be contented to state our deduction, 
 or corollary, respecting the share which the first properties of the 
 ovum have in subsequent phenomena, whether of health or of disease. 
 
 29, If the original properties of the ovum have, with respect 
 to the subsequent processes, the importance only of remote causes, 
 then the nature, order, &c. of such changes are determined by 
 these properties of the ovum, although the respective effects which 
 occur in catenated causation may be constituted by properties 
 acquired from the external world. And whatever differences might 
 occur in the development of two animals of the same species, they 
 are to be referred to an original peculiarity in the respective ova, 
 which, being differently constituted, run through a series of different 
 relations, and of course exhibit different phenomena. If the pro- 
 cesses of development, c. are to be attributed to progressive 
 change, going on between properties originally possessed by the 
 ovum, each property, as it passes from the latent to the active 
 form, producing as a constituent its own effect, then also the 
 phenomena of development, conversion, c. are to be attributed 
 to the original constitution of the ovum: in their first case this con- 
 stitution is preparatory to subsequent occurrences; in the second 
 case they are contributary, or have the importance of a real cause, 
 which is that without which the effect cannot exist. We have, it 
 is said, no satisfactory criterion by which either of these alternatives 
 may, in particular cases, be positively adopted. 
 
 30. We observe in the intellectual system, that its phenomena 
 concern chiefly the acquired properties, viz. the ideas which are ac- 
 quired, or formed with the help of the intellectual predisposition. 
 We see also that the information of the mind and its peculiarities in 
 individuals, take their determinate character from the intellectual 
 predisposition; it is this which directs and produces all the variety 
 of opinion, and the infinite motives to action in different individuals, 
 surrounded by the same externals, or existing in nearly similar cir- 
 cumstances. Yet here there is similitude in the offspring to an 
 original in the parent, as in the corporeal phenomena. The testes 
 begin to secrete at sixteen ; a person becomes consumptive at five- 
 and-twenty, whose mother died of consumption perhaps at about the 
 same age; a person at three-and-thirty becomes deranged in mind, 
 whose father or grandfather was deranged at about the same period. 
 Here it would appear, as if properties, in all these cases, which 
 could specifically determine these events^ belpnged to the ovum, 
 and remained latent until they were developed by that progressive 
 causation which we have attempted to describe. On the other hand, 
 we know that insanity engages principally the acquired properties 
 of the mind or its ideas ; for the form of insan.ity may consist in 
 disordered judgment or inference, and perhaps only on one subject, 
 the act of which consists in the comparison of ideas, from the ana- 
 logy of which an inference is made: or tlje form of insaiiity may 
 
271 
 
 be one of disordered association only ; comparison, or association, of 
 what? of ideas; or of that which is not obtained from parents, or 
 possessed by the ovum. It is perfectly clear, that if a man were born 
 of mad parents, and had in ever so strong a degree the hereditary 
 taint, he never could have either of the above forms of insanity, viz. 
 of disordered comparison or disordered association of ideas, if he were 
 so circumstanced from his birth as to be precluded the acquisitions 
 from externals, as, if he were enclosed in a dark room and never 
 permitted to hear an articulate sound. Yet in these forms of 
 insanity the predisposition is hereditary, although the form itself is 
 principally constituted by the acquirements from without, and de- 
 pendent perhaps upon education and a long train of connected 
 causationi In this case, although the acquired properties or ideas 
 have a principal share in immediately constituting the insanity, and 
 in determining the consequent acts of volition, yet we must suppose 
 the predisposition to ideas to have a share, or in fact, if it is a 
 principle of consciousness, to be the basis of their individual 
 existence. Here, then, we may look for the cause, or a cause, of 
 the insanity; and as the insanity cannot arise out of the mere pre- 
 disposition, but is principally dependent upon relations of ideas, so 
 in this, as in the corporeal instances, we perceive the probability 
 that the original and the acquired properties are mixed in the 
 causation of progressive phenomena ; and in this case too, as in the 
 other, we perceive the impossibility of pronouncing, such a share 
 have the original, and such the acquired properties in these occur- 
 rences. We must for the present be content with our alternatives. 
 
 31. From this view it appears that we cannot fix a period to 
 the commencement of the processes which are preparatory to 
 disease; the necessity of a progressive change, leading up to this 
 state of disease, is demonstrable; and, with respect to the causes 
 which constitute the disease, we cannot lay down any general 
 criterion by which to distinguish whether they belonged to the 
 ovum or whether introduced from without. In cases of contagious 
 and infectious disease, &c. we know that a cause is obtained exter- 
 nally; but the share of this cause and that of the original proper- 
 ties, as we may conjecture that they produce effects in conjunction, 
 we cannot even here discriminate. 
 
 32. That state of the properties which is the stage of pro- 
 gressive change, immediately preceding disease, is called predis- 
 position ; any change, the tendency of which is finally to impair 
 functions, &c. may be said to comprise a diseased state. But there 
 is convenience in the distinction between predisposition and disease: 
 according to our notion of the difference between these two, pre- 
 disposition is a change of the state of perfect health which does not 
 produce symptoms: disease is also a change of the state of health, 
 but it is manifested by symptoms : the former change is not related 
 with our faculties of perception, &c.; the latter change is related 
 with our faculties of perception. The most healthy state may be 
 
1272 
 
 predisposed to disease, because there is no state which does not 
 somewhere find a relation capable of producing change with some 
 or other external. Thus all bodies are predisposed to disease and 
 death by the relation of their properties with arsenic; nearly the 
 same thing may be said of the plague, of morbid poisons, &c. But it 
 is proper to confine the use of the term predisposition to those 
 states which have a relation productive of disease with natural and 
 habitual properties, or with those to which the same subject at other 
 times, and the rest of the species, may be regularly or occasionally 
 exposed without the supervention of disease. 
 
273 
 
 
 CHAP. II. Origin of Disease in one Seat. 
 
 1. DISEASE (or symptoms) may commence in any given 
 seat from a progressive causation which is uninterrupted, or from 
 preparatory changes which have rested in the state of predisposition ; 
 and then a new causation is begun, which terminates in the exhibi- 
 tion of symptoms, or in death. By these principles the question 
 must be answered, why does disease commence] 
 
 2. When the changes which terminate in disease are uninter- 
 rupted, each internal change is a predisposition, which is related 
 with existing causes. When one series terminates in a predisposition, 
 the progression towards disease is renewed, or the state immediately 
 established, only by the operation of causes which, though perhaps 
 common and natural ones, did not obtain when the former changes 
 rested in the state of predisposition. This latter has been exempli- 
 fied in physiology, if is necessary to illustrate both a little further by 
 a short comparison with the histories of disease. 
 
 3. In our example of consumption, we have supposed no ex- 
 ternal assignable cause; but admitting that such a cause did obtain, 
 its first operation is not to establish the symptoms which identify the 
 disease; that is, the lungs do not at once, by a casual exposure to 
 cold, become ulcerated, &c.; but a trivial symptom, as a slight 
 cough, or some change preparatory to the complete establishment 
 of the disease, is the result of the operation of this cause. From 
 this change the series is uninterruptedly progressive; for the relation 
 is constant between each change and the existing causes. This is 
 an instance of the production of symptoms in an uninterrupted 
 series. The history of predisposition might be different; it might 
 consist of interrupted gradations, which are next to be exemplified. 
 
 4. A woman might have a small tumour in the breast ; it might 
 remain, without change for many years: this tumour has formed by 
 a train of causation indicated in the preceding pages; this series has 
 rested in a state of predisposition to the condition which the 
 tumour afterwards assumes; it rests in this state, because its con- 
 stituents no longer hold a relation of change with existing causes. 
 If this state is altered, it must be from the influence of some new 
 cause; this cause may be produced from change going on internally 
 among connected agents, which having attained a certain state, may 
 o o 
 
274 
 
 then become related agents. Thus, while our tumour is at rest, 
 suppuration might take place in the axillary glands, and the tumour 
 might disappear, while the contiguous parts are running a long 
 course of disease; or, the tumour being at rest, an habitual diarrhoea 
 might occur, and the tumour disappear; or the tumour might re- 
 main at rest until the cessation of the catameuia, and then it may 
 begin to increase in size, become painful, and finally degenerate 
 into cancer; or, by some accident, the tumour in its state of rest 
 may receive a blow; it may in consequence inflame, suppurate, and 
 disappear; or it may become malignant from this cause. This illus- 
 tration is sufficient : the axioms I mean to establish, with respect to 
 the general history of causes in the production of disease, are, 
 
 1st, That every primary, spontaneous, disease is produced by 
 progressive change in the constituents of its seat. 
 
 2nd, That this progression may be interrupted, when the present 
 state ceases to find a causative relation with existing causes. 
 
 3rd, That if the progression of change is resumed, it is because 
 new causes obtain a relation which did not before exist with the 
 constituents of its seat. 
 
 4th t That these new causes may come to produce change in a 
 given seat, either from progressive internal change among connected 
 properties, or from exposure to an external cause which is related 
 with the present predisposition of the seat; these might be 
 complicated. 
 
 5. If then we would trace the history of spontaneous disease, 
 we should indeed, although the general laws are so few, undertake 
 a perplexing inquiry. Say a tubercle forms in the 'lungs: why does 
 it form there? the part, it may be said, becomes thickened by 
 coagulable lymph, which then becomes organized, grows, suppurates 
 imperfectly, &c. Why was the lymph thrown out? from inflam- 
 mation; why did the inflammation occur? excited by cold; how 
 can^e the part predisposed to such a relation with cold ? it has some- 
 how attained such a state. Now my abstract refers to this word 
 ' somehow ;" and if this somehow is to be answered, the only reply that 
 can be given will be found in the above propositions, which I have 
 called axioms. To leave then this subject of the manner in which 
 disease begins, and without taking any further with us the incum- 
 brance of these views, we will simply say, when disease occurs 
 spontaneously without any assignable external cause, that it happens 
 from the development or operation of latent causes, about which we 
 have been of late so busy; and that when disease happens from an 
 external assignable cause, which does not produce the same effects 
 in others, or in the same individual at other times, we will say that 
 a predisposition existed to the operation of such cause, of the 
 nature of which predisposition also enough has been said in 
 the way of indication. 
 
 6. We have assigned in our physiology three sets or classes of 
 properties which concur to constitute an animal, viz. those belong- 
 ing to the vital, the chymical, and the mechanical departments. 
 
275 
 
 The phenomena of disease exhibit deviations from the state of 
 health in each of these departments. We have to determine in this 
 place, whether a predisposition, and then the symptoms of disease, 
 might originate in either of these; and if so, we have to suggest a 
 method of discriminating the instances, or whether the origin of 
 predisposition and disease belongs exclusively to the properties of 
 one class, by which those of the others are influenced consecutively, 
 
 7. We will select as an example a disease which appears to con- 
 sist chiefly of a change of structure, or of some mechanical impedi- 
 ment; supposing that if disease does not originate in the structure, 
 in those instances in which the structure is visibly changed, we 
 are not to expect an origin of disease in the mechanical department 
 in cases in which this order of components does not sensibly 
 participate. We will take for example a scrophulous abscess, and 
 trace its history with the above view in our analytical way. 
 
 8. Why is a collection of matter formed? it is formed by an 
 inflammation of a peculiar sort, &c.; matter is produced (says our 
 reply) by inflammation: the causes which constitute inflammation, 
 and which produce its phenomena, belong either to the vital, chymi- 
 cal, or mechanical properties, or else these concur. To proceed: 
 pus is a change of the fluids belonging to the seat in which it is pro- 
 duced; why are the fluids changed? Supposing the fluid which 
 furnishes the material for the conversion to be blood (though most 
 probably it is not blood), supposing the fluid to be blood, why is the 
 blood of a part changed ? say (arguing for the chymists) spontaneous 
 decompositions and combinations take place in blood, the result of 
 which is the formation of pus; why do these decompositions, &c. 
 occur in blood ? from some previous change, for they would not 
 spontaneously occur in blood healthily disposed. But the blood in 
 this part where pus is formed is the same, from the same vessels, 
 and no fixed or specific quantum of blood, as circulates elsewhere. 
 This part must then have properties, holding a relation with blood, 
 different from any to which it is elsewhere exposed. To these pro- 
 perties, then, and not to the mere internal causation of blood itself, 
 is to be attributed the conversion of blood into pus, or perhaps 
 more correctly the formation of pus from blood. These properties 
 we are to inquire after. 
 
 9. These properties belong to the structure forming the seat 
 of the production of pus: are these efficient properties of a chymical 
 kind? we have no reason to think that they are; but granting it 
 which is the most that can be required, if these properties are of the 
 chymical kind, how came the seat to be possessed of an unnatural 
 or a diseased chymical constitution? Here we must recur to our 
 physiology, and ask why there are any chymical constituents at all 
 in this seat? They are held together in a forced allegiance during 
 life, and by life; left to their natural propensities, they separate and 
 dissolve into their elements. It is to life, then, or the properties 
 which constitute it, that the chymical constituents are indebted for 
 their local existence; these chymical constituents are formed from 
 
276 
 
 a common material, from the same material as a tree is formed. If, 
 then, their state is peculiar in the several instances, the source of 
 this peculiarity is not in their common origin, but in related proper- 
 ties; these are the properties of life. 
 
 10. If, then, the properties of life produce chymical combina- 
 tions conformable with their own nature, suppose a deviation from a 
 given or natural state to take place in the chymical properties, it 
 must arise either out of the nature of the first chymical disposition, 
 as formed from the spiritual properties, or from a new state of the 
 spiritual properties; in either case, the origin is alike in the state of 
 the properties of life. 
 
 11. We cannot quote a more striking example of mechanical 
 disease than a stone in the bladder; although in this case the chief 
 phenomena of the disease ,are produced by this mechanical cause, 
 we shall not find that the origin of the processes by which the cal- 
 culus was formed, belonged to the mechanical department. The 
 stone is formed, it is said, by excess (or something else) of uric acid; 
 \vhat makes the excess of uric acid? say, merely by way of defining 
 a seat, that it arises from a faulty secretion of the kidneys: now the 
 blood in the kidneys is a common material (or if the seat is else- 
 where, we must still trace up to a common material, even though 
 we should arrive at the digestive organs); if from this common ma- 
 terial a product arises which is peculiar, we must seek for the 
 cause of the peculiarity in the related properties, and not in those 
 which are common. The related properties in this case have their 
 seat in the kidneys, and belong to that class without which urine 
 would not be secreted at all. If, in this case, instead of saying that 
 these related properties are vital, we say that they are chymical, we 
 do but defer arriving at the result of analysis: for if the chymical 
 properties are peculiar, they being first made, and afterwards main- 
 tained, and renewed, by the related ones which are spiritual, we then 
 assign to these latter a mediate, instead of a direct agency. 
 
 12. Thus it appears that the origin of change, even of that 
 progressive kind which has been indicated, is from some property of 
 life, which must be peculiar in every case. But in the course of 
 a series of progressive changes either the cbymical or the mechanical 
 agents may operate as a cause, by which either the changes of pre- 
 disposition are multiplied, or perhaps the phenomena of disease 
 produced. 
 
 13. The properties of the chymical or the mechanical depart- 
 ments may become re-agents: their varieties are first produced, 
 either by an affection of the spirit by a foreign external, or by an 
 original peculiarity of the spirit, under a relation with common or 
 natural externals. 
 
 14. However complicated the re-agencies of these three depart- 
 ments might be, in order to determine the share, or how much, or 
 what phenomena, are to be attributed to the agency of life, or the 
 organic spirit; we have only to ascertain whether the phenomena in 
 question are peculiar to the living state ; for whatever the origin 
 
277 
 
 might be, whether in the seat of the symptom or in a related one, 
 whether in the first formation of the ovum, or in a subsequent 
 spiritual change ; or whether produced by a chymical or mechanical 
 cause, which being itself an effect, in turn becomes a cause; whether 
 arising from internal causation or produced by a foreign external: 
 whatever may be the process by which a symptom takes place, as 
 much is to be attributed to an altered condition of the spirit as can- 
 not take place without it. Thus, in an inoculated disease (as the 
 small-pox), say a peculiar chymical substance is introduced into the 
 body whose effect is to produce eruptions, &c.; these eruptions are 
 formed by a suppurative process : now although the cause, for the 
 sake of the argument, may be granted to be chymical, yet would 
 not the animal phenomena which succeed to its introduction take 
 place unless the properties of life were under a state of preternatural 
 affection. It is the history of the spiritual properties which I wish 
 chiefly to trace; and as every form of disease is peculiar to the living 
 state, so the laws of the properties and affections of life admit an 
 analysis which will refer to the general character of disease; and 
 this analysis must be principally founded upon our physiology. 
 
 15. Having shewn in part the importance or share in disease 
 which might be attributed to the chymical and mechanical depart- 
 ments ; having shewn that spontaneous change in the properties of 
 these departments is always secondary, but that they might become 
 re-agents ; I shall now proceed to speak of disease, as more exclusive- 
 ly concerning the state of the organic life; and the future employ- 
 ment of the term disease will be understood with the qualification 
 here hinted at. 
 
278 
 
 CHAP. III. General Nature of Disease of the Spirit. 
 
 1. IT has been remarked, that the most intimate know- 
 ledge to which we can arrive of the nature of disease enables us to 
 say only, that health being a given state of the principle of life (or 
 of its properties), disease is a change or deviation from this state. 
 We cannot specify in what the identity of health consists, or in 
 what the deviation from this state consists, because in neither case 
 do we possess the faculties necessary for such a specification; or, in 
 other words, we are not qualified to take cognizance of the objects. 
 
 2. Disease is transient, continued, or permanent : upon what 
 laws does its duration depend 1 
 
 3. Disease first depends upon its causes: the causes of disease, 
 with reference to our question, are of two kinds: 1st, those which 
 being related with the spirit have the power of affecting it, and pro- 
 ducing disease as often as they are communicated, or as long as they 
 continue to reside with the spirit; 2nd, those which may modify for 
 a time or permanently the identity of the spirit, even though the 
 operation of the primary cause should have ceased. The state of 
 the spirit produced by the first class of causes is not an assimilating 
 one: the state produced by the second is either maintained by 
 assimilation or runs into a succession of modified states, each capa- 
 ble of assimilation. 
 
 4. 1 . Life, as explained in our former sections, is no fixed sum, 
 but is produced from its elements, unites its elements, contained in 
 blood, and immediately changes its form. In this way a similitude 
 is perpetuated, although the quantum existing at a subsequent, is 
 never the same as that which existed in a preceding moment. If, 
 therefore, the identity of life be affected by a cause (as one pro- 
 ducing disease), this cause must be repeated or renewed for each suc- 
 cessive quantum of life, unless uniting with life it is renewed by 
 assimilation, or, in other words, unless it finds its similitude in 
 arterial blood. If a cause produces temporary change, which 
 endures only so long as it may be supposed to continue, or as is less 
 equivocal, if the effect ceases as soon as the identical cause is re- 
 moved, we then infer that it has not occasioned a disordered assimi- 
 lation of the spirit. 
 
279 
 
 5. To illustrate this class with an obvious example : suppose 
 the brain to be compressed, the properties of the brain which con- 
 tribute towards the function of respiration would by this cause be 
 modified or disordered, or even their office might be suspended. 
 A healthy state of these properties may be immediately resumed as 
 soon as the compression of the brain ceases.* The efficient cause, 
 whatever it was, which in this case disturbed or altered the vital 
 properties of a sphere, had no assimilating relation with the material: 
 if it had, the state which was produced by the operation of this 
 cause would have been continued after the causation occasioned by 
 the pressure had ceased. Thus also (though less obviously) wine, 
 brandy, &c. taken into the stomach, produce a disordered state of 
 the properties of life, perhaps in many spheres, which disordered 
 state continues as long as the quantum of these spirits, or of the 
 related properties which they contain, may be supposed to last. 
 We find that their effects endure in proportion to their quantity, 
 provided they are not, in the examples, rejected by vomiting, &c. 
 
 6. To this class also belong many of the phenomena of related 
 disease. Thus a disease set up in one organ or part may affect 
 distant ones, which either do or do not, during health, afford evi- 
 dence of an intimate connection: thus the local injury incident to a 
 fracture of the leg will perhaps raise the action of the heart to 130 
 beats in a minute; when the violence of the local injury has sub- 
 sided, the heart will resume its former action, which might be at the 
 rate of 70 beats in a minute. Thug, also, irritation of a nerve will 
 produce convulsions, which cease as soon as the irritation is discon- 
 tinued : thus, a blow on the head will produce vomiting, the properties 
 engaged in which action do not perpetuate their state when the brain 
 has recovered from the effects of the blow, in which primary organ 
 with respect to the duration of the effects of the injury the same thing 
 is also to be remarked : thus, also, the irritation of a stone in the blad- 
 der will maintain a chronic disease of this viscus as long as the stone 
 remains, and the irritation of it will perhaps produce a wasting and 
 hectic state of the whole body, which effects cease when the cause 
 of the disorder is removed. To this class also belong the great bulk 
 of medicinal preparations: purgatives, emetics, diuretics, sudorifics, 
 &c. produce respectively, a state of the local properties conformable 
 with their character, which state lasts so long as the cause which 
 produced it resides with them. The reason why these effects do not 
 outlive the application of their causes respectively is, that neither 
 are these causes assimilated from arterial blood, nor do they lead 
 to processes of causation which produce a modified assimilating spirit. 
 
 7. 2. We have no means of discriminating, in all examples, 
 when causes of disease unite with the spirit, and finding their simili- 
 tude in arterial blood, are maintained as the spirit itself is maintained; 
 
 * An experiment of this sort, with such a result, has been made on the 
 human subject, in a case in which a large removed portion of the cranium has 
 uever been reproduced, The compression was made with a handkerchief. 
 
280 
 
 that , we are not in all cases able to pronounce when disease is 
 continued by assimilation of the external (for instance) which pro- 
 duced it, and when disease is continued in consequence of a causa- 
 tion among the properties of the spirit, in which the primary cause 
 (the external) has no subsequent share. 
 
 8. That some causes of disease have an assimilating relation 
 with blood is proved by the phenomena of the morbid poisons : 
 thus the matter (as is said) of sm&ll-pox produces matter endowed 
 with its own qualities; it is not that there is any relation between 
 the small-pox matter and blood, by which a similar pus is pro- 
 duced in the inoculated person, for inoculation will not produce 
 small-pox in the dead subject; but it is, that there are properties 
 in the virus which unite with the spirit, assimilate similar proper- 
 ties from blood, and these holding the same relation as their 
 prototypes with the constituents of blood, produce and ally them- 
 selves with the same secretion. The phenomena of syphilis, per- 
 haps the plague, and most or all of the causes of infections or con- 
 tagious disease, are capable of being continued by assimilation. 
 Assimilation, however, is not the only process of these causes: in 
 some part of their series of consequences they fall under another 
 department, expressed in the definition of our second class. 
 
 9. But although assimilation, or the production of a likeness 
 from arterial blood, is sufficiently clear in the above instances, it is 
 not so in others. A person, from exposure to an easterly wind, may 
 get an attack of pneumonia. Can we say that the properties of 
 this wind, which affected the spirit, are retained or united with it, 
 and, rinding their similitude in arterial blood, produce the pheno- 
 mena of continued disease? or, if a person receives a blow in the 
 breast, in consequence of which a tumour forms, which in time 
 becomes schirrhous, can we say that the modified assimilating 
 state of the spirit, necessary to the disease, is maintained by the 
 properties originally imparted by the cause of injury? we should 
 exceed our warrant if in these and in similar cases we were to 
 pronounce an affirmative. Any argument derived from predisposi- 
 tion is here nugatory: for if it be said, these causes do not assimi- 
 late, because they do not in general produce such effects, it may 
 be replied, if they have no assimilating relation with the state of 
 perfect health, it does not follow that they should have none with 
 the state of predisposition ; at the same time their producing such 
 effects with the aid of predisposition, does not prove that they do 
 it by the process of assimilation, which we have described. 
 
 10. When the evidence does not furnish a fair conclusion, we 
 are warranted only in defining the facts: certain causes, such as 
 those above adverted to, produce continued disease, and at the 
 same time produce their own likenesses, or similar properties. 
 Other causes produce continued disease, which remains without a 
 repetition of the causes; these latter do not obviously assimilate, 
 but they produce internal causation or progressive change, 
 which terminates in recovery or death. The nature of the 
 processes which regulate occurrences is to be further considered. 
 
