From the ''Fortnightly Ri-vifw," for February, 1869. 
 
 07V" (-r^E 
 
 Vc- 
 
 Physical JBasis of Life 
 
 r. H. FIUXLEY, LL. D., F. R. S. 
 
 |]:ile (t,oilec|c, ^eir jharen, :(),onn. : 
 
 T H TG C C> Tj L IT, G- iHi C O TJ R A ]Sr T 
 
 i86g. 
 
From the "Fortnightly Review," for February, 1869. 
 
 OJ<r Ql^B 
 
 Physical Basis of Life. 
 
 BY 
 
 T. H. HUXLEY, LL. D., F. R. S. 
 
 THE dOXjLElQ-E COTJR^ICXi 
 
INTRODUCTION 
 
 The following remarkable discourse was originally delivered in Edin- 
 burgh, Nov. 18th, 1868, as the first of a series of Sunday evening addresses, 
 upon non-religious topics, instituted by the Rev. J. Cranbrook. It was 
 subsequently published in London as the leading article in the FortnigMly 
 Review, for February, 1869, and attracted so much attention that five edi- 
 tions of that number of the magazine have already been issued. It is now 
 re-printed in this country, in permanent form, for the first time, and will 
 doubtless prove of great interest to American readers. The author is 
 Thomas Henry Huxley, of London, Prof, of Natural History in the Royal 
 School of Mines, and of Comparative Anatomy and Physiology in the Royal 
 College of Surgeons. He is also President of the Geological Society of Lon- 
 don. Although comparatively a young man, his numerous and valuable 
 contributions to Natural Science entitle him to be considered one of the 
 first of living Naturalists, especially in the departments of Geology and 
 Palaeontology, to which he has mainly devoted himself. He is un- 
 doubtedly the ablest English advocate of Darwin's theory of the Origin of 
 Species, particularly with reference to its application to the human race, 
 which he believes to be nearly related to the higher apes. It is, indeed, 
 through his discussion of this question that he is, perhaps, best known to 
 the general public, as his late work entitled " Man's Place in Nature," and 
 
other writings on similar topics, have been very widely read in this country 
 and in Europe. In the present lecture Professor Huxley discusses a kin- 
 dred subject of no less interest and importance, and should have an equally 
 candid hearing. 
 Yat^k College, March 30^A, 1869. 
 
■' Library* 
 
 ON THE PHYSICAL BASIS OF JJFE. 
 
 Ill order to make the title of tliis discourse generally intel- 
 ligible, I have translated the term "Protoplasm," which is the 
 scientific name of the substance of which I am about to speak, 
 by the words "the physical basis o|^j^^ I suppose that, to 
 many, the idea that there is such ^^^^^^^ physical basis, or 
 matter, of life may 1)0 novel — so A^^^^^^^Pd is the conception 
 of life as a sometliing whicli works^^^^Hr matter, but is inde- 
 pendent of it ; and even those wh(^reaware that matter and 
 life are inseparably connected, may not be prepared for the con- 
 clusion plainly suggested by the phrase " the physical basis or 
 matter of life," that there is some one kind of matter which is 
 common to all livino- beino-s, and that their endless diversities are 
 bound together by a physical, as well as an ideal, unity. In fact, 
 when first apprehended, such a doctrine as this appears almost 
 shocking to common sense. ^ What, truly, can seem to be more 
 obviously different from one another in faculty, in form, and in 
 substance, than the various kinds of living beings ? What com- 
 munity of faculty can there be between the brightly-colored 
 lichen, which so nearly resembles a mere mineral incrustation of 
 tlic bare rock on which it grows, and the painter, to whom it 
 is instinct with beauty, or the botanist, whom it feeds Avitli 
 knowledge ? 
 
 Again, think of the microscopic fungus — a mere infinitesimal 
 ovoid particle, which finds space and duration enough to multiply 
 into countless millions in the body of a living fly; and then of 
 the wealth of foliage, the luxuriance of flower and fruit, which 
 lies between this bald sketch of a plant and the giant pine of 
 California, towering to the dimensions of a cathedral spire, or the 
 Indian fig, which covers acres with its profound shadow, and en- 
 dures while nations and empires come and go around its vast 
 circumference '? Or, turning to the other half of the world of 
 life, picture to yourselves the great Finner whale, hugest of 
 beasts that live, or have lived, disporting his eighty or ninety feet 
 of 1)one, muscle and l)lubber, with easy roll, among waves in which 
 
tlie^stoutest sliii^ that ever left dockyard would founder hopelessly ; 
 and contrast hhn with the invisible animalcules — mere gelatinous 
 specks, multitudes of which could, in fact, dance upon the point 
 of a needle with the same ease as the angels of the schoolmen 
 could, in imagmation. With these images before your minds, 
 you may well ask what community of form, or structure, is there 
 between the animalcule and the whale, or between the fungus and 
 the fig-tree? And, a fortiori^ between all four? 
 
 Finally, if we regard substance, or material composition, 
 what hidden bond can connect the flower which a girl wears in 
 her hair and the blooc^^ych courses through her youthful veins ; 
 or, what is there ^^^^^^^^ between the dense and resisting 
 mass of the oak, o^^^^^^^g fabric of the tortoise, and those 
 broad disks of glasl^^^^^Kich may be seen pulsating through 
 the waters of a calm s^^HI Avhich drain away to mere films in 
 the hand which raises them out of their element ? Such objec- 
 tions as these must, I think, arise in the mind of every one who 
 ponders, for the first time, uj^on the conception of a single phys- 
 ical basis of life underlying all the diversities of vital existence ; 
 but I propose to demonstrate to you that, notwithstanding these 
 apparent difficulties, a threefold unity — namely, a unity of power 
 or faculty, a unity of form, and a unity of substantial composi- 
 tion — does pervade the whole living world. Ko very abstruse 
 argumentation is needed, in the first place, to prove that the 
 powers, or faculties, of all kinds of living matter, diverse as they 
 may be in degree, are substantially similar in kind. Goethe has 
 condensed a survey of all the powers of mankind into the well- 
 known epigram : 
 
 " Warum treibt sicli das Volk so unci schreit ? Es will sicli ernitliron 
 Kinder zeugen, und sie nahren so gut es vermag. 
 
 Weiter bringt es kein Mensch, stelV er sicli, Avie er audi will." 
 
 In physiological language this means, that all the multifarious 
 and complicated activities of man are comprehensible under three 
 categories. Either they a^b immediately directed towards the 
 maintenance and development of the