281 
 
 11. External causes which are common or habitual, as we 
 have seen, never produce disease without those preparatory 
 changes which establish the state of predisposition; and with the 
 aid of this predisposition they do not at once establish the disease 
 which follows. A person during the exposure to cold may feel 
 only a slight shivering: pneumonia or fever may succeed at a short 
 interval after the exposure. Hence, it is not the property of this 
 cause, viz. cold, to constitute the subsequent disease, nor can it, 
 unless it assimilates, have any immediate share in the state of 
 disease; and whether it assimilates or not, the disease is esta- 
 blished only by progressive causation or by successive changes. 
 
 12. Predisposition then, as belonging to the department which 
 we are considering, is one state (a modified one in comparison to 
 the state of health) of the organic spirit ; the predisposition is pro- 
 duced by changes of the latent properties of the spirit; the con- 
 dition thus produced is so related with an external, as to suffer, 
 upon exposure to it, another change which exhibits symptoms; 
 this change also, or this state, is made by latent properties, in 
 which the external has no share as a cause (accord ing to our defini- 
 tion of a cause) unless it endures with the spirit, and is renewed 
 like the spirit as fast as this latter passes away or dies. 
 
 13. This state, produced conjointly by predisposition and 
 exposure to a related external, is one of disease: it may occur 
 without any assignable external cause, in the way before described. 
 The identity of the diseased state is dependent upon the causes 
 producing it, which cannot be defined because the state itself is 
 not susceptible of analysis. Disease being established, its present 
 form may endure for a time with little variety, or it may run 
 through a series of changes, or it may occupy only one seat, or it 
 may be extended to others, or diffused over the whole system. 
 
 14. During all these changes life still maintains itself by 
 assimilation: that is, life admits all this, which is a considerable 
 variety, and still preserves its character as an assimilating princi- 
 ple. The identity of this principle at any time or in any stage is 
 dependent upon the combinations of its own properties, and its 
 participation of related ones, whether external, derived from a 
 related sphere, or existing in the blood. Let us now return to 
 our example of a disease, that of phthisis pulmonalis, and see how 
 far these doctrines agree with its phenomena, or elucidate the 
 minuter history of its formation. 
 
 15. Predisposition, established by that progressive internal 
 causation before described: this predisposition consisting of a 
 modified or peculiar state of the spirit; this state of the spirit has 
 one seat in the structure of the lungs; this state of the spirit is one 
 which is related with a condition of the atmosphere ; the effect of 
 this relation is perhaps to produce inflammation; the tendency of 
 this inflammation is governed by latent properties, which belong to 
 the spirit: by these it is decided whether the inflammation shall end 
 in resolution, or whether it shall advance towards a quick or slow 
 p P 
 
282 
 
 suppuration ; by the development of these latent causes, by those 
 varieties of combinations which make progressive change, all the 
 circumstances of this local disease are decided; by these it is de- 
 termined whether an imposthume forms, which ulcerates speedHy, 
 and discharges its contents; by these it is decided whether the 
 bursting of this abscess shall be followed by re-generative pro- 
 cesses, by which health is re-established, or whether ulceration is 
 extended, or whether a slow inflammation remains, which pro- 
 duces further thickening of the structure; by these it is deter- 
 mined, whether such thickened structure, or the adventitious mat- 
 ter composing it, shall be absorbed, or whether the suppurative 
 processes shall be renewed ; by these the quality of the pus is de- 
 termined; by these scrophulous matter may be produced, or phos- 
 phate of lime may be deposited. The predisposition is perhaps 
 not originally confined to this structure; the properties which 
 animate the heart may also have attained a predisposed state; 
 this state may be attained by complex relations; it may be attained 
 by progressive changes of the assimilating life of the heart ; or the 
 original seat of change may be in the sources of the regular de- 
 pendent properties; or the heart may be affected by those of the 
 occasional kind, as if the disease of the lungs communicated pro- 
 perties to the heart which raised its actions to 130 in a minute: 
 this, however, would not take place except the state of the spirit 
 which governs the movements of the heart was a peculiar or pre- 
 disposed one. By these latent properties, also, is determined the 
 fate of the arteries, in the seat of the local disease: their cohesion 
 is firm, and they retain their blood; their state is otherwise pre- 
 disposed to rupture, and this prevails either in the minute branches 
 or in the trunks, and we find among our symptoms small expecto- 
 rations of blood or great hemorrhages. By these the changes of 
 the chymical and of the mechanical circumstances of the struc- 
 tures are regulated ; by these the changes succeed which result 
 from those modifications of the structures; to these are to be 
 assigned the phenomena which are produced by the new relation 
 opened between a modified state of the spirit and a modified state 
 of its chymical and mechanical alliances. By these the sphere of 
 disease is settled, whether confined to one seat or extended to 
 others, and to what others it is extended; by these, latent changes 
 proceed in a series; by these, phenomena, which we call symp- 
 toms, are every now and then exhibited, as the sensible tokens of 
 these latent changes; by these it is decided whether life remains 
 permanently a modified principle, compatible with health,* 
 whether the identity of health is restored, or whether the series of 
 progressive change terminate in producing a state of the spirit in 
 which it can assimilate no longer, or in the condition of death. 
 
 * The small-pox, and those diseases which can occur but once, are in- 
 stances of the production of a permanently modified assimilating principle, 
 without interruption of the functions and phenomena which characterize health. 
 
283 
 
 ' 
 
 16. Although the spirit may be said to be liable to change 
 which respects either its combinations or its quantum, we can 
 scarcely insist much upon such a division, for that which we may 
 attribute to excess or deficiency may arise only from a different 
 disposition of its properties, and possibly changes in the combina- 
 tions of properties may occur from defect or excess of quantity. 
 These latter states must, however, be dependent upon the blood, 
 and the blood being dependent upon the preparatory organs, and 
 the phenomena of these organs being regulated by the disposition 
 of the life that resides in them, the phenomena in question, even 
 the defects or excess of the quantity of the principle, may come 
 ultimately to be referred to its identity or disposition in some or 
 other of its seats. 
 
284 
 
 CHAP. IV. 
 
 Disease of the assimilating, of the regular dependent, and of the 
 occasional Properties of Life* 
 
 1. THERE are but few (perhaps not any) examples of 
 disease which is confined wholly to one part. There are many 
 instances of disease of one part, in which the organic system else- 
 where does not perceptibly suffer: but these are attended with 
 pain or disordered motion, which is sufficient to prove an exten- 
 sion of the diseased state. In the organic system however a per- 
 son may have an ulcer in the leg, or a tumour upon the shoulder, 
 or an herpetic disease upon some spot of the skin, or a stricture of 
 the urethra, &c. without any sensible derangement of the same 
 system elsewhere. But even in these instances we cannot prove 
 that the change is entirely local, unless it may be shewn, 1st, that 
 the natural condition of the seat is not a dependent one, by which 
 disorder might originate in another sphere; and, 2nd, supposing 
 the disease to originate in its apparent seat, that no other is so 
 connected with it as to participate in its modifications. But if it 
 is possible that any part should possess only an assimilating life, 
 that no other part is dependent upon it, and that the condition of 
 disease does not open any new or preternatural relation, then it is 
 possible that the assimilating life of such part may become exclu- 
 sively diseased by that progressive causation which has been 
 described. 
 
 2. It happens however in most instances of disease, that this^ 
 state prevails in more than one seat. In such instances these two 
 alternatives are to be discriminated: 1st, whether the diseases 
 occupying different seats are not independent of each other? 2nd, 
 whether the primary produces the secondary disease? 
 
 3. If in the course of a fever an abscess should form in one 
 axilla, and a week afterwards an abscess should form in one groin; 
 if the eruption of the small-pox should appear first in the face and 
 then be extended over the whole body; if a tubercle should form in 
 the liver, and a month afterwards a vomica should burst in the 
 lungs; if a venereal ulcer should form in the throat, and six weeks 
 
285 
 
 afterward* a node on the tibia: we should scarcely in these (and 
 there are many such) cases assert that the disease occupying the 
 first seat was the cause of the disease occupying the second. 
 
 4. But if one half of the body should be paralyzed by the 
 rupture of a blood-vessel of the brain ; if vomiting should succeed 
 to a blow on the head ; if disordered respiration should succeed to 
 the operation of a cause of pressure on the brain ; if atrophy should 
 succeed to disease of the mesenteric glands; if the secretion of a 
 gland should be suspended during an inflammation of it; if con- 
 vulsions should succeed the irritation of a nenre; if paralysis of 
 the sphincter of the bladder should succeed to an injury of the 
 spine, &c.: we have no hesitation in these cases in affirming that 
 the primary is the cause of the secondary affection, because we 
 know that the healthy state of the properties engaged in the 
 secondary, acknowledge the regular dependent relation,, with those 
 engaged in the primary seat of affection. 
 
 5. Again, if vomiting should succeed the formation or (intro- 
 duction) of a calculus in the gall-duct, or to the passing of a cal- 
 culus along the ureter; or if a pain in the shoulder should succeed 
 an inflammation set up in the liver; or if hernia humoralis should 
 succeed to an affection of the urethra, perhaps produced by an 
 injection; or if tetanus should follow a punctured or lacerated 
 wound; or if pain in the breasts should succeed conception, &c.; 
 we have in these cases no hesitation in saying, that the secondary is 
 produced by the primarj change. 
 
 6. These are examples of the classes of related disease. 
 Disease of one part, or one state of disease, might produce 
 another: 1st, by disturbing an habitual dependence; and, 2nd, 
 by the influence of an occasional cause. The first is illustrated 
 above; as if an injury of the brain should paralyze nerves whose 
 functions are dependent upon the brain, or as if respiration should 
 become laborious, or perhaps cease, by the operation of any cause 
 of pressure upon the brain, &c. The second is illustrated in those 
 other examples, in which a relation is exhibited under circum- 
 stances of disease, which was not manifested as one of dependence 
 for a natural office, during health. 
 
 7. The affection of a dependent seat in consequence of a 
 disordered state of the seat from whence its functional properties 
 are derived, is by no means a regular occurrence. We know that 
 there might be a violent pain in the head, a throbbing of all its 
 vessels, as if the whole brain was violently disordered, and yet the 
 function of respiration, which depends upon the brain, may be but 
 little or not at all interrupted ; at the same time, a slight pressure 
 upon the brain shall impair or prevent these dependent functions. 
 The reason is, that properties are not indifferently related with 
 any cause of disorder : but their relations are precise ; as, proper- 
 ties of the brain animate the organs of respiration, these properties 
 related with the agency of pressure, not related with causes merely 
 producing pain or even inflammation; the dependent function. 
 
286 
 
 impaired by the former, because the former is related with the 
 properties engaged in the dependence; not related with the latter, 
 because although they produce a certain affection of the seat of 
 the properties which animate the respiratory organs, they do not 
 produce a change in the nature and relations of these properties, 
 to expect which would be like expecting that paralysis of nerves 
 should not occur from pressure upon a part of the brain, because it 
 still retains some properties of life. 
 
 8. It has been stated that related disease happens in two 
 ways, which may here be repeated: 1st, by disturbing an habitual 
 relation of the regular dependent kind; 2nd, by a new relation 
 which is opened between parts not before connected by intercourse 
 of function, in consequence of a new condition which one of them 
 has assumed; it has been stated (and examples given) that disease 
 might occupy a succession of seats without the existence of any 
 causative relation between them. It is necessary before we pro- 
 ceed any further to inquire after the method of distinguishing be- 
 tween diseases which, though occurring in a series, are independent 
 of each other, and those in which the subsequent, is produced by 
 the preceding disease. 
 
 9. In making this distinction we are liable to frequent error: 
 the only grounds of the distinction, however, are as follow. Mere 
 succession, as has before been insisted, can never prove causation : 
 but it indicates causation, from the analogy of succession to those 
 palpable instances of causation in which the dependence of the effect 
 upon the assigned cause may be proved by the result of analysis and 
 of synthesis: of taking a way (or witholding), and of combining the 
 causes. Succession then, upon this ground of analogy, which has 
 been more fully explained, may indicate causation; and yet we do 
 not suffer every instance of succession to suggest ever so faintly 
 an inference of causation. 
 
 10. The succession of an effect to its true cause is invaria- 
 ble! from analogy in this respect, we infer positively the operation 
 of a cause in all instances of invariable succession; thus day and 
 night invariably succeed the presence or absence of the sun. But 
 we presume still further upon this analogy, we infer the operation 
 of a cause, when the succession of the same consequence to the 
 same antecedent is frequent, but not invariable; thus, an ounce 
 and a half of laudanum taken into the stomach will commonly, but 
 not always, produce death; we have no hesitation in assigning the 
 laudanum as the cause of death, in those instances in which death 
 takes place, notwithstanding there are other instances where the 
 obvious circumstances are alike, in which it is not followed by 
 death. "Invariable succession bears so strong an analogy to causa- 
 tion, that we scarcely suspect the possibility of oilr being deceived 
 in an inference grounded upon it; and yet we do sometimes make 
 a false inference founded upon past invariable succession, as is 
 proved by additional, or subsequent experience. Frequent suc- 
 cession of like to like, bears an analogy to the- invariable, and 
 
287 
 
 upon this analogy we found an inference of causation ; the point 
 of analogy is between the frequent and the invariable, consequently 
 the analogy must be established or presumed upon, in proportion 
 to our experience of the frequency of the succession of like conse- 
 quences to like antecedents. These grounds of the inference of a 
 cause as is just stated are imperfect, and must admit frequent error, 
 for we cannot define what number of successions of like conse- 
 quences to like antecedents, are an adequate number to prove 
 causation. 
 
 11. Hence then, although we infer causation from succession, 
 we are obliged to confess that we can do this only in certain cases; 
 before we can admit the truth of an inference of causation, we must 
 have had an experience of a sufficient frequency of a like succes- 
 sion. Different men will hold different opinions with regard to 
 what constitutes a sufficient frequency, and the want of a possible 
 definition in this matter admits a great diversity of opinion upon 
 important points, and gives room for the distinction of close, and 
 loose reasoners. 
 
 12. But when once we have had experience of what is con- 
 sidered a sufficient frequency of like succession, we then infer 
 some difference (where it is not perceptible) in cases in which the 
 same consequences do not succeed the same antecedents. In such 
 instances, we balance an account between like, and dissimilar sue- 
 cession; and we assign a cause only, where the frequency of the 
 same succession (approaching to the invariable) exceeds that of 
 the exceptions. Thus (not to quit our subject), if the exhibition 
 of a particular medicine should be followed by recovery from 
 phthisis pulmoualis in one instance, this succession would, where 
 men are disposed to catch at straws, indicate a possible causation; 
 if the same event succeeded to its exhibition in ten instances, its 
 credit would be better supported; if in a hundred, better still. If 
 it should succeed in five and fail in five, we should hesitate perhaps 
 to assign it as the cause of recovery in the first five; if afterwards 
 it should fail in fifty cases, we should say that in the five in which 
 it was followed by recovery the cure was owing to other causes. 
 If it should succeed in a hundred and fail in fifty, we should then 
 perhaps judge the hundred to amount to an adequate number to 
 establish the relation of the medicine, as a cause of recovery ; 
 while we should explain its failure in the other fifty, by supposing 
 some diversity of circumstances, by which its relation as a cause 
 was modified, to have prevailed. The conclusion amounts to this : 
 we infer that a secondary is produced by a primary disease, upon 
 an experience of a frequent succession of the one to the other^ 
 provided at the same time that our experience furnishes us with 
 no stronger analogies to sensible causation, by which we are rather 
 justified in considering them distinct. 
 
 
288 
 
 CHAR V. General Nature of Related Disease. 
 
 1. THE production of a secondary by a primary disease 
 is accomplished by one or both of those modes of causation which 
 we have assigned to be universal, viz. by addition or abstraction 
 of constituents. The part which becomes the seat of the secon- 
 dary disease is now identified by its causes as a state of health. 
 This state is changed when the secondary disease happens changed 
 by what? by something added or something taken away; as, how- 
 ever the condition of disease always respects either exclusively or 
 principally the properties which have been called spiritual, we are 
 precluded an analysis of related disease, conducted with a view to 
 be informed of precise states and efficient causes. 
 
 2. In those cases of related disease which happen between 
 seats which are connected by function, we are sometimes able to 
 say, as in the case of paralysis, happening from injury of the brain, 
 the secondary disease is here produced by privation of accustomed 
 properties, &c.; in a case of convulsions, we should perhaps be 
 inclined to say, in consequence of disturbance or injury of the 
 brain, properties are communicated to the muscles which produce 
 such and such phenomena; this, however, would be only an as- 
 sumption, though perhaps it might appear upon further inquiry 
 to be a probable one. But, in a general way, no advantage can 
 result from an attempt at investigating according to this division, 
 because, although it is the only one by which we can seek for 
 sensible evidence, it is not adapted to subjects where our best in- 
 formation must be inferential, and that too founded upon analogies 
 both numerous and obscure. 
 
 3. Conditions of seats may be related either directly, as by 
 the properties of life occupying the seats, or indirectly, as by 
 relation of the properties of life of a seat with the preparation or 
 distribution of the fluid material, which again is related with other 
 seats. Sufficient has already been said by way of indicating that 
 complexity which must be unravelled by him who is ambitious of 
 giving a complete analysis of any one case which might be chosen 
 as a specific subject. Without here attempting any further an 
 analysis which belongs to particular inquiry, I shall consider 
 related disease after a looser fashion. 
 
289 
 
 4. When a secondary succeeds to a primary disease, if they are 
 to be considered according to the rules laid down, as hqlding a 
 causative relation with each other; in every instance of related 
 disease one of the following results ensues: 1st, either the primary 
 disease ceases upon the occurrence of the secondary; or, 2nd, the 
 primary disease preserves or changes its character, according to the 
 relations of the properties of the secondary, with those of the 
 primary seat; or, 3rd, one of the preceding results on the primary 
 disease happens either by a relation with more than one secondary 
 seat, or by an extension from a secondary seat by which, perhaps 
 through many mediate relations, the primary seat may come to be 
 affected, according to one of the above results, by processes to which 
 it gave origin ; or, 4th, the primary disease may produce a secon- 
 dary, and the affection may from thence be further extended, and 
 the disease in each seat might run the same course as if only one 
 seat were the subject of it. This elaborate division admits of being 
 reduced to two classes of related disease, viz. 1. those secondary 
 diseases which tend to cure the primary; and, 2. those which do not 
 tend to such a result, but on the contrary add only to the com- 
 plexity of the symptoms, and perhaps ultimately convert disease 
 into death. 
 
 5. That certain diseases are related with each other in the way 
 of cause and effect, is a remark which is cotemporary with the earliest 
 records of medical observation. It is also a piece of information, 
 popular with all classes, that the cure of one disease, whether spon- 
 taneous or by art, is sometimes followed by the occurrence of 
 another. Thus, it is common to expect a favourable change of 
 some internal disease, upon the occurrence of a cutaneous eruption; 
 thus, also, it has fallen under the observation of the ignorant and 
 unprofessional, that a cutaneous disease cured by external applica- 
 tions often produces visceral disease. The language of the vulgar 
 in the first of these cases is, that the internal disease is coming out ; 
 in the second, that the disease of the skin is thrown in y or settled 
 upon the lungs, for instance. To all physicians the class of facts 
 here adverted to is well known ; they have been made the subject of 
 express treatises, and have been remarked upon in every age, and 
 explained according to the prevailing pathology of the limes. But 
 the professors of medicine have of late been rather sceptical with 
 respect to the assigned agency of the phenomena in question, though 
 it is not improbable that their exception was taken rather against the 
 doctrine of humours, &c. by which the phenomena were explained, 
 than against the more modest inferences which they might be al- 
 lowed to furnish. To all physicians of the present day the class of 
 facts, designated as those of related disease, is well known : by some, 
 these facts are not suffered to furnish an inference of a relation, 
 that is, they are considered independent of each other; others 
 admit the relation, and explain it in the language of the vulgar; 
 others say that one disease, instead of falling or being thrown upon 
 another part, is converted into a disease of another part : some 
 Q 9 
 
290 
 
 physicians admitting the class of facts, and admitting also the in- 
 ference of a relation, believe that the examples are very rare; others 
 are inclined to think them universal, aye, and to allow them only 
 one tendency, although they might tend to 50, or 500 different 
 effects. It will appear from this account that the existence of 
 related disease has been long known, that the knowledge of it has 
 become popular, and consequently there is no novelty in the state- 
 ment of the fact. If we would improve our knowledge with 
 fespect to such disease, it must be, not by ignorantly generalizing a 
 single limited class, but by a just analysis of its laws, by an in- 
 quiry into its nature, its frequency, and by an accurate discrimina- 
 tion of its instances. The first subdivision which we have proposed 
 of this class is that of related secondary disease, tending to cure, 
 the primary. 
 
 6. Perhaps the most unequivocal examples of related secon- 
 dary disease, tending to cure that which occurs in a primary seat, are 
 those of metastasis. A person might have pneumonia clearly charac- 
 terized by its symptoms: the symptoms of this local disease on a 
 Sudden shall cease, and the subject become immediately affected 
 with phrenitis, which shall be followed by death within eight and 
 forty hours. These occurrences may be confirmed after death by 
 dissection (quod Vidimus testamur). If we inquire into the causation 
 in this example, Were are those to whom the whole process is per- 
 fectly clear, who will reply, the inflammation left the lungs and went 
 to the brain; was it then the same inflammation, and if so, what was 
 the object of its journey, or why did the inflammation take it into 
 its head to travel ? To analyze a little more curiously : 
 
 7. Inflammation exists in the lungs: why does it cease in the 
 lungs? either from that progressive causation (which has been d- 
 scribed) taking place in the lungs, or from a progressive causation 
 taking place elsewhere, by which a relation is opened between the 
 seat of such progressive change and the properties engaged in tht 
 disease of the lungs, the end of which relation is, that disease is 
 established in a secondary, and ceases in the primary seat. 
 
 8. The evidence in this case derived from the order of suc- 
 cession is, that the disease in the lungs being the antecedent, is also 
 the cause of the disease in the brain which succeeds to it; in other 
 words, the properties constituting inflammation of the lungs leave 
 this seat and are transferred to the brain. But if the pneumonia is 
 the antecedent to the phrenitis, what is the antecedent to the metas* 
 tasis? or why does a disease leave a seat in which it is established I 
 The alternatives which must form the answer to this question are 
 suggested above : either a change takes place in the properties of 
 the lungs, by which they no longer admit the state of inflammation, 
 which is then assumed by some other viscus, already in a predisposed 
 state to take up inflammation upon the cessation of it in another 
 seat; or else the brain (continuing our example) assumes a state 
 which is so related with the properties engaged in the inflammation 
 f the lungs, as to produce a cessation of the inflammatory condition 
 
291 
 
 in this seat. From this view it is obvious that the sensible succession 
 is inadequate to determine the causation; for the brain may be the 
 the first to assume a change, by which it cures the disease in the 
 lungs; or the disease may cease in the lungs, from causation pro- 
 ceeding in this seat, and be assumed by the brain, or any other seat 
 which is predisposed to this result, under the relations which obtain 
 upon the cessation of a disease in a seat which it had hitherto 
 occupied. 
 
 9. The alternatives here suggested must obtain in every case 
 in which the primary ceases upon the occurrence of the secondary 
 disease, but they do not necessarily obtain in all cases of related 
 disease: thus we say dentition disorders the bowels; this is a 
 case of simple succession, which, by analogies before explained, we 
 infer to be also one of causation. If, upon the occurrence of disorder 
 of the bowels, the process of dentition were suspended, we should 
 then have to determine whether the change preparatory to the 
 metastasis took place in the bowels or in the maxillary nerves. The 
 progress of consumption might be suspended upon the occurrence 
 of pregnancy: here consumption, as a related state, preceded 
 pregnancy, yet we know, as the cause in this instance is palpable, 
 that the seat of that change which produced the metastasis was the 
 uterus, or secondary related seat. Thus also the catamenia may be 
 checked by an exposure to cold which will produce rheumatism; 
 the change preparatory to, or causative of the metastasis is here also 
 in the secondary seat. From these and many similar examples, we 
 may perhaps conclude very generally, that the primary disease in 
 metastasis does not produce the secondary, but that the metastasis 
 itself is determined by a change which takes place in the secondary 
 seat. Yet this conclusion must not be universal, for we know that 
 the change which is preparatory to the metastasis may take place in 
 ihe primary as well as in tUe secondary seat, as when inflammation 
 of the brain succeeds the cure of erysipelatous inflammation of the 
 arm or face, by means of cold lotions: this also I have seen in"Ta 
 fatal example. We must rest then with the alternatives which will 
 respectively be adopted in the several instances, according to sensi- 
 ble evidence where this can be had, and according to the nearest 
 analogies from defect of better proofs. Without, then, comparing 
 instances which cannot be done accurately, so as to deduce a general 
 rule of probability, with respect to the origin of the processes of 
 metastasis, we will simply state the facts by a designation which will 
 agree with either of the above alternatives of the mode of causation. 
 
 10. Related disease, according to our reduced division, is of 
 two kinds: 1st, as when a primary disease ceases upon the occur- 
 rence of a secondary; and, 2nd, as when a secondary merely suc- 
 ceeds to a primary disease. The former instances have been ex- 
 pressed by the word metastasis, which implies that the disease leaves 
 one seat and goes to another: this, however, is a conjecture without 
 proof, for an inflammation of the eye may be cured by a spon- 
 taneous diarrhoea; if the identical properties of the primary disease 
 
292 
 
 went to the seat of the secondary, these properties, being those oi 
 inflammation, should produce inflammation of the bowels rather 
 than a diarrhoea, which rarely occms in inflammation of the bowels. 
 If the identical disease of a primary is in metastasis transferred to a 
 secondary seat, as the character of the secondary is commonly very 
 different from that of the primary disease, it is necessary to infer 
 that the identical nature of the primary disease is liable to be modi- 
 tied by peculiarities which belong to the secondary seat. Laying 
 aside the word metastasis, by some it is said that one disease is con- 
 verted into another. This term " conversion" is one which either 
 does not carry a clear meaning, or if a certain meaning shall be 
 agreed upon, it implies a theory which will require proof's. Either 
 trie word " conversion" implies the operation of a cause which pro- 
 duces its own similitude, as one man is converted to the same 
 opinion as another; or as life converts constituents of food and air 
 into life, &c. ; or else it is employed with greater latitude, as water 
 is converted into ice, &c, or as wine is converted into vinegar; if 
 employed in the former sense, it is not applicable in the present sub- 
 ject, for we cannot suppose that the properties constituting inflam- 
 mation are made those of a diarrhcea, or that they are converted 
 into an effusion of blood, &c.: if the term is employed in the latter 
 sense it designates no one species of causation, but may apply to any, 
 as cold converts water into ice, that is, cold and water make ice; 
 or sulphuric acid will convert magnesia into a neutral salt, that is, 
 sulphuric acid and magnesia constitute a neutral salt. I would not 
 be understood that the term is violently objectionable, or that some- 
 thing may not be said on both sides respecting its use in these cases, 
 but its implication in the first definition will bear a cavil, and iu the 
 second it is no term of distinction. 
 
 11. The first class of related disease, viz. that in which a 
 primary ceases upon the occurrence of a secondary disease, may be 
 called substitution of disease, which merely expresses the fact that 
 one disease has taken place, while another has ceased; the word 
 " vicarious," which is familiar in medicine, expresses the same thing. 
 The second class of related disease, viz. that in which the primary 
 does not cease upon the occurrence of the secondary, may Le called 
 related extension of disease (the causative relation being in both 
 cases assumed upon the grounds before stated). 
 
 12. The examples of substituted disease are very numerous, 
 and it is upon this experience of their frequency that the relation of 
 cause and effect in some or other of its modes comes to be inferred 
 to subsist very generally between them. We cannot, however, upon 
 this point compel belief. 
 
 13. Although the examples of substituted disease are very 
 numerous, they are not sitliiciently regular to admit a classification of 
 those primary diseases which are likely to be cured (to beg an ex- 
 pression) by the occurrence of secondary ones. We can rarely, 
 (owing to this irregularity) perhaps we can in no case anticipate the 
 i ure of a primary disease by a secondary one; that is, we cannot 
 
293 
 
 pronounce that a certain secondary disease will succeed to the 
 primary, and that the latter will then cease. We more frequently 
 expect the cessation of a primary disease, when the symptoms of a 
 secondary one, of the tendency of which we have had experience, do 
 actually appear, than we anticipate a substitution of disease, while 
 the existing symptoms occupy exclusively the primary seat. There 
 is, however, an exception to this remark, when the same secondary 
 has been substituted for the same primary disease, in one or more 
 instances. 
 
 14. It is desirable on this subject that the collective experience 
 of individuals should be possessed, in order that our reasonings may 
 receive the advantage which must be derived from a correct estimate 
 of the frequency and peculiarities of substituted disease. My own 
 experience of these diseases is pretty extensive, and I have elsewhere 
 made some progress in an attempt at their classification; at least, I 
 have collected and arranged many detailed cases. In this place a 
 few only of the instances can be adverted to, as illustrative of the 
 cessation of one disease by the substitution of another. In this way, 
 
 1. Chronic pain in the head may cease upon the occurrence of a 
 chronic diarhoea. 
 
 2. Violent pain in the head, accompanied for a considerable time 
 by general derangement of the health, and particularly of the nervous 
 system, may be cured, to use a common term, by the formation of an 
 abscess in the back. 
 
 3. Pain in the head, disorder of the nervous system, which has 
 proceeded to insanity of three weeks' duration, may all cease upon 
 the formation of a carbuncle in the back. 
 
 4. Chronic plethora of the vessels of the head, producing vertigo, 
 lethargy, &c. requiring frequent depletion by cupping or by the 
 lancet, may cease, so as never again to require these artificial mea- 
 sures, upon the occurrence of a large incurable ulcer in the back. 
 
 5. Insanity, which had existed a twelvemonth, ceases perhaps 
 under an enormous accumulation of fat. The formation of fat is of 
 all others the most frequent instance of substituted disease. It 
 cures habitual disorder, improves the condition of that which is 
 called a delicate constitution when it occurs. The formation of fat 
 tends to maintain health by defining a harmless seat of disease while 
 it lasts, and it is seldom spontaneously removed without the occur- 
 rence of a substituted disease in some less convenient seat. 
 
 (J. Vertigo, alternating with asthma, may cease upon the for- 
 mation of an abscess of the foot; this abscess may produce a 
 troublesome wound, upon the healing of which apoplexy may take 
 place, followed by paraplegia and fatuity; to this may succeed 
 swelling of the legs with improved motion, and recovery of the 
 intellectual powers; to a cessation of the swelling of the legs may 
 succeed spasmodic breathing, which ceases again upon the return of 
 the swelling of the legs; this again ceasing, apoplexy and death 
 supervene. 
 
294 
 
 7. Apoplexy followed by delirium, continuing for a fortnight, 
 might cease upon the occurrence of a cutaneous eruption. 
 
 8. Tic douloureux of the sciatic nerve may succeed to the cure 
 of a prodigious cutaneous eruption by external applications; this 
 disease in the nerve might be intense for a time, and cease upon a 
 return of the disease of the skin; it may return when the disease of 
 the skin has again ceased, and be again suspended by pregnancy, 
 and the offices of suckling, &c. 
 
 9. Convulsions, repeated at short intervals for a week, in a child 
 may cease entirely upon the occurrence of a considerable sedematous 
 swelling of one arm. 
 
 10. A violent pain in the stomach, occurring in the form of two 
 paroxysms a day for many years, each paroxysm ending spon- 
 taneously by vomiting, may be suspended during seven months of 
 pregnancy, and return a fortnight after premature labour at this period. 
 
 11. Excessive sensibility of the retina, producing violent pain 
 under an exposure even to a moderate light, may continue for years 
 and bid defiance to remedies, and finally cease under a spontaneous 
 chronic diarrhoea. 
 
 12. Sense of fluctuations and noises, as of waterfalls, in the head, 
 sometimes attended with irregular fits of insanity, may cease upon 
 the occurrence of temporary diabetes, or a most profuse secretion 
 of urine, continuing riot more than two or three days. The same 
 disorder of the head may continue for months in the same subject, 
 and cease in the same manner in two or three distinct attacks. 
 
 13. A catarrhal disease of the bronchiae, attended with an ex- 
 pectoration of perhaps a pint and a half of mucus* in twenty-four 
 hours, may succeed to the cure of an extensive and inveterate 
 cutaneous disease of the back. 
 
 14. Veitigo and pain in the bead may alternate for days, with a 
 spitting of blood from the lungs for weeks or months. The spitting 
 of blood having ceased, the subject may become mad, and finally 
 die of apoplexy. 
 
 15. The instances of vicarious disease from the suppression of 
 the catamenia form a numerous and well-known class, to the familiar 
 examples of which it is unnecessary to add. 
 
 16. Vertigo might cease upon the occurrence of hydro-thorax ; 
 this latter disease may cease under an enormous swelling of the 
 legs, and this latter terminate in a prodigious secretion of urine. 
 This order may be observed in three attacks, and the subject finally 
 die of apoplexy. 
 
 17. Fever with delirium and a pulse of lit) may continue for 
 six days, and the patient effectually resisting the administration of 
 a single mtdicine, may from that time have had no evacuation from 
 the bowels; at this time a .diarrhoea occurs, the patient may have 
 fourteen or fifteen stools in as many hours, the fever may immediately 
 abate, the tongue become clean, the delirium cease, and the patient 
 may be in every respect convalescent in two days after the occur? 
 rence of the diarrhoea. 
 
295 
 
 18. The substitutions of seats in gout are too numerous antl 
 well-Known to require a single illustration. 
 
 These cases here so rapidly sketched have fallen under my own 
 observation. I could swell the list to five times, or may be ten 
 times this number: these however must suffice where .my business is 
 rather to indicate generally, than to enter into particular details 
 and inquiries. 
 
 15. It has been remarked that there is nothing new in the 
 observation of this class of diseases, Hipocrates was as well aware 
 if them as any of those who have succeeded him. But tSiere would 
 be something new in the inference that all diseases which succeed 
 rach other in the different seats hold, like the substituted ones indi- 
 cated above, a curative relation: this inference would indeed be new, 
 and it would be no great difficulty to prove it false. We will keep 
 tliis refutation a little in view, in our exhibition of a few examples 
 of our second class of " extension of disease." 
 
 1. A schirrous tumour of the breast, of a small size, proceeds 
 on to the ulcerated stage of cancer; the axillary glands which are 
 in the course of the absorbents, proceeding from the seat of the 
 primary disease, become swelled, indurated, and finally, perhaps, 
 the skin covering them ulcerates or sloughs, and the secondary 
 disease resembles in its phenomena the primary one. The primary 
 disease in the mean time runs its course, sloughing and ulcerating 
 mid bleeding, &c. until the patient dies. The only result of the 
 econdary disease in this case is, that the patient has a cancerous 
 disease in two seats instead of one. During these processes the 
 constitution also participates in the local disease; to mention only 
 one consequence, a febrile diathesis is produced. It would be diffi- 
 cult to shew how cancer of the axillary glands is likely to cure cancer 
 of the breast, or what tendency fever has to arrest the progress of 
 an irritable ulcer of such a kind, when we know that all its symp- 
 toms are aggravated by any causes which produce fever or quicken 
 the circulation. This is one instance of extended disease. 
 
 2. A chancre on the prepuce, left to spontaneous processes, con- 
 tinues to ulcerate ; from this primary arises the secondary disease of 
 an abscess in the groin : we should not in this case expect the 
 primary to be much benefited by the secondary disease; we knovr 
 that the chancre spreads and the bubo will spread ; that from these 
 teats the disease will be extended to the skin, to the throat, and to 
 the bones. From all this extension of disease the primary one, the 
 chancre, does not derive the least benefit; all the consequences of 
 it tend to death, and before this event happens the primary disease, 
 which, according to some reasoners, should have been cured by 
 the consecutive processes, has unluckily destroyed without a 
 vestige the whole organ in which it was situated, together perhaps 
 with some collateral ones belonging to the same system. If, again, 
 the tendency of the consecutive phenomena should be inquired after, 
 we have only to observe, in regard to the primary disease, that 
 the local destruction of parts goes oa the more rapidly, iu propor- 
 
296 
 
 tion as the constitution suffers, and the seats of the disease become 
 extended. 
 
 3. Strictures in the urethra produce hernia humoralis. This is 
 another instance of complication of disease without curative results. 
 
 4. Disease of the liver obstructing the return of blood from the 
 veins which unite in the ven. port, produces ascites. Unless dropsy of 
 the belly may be supposed to benefit an enlarged and indurated liver, 
 by affording it the advantages of a warm bath, it would be difficult 
 to say in what other way the secondary tends to cure the primary 
 disease in this instance. 
 
 5. Ulcers of the legs are produced by a varicose state of the 
 veins. The secondary disease in this case has never been suspected 
 as the spontaneous cure of the primary one. 
 
 6. The irritation of a tubercle in the lungs produces fever; fever 
 accelerates the suppuration of the tubercle; fever maintains ulcera- 
 tion in the primary seat; ulceration tends to perpetuate fever; these 
 processes in regard to each other are not remedial, on the contrary, 
 each disease is increased by the other, and both concur to 
 produce death. 
 
 7. Water in the brain may produce paralysis of the optic nerve. 
 It would be difficult to shew the tendency of blindness to cure hydro- 
 cephalus; the water increasing, the pressure of the fluid impairs 
 respiration, and finally causes it to cease; an extension of disease 
 which stops a person's breath is not the likeliest method of prolong- 
 ing life, which it must be presumed is the end of every agency 
 which may be termed curative. 
 
 8. A wound of the foot may produce tetanus: it has never been 
 found that the state of tetanus was particularly conducive to the 
 healing of a wound. These instances, as well as those of our first 
 class, may be greatly multiplied; but we rather want to make correct 
 inferences from these examples than add to their number. 
 
 16. Our conclusion from these facts brings us back to the 
 division which was prefixed to them, viz. of related diseases ; some 
 exemplify a substitution, and others a mere extension of them : in 
 the former, the secondary is curative of the primary ; in the latter, the 
 phenomena of disease are multiplied, and in every seat they run their 
 own course, sometimes with an obvious aggravation of the primary 
 by the re-action of the secondary disease, but more commonly with 
 no other communication or influence than that which is inferred of 
 the secondary in regard to the primary disease, from analogy with 
 sensible causation. 
 
 17. But, it may be inquired, although in these cases of extended 
 disease the secondary does never cure the primary, may not the 
 tendency of it be to cure? would it not cure the primary, provided 
 it did not kill in the attempt ; or, by being extended to the wrong 
 seat? There is absurdity in these questions, although there are not 
 wanting those who would be so simple as to ask them. The ques- 
 tions amount to this: if a wound which produces tetanus, instead 
 of affecting the nervous and muscular systemi in this manner, were 
 
297 
 
 to produce a gentle diarrhoea, would not then the state of the wound 
 be probably benefited by such a consequence? The question is 
 best answered by observing, that if no other relations were exhibited 
 but such as are curative, we should then have curative relations in 
 disease, and no others. If a disease of one seat cannot get well 
 unless it is cured by disease of another, how happens it that the state 
 of disease ever ceases at all? A first disease, it is said, requires a 
 second to cure it; and what cures the second? a third, it must be 
 replied; and so on in infinitum. It is obvious that some organ must 
 have the power of returning to health without being restored to this 
 state by additional disease; and there is no reason why the secon- 
 dary seat should be more lucky in this respect than the primary seat 
 of disease. The same sagacious reasoners observing that one 
 disease is sometimes preventive of another, as a diarrhoea of a 
 disorder of the head, or a cutaneous eruption of a disease of I he lungs, 
 have wisely concluded that disease is salutary: to this magnanimous 
 inference it may be modestly replied, that though it is better to have 
 a little disease than a great one, yet it may be doubted whether it is 
 not better to enjoy the state of uninterrupted health without any 
 disease at all. The most that can be said of diseases, which, as they 
 exist, are merely extended, is, that from their analogy to the substi- 
 tuted diseases, they may sometimes be expected to operate favourably 
 upon the state of primary disease by progressive causation; that 
 one would not always check a secondary disease in a safe seat, upon 
 the ground that secondary is sometimes remedial of primary disease. 
 
 18. There are others who would attribute all diseases to some 
 particular accompaniment of disease: thus, fever, say they, is pro- 
 duced by an accelerated action of the heart; and what accelerates 
 the action of the heart? a previous change of the principle which 
 governs its motions ; a change, the general history of which it has 
 been attempted to describe. Another disorder is said to be pro^ 
 duced by a determination of blood, as to the head or lungs; and 
 why does a particular determination of blood take place to any seat? 
 say it arises from an enlarged or disproportional calibre of its vessels ; 
 and why does this disproportionate calibre take place ? either from de- 
 fect or modification of a vital property which governs the calibre of 
 vessels, or from a fault in their mechanical constitution: if the former, 
 we understand no more than that vague notion that some change has 
 taken place in the identity of the governing principle, which directly 
 produces the effect or symptom in question; if the preternatural 
 calibre arises from a fault in the mechanical constitution of vessels, 
 this modification of a structure must be preceded by that peculiarity 
 of the principle which forms it, to which, directly or indirectly, in 
 some or other of its seats (as has been many times shewn), peculiarity, 
 whether in the chymical or the mechanical department, is ultimately 
 in every instance to be attributed. 
 
 19. There are others who will talk about spasms: thus, say 
 they, fever is produced by spasm of the extreme vessels. To say- 
 nothing about the bare assumption in this case, if spasm produces 
 K R 
 
298 
 
 fever, what produces the spasm 1 ? cold, say they: let heat be substi- 
 tuted for cold, and let the spasm be relaxed, as they allow it might, 
 what still produces fever] the return of spasm: and what produces 
 the return of spasm? not cold again, for the patient may be in a 
 warm bed. This question they will attempt to evade by replying, a 
 disposition to spasm; allow it: and what shall we say of this dis- 
 position? simply this, that it is some change which we do not under- 
 stand; and why not say this at first? 
 
 20. Another set will affirm, that all diseases are produced by 
 increased or diminished excitement. To these I would suggest that 
 we have no standard by which to measure the quantity of excitement. 
 But if, par hazard, their ingenuity should discover one, it may then 
 be asked what is meant by the term excitement ? say it is the power 
 of action which prevails in a living body. This power of action, say 
 they, is either too great or too little; and lo one of these varieties 
 are to be attributed all the phenomena of disease. A power of 
 action refers either to the voluntary or the involuntary muscular 
 system: to take a specimen of the first, inflamed muscles (or the 
 muscles in that state of a limb which succeeds to a violent injury, 
 as a compound fracture, followed by the most intense inflammation) 
 are not capable of performing voluntary motion, this is a diminished 
 power of action; if the limb is paralyzed by ligature, or division of 
 its nerves, the muscles are thus also rendered incapable of voluntary 
 motion: this likewise is a diminished or lost power of action, yet it 
 will hardly be said that the two states are the same; they have the 
 same effect upon the limb, or they agree in being a privation of the 
 power of motion, but the state of the moving powers has undergone 
 a change in either case, which is not distinguished by a term ex- 
 pressive only of one particular, in which they agree; in the one case, 
 motion is prevented by a modification or disease of its power, in the 
 other case it is lost, by an intercepted communication with its source. 
 
 21. In the second department, the power of motion in the 
 heart may be such that the actions of this organ are at the rate of 
 120 in a minute: with this power of action of the sanguiferous sys- 
 tem, there may be either consumption or cancer, or a gun-shot 
 wound, or phlegmonous inflammation, or inflammation of the liver, 
 &c.; or there may exist no other symptom of disease, save this in- 
 creased action of the heart, as in some temporary states of nervous 
 disorder. If the power of action is the cause of disease (the same 
 action being produced by the same power), the same actions should 
 produce the same diseases; if they do not, there is another cause of 
 disease besides the power of action; the blood may be moved 
 through a cancerous ulcer and an ulcer that is not cancerous with 
 the same velocity ; there may be an agreement of the pulse in both 
 instances, yet the diseases are different. Oh! yes, say the sup- 
 porters of this doctrine, there is a different disposition in the diffe- 
 rent diseases; and that this difference may be something besides a 
 variety in the powers of motion may be guessed from the facts that 
 fluids may be urged through all the vessels in the body by a common 
 
399 
 
 power of motion, and yet with the same rate of actions: in one per- 
 son a lumbar abscess shall form, in another a tubercle in the brain, 
 in another an exostosis or a node of the tibia, in another a mortifica- 
 tion of the toes, in another a gall-stone, in another the conversion 
 of a kidney into fat, in another dropsy, in another calculus of the 
 kidney, bladder, or prostrate gland, in another ossification of the 
 aorta, in another rheumatism, in another necrosis, in another ulcer of 
 the leg connected with varicose veins, &c. Then, say they, the local 
 powers of action are not the same. Before this can be asserted, a 
 test should be proposed by which we might estimate their difference, 
 so far as they can be judged of by the pulse in the respective seats 
 they are all the same, or they might in several examples be found 
 the same; and if pus is formed and variously modified, and calculus 
 is formed, and the textures in one instance preserve their integrity, 
 and in another ulcerate, and in another mortify, and in another pro- 
 duce chalky depositions about joints, and in another throw out a 
 preternatural growth of bone, and in another produce an enormous 
 steatomatous tumour, in another a schirrous tumour endowed with 
 all its predisponent propeities, &c. it may be guessed that these 
 instances shew the agency of properties which are not comprised in 
 an increased or diminished power of action, seeing, also, and setting 
 aside other proofs, that the power of motion estimated by the only 
 test which can be proposed, may be in all these insstances the same. 
 
 22. Others there are who faucy they explain diseases by calling 
 them associated motions, catenated movements, associated sensations, 
 &c. This jargon can scarcely be meant to designate a causation of 
 disease, it is an attempt at a classification (or else it is an attempt at 
 nothing) upon grounds so absurd as to be altogether below a com- 
 ment. We may make motion and sensation a general test of the 
 presence of disease, as there is no disease which does not either affect 
 motion or produce sensation of some kind ; but different states of 
 disease may be connected with the same movements (as in the circu- 
 lation, for example,) or with the same sensations. We form our 
 opinion of the nature of disease frequently from the motions, or the 
 sensations of its seat ; but the circumstances of sensation and motion 
 are only tjie symptoms which indicate particular states of disease 
 upon analogy; that is, because such sensations have been found to 
 accompany certain states of disease. The instances in which a single 
 symptom can stand as the representative of a disease are very rare: 
 perhaps there is no disease which may be defined without the 
 enumeration of many symptoms; symptoms are the sensible results 
 of invisible changes, and they become in turn the causes of disease, 
 as in those examples in which certain symptoms produce the conse- 
 quences of related disease, as a pulse of 140 may be produced by a 
 compound fracture, and the brain in this case, unable to sustain this 
 vehement circulation, exhibits under it the phenomena of phrenitis, 
 as delirium, &c. 
 
 23. There is one other doctrine, which, as it is adopted to some 
 extent, appears to require a notice. The doctrine in effect is this. 
 
son 
 
 no local disease would exist if the general health were good: there 
 is no general disorder of health which does not originate in 
 some of the abdominal viscera. This doctrine is at least very 
 comprehensive and apparently very simple. We shall examine a 
 little the grounds of it, or how far it is likely to be true. To re- 
 duce it to its greatest simplicity, all, or we will put in a saving 
 clause and say most, diseases originate in disorder of the stomach 
 and bowels, &c. 
 
 24. The evidence by which it is attempted to support this 
 doctrine is, 1st, there are few diseases in which the symptoms of 
 disorder of these viscera, or of some of them, are not present ; 2nd, 
 these diseases get well as the symptoms of disorder of the prepara- 
 tory organs disappear. To reduce the question as much as possi- 
 ble without forsaking the doctrine, instead of including all these 
 viscera, we will speak of one merely as a representative of the rest, 
 or of as many as may be disordered, and this one we will say is 
 the liver: " all or most diseases originate from disorder of 
 the liver." 
 
 25. The liver is disordered in most diseases, therefore 
 disorder of the liver is the cause of most diseases; this is the 
 argument : we will suppose the disorder of the liver to be indicated 
 by furred tongue, loss of appetite, irregular bowels, &c.; it is best 
 to agree upon one sign, to avoid a multiplicity of words: let a 
 furred tongue then be, if occasion requires it, the representative 
 of all the other symptoms of disorder of the digestive organs. 
 
 26. Disorder of the liver can be assigned as the cause which 
 produces other disorder only upon the argument of succession, 
 which is analogous to causation. There is disorder of the health 
 accompanied by a furred tongue: can it be settled in all cases 
 which of these is the antecedent, and which the consequence? can 
 it be said whether the liver is disordered first and then the health, 
 or whether other disorder precedes that of the liver? the succession 
 is not clear; and if this fails the argument loses its principal, if not 
 its only support. There are other cases in which the succession is 
 clear: a person from exposure to the weather has a rigor, he feels 
 a lassitude with dull aching sensation over the whole body, these 
 are the first symptoms; the pulse is quickened, and the tongue 
 becomes furred, and there is loss of appetite, such is the sensible 
 order of occurrence. In this instance it is clear, from the obvious 
 succession of symptoms (and we have nothing else to trust), that 
 other disorder precedes that of the digestive organs. Take another 
 case: a person receives a deep wound, a lacerated one, or a gun- 
 shot wound ; his tongue was clean enough before this happened, 
 but in thirty-six hours from the infliction of the wound the tongue 
 is furred and there is loss of appetite. From these facts, and there 
 are many such, it is proved that disorder of the digestive organs 
 may be produced by disease originating e/seivhere, at least as truly 
 as that disease elsewhere might be produced by disorder of the 
 digestive organs. These facts refute the doctrine as an universal 
 
301 
 
 one : if it is still asserted to be true, it can be so only iu particular 
 cases which remain to be discriminated. The argument now 
 stands thus: there are cases in which the processes of disease in other 
 seats palpably precede disorder of the digestive organs; but there 
 are no cases yet cited in which disorder of the digestive organs 
 obviously precedes all other disease, for in general a furred tongue 
 is only the accompaniment of other disease, and it would be diffi- 
 cult, perhaps in most cases impossible, to establish a priority 
 of occurrence. 
 
 27. But other diseases get well, it is said, as the symptoms 
 of disorder of the digestive organs disappear. This would very 
 naturally happen if disorder of the digestive organs were main- 
 tained by a disorder elsewhere, which, subsiding, admits the re- 
 covery of the digestive organs ; as the irritation of a gun-shot 
 wound having abated, the appetite returns and the tongue becomes 
 clean. The priority of the symptoms alluded to cannot in most 
 cases be discriminated ; hence, in most cases we are not warranted 
 in assigning disorder of the digestive organs as the cause of disor- 
 der elsewhere, with which it might be connected, while the con- 
 trary, or that other disease precedes that of the digestive organs, 
 is obvious in some other instances. 
 
 28. Granting then the assumption which, to favour the doc- 
 trine in question as much as possible, was supposed to be con- 
 ceded, we find that the evidence cited to prove the dependence of 
 disease in general upon the state of the digestive organs is alto- 
 gether inadequate; it fails of supporting the doctrine, even if the 
 assumptions it involves are freely granted. To assert that disease 
 can take place only as a consequence of disorder of the digestive 
 organs, amounts to saying that disease can originate only in one 
 seat, or that there can be only one seat of primary disease; or, 
 to return to our reduced illustration, no disease can take place 
 without disorder of the liver. 
 
 29. If, then, disease cannot take place without disorder of 
 the liver, how happens it that the liver itself becomes diseased? 
 The very occurrence of disease of the liver proves that disease 
 might happen without being preceded by disease of the liver; and 
 if it might originate in this seat without being produced by disease, 
 as it must, when from a healthy a disordered state of the liver 
 takes place, why may not disease in other seats have an equally 
 independent origin? 
 
 30. But granting, still further, all sorts of postnlata, can it in 
 any case be proved that disease originates in the liver? Take for 
 example a tubercle of the liver: why is a tubercle formed in the 
 liver? from a predisposition, it must be answered, which exists iu 
 the liver; and what is the history of this predisposition of proper- 
 ties of the liver to form a tubercle? the predisposition, it must be 
 replied, takes place in the series of that progressive change which 
 has been described; and did the first processes of this progressive 
 change take place in the liver, or in a related seat? we have reason 
 
302 
 
 to think that the liver obtains properties of the regular dependent 
 kind, perhaps from a nervous centre ; at all events, \ve cannot prove 
 that the first processes of the predisposition to * tubercle origi- 
 nated in the liver, unless we can first prove that its life is inde- 
 pendent of all other seats, and that the properties determining the 
 earliest processes of progressive change have been allied to the 
 assimilating life of the liver from its first development in the uterus. 
 31. But not to encumber a plain argument with subtleties, 
 the preceding exposition of the force of the evidence is sufficient 
 to shew that such a doctrine cannot be rationally entertained ; fur- 
 ther, that it must be positively rejected. There is, however, one 
 other argument, cited perhaps in favour of the doctrine, upon 
 which also we might bestow a short notice: this argument is de- 
 duced from the operation of remedies, and, fairly stated, is as fol- 
 lows: the diseases which are affirmed to be dependent upon the 
 digestive organs get well (sometimes) under the operation of reme- 
 dies which are designed to correct their disorder; which fact, it 
 may be continued, must be allowed to be a proof of their depen- 
 dence, <S:c. The question is, not what these remedies are de- 
 signed to do, but what they actually do; and as for what this argu- 
 ment must be allowed, we shall examine a little further before we 
 allow it any thing. 
 
 32. Suppose a disease of the skin to be cured by blue pill; 
 suppose that the alvine excretions become regular and good; sup- 
 pose that the secretion of bile is improved, that the appetite re- 
 turns, that the tongue becomes clean, and that the disease of the 
 skin gets better, and finally well, under the use of the blue pill; 
 does it therefore follow that the disease of the skin was produced 
 by any of, or all these circumstances belonging to the abdominal 
 viscera? the operation of the blue pill may be upon a seat which is 
 only related with the liver, bowels, &c. as well as directly upon 
 these viscera; or the disease of the skin may be cured, as by a 
 remedy which is applied to its seat through the medium of the 
 circulation; there may be no dependence at all between these 
 phenomena, but they may all cease, as accompaniments only, 
 under the operation of an agent whose properties are remedial in 
 regard to them all; or, granting further all that is required, viz. 
 that the blue pill acts exclusively upon the liver, stomach, bowels, 
 &c. and that the disease in the skin gets well under the mercurial 
 excitement produced in these parts, yet it does not follow that the 
 disease of the skin was produced by their disorder, for the preter- 
 natural affection produced by the mercury may have a curative 
 relation \vith the disease of the skin; the mercury may operate 
 upon a common principle of change, the preternatural affection 
 of the abdominal viscera may cure the disease in the skin in the 
 same manner as mustard plasters on the soles of the feet may cure 
 gout in the head, or as a blister on the side may cure a pleurisy. 
 Yet in these cases, which are the most level to our experience, we 
 do not set up a causative relation: no one will employ this, which 
 
303 
 
 is a parallel argument, viz. gout in the bead is produced by disor- 
 der of the feet, or pleurisy is produced by a state of the skin 
 covering the side, because agents applied to these parts will cure 
 diseases occupying other seats. Nothing can prove causation 
 between diseases where the succession is not clear; and even where 
 the succession is clear, this must be admitted as a proof only, with 
 the restrictions before mentioned. 
 
 33. But, it will be further insisted, in those diseases which 
 blue pill cures, the stools are black, the secretions depraved, &c. 
 This fact, singly, proves only associated, or concomitant disease in 
 different seats. " If upon a spontaneous evacuation of similar mat- 
 ter from the bowels connected disease should cease, according to 
 the only rules of reasoning which can be defined, we are then to 
 infer an example of that class of related disease which is by sub- 
 stitution; that is, the disease elsewhere is cured, according to such 
 evidence from symptoms, by disease of the abdominal viscera. 
 
 34. That disease of the stomach, liver, &c. may, as well as 
 any other parts, become the seats of related disease, whether 
 of substitution or of extension, cannot be denied. Indeed, in our 
 sketch of an illustration of related disease, this degree of impor- 
 tance has been assigned to these viscera: thus, an excessive irrita- 
 bility of the retina which existed for years, while the health was 
 in every other respect good, has been cured by a spontaneous 
 chronic diarrhrea; and of the class of simple extension, thus, a 
 local disease, say in order jto avoid a cavil an artificial one, as a 
 gun-shot wound, with diseased bone, may impair the appetite and 
 totally disorder the functions of the abdominal viscera : this 
 disorder began perhaps in the leg; it may be extended to the brain 
 and nervous system; or it may be extended from this system to 
 that of the preparatory organs, and, fvom disorder of these organs 
 in an adequate degree, the disorder may be extended more or less 
 to the whole system. This js the greatest share which can be al- 
 lowed to these organs in the complexity of disease: they may be- 
 come the seats of related disease, this may be disease either of 
 substitution or of extension, and these organs may, in common 
 with other parts, become the seats either of primary or of secondary 
 disease. But, as the seat of an universal origin of disease, the 
 notion can be supported only by arguments which will scarcely 
 bear the slighest examination, and which may with the greatest 
 ease be refuted, even though arguments of a similar description 
 should be multiplied a hundred fold. 
 
 35. The discussion here pursued with respect to the nature 
 of related disease, may be nearly comprised in a summary of the 
 following kind: 
 
 1. By related disease is implied conditions of the properties 
 of a seat which produce effects, either curative or not, in the way 
 of causation. 
 
 2. Causation between phenomena in animal bodies is inferred 
 from succession in a sufficient number of instances, either of the 
 
304 
 
 some phenomena or of different phenomena, which so far resemble 
 others, of which we have had a satisfactory experience, as to 
 admit an enumeration under the same class. This evidence is ' 
 founded on analogy to the synthetical test of causation : if we 
 require it to be confirmed, we must employ also the analytical test, 
 as before explained. 
 
 3. Disease may be related either in its own or in another seat. 
 The first, as inflammation of a part, is related with suppuration, or 
 as schirrus is related with cancer; the second, as a disease of a 
 nerve, may produce disorder of the brain, and convulsions over the 
 whole body. 
 
 4. Related disease in the same seat is a progressive causation 
 among the properties which belong to the seat, in the course of 
 which different phenomena are exhibited, according to the rela- 
 tions subsisting between properties. 
 
 5. If a primary produces a secondary disease, the seat of the 
 secondary either receives properties from that of the primary 
 disease, or properties are withheld or abstracted from the seat of 
 the secondary by the state of the primary disease. 
 
 6. We suppose that the properties producing disease are com- 
 municated, when a secondary happens as a consequence of primary 
 disease, the seats of which have no natural relation of the depen- 
 dent kind in the condition of health: the phenomena of irritation 
 and sympathy may be supposed of this kind, as dentition affecting 
 the brain mediately or directly, and producing fits; biliary calcu- 
 lus producing vomiting; inflammation of the liver producing pain 
 of the shoulder, &c. 
 
 7. We conclude that disease is produced by privation of pro- 
 perties in the secondary seat, when the healthy state of this seat 
 is dependent for natural communicated properties upon the seat of 
 the primary disease, and when the function which is dependent 
 upon such communication is lost: thus disease of the brain may 
 paralyze the retina, or produce the same effect in this secondary 
 seat as a ligature upon the optic nerve. 
 
 8. But disease of a primary may produce disease of a secon- 
 dary seat, where a relation subsists of the regular dependent 
 kind by communication of properties, as when the relation is 
 disordered, as perhaps irritation of the brain producing convulsions 
 of the muscles. 
 
 9. It is also possible, according to our causation, that secondary 
 might be produced by primary disease, by privation of properties 
 where no natural dependent relation subsists between the seats; as 
 if a preternatural relation were opened, the effect of which is to 
 render the secondary seat a source of properties to the primary 
 one; thus leaving the state of the secondary seat to be identified 
 by remaining properties, which are deficient in those which would 
 constitute its healthy condition. The discrimination of the mode 
 of causation in these instances must always be diflicult, and the con* 
 elusion very dubious ; such, however, are the alternatives. 
 
305 
 
 10. If a primary ceases upon the occurrence of a secondary 
 disease, it ceases, either because the primary disease, has left its 
 seat, and produces the secondary, or because the secondary, being 
 established by causes either wholly or in part independent of those 
 engaged in the primary disease, is so related with, as to cure the 
 primary disease. The first of these happens from progressive 
 change, in the seat either of the primary or secondary disease; the 
 second, either from communication of properties from the secon- 
 dary independent state of disease to the primary one, or from 
 privation of the properties of the primary, in agreement with a 
 new relation opened between it and the properties engaged ia 
 the new state of secondary disease. The causation also in these 
 cases must be dubious: such again are the alternatives. If this 
 subject were not already sufficiently complex, it may be suggested 
 that, in an analysis of these processes of disease, we have also to 
 define the share in them which might belong respectively to the 
 properties of life, to the mechanical state of the structures, and the 
 chymical conditions of the fluids. These latter are to be con- 
 sidered as re-agents. 
 
 11. In attempting to discriminate the mode of causation ia 
 related diseases, we can only scrutinize the succession, which will 
 rarely afford much light, because the processes of disease in related 
 seats, although in the beginning there might be an obvious antece- 
 dent, will in their course appear synchronous, or so mixed that a 
 precise order cannot be distinguished. Such, however, are the 
 indications for minute inquiry; and, to obviate a reliance upon the 
 false theories which would explain these phenomena, it has been 
 proposed merely to state the facts, that, of related diseases some 
 are substituted, or curative, and others are a mere extension of 
 disease to related seats. It appears from the facts, that disease in 
 some, or many seats, may be cured by an agency which is extended 
 from a related seat; and this agrees with the design of employing 
 remedies which operate not upon the seat of the disease, but upon 
 some other. This agreement, and the foundation of the design, 
 we shall presently have occasion to examine. 
 
 s 
 
CHAP. VI. Tfurapcvtici. 
 
 1. IN speaking of the general nature of disease, it has 
 been observed, that our means of analysis do not enable us to de- 
 fine in what its variation from the state of health consists: we 
 cannot say what properties are foreign, what deficient ; what com- 
 binations have taken place, what combinations it is necessary to 
 separate, what combinations it is necessary to restore, or what new 
 ones to produce, &c.; we do not know in what disease consists. 
 Yet, with this profound ignorance, we boldly employ agents of 
 various powers; and he who understands in the common way the 
 adaptation of these agents to certain cases, will sometimes succeed 
 in restoring health where death would have been the spontaneous 
 event; and will very frequently restore health in a short time, in 
 those cases in which nature would perhaps have accomplished the 
 same end by a series of lingering and protracted operations. The 
 modus operand! of medicines is what I now propose to con- 
 sider briefly. 
 
 2. By the exhibition of medicines it is intended to change 
 the existing or diseased, and to restore the former or healthy 
 identity of the properties constituting an animal body; whether 
 these changes respect the system generally, or some individual 
 part or parts of it. The exhibition of medicines being an intro- 
 duction of foreign properties, if the cure proceeded on a direct 
 principle of causation, it must be pre-supposed that disease consists 
 in a deficiency of properties, and that those of the medicines are 
 the identical properties, the privation of which produces disease. 
 
 3. There would be absurdity in attempting to establish this 
 as a general principle of cure: and yet there are some cases in 
 which it would be difficult to prove that this was not the mode of 
 cure. We must, however, take a general view of the facts which 
 relate to the question, if we would attempt the discovery of a 
 general principle. Mercury cures syphilis: is there any reason 
 to think that the disease which we call syphilis consists of a de- 
 ficiency of mercury, local or constitutional? Sulphur cures the 
 itch : yet we can scarcely presume that the itch arises from defect 
 of sulphur; or that fever arises from defect of antimony, because 
 *t might be cured by James's powder; or that fever consists in 
 
307 
 
 the absence of calomel, because this also might cure fever; or that 
 pleurisy consists in a deficiency of nitre, or in the want of a blister 
 on the skin; or, pursuing the direct principle of causation, that 
 pneumonia happens from excess of blood, because it may be cured 
 by repeated bleedings: we cannot attribute the disease to such a 
 cause, seeing that the pneumonia might happen the day after a 
 pint of blood has been taken from the arm, at which time there is 
 a pint of blood less in the body than existed in it a week before, 
 when pneumonia was not present; or that apoplexy is produced 
 by excess of blood, seeing that fatal apoplexy may take place in a 
 subject who has been bled twice a week for a month previously, 
 and lived upon gruel; there must certainly be less blood in the 
 body at the end of such a month than there was two mouths before, 
 when the subject was in good health and in habits of full repletion. 
 If it be said these diseases are produced by a local excess of blood, 
 I ask what occasions such local excess? it must be answered, pre- 
 vious disease: such illustration may be greatly extended r To 
 this may be added examples of the following kind: a person having 
 a pain in the head with a furred tongue, may become free from 
 the pain in the head and the tongue might become clean, after 
 losing twelve ounces of blood from the back of the neck by 
 cupping, without the use of any other efficient remedy: the same 
 result, in a case of a similar character, may be produced by 
 emetics; the same by bleeding from the arm, or from the temples 
 by leeches, or bydigitilis; the same from aloes, antimony, blue 
 pill; by an issue; or a blister on the scalp; by change of air; 
 perhaps by laudanum, &c. The inference from these facts (and 
 there are hundreds of such) is, that the same results might be ac- 
 complished by different means. If the state of disease is changed 
 and the condition of health restored by agents which supply pre- 
 risely those properties which are deficient, or remove those precise 
 ones which are in excess, how happens it that the agents producing 
 this similitude of effects are so greatly diversified? 
 
 4. The question, how many different agents produce the same 
 effect? may be answered thus, by one determined to support the 
 doctrine of the direct causation : " All these various remedies may 
 have some precise properties in common, with which alone the 
 state of disease is related; these properties being allied with diffe- 
 rent substances, may appear to form a multiplicity of means of ac- 
 complishing one purpose, while in reality the efficient properties 
 are alike and common to them all." This observation is perfectly 
 just, and unanswerable in some other cases of causation: thus, a 
 bullet may be propelled from a tube either by the force of air or of 
 gunpowder, or perhaps steam; these three are different, but act 
 by a common property, viz. a force of expansion with which the 
 effect is related. Thus, also, ipecacuanha, antimony, zinc, &c. 
 are capable of exciting the action of vomiting, which would not 
 take place unless these substances contained a common property 
 which identified the state necessary to vomiting; thus, alio, toe 
 
308 
 
 skm may be destroyed by boiling water, by a hot iron, by the 
 flame of a candle, by melted lead, by a heated coal, by boiling oil, 
 &c.; these appear different causes, that is, the efficient cause, vix. 
 heat, is differently allied. 
 
 $ 5. But, iu the cases of disease, the analogy to these latter 
 instances does not obtain: a disease consists either of defective or 
 of foreign properties compared with the state of health; if it is 
 only one of these, or both (and there is no alternative), the cure, or 
 restoration of health, must require either that the deficient proper- 
 ties be supplied or the foreign ones removed, or both; here again 
 there is in the efficient causation no other alternative. But the 
 cure by remedies is accomplished in contradiction to these modes, 
 and therefore these modes, which are the only ones of direct causa- 
 tion, cannot be the modes by which remedies act : thus, suppose 
 our pain in the head to arise by defect of the tonic power of the 
 arteries, by which a preternatural dilatation is admitted, emetic 
 tartar and aloes will cure this defect of tonicity: if they do it by 
 supplying the tonic power which was deficient, how happens it that 
 leeches, or bleeding from the temporal artery, both of which 
 abstract blood, and do not supply deficient properties, will also 
 produce the same effect? or, suppose the pain in the head to be 
 produced by some properties deficient and some foreign, a bleeding 
 from the head can be supposed with the greatest latitude of as- 
 sumption only to remove properties which are foreign to the state 
 of health. Yet the disease ceases, leaving the supply of the de- 
 ficient properties unaccounted fpr. 
 
 6. It is sufficiently plain from these considerations (and in- 
 deed by a little further discussion, which seems superfluous, it 
 might be demonstrated) that the general operation of remedies is 
 not by supplying deficient, or removing foreign properties, in the 
 direct or efficient mode of causation, as if disease of the bowels 
 consisted in a deficiency of some properties which exist in rhubarb, 
 &c. but that these properties produce their effects by an indirect 
 causation. 
 
 7. We find that this inference, deduced in conformity with 
 our minuter reasonings, is equally supported by the palpable effects 
 of remedies: so far from unchanging the diseased, and restoring 
 the healthy state by the communication, or the removal of precise 
 differential properties; so far from this, all the remedies which 
 have a sensible operation are themselves, as is well known, the 
 causes of disease, or all tend to produce preternatural conditions. 
 This effect will be recognized by enumerating a few of the reme- 
 dies chiefly relied on : such as mercury in its various forms, aloes, 
 scammony, jalap, colocynth, elateriuni, gamboge, neutral salts, 
 senna, antimony, ipecacuanha, squill, digitalis, nitre, assafoetida, 
 bleeding, blisters, warm bath, opium, brandy, wine, ammonia, 
 aether, arsenic, hemlock, c.; all these remedies which have sensi- 
 ble effects are not the direct causes of health, but of diseased 
 states. If, then, an agent, whose direct operation is to produce 
 
309 
 
 disease, has also the property of restoring health, we must seek 
 after a mode of causation by which this latter effect is accomplished 
 in an indirect way. The question, otherwise stated, is this, how do 
 remedies, whose immediate effect is to disorder the seats of their 
 operation, produce health? 
 
 8. The answer to this question is, that they do it in general by 
 mediate relations, or they do it by a series of causation : ultimately, 
 disease must cease and health be resumed by the efficient causation, 
 so many times described ; but medicines do not commonly operate in 
 this way, they lead up to these results. 
 
 9. Curative medicines may be divided into three classes: 1st, 
 those that cure by a direct relation with the cause of disease; 2nd, 
 those which cure by removing or obviating a perceptible (or sensible) 
 cause of disease by an intermediate relation ; 3rd, those which cure 
 by latent causation. First, to exemplify these. 
 
 1. It is possible that a cause of disease may be removed in a 
 direct way, that is, the artificial means may be related with the 
 perceptible cause of disease, without any intermediate relation: as 
 if a remedy should be found, which being taken into the circulation 
 is chymically related with gall-stone so as to dissolve it, thereby 
 curing jaundice (supposing it to arise from an obstruction of this 
 sort in the biliary duct); or, as if a fluid should mix with indurated 
 faeces, soften them* and so admit a natural evacuation of them ; or, 
 as if a solvent should be discovered for calculus in the kidneys or 
 bladder. The cure of diseases in this way, by medicine, is similar 
 to that of the cure of diseases by the operations of surgery: thus, by 
 lithotomy a stone is removed from the bladder, and the disease 
 which its presence produced ceases; thus amputation is performed 
 above a diseased joint, and the hectic state of the constitution, which 
 was produced or maintained by the local disease, ceases; or, the burst- 
 ing of an aneurism is prevented by intercepting the supply of blood 
 by a ligature, &c. But the instances of the direct relation of an 
 artificial means with the cause of disease, in medicine, are rare. 
 
 2. Recurring to an example, jaundice, we will say, is produced 
 by obstruction of the biliary ducts; under the exhibition of mercury, 
 this obstruction is removed, and the jaundice is cured. We will say, 
 for the sake of a specification, the cause of the disease is a gall- 
 stone. There is no direct relation between the mercury and the 
 gall-stone, by which the latter may be removed ; the gall-stone 
 would not be removed by putting calomel or blue pill into the 
 stomach, or into the gall-duct of a dead man. Mercury, then, re- 
 moves the gall-stone by its relation with some of the properties of 
 life, in some or other of its seats: say that mercury quickens the 
 action of the heart, and increases the impetus of the circulation, and 
 that thus mechanically, by a visa tergo, the obstruction is removed: 
 the relation then of the mercury is with the heart; if any other 
 modus operand! is assigned, then the mercury removes the gall-stone 
 by another intermediate relation. Disorder of the stomach is pro- 
 duced by the presence of bile: this is removed by an emetic, and 
 
310 
 
 the disorder ceases; the relation of the emetic is with certain pro- 
 perties belonging to the structures, which, in conjunction with it, 
 produce the state necessary to the act of vomiting; by this action 
 the bile is ejected. Disorder, dependent upon the presence of in- 
 durated faeces in the colon, is cured by purgatives; the relation of 
 the purgatives is with the secerning function of the internal coat of 
 the intestines, perhaps also with the mesenteric absorbents, and with 
 the properties concerned in the peristaltic motions of the intestines. 
 The indurated faeces are removed from the colon, as a consequence 
 of the state produced by this mediate relation. 
 
 3. The remedies belonging to the third class are the most 
 numerous, and it is upon these that we rely (and the grounds of 
 this reliance will come to be examined) in all cases in which the 
 efficient cause is not known. To exemplify this class of medicines 
 which cure by latent causation: a disorder of the head may be cured 
 by repeated bleedings, local or general; long before the period at 
 which the disorder ceases, there may be much less blood than is 
 compatible with perfect health; that is, the disease continues when 
 the quantity of blood in the system is considerably less than at a 
 former period of health; bleeding then in this case does not cure by 
 removing a sensible cause of disease. A fever may be cured by 
 bleedings, purgatives, antimony, &c.: we do not know the cause of 
 fever, or if we can assign any cause it may be a remote one, which 
 has ceased to operate, such as cold; the phenomena of fever are 
 produced by a modified state of the principle of life; who can say 
 in what this modification consists? or, what cause (supposing the 
 state to be produced by some foreign properties) is removed by the 
 remedies? or, supposing the state to consist of deficient causes, 
 what properties, or whether any existing in the remedies, are the 
 identical ones which the spirit requires in order to have its state of 
 health restored? An berpetic eruption on the skin may be cured by 
 arsenic : who can specify the causation among the properties engaged 
 in these processes of the subversion of disease, and the restoration of 
 health? Not to be tedious in enumerating instances, we may briefly 
 say, that the precise causation by which remedies cure diseases is 
 never known, or is latent, except in those instances where the cause 
 which produces disease is a sensible one, or in which we infer a 
 sensible cause from analogy. These exceptions belong most fre- 
 quently to that class of remedies which cure diseases by an inter- 
 mediate relation, examples of which are specified under that class. 
 Inflammation, as pneumonia, is diminished by agents which reduce 
 the action of the heart, and diminish the volume of the circulating 
 fluids: the means which produce these effects are blood-letting, 
 which is perhaps directly related with the action of the heart, and 
 this action mediately with the state of inflammation; purgatives, 
 which are related with the properties of the intestines, and again 
 mediately with the state of inflammation; to which may be added 
 such medicines as nitre, ipecacuanha, emetic tartar, squill, digitalis, 
 &c. These means do not remove a supernumerary, or supply a 
 
311 
 
 deficient cause: they are employed without any reference to the 
 cause of disease, either sensible or inferred. The causation of reme- 
 dies which is insensible or imperceptible, and which is not to be in- 
 ferred by rules of analogy, may be expressed as latent. To extend 
 a little our consideration of these classes respectively. 
 
 1. The known examples of agents which produce effects by 
 direct relation with the cause of disease are few, and are chiefly con- 
 fined to the means of operative surgery. It is, however, possible 
 that some medicines may operate in this way insensibly, or where the 
 cause of disease is not suspected, and where the properties contained 
 in the remedy and corrective of this cause, are not known. In order, 
 however, to restore health, the assimilating healthy state of life must 
 be restored, which is seldom or never the case with palliatives, 
 forming chiefly the class of medicines here hinted to operate in the 
 direct manner; as a violent pain in the bowels may be suspended by 
 a dose of laudanum; but the pain will perhaps return, which would 
 not be the case if the laudanum restored health by the direct causa- 
 tion which produces in every respect the state of health. The 
 laudanum only produces a change in the condition of the disease, 
 the result of which is the mitigation of pain, &c. The remedies 
 which are known to cure by removing the cause of disease are 
 related not with primary, but with secondary, or the effects of 
 primary disease. 
 
 2. Medicines that remove the cause of disease by intermediate 
 relations. These remedies are mediately related with the conse- 
 quences of primitive disease, and cure the diseases dependent upon 
 the re-action of these consequences, or the continuance of such 
 causes. Thus mercury, by merely quickening the circulation (to 
 specify a possible mode), may remove biliary obstruction, and the 
 phenomena would cease which are dependent upon such obstruction: 
 thus also purgatives remove worms, the presence of which may have 
 occasioned epilepsy; but neither the biliary obstruction nor the 
 worms would have been formed without that previous change of 
 the slate of health, which we have called predisposition. The 
 jaundice ceases and the epilepsy ceases, because an agent is employed 
 which mediately removes the causes upon which these remote con- 
 sequences of primitive disease depend. The remedies of this class 
 may cure primary disease ; but this does not happen by the removal 
 of a known cause, simply for the reason that the cause belonging to 
 the properties of life is not to be known. 
 
 3. Remedies which cure by latent causation. Remedies which 
 operate in this way do it by directly supplying or removing unknown 
 properties, &c. or by accomplishing this end indirectly, or by 
 mediate relations. They rarely, if ever, accomplish this work of 
 restoration directly, as above remarked. We infer this from the 
 fact that the state of health does not immediately succeed the exhi- 
 bition of the remedy, which it should do if this remedy directly 
 removed or supplied a property which was differential in comparison 
 with health. The only answer which can be made to this remark w. 
 
312 
 
 that remedies of this kind, curing by repeated doses, the direct 
 causation might obtain, and yet the state of health not be im- 
 mediately restored because the quantity was deficient. This answer 
 is, however, invalidated by the additional fact, that if the quantity 
 is increased, so far from improving the effect, it may produce death, 
 as arsenic, for example, which nevertheless cures by a repetition of 
 small doses. The perceptible effect, also, of most remedies of this 
 kind is to produce a state different from health: they cannot there- 
 fore on this account be admitted to operate in the direct way. The 
 inference is therefore warranted, that medicines which operate by 
 latent causation, do it by a process the result of which is attained by 
 intermediate relations. 
 
 10. The subdivisions of the third class, or of remedies which 
 operate by latent causation, are, 1st, those that cure without a sensi- 
 ble operation; 2nd, medicines that produce cure by sensible change, 
 or by sensible effects; 3rd, medicines that cure by employment 
 upon the seats of disease, with or without sensible effects; 4th, 
 medicines that cure by an operation upon related seats, with or 
 without sensible effects. To speak now more particularly of the 
 relation which each of these classes has with the condition of disease. 
 
 1st, Medicines that operate without sensible effects. In this 
 manner arsenic may cure intermittent fever, scorbutic disease, &c. 
 In this way diseases are cured by bark, by antimony, and mercury, 
 in small doses, &c. The cure in these instances is accomplished by 
 successive causation, and consequently the relation of the remedy 
 with the condition of the disease is mediate. 
 
 2nd, Medicines that cure, producing sensible effects or disorder 
 of their own. The remedies which fall under this class are by far 
 the most numerous: to this class belong all the emetic and purga- 
 tive medicines, arsenic and mercury, in large or frequent doses, 
 antimony, steel, henbane, hemlock, digitalis, blisters, bleeding, 
 issues, &c. These remedies also operate by successive or inter- 
 mediate causation, without removing, in the cases we are supposing, 
 known causes. 
 
 3rd, Medicines that cure by employment upon the seats of the 
 disease. In this way all those remedies act which are applied to 
 individual seats through the medium of the circulation. In this way, 
 also, the topical remedies act, such as cupping, lotions, blisters, &c. 
 These operate by mediate relations; and in the cases we are sup- 
 posing, that is, where the precise cause of disease is not ascertaina- 
 ble, by a train, or succession of latent processes of causation. 
 
 4th, Medicines that cure by an employment upon related seats. 
 Thus, a disorder of the head is cured by emetics, or anasarca of the 
 legs by purgatives; or a disorder of the head existing beneath the 
 cranium, by the actual cautery to the scalp ; or a disease of the eye, 
 by an issue in the arm or a seaton in the back of the neck; or as a 
 disorder of the stomach is cured by purgatives, or an inflammation 
 of the pleura by blistering the skin; or as a disease of a joint is cured 
 by a caustic issue, &c. These remedies act also by successive 
 
313 
 
 causation, or by a series of related processes. I am not conscious 
 of any medical agent that ever has been employed, or that can be 
 employed, with any view, or any mode of operation, which is not in- 
 cluded in one or other of the preceding divisions. We have now 
 to consider something of the laws which regulate the results of the 
 operation of those remedies, concerning which we have no further 
 experience than that they are capable of affecting the condition of 
 disease, by intermediate or related processes. 
 
 1. Primary disease in all instances consists in a change, or modi- 
 fication of the principle of life, compared with the state of health. 
 
 2. Primary disease is a state of the principle of life compatible 
 with its assimilation; and in this way it is maintained. 
 
 3. Secondary disease may be maintained after primary disease 
 has ceased. 
 
 4. Secondary, or rather consecutive disease, may be maintained 
 in two ways after the primary disease has ceased : 1st, if such is the 
 relation bettfeen the life of different seats, the influence of the 
 primary upon the secondary may be to produce a modified assimi- 
 lating state of it, as if a sxvelled testicle should follow the irritation, 
 of an injection, and degenerate into schirrus, long after the urethra 
 has resumed its state of perfect health; 2nd, the consecutive disease 
 may be maintained by an effect of the primary, which does not arise 
 out of a direct relation between vital properties, as when primary 
 disease changes the textures or the secretions, or produces foreign 
 substances, &c. The consecutive disease of the spirit may then be 
 maintained by these causes, and these causes being removed, it ceases, 
 because the relation of their properties with the spirit is not to pro- 
 duce a modified assimilating state of it. These causes, or effects of 
 primary disease, may be distinguished as the material occasional 
 causes. 
 
 5. But primary disease may maintain consecutive disease by 
 direct relation of the properties of the principle; and this secondary 
 state continuing only so long as the primary lasts, the properties pro- 
 ducing the secondary disease may be distinguished from those pro- 
 ducing a modified assimilating state, as the occasional spiritual 
 causes of disease: as when the respiratory organs are disordered by 
 pressure upon the brain, as by bone, and resume their natural state 
 of properties when this pressure is removed. 
 
 6. Every disorder of the spirit which is not maintained by the 
 occasional material causes, is maintained by assimilation: for if the 
 disorder should be of the secondary kind, and does' not assimilate in 
 its seat, it is dependent upon a disorder which assimilates in some 
 ether seat, the present sum or quantum of the spirit requiring to be 
 perpetually renewed, and acknowledging no other source than that 
 of assimilation. v 
 
 7. Remedies operate either by removing a known cause or by 
 latent causation. It is an object in medical investigation to discover 
 the cause of disease ; for though every internal cause which we are 
 capable of knowing must be a consequence of previous disease, being 
 
 T T 
 
once formed, its existence may be independent of that primaty, or 
 previous disease which produced it. In such a case the only present 
 condition of spiritual disease may be that dependent upon a material 
 occasional cause, which being removed the existing spiritual disease 
 ceases; as when by the operations of surgery (lo advert to palpable 
 instances) the material effects of previous diseased actions, as they 
 are called, are removed, febrile or other consecutive constitutional 
 disease, engaging properties of the spirit and maintained by such 
 occasional material causes, ceases. 
 
 8. But most remedies operate by latent causation, or by succes- 
 ive causation. The operation of remedies may in this way acknow- 
 ledge a complication equal to that which has been described of 
 disease. The relation of remedies may be directly with unknown 
 material occasional causes, or indirectly with such causes; or, in a 
 few instances, directly with the state of primary disease; or, more 
 frequently, indirectly with the state of primary disease; or with 
 secondary assimilating disease, directly or indirectly; of directly, or 
 indirectly with secondary occasional disease. 
 
 9. Those diseases are the most numerous in which no cause, as 
 of the material occasional kind, can be assigned. We are not justi- 
 fied, in these instances, in inferring the existence of such cause by 
 general analogy, or merely for the reason that diseases are some- 
 limes known to be maintained by the material occasional causes, 
 since disease must originate independently of such causes in every 
 instance, and since the instances in which such causes are ascertaina- 
 ble are comparatively few. When, therefore, a cause of this sort 
 can neither be known sensibly, nor assigned in agreement with any 
 particular analogies, we are justified in concluding only that the 
 modified phenomena which depend upon spiritual agency are pro- 
 duced by a state of disease which consists of a modification of the 
 healthy state of the spirit. Conformably with this rule, we should 
 infer all diseases of function, which are not dependent upon the 
 material occasional cause?, to consist in a modification of the pro- 
 perties of the spirit. 
 
 10. As all diseases of the spirit are maintained by assimilation, 
 it remains that we should consider the agency of remedies, with re- 
 spect to that process by which disease is maintained. 
 
 11. A relation subsists between the spirit and certain external 
 causes, the result of which is, that the state of the former may be 
 modified or changed by the agency of the latter. 
 
 12. Tlie properties of the external causes are related with the 
 ipirit either directly or indirectly: directly, as when effects are pro- 
 duced exclusively by the combination of the properties of external 
 causes with those of the spirit; indirectly, as when the state of the 
 ipirit is changed by the operation of external causes upon the 
 alliances of the spirit, as upon the fluids or the organized substances. 
 These are possible modes of the operation of external causes upon 
 the spirit. It is in no case possible to demonstrate when the 
 primary relation of externals is with the spirit, and when with it* 
 
315 
 
 llianfes, seeing that both are in all instances at the same time 
 exposed to their operation. If, however, the relation of remedies 
 were in every case with the material or fluid alliances, it would not 
 interfere with our conclusions on the laws of the operation of reme- 
 dies on the spirit: the only difference would be, that, instead of pro- 
 ducing such and such effects directly, the same would be produced 
 mediately. But as it c;m rarely be proved that the change of the 
 spirit is a result of a change of its alliances, and as the change of the 
 spirit itself is in every instance to be inferred from the change of 
 phenomena dependent upon it (which change is the only proof of a 
 causative relation of any kind, in most instances), so it is best, having 
 stated these possibilities, together with the alternatives to which the 
 argument would be liable, supposing them to obtain, to speak of the 
 operation of remedies in general as influencing directly the principle 
 of life, without which influence, the changes which occur in the 
 material or chymical alliances are no more than would result frorn 
 the same causes employed upon the dead subject. 
 
 13. Every change in the organic spirit is according to its rela- 
 tion with the cause that produces it. But different agents will 
 sometimes agree in producing similar effects: thus, a disorder which 
 might be .cured by blood-letting may also be cured by purgatives, 
 or by emetics, blisters, &c. In other instances, particular diseases, 
 or states of the principle, are cured only by some particular means; 
 as certain forms of syphilis by mercury, the itch by sulphur, scurvy 
 by arsenic, &c. The effect which is produced in common by the 
 former means can be identified only by the same causes; we have 
 ihen to determine whether they possess common efficient causes, 
 disguised by different alliances? or whether they have only the 
 force of remote causes to which a series of processes succeed, the 
 result of which, through different relations, may be finally to 
 identify the state of health? 
 
 14. We have thought it necessary, on grounds before stated, 
 to conclude that remedies never restore health on the direct princi- 
 ple of causation, viz. that of supplying deficient properties, &c; at 
 least, remedies can never be employed with this view, except in the 
 instances of the material occasional causes, of which those that fall 
 within the department of medicine are very few, and with which the 
 direct relation of remedies is perhaps altogether problematical; our 
 alternatives are therefore briefly answered: remedies must on this 
 account, with respect to the cure of diseases, have always the force 
 and operation of remote causes. 
 
 15. The manner in which external agents produce change in 
 the condition of the spirit, in the direct way which we are now con- 
 sidering, is by an alliance of their properties with those of life, by 
 which the combinations of the constituent properties of life are 
 modified, and hence exhibit modified phenomena, which are com- 
 monly expressed in symptoms. 
 
 16. The identity which life assimilates is dependent upon the 
 combinations of its integral properties : its phenomena also depend 
 
316 
 
 upon these combinations. The state of life is in general pretty uni- 
 form, but in instances which have been remarked in our physiology, 
 properties before latent are developed, as in the case of puberty, and 
 stilllife assimilates. 
 
 17. A change of the combination of constituent properties 
 produces the phenomena of disease: life assimilates under this state; 
 and as long as this assimilation continues, the state of disease is 
 maintained. 
 
 18. But progressive causation may be going on amons these 
 constituent properties, the result of which, in the state of disease, 
 must be either to exhibit other symptoms in a series, or a return to 
 the former assimilating state of health, or a termination in death. 
 
 19. One particular agent may have such a relation with the 
 existing diseased state of life, as to determine its series of processes 
 towards the restoration of health. This depends upon the relations 
 of integral properties with the agent, and their relations with each 
 other, under the modifications produced by the agent. To this class 
 of agents belong the specifics, mercury, sulphur, and all single 
 remedies for a disease. 
 
 20. But many remedies may have the property of restoring 
 health by a common relation ; as when the existing state of the 
 principle is a diseased one, which will continue, if left to itself, to 
 assimilate in this state, and hence, as long as this state continues 
 disease may in this way be maintained: but this state may be 
 changed or superseded by a variety of agents, by any which have a 
 causative relation with it; to produce a change is a common effect 
 of many agents, and this change having taken place, the further 
 series of combinations is determined by the relations of constituent 
 properties, which obtain under this new state. The tendency under 
 any state is either to a return to the previous state of disease, 
 when the operation of the agent has ceased, or to additional symp- 
 toms which might be called a deterioration of disease, or to recovery, 
 or death. Hence, as every remedy must be productive of one or 
 other of these events, so these events must respectively have a com- 
 mon relation with many remedies. 
 
 21. Particular remedies, or specifics, produce a state under 
 which exclusively the relations of integral properties with the new 
 state of the principle, or the remedial change, is to terminate their 
 series of processes in the recovery of health. 
 
 22. General remedies agree in producing a change of the 
 existing state of the principle, and the result of the change is liable 
 to the four alternatives just specified. 
 
 23. General remedies may produce a change in the seat of the 
 diseased principle, either by an operation upon this seat, or by an 
 agency upon a related- seat : thus, disorder of the head may be 
 cured by bleeding from the temporal artery, by long-continued purge- 
 ing, or by nauseating doses of antimony, &c. or by an issue, perhaps, 
 in the leg. They have the common property of changing the existing 
 state of disease, which would maintain itself by assimilation, or of 
 
317 
 
 modifying a tendency to deterioration of disease, supposing such 
 tendency should exist : and the final result of the change is then 
 governed by relations among constituent spiritual properties, all of 
 which are latent. 
 
 24. We here perceive an agreement between the operation of 
 general remedies and the results of substituted disease. Thus, a 
 man may have inflammation of the liver ; this may cease upon the 
 occurrence of phrenitis, and this may cease upon the occurrence of 
 profuse discharge of blood from the rectum. This series is related 
 in curative order; but in another case, as in those cases cited of 
 extended disease, the secondary may have no curative relation with 
 the primary disease. 
 
 25. There is, as just remarked, some analogy between those 
 instances of spontaneous cure by substituted disease and the opera- 
 tion of general remedies: thus, the spontaneous termination of 
 nervous disorder, pain in the head, &c. may be in an attack of 
 cholera. A similar termination may perhaps be artificially produced 
 by agents which also occasion vomiting and purging. A disorder of 
 the head may be cured spontaneously by an abscess: if we were 
 called upon to treat artificially the same disease, we should perhaps 
 employ a caustic issue, or a perpetual blister, &c. The point of 
 analogy is, that in both instances primary disease ceases, under the 
 occurrence of secondary. 
 
 26. But there appears a certainty in the curative result of spon- 
 taneous secondary disease, which does not always obtain when we 
 attempt to imitate it by artificial means: thus insanity may be cured 
 by a spontaneous abscess of the back, but we should be disappointed 
 iu another case, if we were to expect a cure by making a caustic 
 issue in the back, in a situation corresponding with that of the 
 abscess; thus, also, a primary disease, in which purgatives have 
 failed totally, may be cured by a spontaneous diarrhoea. We shall 
 be at no loss to reconcile this diversity of result, when we recollect 
 that substituted spontaneous disease cures, either because precise or 
 identical properties of the primary disease pass to the secondary 
 seat; or because independent disease, established in the secondary 
 seat, must in all the examples of substituted disease (taking the suc- 
 cession as a proof of causation) have a curative relation with the 
 state of primary disease: on the other hand, artificial disorder maj 
 fail for want of agreement in these respects; that is, 1st, because 
 the properties of the primary disease may remain in their seat not- 
 withstanding a relation with anew disease, which only modifies their 
 phenomena in some respects; and, 2nd, because there may be no 
 relation between the seat of artificial affection and that of primary 
 disease. If there is a relation, and this is not of the curative kind, 
 then remedies which disorder, instead of irritating the substituted, 
 exemplify the extended disease. 
 
 27. The preceding sketch exhibits a history of the general 
 nature and cure of diseases. If it is desired to trace more minutely 
 the laws of disease and the operation of remedies, it may be done, 
 
318 
 
 pursuing the clews here suggested, to a considerable extent, when 
 the investigation is employed exclusively upon one object. We 
 know nothing of the efficient causation of diseases: we reason upon 
 this causation on grounds of analogy; but the causes concerned can 
 never be specified, because they are not objects cognizable to the 
 senses. We aspire occasionally to the removal of remote causes, as 
 when we take blood from a vein, or remove a stone from the bladder, 
 but in these cases, the latter of which is the least equivocal, we are 
 ignorant of the efficient or real cause : a stone in the bladder, it may 
 be said, is the cause of irritation; remove this stone, and the cause 
 is removed, and the irritation ceases; very true: the cause is re- 
 moved with the stone, but what is the cause? The effect of the 
 stone is to produce a certain state, which we call one of irritation of 
 animal properties; these properties can be modified only by an 
 union or combination of other properties: it would be absurd to say 
 that a stone combined with life, and modified its identity. The 
 efficient cause must be looked for in the properties of the stone, 
 which are related with life; what these properties are we cannot 
 define, because they, like the properties with which they are related, 
 are not cognizable to the senses. Indeed, in this case the distinction 
 remains to be drawn and the grounds of it stated, whether the rela- 
 tion of the properties of the stone is direct or mediate; whether by 
 latent properties common to matter related with life (such as are 
 indicated by food, or nutritious substances), to be classed neither as 
 chymical nor mechanical; or whether by simple gravity modified in 
 its agency by shape and asperities, and related with the spirit by 
 means only of a primitive relation with the mechanical structures, 
 with which the spirit is in alliance. It suffices, however, in these 
 cases, without looking for true or efficient causes, that we are 
 enabled to remove these causes by our knowledge of their alliance 
 with sensible substances. 
 
 28. The sum of our experience (or, perhaps more correctly, of 
 our information, for it is mostly inferential), is, 
 
 1st, That some remedies will cure some diseases, and that others 
 will not. 
 
 2nd, That the employment of remedies is founded upon 
 analogy; that is, such diseases have been cured by such remedies, 
 and, in agreement with the analogy, we employ the same remedies 
 when we meet with the same diseases. The practice of medicine 
 upon this principle has been called empirical. The difference be- 
 tween empirical practice and that which is distinguished as scientific 
 is, that the analogy in the first is general, and in the latter it is par- 
 ticular. The empiric founds his practice on a partial observance of 
 the analogy of symptoms, and on the general results of remedies; 
 the man of science does not employ remedies simply because they 
 Lave been found to cure, but he employs them with a view to a par- 
 ticular mode of operation. The empiric would give a purgative where 
 disease was accompanied by long-accustomed torpor of the bowels : 
 the man oi 'science would perhaps give a purgative iu the same case, 
 
319 
 
 in order to remove sejbala, upon which he infers the disease to de- 
 pend: one practises from the curative result, the other with a view 
 to causes; one gives the purgative upon the general analogy that 
 such symptoms have been so cured, the other gives it on the par- 
 ticular analogy that in resembling cases scybala have been found in 
 the bowels, upon the removal of which the disease has ceased; on 
 is a loose, and the other is a minute observer. They have respec- 
 tively their disadvantages: the empiric may fail by overlooking the 
 particular analogy, which may be of principal importance; the man 
 of science may fail also, by an erroneous inference with respect to 
 the cause; a thing which happens every day, and nine times out of 
 ten, when we presume to assign a cause, where the agents of the pro- 
 cesses are not objects of the senses. 
 
 29. It may be asked, what advantages then has the man of 
 science over the empiric? Where is the difference, whether the 
 same remedy be given with a particular design, the result of minute 
 observation, or whether it be given upon the general principle that 
 such a remedy has been found by experience to be curative? To 
 this I reply, as the same result would generally be attained in either 
 case, so in general the loose, and the observing practitioner would 
 ply their art with equal advantages. But the empiric may some- 
 times push a treatment, when the man of science would suspend it; 
 or, vice versa, the empiric would say, I have tried this remedy which 
 used to succeed, it has failed and I will abandon it : the man of 
 science would say, in the same case, this remedy which has hitherto 
 failed must be continued, or its doses increased, because it has not 
 yet produced that particular effect upon which I have observed the 
 restoration of health to depend. The chief advantages of the ob- 
 server are, that he has ascertained the dependence, or laws of the 
 disease, and he directs bis means according to his knowledge of these 
 laws, rather than from a vague expectation of a final result, to be* 
 accomplished he knows not how. 
 
 30. If we would define this matter with greater precision, we 
 may say, the use of observation in medicine is to extend our know- 
 ledge of the particulars of the several states of disease, by which 
 we might be enabled to say, in a comparison of cases, in these re- 
 spects they agree, in these they differ; and direct or modify our 
 practice according to the circumstances of analogy or diversity. 
 
 31. A remedy is employed for the cure of a disease, with a 
 view to the removal of a cause, either known or inferred. Nothing 
 is more common than for men to practise with this design; but the 
 instances in which the cause is known, are indeed very few, and 
 those in which a cause is inferred are mostly erroneous or equivo- 
 cal. This has been shewn in our preceding pages, where one 
 says disorder of the liver is the common or universal cause of 
 disease, another says the same of the stomach, another of the 
 excitability, &c. ; all this is fanciful: in these cases a cause has 
 been inferred, without analytical inquiry. We know that we re- 
 move a cause of vomiting aud constipation when we set free a 
 
320 
 
 portion of strangulated intestine, or We know that we remove a 
 cause of extended disease when we remove a stone from the blad- 
 der, or amputate a diseased limb. These causes are unequivocal : 
 but in medicine, with a few admissible instances, the rest are for 
 the most part conjectural and assumed. At the same time, 
 it must be allowed that to keep in view the discovery of the cause 
 of a disease, is always an object worthy emulation, since the suc- 
 cess of our practice is never so certain as when, with adequate 
 means, it is directed to the removal of a known cause. 
 
 32. When a remedy is employed without any view to the 
 removal of a cause, known or inferred, we must confess that it 
 operates by a latent causation, or by a process, with the agents of 
 which we are not acquainted. But although the cause is not 
 known, we may observe a remedy is curative which produces cer- 
 tain effects; and we infer a dependence of the cure upon such 
 effects: for example, we know that mercury will cure syphilis; 
 but observation has instructed us that mercury will not cure 
 syphilis unless it produce certain constitutional effects. We know 
 that disorders of the head or eyes may be cured by antimony; but 
 it is the business of observation to point out the terms upon which 
 antimony will cure these disorders. Their terms of cure, we 
 otherwise call dependences. In case of disease, in which there 
 is analogy of symptoms, we infer analogy of dependence; and 
 hence we employ the same remedies, upon the expectation of a 
 similar dependence of cure, in different diseases. Particular indi- 
 cations of treatment are founded upon precise analogies ; general 
 indications, upon analogies which are general, only because they 
 have a partial resemblance. 
 
 33. Diseases have a general resemblance in this respect, viz. 
 that if they re not maintained by the material occasional causes 
 (which are those we aspire to remove) they are maintained by 
 assimilation: this is a general point of agreement in the nature of 
 disease. The corresponding general agreement in the operation 
 of remedies is, that the present assimilating state must be inter- 
 rupted before health is restored. Many agents must inevitably 
 agree in this effect; and we are.therefore furnished with a general 
 indication of cure, upon which we might presume, in the absence 
 of a particular one. The agents which agree in this effect are 
 numerous, we employ them upon analogy; and this analogy also 
 way be general or particular: general, as we find that most reme- 
 dies which produce sensible effects will influence the condition of 
 disease; particular, as when it has been ascertained that some 
 remedies will influence the condition of disease, and that others 
 will not. In the treatment of diseases upon a general principle, 
 or in all cases in which the operation of remedies is not to remove 
 known causes, the result of the modification they produce in the 
 state of disease is dependent upon the relations of constituent 
 properties of the spirit, under the artificial state produced by 
 remedies, and it is to the chances of these relations that w* 
 
321 
 
 trust leading up to the events of recovery, extended disease, 
 or death. 
 
 34. But we observe that the general tendency under preter- 
 natural affection is to the recovery of health: this has given rise 
 to the " vis medicatrix naturae," which is produced by the same 
 properties naturally as those which determine the same event 
 under preternatural circumstances. It is by the series of causa- 
 tion which constitutes this tendency, that health is invariably re- 
 stored, under the operation of remedies which cure by indirect 
 processes. The immediate effect of remedies is to produce 
 disease: if health arises out of this disease, the properties which 
 determine it are not those of the external, whose invariable pro- 
 perty is to produce disease, but those which decide latent causa- 
 tion in a series, the termination of which is in health. 
 
 35. A particular indication of treatment is to remove a 
 known cause by a known remedy; or, when the cause is not 
 known, to employ a particular agent, which has been found in a 
 sufficient number of instances to be curative, without our being 
 able to assign the manner how, in a disease identified by such 
 symptoms: particular indications are founded upon precise 
 analogies. A general indication of treatment is to employ reme- 
 dies which have been found to succeed in cases analogous in some 
 respects. The chief object of medical inquiry is to obtain a par- 
 ticular, in exchange for a general indication of treatment (and 
 hence the chief advantage of a methodical nosology, by which 
 diseases are classed according to their resemblance) ; whether with 
 regard to that particular indication which is founded on a know- 
 ledge of causes, or to that tendency, which is ascertained, in a 
 sufficient number of instances, to determine the processes of causa- 
 tion towards the recovery of health. The attainment of this 
 object is the business of observation: when this object is not at- 
 tained, or perhaps attainable from defect of experience, or defect 
 of faculties, the treatment must be conducted according to the 
 general indication, the next object of which is, by increasing the 
 knowledge of facts, to multiply or improve the points of analogy. 
 When the indication of cure is no further particular, than that it 
 directs a change in the existing state of disease, we are left to 
 select our remedies from our experience of those which in general 
 accomplish most effectually this end; and, conformably with our 
 experience, in the absence of specific remedies, and remedies 
 directed to remove known causes, the method of changing the 
 condition of disease, with a view before explained the most fre- 
 quently successful, is by the repeated employment of purgative, 
 emetic or nauseating medicines, or by bleedings, issues, &c.; these 
 succeed in this end because their relations are general, or their 
 operation is upon seats which are the centres of many sympathies. 
 V 36. It has been observed that the cure of a disease requires 
 the continuance of remedies which affect or change its condition, 
 and this change is indicated completely to have taken place only 
 u u 
 
322 
 
 by tfie cessation of the symptoms of the disease. It is a point 01 
 nice discrimination, to decide how far remedies are to be urged 
 When the condition of disease appears to be subverted, so ais on 
 the one hand to subvert also the tendency among constituents, 
 which first produced it (or in other words to prevent a relapse) ; 
 and, on the other, id avoid the danger of deteriorated disease, 
 which may end in death, by the processes which succeed to the 
 continued employment of the remedy. This matter is exemplified 
 familiarly in syphilis; and the point of discrimination is to ad- 
 minister enough mercury to cure venereal without producing mer-' 
 Curial disease: the same or a greater nicety of discrimination is 
 required in the treatment of many chronic diseases. For the pur- 
 purposes of this distinction we must trust to our experience Irs 
 particular cures; as if squill and calomel should cure a dropsy, 
 which will return when the medicine is left off, we must consult 
 odr experience in order to judge what continuance of the preter- 
 natural, or remedial affection is sufficient, not only to remove the 
 present symptoms, but to subvert that tendency to dropsy which 
 first produced it, and may produce it again ; or how long the 
 remedy must be employed to produce a totally new predisposition : 
 our experience also in these cases must be consulted, in order to 
 decide how far, under certain states of constitution, remedies may 
 foe pushed, with this view of subverting diseased tendencies, with- 
 out risking the substitution of a new, and perhaps a worse disease. 
 37. To repeat: the basis of every treatment is the analogy of 
 disease, and the experience of the results of remedies. We say 
 experience of the analogy of disease, and experience of the effects 
 of remedies; but our experience in these respects is imperfect 
 or equivocal. If we were capable of experiencing the similitude 
 of diseases we should never be mistaken in theii* character ; but 
 we often are mistaken. We may experience a resemblance in certain 
 Symptoms, but different latent causes may be associated with a simi- 
 lar exhibition of certain symptoms; these causes are developed in 
 the progress of disease, and then we confess the inadequacy of our 
 experience. In strict truth, this which we call an experience of 
 the similitude of diseases is only an inference, or in part an in- 
 ference: we infer a similitude of the entire state of disease from 
 a sensible analogy in some circumstances. So also with respect 
 to our experience of the effects of remedies: we experience only 
 the succession of events; and disease frequently ceasing from 
 latent, spontaneous processes of causation, under the exhibition of 
 remedies, we infer that the remedies produce the cure because 
 the recovery of health succeeded to their employment. Hence it 
 is that so many remedies have obtained credit for curing diseases, 
 which, upon further trial, have been found to possess no such 
 power. There is only one way (rarely practicable) of guarding 
 against error in making these conclusions, and that is, not to admit 
 succession as the proof of causation, until the succession by its 
 frequency approaches td the invariable, upon which analogy an 
 
inference of causation may be allowed, in the manner and wkfa the 
 exceptions before more fully explained. 
 
 This analysis of the nature and cure of diseases has been at- 
 tempted in conformity with those doctrines of causation, the ap- 
 plication of which has been said to be universal. It is impossible 
 to make a view so complex, embracing so many topics, appear 
 simple, and at first sight intelligible. I have traced the processes 
 of nature in this sketch, with a minuteness which ou untried 
 ground can scarcely be exceeded. Nature is said by some to 
 be very simple in her operations: she is simple enough to one 
 who contemplates things in the gross; whose sum of philosophy 
 consists in stating results, without troubling himself about the 
 machinery by which they are accomplished. If this analysis of 
 disease should be reproached as obscure, I say the obscurity be- 
 longs to the subject. I wish it had been possible to make it clearer: 
 but if the same objects should be attempted by one who would 
 make this obscurity a reproach, he would rind it difficult to give 
 a readily intelligible account of them, though this subject alone 
 should be drawn out to the length of a respectable volume. 
 
 
 

325 
 
 SECTION V. 
 
 DEATH OF THE ORGANIC LIFE. 
 CHAP. I.- Death in Connexion with Disease. 
 
 1. BY the term " death" is implied a cessation of the 
 phenomena which characterize the state of life. It has been said 
 that life is distinguished by its preserving the cohesion of the 
 structures. This is to some extent true; yet we cannot estimate 
 the continuance of life by the preservation of the structures, for 
 their integrity remains many days after death. We must then 
 enumerate some other of the phenomena of life, by the cessation 
 of which the state of death might be distinguished. Without 
 waiting for the dissolution of the textures, we may say that death 
 has happened when respiration has ceased, and when the action of 
 the heart has ceased; when the blood, no longer in motion, has 
 coagulated in the heart and in its vessels; and when the tempera- 
 ture of the body is reduced to that of the medium by which it is 
 surrounded. It will scarcely be imagined that a man is not dead 
 when these things have taken place. Life is a state of properties 
 which produces phenomena before enumerated, and readily agreed 
 upon: death is a state of properties incapable of producing any 
 of those phenomena characteristic of life. 
 
 2. In a case, as of sudden, death, all the properties which 
 accomplished the phenomena of life still inhere with the subject, 
 or are involved in his structures: the change is one of combina- 
 tion, by which an elementary or separated state, has succeeded to 
 the formal state, of the properties which identified life. In what 
 the change consists we cannot specify; nor can we say with what 
 substances or properties those of life are related at the period of 
 this change, because our senses are not qualified to take cogni- 
 
326 
 
 jcancc of such objects: the most that we can do is to reason upon 
 this change on rules of analogy, which, if these rules are universal, 
 as has been assumed on physical proof of those of causation, are en- 
 titled to the same reliance in this, as in other subjects of inference. 
 
 3. Death happens either 
 
 1st, From defect or modification of those causes which main- 
 lain life, and which have been sketched in our physiology; or, 
 
 2nd, From the operation of certain related externals. 
 
 4. Of the causes which maintain life, the first to be spoken 
 of are those which constitute the living spirit. All that we can 
 say of these causes is, that in one particular state they produce 
 the phenomena of life and health; that if this state is modified, 
 they produce the phenomena of disease; that a further, or other 
 modification of them is followed by death. We have seen, in the 
 article on Disease, that the origin of every spontaneous modifica- 
 tion of the living state js in the properties of life. The spirit is 
 constituted by many properties, among which subsist certain rela- 
 jtions: from the relations between these properties, changes take 
 place in their combinations, which are progressively continued, or 
 suspended, and renewed, by the operation of an external, or main- 
 tained by consecutive effects, as those of the material occasional 
 .causes, of disease; or maintained by spiritual assimilation, &c. 
 As the first modification of the healthy spirit might originate from 
 relations in its own properties, so .it is probable that the pro- 
 gression might be continued in this spiritual department, until the 
 identity of it is so far changed, as to be incapable of assimilating a 
 state of properties productive of the phenomena of life. But, in 
 general, death is preceded by changes in the material alliances of 
 life, which might contribute more or less essentially towards this 
 event. The case which comes nearest to exemplify the occurrence 
 of deatti, by the exclusive change of the spiritual state, is perhaps 
 furnished in some of the forms of mortification incident to old 
 people; where death suddenly happens in a part while it is still 
 supplied with the same arterial blood as other parts, and where 
 the textures are not perceptibly more impaired. 
 
 5. Three conditions are required for the maintenance of life 
 in every seat: 1st, a healthy state of the principle of life; 2nd, 
 the integrity and fitness of the structures; 3rd, an adequate and 
 correct supply of well-formed arterial blood. As long as these 
 conditions are observed the state of life is maintained, and it con- 
 tinues until one or all of these conditions are infringed. 
 
 G. Death commonly happens through the medium of disease: 
 when death takes place suddenly and spontaneously, without pre- 
 vious disease, the difference is, that whereas in disease the changes 
 preparatory to death are indicated by symptoms; in death, with- 
 put disease, the preparatory changes do not produce symptoms, or 
 they are latent; in which latter case, death follows predisposition. 
 
 7. Disease and death agree in being modified states of life: 
 .but the state of disease is stjll productive of the phenomena o'f life; 
 
327 
 
 ifie principle assimilates, though a modified identity: the state of 
 death is one in which these phenomena cease, and cannot be re- 
 newed; this is the result of the series of changes which are at 
 first latent, or in the state of predisposition, then exhibiting symp- 
 toms, or constituting disease; then a further change being at- 
 tained, the state is that of death. 
 
 8. The history of disease is the history of death, np to that 
 point of the series in which the final change of disease into death 
 takes place. We can no more say, why predisposition should be- 
 come disease, than why disease should lapse into the state of 
 death. They are catenated processes of causation, the agents of 
 which are not objects of the senses. 
 
 9. The history of death begins with the history of disease. 
 The origin of disease has been said to be in latent properties of the 
 spirit, which determine that course of changes indicated in our 
 sketch of the nature of progressive causation. Accordingly, our 
 divisions of the modes of disease will furnish those of death, or 
 \vill exhibit the modes by which the conditions of life, just men- 
 tioned, are infringed. The origin of the spontaneous processes, 
 which terminate in death, is in the spirit: but death may take 
 place in a seat either, 
 
 1. From primary, or, 
 
 2. From secondary, disease. 
 
 10. Death happens from primary disease when changes take 
 place in the properties of the spirit belonging to the seat of death, 
 whether local or universal, the termination of which processes is 
 in an unassimilating state of life, without the influence either of a 
 modified state of the spirit in another seat, or of a modified con- 
 dition of the blood or structures. 
 
 11. Death happens from secondary disease, either directly or 
 indirectly: directly, as when the relation of a disease or of death 
 in a primary seat is, by the intercourse of vital properties, to im- 
 pair, and finally destroy, the assimilating life of a secondary seat; 
 indirectly, as when the relation which should subsist between, 
 the life of a seat and its fluid and structural alliances, its material 
 products, is impaired or wholly frustrated by the changes which 
 the quantity or constituents of these alliances have undergone, by 
 the previous operation of disease, either in the seat of death, or in 
 one which thus, indirectly, comes to be related with it. 
 
 12. 1. Death happening from primary disease exclusively, is 
 an occurrence, the possibility of which is conformable with our 
 general principles; but our experience of death furnishes us but 
 one apparent instance in which the existence of secondary disease 
 is not perceptible : that instance, before cited, is one of mortifica- 
 tion: as when, without previous pain or inflammation, a black spot 
 may appear upon some part of an extremity, perhaps it may be 
 discovered accidentally (this has happened) ; this spot is found to 
 have lost its sensibility, to have lost its characteristics of life. 
 From such a beginning the mortification spreads; and it appears 
 
328 
 
 to spread, as if the principle of life in this seat spontaneously be- 
 came extinct, and as if the structure of the part suffered no 
 change save that which might be imputed to the extinction of the 
 living principle. This is the only case which occurs to me, 
 arising out of our experience, in which death may be attributed to 
 exclusive change in the life of a seat, terminating in the cessation 
 of this principle; and even this case is not unexceptionable. If 
 may be argued against, by observing that latent preparatory 
 changes might have been going on in the structure of the blood- 
 vessels of the part. It will be observed, that their phenomena are 
 not those of a mere extinction of life, with preservation of a healthy 
 state of the organization : life, it will be urged, becomes univer- 
 sally extinct in every instance of death, yet we do not find that 
 the whole body immediately assumes the appearance presented by 
 a gangrenous state of the structures. The mortification also, it will 
 be observed, is a sloughing process; no such process supervenes 
 to death in other instances : half the integument of a foot may 
 slough away in three or four days, while the integrity of the same 
 textures may be preserved, in ordinary death, perhaps for weeks. 
 Hence it would appear, that if a long series of preparatory pro- 
 cesses did not take place in the structures of the blood-vessels 
 previous to death, these structures were peculiarly influenced 
 by the agency of life, previous to its extinction. It would remain 
 to discriminate whether such changes of the textures were merely 
 the effects of a tendency of the principle, which run its course of 
 disease, independently, to its final extinction; or whether its ten- 
 dency to extinction was affected, or in part produced, by the 
 re-agency of the condition of the structures: under these doubts, 
 we must say that we have no unequivocal example of death by 
 exclusive changes among the properties of life; that such a mode 
 of death is indicated by some of the phenomena of mortification : 
 at the same time, that the possibility of such a mode of death is 
 conformable with general principles. 
 
 13. Thus much may be said modestly, and with strict respect 
 to the evidence. But, it must be remarked also, in favour of this 
 mode of death (by exclusive spiritual causation), that although, in 
 the instances in which it might be supposed, it is not impossible 
 but the event may be assisted by the re-agency of a preternatural 
 condition of the fluid or structural alliances; yet, on the other hand, 
 it can rarely be proved, where these secondary states of the 
 materials are the most obvious, that they help in any degree the 
 extinction of the spirit; or that this latter does not run its own 
 course of change, independently of such supposed re-agents. 
 Thus, for example, suppose death to happen by phrenitis: the 
 secondary material effects of the primary conditions of the spirit 
 are turgescence of the blood-vessels, the effusion of patches of 
 lymph, perhaps rather more serum in the ventricles than ought to 
 be found in them, &c. I would ask what is the proof that these 
 secondary diseases, these material changes, contributed to the 
 
329 
 
 extinction of life? or what is the proof that the spiritual change 
 which began, may not proceed by that progressive causation de- 
 scribed, independently, to the termination of the series in death? 
 What is the proof that these perceptible phenomena were re-agents, 
 or in turn causes of change, to the spirit, rather than mere accom- 
 paniments? There is no positive proof, the state of phrenitis never 
 takes place without these phenomena ; but because a modified con- 
 dition of life necessarily produces these effects, it is not to be con- 
 cluded that these effects become causes, and in turn help to produce 
 the extinction of life, until the existence of such a relation is made 
 clear on other grounds. Such a relation, or something approaching 
 to it, is indicated : we know that, in inflammation, the throbbing of 
 the pain corresponds with the systoles of the heart; and hence we 
 conclude that the circulation may re-act upon a similar state of 
 disease: and we know that pressure upon the brain will kill (though 
 in fact this happens indirectly) where there is no previous disease; 
 and hence we conclude that effusion into the ventricles may be a 
 cause of death in phrenitis, as when the symptoms of this disease 
 are exchanged for those of apoplexy. But because we have proofs 
 that the impulse of blood into inflamed vessels will produce pain, 
 and that distention, under certain diseased states, will increase pain, 
 and that pressure upon the brain will kill ; it does not follow, when 
 these things happen as effects of other previous and progressive 
 disease, but that the finale of this progression, viz. death, might 
 take place without their assistance ; which is further proved by the 
 fact, that a disease of the brain of long standing, sometimes pro- 
 ducing convulsions, and finally delirium, and coma, followed by 
 death, has not been found on dissection to have been accompanied 
 with perceptible disease; on the contrary, the structure of the brain 
 has appeared natural, and its vessels preternaturally free from blood. 
 If it were worth while to push further a discussion which was de- 
 signed to shew only the manner in which our inference of death by 
 primary disease is capable of being considered and supported, it 
 may be remarked, that the re-agency of the circulation upon 
 disease, on the evidence just cited, is founded upon an assumed 
 extension of analogy. We experience that pain is increased, as in 
 whitlow, at each systole of the heart; this experience of ours re- 
 spects a relation between the circulation and sensibility, arid we 
 assume a similar relation with respect to the organic life. This is a 
 mere assumption: if it were investigated perhaps, the assumption 
 would be confirmed on other evidence ; there is no reason, a priori, 
 why the organic life should be disturbed in an inflamed seat by the 
 fulness of its vessels, or by the systole of the heart, unless such rea- 
 son should be furnished by a physiology which shews that such dis- 
 turbance might take place in consequence of the natural relation 
 subsisting between the quantity and the properties of the blood, 
 and a defined state of the textures, and the organic spirit. It is not 
 necessary to pursue this matter further at present, we may hereafter 
 x x 
 
330 
 
 have some other topics which may require to Ue connected with the 
 considerations here hinted at. 
 
 14. Death is either local or universal : mortification and 
 ulceration both, exemplify local death. Universal death is never 
 known to take place, unless there is a seat of death in a functional 
 organ, whether originating, or produced secondarily, in such organ. 
 The organic life of a functional organ is commonly made to cease by 
 the impairment of the function (in which case the death of the organ 
 is produced in a way common to every other part), and not by the 
 primary extinction of its own organic life. Not however to antici- 
 pate the order we have proposed, we must proceed to illustrate our 
 other mode of death, viz. by secondary disease. 
 
 15. 2. Secondary disease produces death, directly or indirect- 
 ly: directly, as by relations of spiritual properties; indirectly, as by 
 the changes of the material alliances in the seat of death. 
 
 16. Death produced directly by secondary disease is of two 
 kinds: 1st, when the secondary seat of disease (or death) holds with 
 respect to the primary a relation of the regular dependent kind; 
 2nd, when a new relation is opened between the spiritual properties 
 of seats, by disturbance or change of these properties in one of 
 them, where no previous natural relation subsisted. 
 
 17. The first class is illustrated in all those organs to which a 
 dependence has been assigned. Thus a disease, or injury which im- 
 paired or destroyed the life of the brain, would produce secondary 
 death of the lungs; because the influence of the brain, dependent 
 upon a healthy (or certain) state of its life, is necessary to respiration. 
 Thus also, if an influence from the brain or spinal marrow is 
 necessary to the life of the heart, the death of the heart would suc- 
 ceed to a certain disturbance or destruction of the life of the brain 
 or spinal marrow ; and the death of a secondary seat would happen 
 in consequence of the same relation, in any other case in which such 
 relation can be proved to exist. 
 
 IB. The second class, or those cases in which secondary death 
 is directly produced by primary disease, in seats having no natural 
 dependent relation, is exemplified the most unequivocally in cases 
 of injury, and frequently enough in cases of spontaneous disease. 
 Thus the irritation (for the sake of a name) produced by a fractured 
 leg may be extended to the heart, and raise its actions to 140 in a 
 minute; this happens from direct relation between vital properties: 
 finally, thf heart in consequence of such injury, may cease to act at 
 all. In this case a new relation is opened where there was before no 
 regular dependence, except that common one for the supply of 
 arterial blood; for the whole leg might be cut off, and the heart 
 will not die, which it would do, if there were any relation of de- 
 pendence. To the same class belong most of the examples of the 
 sympathies, in which, as before sufficiently insisted upon, secondary 
 is produced by primary disease, and consequent death, in seats hold- 
 ing no natural relation. 
 
381 
 
 19. I have applied the term " death," in these cases, in com- 
 pliance with common language. When the heart ceases to act, this 
 has been called the death of the heart ; the same of the brain, when 
 the phenomena of life and health, which are imputed to it, no longer 
 occur; and the same of the lungs, when respiration ceases. I would 
 be understood (for it is a point of doctrine of importance) that these 
 are not instances of the causation of death of the organic life, but 
 of suspension, or extinction of function; producing consecutively, 
 by a relation common to all parts, the death of the organic life. 
 Death, or extinction of the organic assimilating life, in one seat, can 
 never produce directly death of the organic life in another; for the 
 organic life, as has been satisfactorily proved, is every where depen- 
 dent only upon its own existence, and upon the supply of blood. 
 Hence, if one leg were to die, the organic life on one side the line 
 of mortification would not be at all affected by the death of the leg, 
 provided it were itself a correct assimilating principle, and was sup- 
 plied with arterial blood. The sympathies of disease in the organic 
 life may lead to processes of causation in related seats, which may 
 terminate in death, in such secondary seats: but this would happen 
 from communication of the same properties, whether life were 
 afterwards preserved or extinct, in the primary seat; for relations of 
 life cease, when the change of life into death has happened; and as 
 no phenomena can then be produced by relation of the primary with 
 a secondary seat, except loss of function in the cases of that which 
 has been called regular dependent life, so it follows that the organic 
 life of one seat cannot suffer by the death of the organic life of 
 another, since the organic life is never dependent for the constitu- 
 tion of its principle upon another seat, but lives by assimilation. 
 
 20. Hence, death of the organic life in one seat never pro- 
 duces death of the organic life of another directly; but it may pro- 
 duce loss of function directly, as in the instances mentioned : as, if 
 the brain should die, respiration would cease, because respiration is 
 dependent upon the life of the brain; or, if the spinal marrow 
 should die (if this is a true relation of the kind), the action of the 
 heart would cease ; but such death of a primary seat, producing, 
 first, loss of function in a secondary seat, directly, and then universal 
 death indirectly, produces universal death, or death of the organic 
 life, by the relation which functions have with the formation or cir- 
 culation of the blood, upon which the existence of the assimilating 
 life in every sphere depends. 
 
 21. Death is, as before remarked, produced by secondary 
 disease, directly; and the modes of death, according to causation 
 here, are the same as the modes of the extinction of function, viz. by 
 addition or subtraction of properties: as the properties are not 
 objects of the senses, we cannot determine by analysis which of these 
 modes obtains in the several examples. But, in agreement with a 
 loose rule of analogy, before proposed, we should be inclined to in- 
 fer, that death happens by privation of properties, where it succeeds 
 
33*2 
 
 in a secondary, to death of a primary seat, between which there 
 subsisted a natural relation of dependence; and that the mode was 
 that of addition of properties, in cases of secondary disease, termi- 
 nating in death, produced directly by primary disease in seats which 
 acknowledged no natural dependent relation. 
 
 22. Those effects of primary disease which consist in modifica- 
 tion, or preternatural formation of substances, allied or related with 
 the principle of life, produce local death in or near the seat of such 
 effects, either by direct relation with the life of such seat, as when 
 a disease of a bone, perhaps a dead portion of a bone, produces or 
 maintains ulceration (which is one kind of death) of the contiguous 
 parts, or by the influence of such effects upon the circulation, as 
 when a tumour, together with the adjoining substances, sloughs from 
 an interrupted supply of blood, caused by the pressure of a foreign 
 growth ; or as when, by long processes of disease, extreme vessels 
 give way, and the life of the part becomes extinct, because the cir- 
 culation has ceased. The examples which fall under this class arc 
 not very numerous. 
 
 23. Secondary indirect disease produces universal death by 
 influence upon the blood and circulation, upon which the existence 
 of the diffused spirit depends. Secondary, indirect, disease operates 
 by this medium in two ways: Jst, by producing secondary direct 
 disease, which to produce death is commonly related with a 
 functional organ, upon which life depends, and upon which life de- 
 pends in no other way than by the importance of this function with 
 respect to the blood; 2nd, by preventing the adequate supply of 
 blood to the whole system, with or without any mediate relation, 
 with a function or organ, subservient to the formation and circula- 
 tion of the blood. 
 
 24. The first is illustrated in the cases of death produced by 
 occasional material disease; as when death takes place from irrita- 
 tion, as from that of a stone in the kidney, a diseased bone, &c.; 
 in these cases, these material effects of primary disease affect, 
 impair, and finally destroy the action of some functional organ, as 
 of the heart, in consequence of which universal death succeeds. 
 
 25. The second is exemplified when death happens from the 
 pressure of a tumour upon the trachea, or when death is produced 
 by spontaneous hemorrhage, as by the bursting of an axillary, or 
 iliac aneurism. 
 
 26. This classification includes nearly all the possible modes 
 of local, or universal death, according to the relations before 
 sketched. The inference, that disease in one seat produces univer 
 sal death by relation with a functional organ, which organ is related 
 with diffused life through the medium of the blood, is founded upon 
 the fact that a local disease never produces death until the functions 
 connected with the blood have ceased to be performed. In other 
 words, all the processes of organic life, as the spiritual assimilation, 
 the secretions, &c. do not cease until the heart has ceased to 
 
333 
 
 circulate blood. The spirit may be universally modified by the 
 same original disease, as that which finally produces death ; and 
 this modification is expressed in the changes of its phenomena, or 
 in symptoms: but the functions subservient to organic life by their 
 relation with the blood, are first impaired, and cease; and then the 
 diffused assimilating life becomes extinct. This is the usual order, 
 with but few exceptions, which belong to the examples of secondary 
 direct disease by communicated properties, possibly terminating 
 their progressive causation in death. 
 
334 
 
 CHAP. II. Death produced by External Causes. 
 
 1. THE modes by which external agents (comprised 
 chiefly in poisons and mechanical injuries) produce death are in- 
 cluded in those which have been assigned as the modes of disease. 
 The difference is, that whereas the origin of death by disease is 
 in progressive causation, predisposition, &c. ; the origin of death 
 by externals is to be considered at the period of their exhibition 
 or infliction. It belongs to specific inquiry to trace the particular 
 relations of the several poisons in the mineral, vegetable, and ani- 
 mal departments. The phenomena of external injuries, also, 
 inasmuch as they differ from those of spontaneous disease, form 
 the subject of a specific analysis. But the general conformity of 
 both with the preceding modes and divisions may be briefly shewn. 
 2. Poisons either destroy life by properties directly related 
 with the principle, so as to render it, by their combination, an 
 unassimilating identity; or else their relation with the diffused 
 organic spirit is not direct, but the vitality of this spirit is de- 
 stroyed by their agency through the medium of a primary influ- 
 ence upon the properties engaged in a function, or upon the 
 material alliances. These are the modes of the operation of 
 poisons, which, it will be seen, are those of disease, and concern- 
 ing which therefore it no more belongs to this place to be particu- 
 lar than to trace the history and varieties, respectively, of every 
 disease which may terminate in death. 
 
 3. Injuries of the mechanical kind, from external causes, 
 may produce either local or universal death. The phenomena 
 in these cases are also reducible to the classes which have 
 been assigned to those of disease. Injuries producing universal 
 death are commonly inflicted upon a functional organ, when death 
 immediately succeeds to such injuries, as upon the brain, heart, 
 spinal marrow, lungs, or great blood-vessels, &c. In these 
 cases, such injuries kill by impairing or destroying the function of 
 the organ on which they are inflicted, or of one holding with it a 
 natural relation of the dependent kind. But injuries sometimes 
 produce speedily universal death, which are inflicted upon seats 
 which are not necessary to the life of the rest of the body ; or, if 
 
335 
 
 necessary, are not so immediately essential but that life may for a 
 time be preserved without them. Thus, a severe injury of a leg 
 may produce death in twenty-four hours, and a wound of the sto- 
 mach or bowels may produce death in the same time: in the former 
 case, death is produced by injury of a part which has no function 
 upon which the life of the system depends; in the latter case, the 
 injury takes place in an organ which has a function necessary to life ; 
 but the exercise of this function, viz. digestion, may be suspended 
 several days without occasioning death. The consecutive processes 
 which follow these injuries are merely additional instances of secon- 
 dary disease, terminating in death. 
 
 4. The only question or difficulty which I feel disposed to 
 suggest, with respect to mechanical injuries, is concerning the mode 
 in which they produce the phenomena assignable only to spiritual 
 change. We find that the point of a needle applied to the skin 
 with a slight pressure, so as not to penetrate the skin, produces pain : 
 we find that a bullet going through the brain will immediately 
 destroy its function, as a consequence of which universal death 
 succeeds. And we observe with respect to these phenomena that 
 any mechanical agent, which produces the same mechanical effect 
 upon the structure, will produce the same effect upon the properties 
 of life. Hence, the relation is not with any peculiar properties 
 belonging to the instrument which inflicts the injury, but with the 
 effect of the injury, or with the condition of the textures, &c. 
 which the injury has produced, and the capability to produce 
 which may be common to many agents, very different in their gene- 
 ral character. To reduce the question, we will ask why the life of 
 a part suffers any change not imputable to loss of blood, from a 
 mere solution of continuity in the structures, as by the thrust of a 
 small-suord? 
 
 5. The palpable effect of such injury is to separate parts which 
 were before united, in consequence of which inflammation, with its 
 accompaniments, pain, increased heat, &c. supervene. The first 
 effect is a mechanical separation of a structure before united ; the 
 subsequent phenomena are those which can be produced only by 
 spiritual change. It is obvious that the spirit, or the imperceptible 
 properties allied with the structures, would suffer no change by the 
 passage of a small-sword through the sphere in which they exist, any 
 more than the air or the still grosser fluid, water; unless indeed the 
 agent possessed properties related with the spirit, which may affect 
 it independently of the mechanical injury, which, for the reason 
 above assigned, is not the case. The only conditions of the main- 
 tenance of the identity of the living principle are, the existence of 
 this principle, and the presence of blood. Now the principle lives in 
 the separated surfaces, and in them may be supplied with blood. If 
 then the principle suffers that change which constitutes one of 
 disease, it suffers this change from one of three effects of the in- 
 fliction of the injury. 
 
336 
 
 1st, The spirit residing in these surfaces receives a modified 
 supply of blood, as by the general injury, the compression, &c. 
 which the vessels must sustain by a breach in a structure before 
 continuous; or, 
 
 2nd, The mechanical change of the structure must directly pro- 
 duce a change in the condition of the spirit; or, 
 
 3rd, The spirit is directly modified by the confusion, or mixture 
 of spiritual properties, which before held distinct spheres. 
 
 1. It is probable that the disordered circulation, necessary to a 
 surface produced by mechanical separation, may (as the circulation 
 is every where so intimately connected with life) contribute to pro- 
 duce that change of the spirit upon which the consecutive pheno- 
 mena of the injury depend. 
 
 2. It has. been shewn in the chapter, " Relations between Vital 
 and Mechanical Properties," that a mechanical agent can have no 
 direct relation with life. Hence, we can assign no agency in these 
 phenomena to mere mechanical influence, except that mediate one 
 implied in our 1st and 3rd alternatives. 
 
 8. The sphere of life in every seat is maintained by the alliance 
 of the spiritual properties with the organic particles of such seat. 
 Hence, if the organic particles are disturbed or displaced, the 
 spiritual properties suffer a corresponding disturbance, and those 
 which should occupy distinct spheres become mixed. Of the ten- 
 dency of spiritual properties of one seat to modify those of another, 
 we have seen enough in the preceding pages. The modes in which 
 such modification may be produced in the present instances are, 1st, 
 by direct change in the life of the separated surface, by union with 
 heterogeneous properties; 2nd, by indirect change, by disturbed 
 relation between the life and the nutrient material of such seat. 
 
 6. According to the nearest and most frequent analogies, I 
 should say that mechanical injuries produce their effects upon the 
 principle of life, commonly, by the confusion of the life which should 
 hold distinct spheres, in consequence of its alliance with the matter 
 which is disturbed merely by a mechanical relation; and by the 
 change which life suffers by mechanical injury of blood-vessels, the 
 state of which life depending upon a regulated supply of blood, 
 suffers also a change, in agreement with the preternatural relation 
 thus mechanically occasioned. From the suddenness with which 
 life is affected by mechanical injuries, it appears as if the spirit 
 suffered most commonly in the way described, without the inter- 
 mediate relation of a disordered circulation, as in cases of wounds, 
 and more especially those happening in the brain, spinal marrow, or 
 nerves. Indeed, from some of these instances, a pretty unequivocal 
 argument might be deduced in favour of this mode of the effects of 
 mechanical injuries; but it is sufficient to have suggested these 
 modes, and to add, that by these modes a state is established which 
 produces further effects, by processes, generally analogous to those 
 of spontaneous disease. 
 
337 
 
 CHAP. III. General Nature of Death of the Organic Life. 
 
 1. WE have spoken in our preceding sections of the 
 manner in which the spirit lives; in this, we have hitherto considered 
 the mode by which it dies: there is only one further stage in in its 
 history, viz. to say, if we can, what becomes of this spirit, our old 
 acquaintance, after it is dead? 
 
 2. The question of what becomes of life at the time of death ? 
 is answered by saying, what becomes of it during life: for the 
 spirit is perpetually dying: it lives by assimilation, or is maintained 
 by succession, or by a perpetual renovation from its elements ; the life 
 which exists at one point of time, resembles, but is not identically 
 the life which existed in a preceding minute. Life exists, and im- 
 mediately changes its form, enduring no longer than while it unites 
 its own elements from earth and air, existing in the nutrient ma- 
 terial with which it is related. Life is, renews itself, and dies. If 
 the life which is present could support a fixed or permanent state, 
 the function which supplies it with air, as a supporter of life, might 
 be suspended, and the living form be still preserved; and the same 
 of the other supporter, containing elements from the earth, viz. food, 
 which might also be withheld : for a principle which is not per- 
 petually passing away, requires no supporters for its perpetual 
 renovation. 
 
 3. One difference between death of the spirit, during the con- 
 tinuance of life, and its final death, is, that the spirit during the 
 living state repeats itself from its elements, before it dies: finui 
 death happens from defect of such repetition. Another difference 
 is, that in final death the spirit, previous to its extinction, is com- 
 monly rendered a modified identity by disease, which is not the 
 identity it preserves when it repeats itself from its elements. This 
 difference may affect the fate of the properties of life in the two 
 instances, disposing them to different relations; but we cannot say 
 in what respects their fates, respectively, may on this account be 
 affected. But this difference does not obtain in the cases of final 
 death, from sudden defect of a supporter of life, as in cases of 
 death by hanging, drowning, hemorrhage, &c. in which examples 
 the spirit was well disposed to assimilate a healthy identity which 
 Y Y 
 
333 
 
 fails from defect of its constituents, which should be furnished by 
 the material. 
 
 4. According to this account, life exists first informally in'food 
 and in air; food is converted by the preparatory organs into blood, 
 which receives from the lungs the addition of air; still life exists in 
 blood, as in the earth and air, informally, though it is in this state 
 prepared for the operation of another agent : this agent is life; so 
 that life exists in blood informally, its elements are then united by 
 life, and then it becomes informal again. Our present question is, 
 what becomes of it? 
 
 5. It is obvious that, in reply to this question, we cannot cite 
 proofs. We have said that life no sooner is, than it becomes infor- 
 mal: we must suppose either that it becomes informal, or that it 
 escapes from its sphere in every seat, and, preserving its form, exists 
 as life in the atmosphere; if it retains its sphere in the textures, then 
 it is necessary that its form must be changed, it would otherwise 
 continue to produce its phenomena, and would not require the means 
 of renovation. That life may escape from the body and preserve 
 its form, is a proposition which cannot be refuted ; at the same time, 
 we are not obliged to refute it, because no argument can be cited 
 for its support. The grossest absurdities which imagination can 
 suggest frequently do not .admit of refutation; we scarcely think 
 ourselves bound to prove them false: we are excused the attempt 
 at refutation in every case in which the proposition is supported 
 neither by experience nor by analogy. But if the life of an animal 
 should preserve its form after escaping from the body, it is of very 
 little use ; at least, we can have no idea of its use or agency, for it is 
 not capable of the phenomena of life which are distinguished or 
 identified only by their relation with the body ; and, therefore, in 
 regard to the phenomena of the living state, it may as well be in- 
 formal. The properties of small-pox may exist in the atmosphere 
 without being allied with matter, and preserve their animal form. 
 If the properties of the spirit of a man did the same, they would 
 neither cf them be capable of their characteristic phenomena, which 
 are relative: the former, with animals disposed for their operation ; 
 the latter, with substances also necessary to the effects by which 
 alone their existence can be inferred. If it be said that an organic 
 spirit, or any spiritual form, may perpetuate its influence by alliance 
 with new animal textures, by a sort of metempsychosis; it may be 
 answered, it is not likely that it should either form structures for 
 itself from elementary materials, or ally itself with structures pre- 
 viously formed, seeing that its palpable tendency was to separate 
 from the organized fabric with which it was actually allied, and in 
 connexion with which it was assimilated. That life, during the 
 living state, which is the same in this respect as the dead, passes 
 away from the body still preserving its form, appears to be a pro- 
 position without proof, and consequently is not to be considered; 
 and that life, becoming informal, then escapes from the textures, is 
 equally without proof. There remains, then, only one other alterna- 
 
339 
 
 tive, viz. that life, becoming informal, allies itself with the textures, 
 and suffers changes, in agreement with relations in which the tex- 
 tures or their constituents are concerned. 
 
 6. If any arguments may be cited in favour of this proposition, 
 they also will be short of proof, although we may perhaps say, that 
 the proposition is indicated by the following considerations: 1st, 
 elementary life has a natural relation or affiuify with the material of 
 the structure; it exists in a state of combination in the blood, and 
 requires nothing less than the operation of formal life to dissolve 
 this union; 2nd, the structures of every animal are found to contain 
 elementary life, and furnish it to plants, and to other animals. 
 Upon the first of these considerations chiefly, we may say, it is indi- 
 cated that life, when it becomes informal, unites with the organic 
 substances and materials from which it was first produced, and 
 among which it lived. Presuming, then, upon this alternative, 
 merely as one which has been said to be indicated, or which is per- 
 haps better supported than any other, the processes of the forma- 
 tion and extinction of life may be thus described. Life existing 
 formally, pervading the structures, unites its own elements, which 
 exist informally in the nutrient material. The life thus formed 
 cannot endure: and as its change or extinction cannot happen from 
 its own causes, which must be those of constitution (except indeed by 
 an internal causation of which there are no proofs), so it is necessary 
 that the conversion of the living spirit into informal life must hap- 
 pen by relation with some causes existing in its sphere. These 
 causes can be no other than those belonging to the material wbioh 
 life pervades; and the decomposition of the living, into the informal 
 spirit, happens by this agency, which must be one of affinity: thig 
 circumstance furnishes additional grounds of indication, that the 
 informal life still resides with the material fabric; which it must do, 
 unless additional acts of causatiou take place, of which we are 
 wholly destitute of proofs. 
 
 7. But although the structures of one animal will maintain the 
 life of another, they will not maintain the life of the animal to which 
 they belong. In other words, an animal may die in four or five 
 days for want of food, although all the life which has been con- 
 sumed in that time still resides with his structures. The death of 
 an animal, under these circumstances, may happen from a deficiency 
 of blood, which is a consequence of starvation; and this deficiency 
 may, it is said, be related with the extinction of life, either in respect 
 to the quantity or the quality of the blood. A sufficient quantity 
 of blood has been supposed necessary, in order to preserve a certain 
 distension, an orgasm, as it is phrased by those who substitute 
 words for meaning, a mechanical fitness, &c. Without disputing 
 the general efficacy of this orgasm, or mechanical distention, &c. 
 it is sufficient to remark, that starvation does not produce death in 
 this way; for the quantity of blood made in four days is not equal 
 to 80 ounces, which may be lost by a man within 24 hours, and his 
 life be nevertheless preserved. We must then adopt the other al- 
 
340 
 
 ternative, and say that an animal dies from starvation in the same 
 way as for want of air, viz. by the privation of a supporter of life, 
 by defect of elementary life, with however this difference, that a 
 Jarger sum of the elements of life from earth, compared with their 
 consumption, exist in the blood than of those from air; and conse- 
 quently an animal will, for a considerable time, sustain the priva- 
 tion of food, but requires incessnntly the renewal of atmospherical 
 air. But our present question is, how happens it that an animal dies 
 from defect of the external supporters of life (seeing that they are 
 only elementary till life makes them formal), when elementary or 
 informal life must every where abound ; and existing in the spheres, 
 is subject to the operation, of the living principle? 
 
 8. The reason why the living principle does convert elemen- 
 tary into formal life in one instance, and not in another, is, that the 
 informal life of the blood is fitted for the relation with the formal 
 life which assimilates it, by the series of processes performed by the 
 preparatory organs; and the life which was elementary in the 
 blood, having become formal, again becomes elementary in conse- 
 quence of its holding a new iclation with surrounding agents; and 
 with this informal state of life the living spirit does not hold, as 
 in the case of that residing in the blood, the relation by which it is 
 assimilated. The only terms upon which the life which has been 
 formal, and has become elementary, can again be converted into 
 life are that the new combinations of it should be superseded by the 
 influence of preparatory organs, and that it should again be reduced 
 to the state of it in respect to the living spirit, in which it existed in 
 blood. So perfect is the adaptation of the preparatory organs to 
 the living principle, that no animal can be supported by means of 
 nutrition which have not passed through the organs subservient to 
 this end ; and although animals of every variety and species, and 
 perhaps vegetables, also, may be fed with a common material, yet 
 each, from the agreement between the preparatory functions and the 
 living principle, takes only those constituents which make up his 
 own identity, and hence the uniformity of their several characters is 
 preserved. 
 
 9. We observe that the organic substances of one animal 
 furnish to the life of another those elements only which are derived 
 from the earth. In other words, the supply of external air is just as 
 necessary to the life of an animal whose food consists of the organic 
 substances which have before been the seat of animal life, as to that 
 of one whose food consists of vegetables. If, then, the life which 
 has become informal in one animal helps to constitute the life of 
 another, the elements from earth are adopted for this purpose, 
 while those of air (which must also exist in the same substances) 
 are obtained from without. This is a circumstance which may be 
 urged in objection to the theory which supposes that life, becoming 
 informal, passes into the surrounding substances, and again con- 
 tributes to identify the life of another animal, into which these sub- 
 stances might pass. But this objection may be obviated or rcu- 
 
341 
 
 dered questionable, by the possible relations of the preparatory 
 organs, which may be to separate from food particles which con- 
 tain only one elementary part of life ; and the relation may be with 
 a certain quantum of these elements, leaving the excrementitious 
 matter still possessed of elementary life; while the other part of 
 elementary life, viz. that derived from air, not being related with 
 the preparatory organs, follows the fate of its other combinations; 
 and consequently these elements, not being received as consti- 
 tuents of blood, require to be furnished from the atmosphere. It 
 must be confessed, that on these relations we can at best speculate 
 but loosely; and their suggestion is rather with a view to future 
 investigations, than intended, upon such weak evidence, to chal- 
 lenge belief. 
 
 10. The state of death is an informal state of life: certain 
 properties concurred as causes to constitute the living state; as 
 long as the relations of these causes are uninterrupted, the living 
 state is preserved. But there is a tendency in these causes, with 
 tlie help of externals, to interrupt or change their relations ; their 
 concurrence to form the living state no longer obtains ; and the 
 properties which before formed life are engaged in new alliances, 
 and contribute to produce new phenomena, in connexion with the 
 new existences with which a new relation is opened. We cannot 
 trace minutely the further history of the respective causes which 
 once made the living state. We can only observe generally of 
 them, that the constituents of the living body of one animal in 
 time revert to something like the state of life which has already 
 been broken upon. The remains of an animal are either taken as 
 food by another, and then by a short process contribute to the 
 composition of such other animal;* or else they are consigned to 
 the earth, where they perhaps again contribute to animal life, 
 working here darkly, or remaining at rest, held by the force of 
 existing relations, and in the lapse of ages, perhaps by some acci- 
 dent come again to play a part in the sensible world ; or they pass 
 through a vegetable form, and from this are perhaps again assimi- 
 lated by animals. Whether there are instances of decomposition 
 so complete, that the causes which have once supported animal 
 life are wholly indisposed to enter into this state again, or contri- 
 bute to it in any shape; whether they can form alliances which no 
 possible change in the relations of the world may dissolve ; is a 
 question not easily settled, and the affirmative of which it is 
 scarcely consistent with analogy t suppose. 
 
 li. We observe that the remains of animals are consigned to 
 the earth, perhaps many feet below its surface; here they supply 
 or originate other forms of life. The auimals thus produced live 
 
 * This is the only possible mode of spiritual translation: and, according 
 to it, the identity of the spirit of a dead animal is not preserved ; for as the ani- 
 mal receiving such properties lives by assimilation, so the translated spiritual 
 properties are only causes which concur to maintain a prwiout nature, no more 
 of them being engaged tbau are ucccssary to this cud. 
 
342 
 
 in a situation which excludes the atmospheric air, or at least the 
 animals from whom they are derived could not exist in such a 
 situation, for want of air. Is it that there are animals who are 
 capable of separating from the remains of others the elements hoth 
 of earth and air which have passed into their organization, when 
 life became informal; or is it that a scanty proportion of air 
 penetrates deep into the earth, and suffices to afford the elements 
 obtained from this source, necessary to such forms of life? This 
 latter solution will be preferred, though it is not free from a con- 
 tradiction, which it is hardly worth while to state. 
 
 12. So far as we are capable of observing, one law appears 
 universal in the translation of life and organic particles, viz. that 
 if the causes of the living state of one animal live again in ano- 
 ther, they live, not according to their own nature, but according 
 to that of the new animal which they help to form, and which pre- 
 serves his identity under any variety of the means of nutrition, 
 provided they are to him means of nutrition; that is, he takes out 
 of them only himself. 
 
343 
 
 INDEX. 
 
 ABSORPTION, perpetual, of the solids 
 
 with respect to assimilation and growth 
 
 additional difficuties concerning 
 
 and the power of aggregation, prevail in succession 
 
 - manner of, with respect to properties of the spirit 
 
 Absorbents, Chap. VI. 
 
 analysis of function oif 
 
 mode of circulation of 
 
 Affinity, simple increase, by a causation of 
 
 of spirit with matter 
 
 general efficacy of " 
 
 of spirit with matter 
 
 Agreement, universal, to what attributed 
 
 B 
 
 Belief, three modes of acquiring ' - 
 
 of things present, first mode of acquiring 
 
 . " second mode of acquiring 
 
 things verified by the causes of . 
 
 Blood in the ovum, formation of ' 
 
 , . no t by atmospherical oxygenation 
 
 privation of oxygen, makes the colour of, darker 
 
 combination of agencies, necessary to the formation of 
 
 oxygenation of, in the ovum 
 
 Relations of, in its vessels, &c. Section III. 
 
 Formation of, Chap. I. 
 
 indication for inquiry, concerning formation of 
 
 Arterial Chap. III. 
 
 formation of 
 
 Relation of, with the heart, Chap. IV. 
 
 other relations of, Chap. V. 
 
 general objects of 
 
 minute relations of, as a material of nutrition 
 
 conversion of arterial into venous 
 
344 
 
 Causation, Chap. II. 
 
 grounds of ,examined in the departments of nature and of art 17 
 
 exemplified in the department of nature 18 
 
 in elements, same as in compound substances as 
 
 necessary in all instances 19 
 
 proved by experience and analogy 19 
 
 Cause and effect, definition of the terms 20 
 
 acts only by supplying itself 20 
 
 Cause, difference between a single cause, and the effect, is made by 
 
 other causes 20 
 
 Cautes, individually, different from their effects 21 
 
 '- operate by supplying their own existence 21 
 
 in producing effects are only disguised 21 
 
 produce the relations of causes and effects 21 
 
 either disguised or recognized in effects 21 
 
 distinguished from associations 21 
 
 and connexions, respective tests of 22 
 
 relations between 22 
 
 Causation, objection to doctrine of 22 
 
 Causes, remote indicated 25 
 
 efficacy of 23 
 
 difficulties with respect to 24 
 
 participation of effects in remote . 24 
 
 difficulty of their limitation 25 
 
 and associations distinguished 30 
 
 __ __ . 3j 
 
 Causation implies necessary dependence 31 
 
 furnishes the only example of necessity 31 
 
 Causes, virtue of, to produce effects 32 
 
 why necessary to produce effects 32 
 
 mode of producing effects 32 
 
 a literal first cause precluded by the axiom, " ex nihilo," &c. 37 
 produce order and adaptation 4t> 
 
 - i independently of intelligence 47 
 
 Causation among properties of the ovum loo 
 
 Change, primitive, spontaneous, is with vital properties - 154 
 
 producible by foreign chymicals 154 
 
 Connexion, necessary testimony of 1 1 
 
 Connexions, frequent, inference founded on 11 
 
 Contractilities, effects of causation among spiritual properties 123 
 
 Creation, origin of the materials of 37 
 
 . . not in mere intellect 38 
 
 opposing difficulties concerning, suggested 38 
 
 appeal to experience with respect to 39 
 
 . respects the forms of things which before existed S9 
 
 D 
 
 Death of the organic life, Section V. 325 
 
 in connexion with disease, Chap. I. 
 
 analysis of 326 
 
 327 
 
 328 
 
 329 
 
 230 
 
 331 
 _ _. 332 
 _ _ 333 
 
 Death produced by external causes, Chap. II. 
 
 external causes of -' 334 
 
 manner of, by external causes 335 
 
345 
 
 Death, subdivision of modes of by external causes -^ 
 
 of the organic life, general nature of, Chap. HI. 
 
 change of life into S37 
 
 informal state of life 338 
 
 fate of the properties of life, converted into 339 
 
 _ 340 
 
 341 
 
 __ 342 
 Deluge, synchronous universality of, not physically proved 305 
 
 106 
 Design, models of, precede the designing capacity 42 
 
 constituted by causes different from itself 43 
 
 Differentials, sexual, doctrines of 100 
 
 101 
 
 102 
 
 Disease, General nature of, Section IV. Chap. I. 261 
 
 origin of, according to causation 261 
 
 and health, definition of 261 
 
 _ _ 262 
 
 classification of 263 
 
 example of 263 
 
 . analysis of , 264 
 
 according to causation f 65 
 
 analysis of spontaneous origin of 266 
 
 _- 267 
 
 . - ' . 268 
 
 269 
 
 270 
 
 _ . 271 
 
 272 
 
 Disease, origin of, in one seat, Chap. II. 273 
 
 _ . analysis of 27S 
 
 274 
 
 275 
 
 _ 276 
 is spiritual 276 
 
 277 
 
 general nature of disease of the spirit, Chap. III. 278 
 
 . analysis of 278 
 
 - 279 
 
 280 
 
 * *~m liOl 
 
 282 
 
 283 
 
 . of the three classes of vital properties, Chap. IV. 284 
 
 .. analysis of - - 284 
 
 285 
 
 286 
 
 causes of, grounds of inferring the 286 
 
 287 
 
 . related, general nature of, Chap. V. 288 
 
 . - analysis of 888 
 
 289 
 
 290 
 
 291 
 
 S9J 
 
 ?93 
 
 *- J94 
 
 295 
 
 *- t96 
 
 Z Z 
 
346 
 
 Pe 
 
 Disease, related, analysis of general nature of 297 
 
 298 
 
 899 
 
 , P. 300 
 
 301 
 302 
 
 summary of 303 
 
 304 
 
 ~ 305 
 
 E 
 
 Effects, produced by more than one cause 20 
 
 and therefore all things 21 
 
 Effect, no new production 21 
 
 Effects, limitation of arbitrary gl 
 
 - - complexity of apparently single 33 
 
 Effect, identity of, requires identity of causes 34 
 
 the cause always exists in the 35 
 
 Evidence, general division of 12 
 
 probable, definition of its grades 12 
 
 designation of the several kinds of 13 
 
 . object of seeking 13 
 
 Existence, of a thing, produced by something different from itself 17 
 
 F 
 
 Foetus, growth of, not a development of miniature organization 89 
 
 by agreement of properties of life 89 
 
 . summary account of 89 
 
 Forms, new, two modes of the production of 33 
 
 Functions, organic, origin of 172 
 
 173 
 174 
 
 . division of life, with respect to _ 175 
 
 ~ 176 
 
 G 
 
 Growth, Chap. III. 131 
 
 . dependences of 131 
 
 relations engaged in 132 
 
 133 
 
 relations by which the ratio of is determined 134 
 
 mutations of structures in the progress of 134 
 
 with respect to a function of absorbents 135 
 
 Growths, morbid, spiritual changes preparatory to 146 
 
 147 
 
 H 
 
 Heat, relation of with fecundated ovum ( 81 
 
 does not operate by direct causation 62 
 
 animal, Chap. IV. 148 
 
 definition of, &c. 148 
 
 not derived from a source in any one organ 149 
 
 .. nor diffused by any medium 149 
 
 animal, source of, a diffused one in the textures 149 
 
 a part or constituent of the vital principle 150 
 
 >. maintained or produced by assimilation 150 
 
 concurrence necessary to the production of 151 
 
 chymical explanation of, defective 152 
 
 .. produced by assimilation, consonant with other analogies 152 
 
347 
 
 Heart, analysis of relation of properties of, with the blood 
 
 I 
 
 Investigation, object of 
 
 . to understand relations 33 
 
 of two kind* 
 
 Inference, examples of 
 
 grounds of, to be first examined 
 
 most frequently true of familiar things *3 
 
 dependences of the truth of 
 
 Inconsistencies, verbal, not to be objected against experienced truths 
 
 Intellect, experience concerning the agency of 40 
 
 the causes of, most precede the existence of 41 
 
 Injury, mechanical, affects phenomena of life indirectly 
 
 Z Z Z 158 
 
 Intestines, Chap. III. 185 
 
 general object of inquiry concerning 185 
 
 chymical changes performed in 
 
 - vital operations concerned in functions of 
 
 relation of function of with diffused life 187 
 
 _ _ ___ 188 
 
 functional life of 189 
 
 _ ^_ 190 
 _ 191 
 
 L 
 
 Life, Post-foetal, Book III. 117 
 
 general relations with respect to, Section I. Chap. I. 119 
 
 mode by which maintained, Chap. II. 124 
 
 generally illustrated 124 
 
 precise mode by which maintained * 125 
 
 by union of informal elements 126 
 
 formation of, preserves the uniformity of species 126 
 
 how maintained in all its properties 127 
 
 latent properties of, live also by assimilation 127 
 
 minute relation of with the material and with organic particles 128 
 
 whether involved in assimilation 128 
 
 organic assimilating, not dependent on related seats 168 
 
 grounds of inference of a dependence of, between seats 169 
 
 dependence of, in different seats 169 
 
 _ _ 170 
 
 Liver, Chap. IV 192 
 
 general objects of the function of the 192 
 
 analysis of function of, indicated 193 
 
 - _ - - 194 
 
 function of, doubtful 195 
 
 - 196 
 
 analysis of function of, indicated 197 
 
 _ 198 
 
 summary with respect to function of 199 
 
 Lungs, Chap.'llt. 213 
 
 - function of, with respect to conversion of chyle into blood 213 
 
 - - 214 
 
 215 
 
 mechanical fnnction of - 216 
 
 217 
 
M P.*. 
 
 Man, organic origin of, Book II. .... .... 60 
 
 departments of constitution of .. ' .. 62 
 
 - origin of, by constitution, Chap. III. .. .... 103 
 
 existence of, perpetuated by derivation 103 
 
 another origin of, indicated . . . . 103 
 
 origin of, in two first parents, not physically proved 
 
 historical evidence concerning 
 
 rests on inspired authority 
 
 in two first parents, not proved by record 
 
 104 
 104 
 104 
 106 
 
 not proved by inverting the order of 
 
 procreation . . . . 106 
 
 .. 107 
 
 .... 108 
 
 period of the origin of .... .. 108 
 
 has not existed eternally . . .... 108 
 
 origin of, by constitution, physical terms of examined . 109 
 
 110 
 
 elementary, prevalence of his constituents indicated 
 
 laws of his first formation not to be specified 
 
 organic spirit of, first formation of the 
 
 . preparatory stages of formation of 
 
 Mesenteric Absorbents, Chap. VII. 
 function of 
 
 conclusions on the 
 
 hydraulic and vital agencies of 
 
 indication for investigating the function of 
 
 Medicines, operation of 
 
 analysis of the operation of 
 classification of 
 
 subdivision of third class of 
 analysis of dependences of cure on 
 
 indications of treatment by 
 
 110 
 111 
 112 
 113 
 113 
 114 
 115 
 116 
 104 
 204 
 205 
 206 
 207 
 208 
 209 
 210 
 306 
 307 
 308 
 309 
 310 
 311 
 312 
 313 
 314 
 31* 
 316 
 317 
 318 
 319 
 320 
 321 
 43 
 42 
 
 prevalence of the notion of, how far a proof of its truth 43 
 not established by alleged physical proofs . . 44 
 
 origin of the notion of, explained .. .... 45 
 
 assigned moral agency of, physical explanation of . . 45 
 though not necessary to order, might mingle its influ- 
 ence with causes .... 45 
 
 N 
 Nature, general exhibition of the scheme of .... .... 51 
 
 Mind, universal, assumed falsely, upon physical analogy 
 compared with principles of causation 
 
349 
 
 Nature, general exhibition of the scheme of 
 
 Nervous system, relations of organic life in, Chap. VIII. 
 
 life of, how maintained .... 
 
 analysis of relations of properties of life in 
 
 electricity as connected with 
 
 Nihility, idea of, founded in experience . . 
 
 from presumed sufficiency of the senses 
 
 example of, in agreement with sensible evidence 
 
 state of, can be interrupted only by a real presence 
 
 Nutrition, relation of with blood 
 
 takes place from extravasated fluids 
 
 analysis of relations concerned in 
 
 summary of analysis of 
 
 O 
 
 Order and regularity, wliat constitutes 
 
 inevitable results of causation .... 
 
 Organization, not a result of mechanism .... 
 
 Organs, preparatory, Section II. 
 
 '. general relations of, Chap. I. 
 
 . - life of .,J|fe: 
 
 Ovum, maternal, Chap. I. 
 
 chymistry not applicable to, inquiry concerning 
 
 molecules composing, aggregated by the organic spirit 
 
 simplicity of component matter of 
 
 latent properties of 
 
 state of, a predisposition to life 
 
 identical, whether derived from first parents 
 
 future phenomena of, depend on latent constituents 
 
 objection to the complexity of inferred properties of 
 
 . answered by general account of properties 
 
 formation of .... 
 
 alternatives with respect to 
 
 latent properties belonging to 
 
 derived from respective parental seats 
 
 summary of doctrines with respect to 
 
 fecundated, Chap. II. 
 
 disposed by fecundation for change 
 
 how fecundated 
 
 change of, which succeeds to fecundation 
 
 agreement of with diffused parental properties 
 
 properties of, whether identical or predisponent 
 
 * 
 
 52 
 
 53 
 
 54 
 
 55 
 
 56 
 
 251 
 
 251 
 
 252 
 
 253 
 
 254 
 
 255 
 
 256 
 
 257 
 
 258 
 
 259 
 
 260 
 
 15 
 
 16 
 
 16 
 
 16 
 
 226 
 
 230 
 
 231 
 
 232 
 
 233 
 
 234 
 
 235 
 
 236 
 
 237 
 
 338 
 
 47 
 48 
 88 
 171 
 171 
 172 
 64 
 64 
 67 
 67 
 68 
 68 
 68 
 69 
 69 
 70 
 71 
 71 
 72 
 74 
 75 
 76 
 77 
 77 
 77 
 78 
 78 
 78 
 79 
 
350 
 
 Ovum, in what differential properties of constitution of consist . . 79 
 
 classification of related properties of .... .... so 
 
 possesses the identical properties of the parents . . . . 80 
 
 C 81 
 
 identical properties of future animal possessed by the .. 82 
 
 spiritual relations of .. .. .... 82 
 
 escape of from the ovarinm .. ..83 
 
 commencement of growth of .. .... 83 
 
 properties of, disposed for activity by fecundation . . 86 
 
 preparatory changes of properties of . . .... 87 
 
 properties of, gradually assume their spheres . . .87 
 
 results of fecundation on the material of 
 . changes of, not the result of organic functions 
 
 . determined by processes of spiritual affinity 
 
 connection of with the uterus 
 
 87 
 87 
 87 
 90 
 91 
 
 formation of the blood of .... .... 91 
 
 concurrence of agencies necessary to the growth of . . 91 
 
 relation of heat with the .... 95? 
 
 viviparous and crustaceous differences between 93 
 
 growth of .... ... 97 
 
 .... .. .. 98 
 
 general summary of doctrines with respect to .... .... 100 
 
 P 
 
 Pancreas, the, Chap. VI. . . . . 203 
 
 general investigation belonging to . . . 203 
 
 Perfection, positive, an inevitable result of causation ...... 43 
 
 ,- .... 49 
 
 Placenta, function of .. ..95 
 
 properties of, with respect to oxygenation of blood .... 96 
 
 ...... 97 
 
 Place, relation of .... .... s>9 
 
 .... .* .. ..30 
 
 Probability, degrees of .. .... 12 
 
 Presence, idea of, may be contrasted ... . . 15 
 
 Proportion, kinds of . . 28 
 
 relation of .. ... 28 
 
 varieties of so 
 
 Production, regular not always the result of design 40 
 
 Principle, vital, general efficacy of - .... 65 
 
 Properties, vital, seats of, determined by spiritual relations 73 
 
 .. precise causes of not known ... 73 
 
 those of the ovum not more inexplicable than those of other 
 
 substances 73 
 
 - of the ovum, reciprocation of influence among .... 88 
 
 acting, agreement among, necessary . . 88 
 
 spiritual, of the ovum, development of .... 98 
 
 . relation of, with the material of nutrition .. .. 98 
 relation of, with sexual differences . . , . . . 99 
 
 Q 
 
 Quantity, definition of .... 26 
 
 . relations of . . . . .... 26 
 
 supposition, ultimate .. 27 
 
 finite by synthesis, infinite by analysis . . .... 27 
 
 . so far as identity depends upon, not divisible . . 27 
 
 R 
 
 Religion, not affected by physical doctrines of causation .... 56 
 is to be accepted as a matter of faith in revelation . . 57 
 
351 
 
 Religion, and doctrines of causation not incompatible ...... 58 
 
 Regeneration of structures .... 140 
 
 __ classification of examples of regeneration and growth .. 141 
 
 -- processes of, in the various examples ... 142 
 
 ------- 143 
 
 --- general description of .... 144 
 
 -- ~- of distinct structures .. .. .. 144 
 
 -- with respect to previous spiritual change J . . . 145 
 
 '.'. ".". .*. ...*. 146 
 
 Relations, vital, chymical, and mechanical, Chap. V. ... 153 
 
 --------- general account of .... 153 
 
 Relation, indirect, of chymical with vital, through mechanical properties 155 
 
 -- of vital with mechanical department, division of . . 155 
 
 ...... 156 
 
 Relations, vital, chymical, and mechanical, summary of ...... 158 
 
 .. ---- 159 
 
 - -- of chymical and mechanical agencies 160 
 
 Relation, general, of the spirit with itself, in different seats, Chap. VI. 162 
 
 .... 162 
 
 -------- , -- in dependent seats ... 163 
 
 .... 164 
 
 ...... 165 
 
 .... 166 
 
 ... 167 
 
 S 
 
 Scepticism, universal, not a consequence of the doctrine of truth . . 9 
 
 Scheme, universal, according to physical evidences, Chap. III. .... 36 
 
 Senses, relation of, with externals .... ...... 15 
 
 -- insufficiency of, allowed in some instances . . .... 16 
 
 Secretion, Chap. VI. . . 242 
 
 - from what blood produced .. 242 
 ...... ...... .. ... 243 
 
 --- not mechanical .. .... 244 
 
 -- not chymical .. .. 245 
 
 --- properties of life with respect to ' .... 245 
 
 .. 246 
 
 -- supersedes filtration ...- .... 247 
 -- general account of .. .. .. 248 
 
 ... ..... - .. .... 249 
 
 ........ .. .. ..250 
 
 Spirit, organic origin of .. .... 66 
 
 - organic relation of, with the material particles of the ovum . . 84 
 ----- admits the application of the laws of causation .... 119 
 --- state and varieties of, not explained by the contractilities . . 120 
 
 ------- by excitement .... 120 
 
 ---- ... 121 
 
 .... 122 
 
 . ---- : -- not explained by any doctrine of degree 123 
 
 -- manner of it existence .. .. 123 
 Spleen, Chap. VI. .. ..'..200 
 
 --- function of . . . . 200 
 
 --- theory of, as subservient to the stomach .... 201 
 
 ----- as subservient to the liver . . . . 202 
 
 Stales, living and dead, distinction between . . .... 64 
 
 .... ---- ...... 65 
 
 State, living, properties of, distinguished from those of matter .... 65 
 
 Structures, not produced by an act of spiritual assimilation . . 129 
 
 -- produced by a subsequent operation ., .... 129 
 
352 
 
 Structures, formation of, described 
 
 Stomach, Chap. II 
 
 - particles of, not decomposed by attrition 
 
 objects of investigation with respect to 
 division of relations of 
 
 spiritual relations of 
 
 other relations of 
 
 . . . liable to the action of three sets of properties of life 
 . series of vital processes belonging to, indicated 
 
 Succession, whether the same as causation 
 
 that only proves causation which proves dependence 
 
 that which does not prove causation - . . 32 
 
 T 
 
 Theism, natural, how far supported by the axiom, " ex nihilo," &c. . 36 
 
 Therapeutics, Chap. VI. 
 Truth, Book 1st, Chap. I. 
 
 - ... synonymous with belief 
 
 established by consciousness 
 
 .. in all examples, rests upon the same basis 
 
 rested on immutable conviction, considered 
 
 distinctions of 
 
 mutability of 
 
 the result of, a relation between our faculties and externals 
 
 artificial 
 
 and natural, established on the same basis 
 
 artificial, fixed by arbitrary consent 
 
 how far, or when immutable 
 
 natural, equally established by contradictory beliefs 
 
 not agreeable with the artificial standard in contradictory belief 7 
 
 accepted as a result of similar constituents of the relation 
 
 130 
 136 
 177 
 177 
 177 
 178 
 179 
 180 
 181 
 182 
 183 
 184 
 184 
 31 
 
 306 
 3 
 3 
 4 
 5 
 5 
 5 
 6 
 6 
 6 
 6 
 7 
 7 
 7 
 
 Truths, sources of the varieties of 
 
 division of . . . 8 
 
 degrees of in relation to evidence .... 8 
 
 . assertions of, are assertions only of belief or conviction . . 8 
 
 V 
 
 Volition, virtue, &c. have only a relative efficacy with organized 
 
 substances .... .... ..39 
 
 W 
 
 World, harmony and adaptations of phenomena of .. ... 39 
 
 how far harmony and adaptation of prove intelligence 39 
 
 ... 40 
 _ present state of, whether the best 
 
 FINIS. 
 
 Wd nJ Co. PriattM, Union-Strut, Btk. 
 
By the same Author, may be had of J. CALLOW, 
 Princes-Street , Soho, 
 
 AN ESSAY ON THE ABSORBENTS; 
 
 Comprising some Observations on the relative Pathology and 
 Functions of the Absorbent, and Secreting Systems. 
 
 ALSO, 
 
 A VIEW OF THE RELATIONS 
 
 OF 
 
 THE NERVOUS SYSTEM, 
 
 IN HEALTH AND IN DISEASE; 
 
 Containing Selections from the Dissertation to which was adjudged 
 
 the Jacksonian Prize for the year 1813; with additional 
 
 Illustrations and Remarks. 
 
CASK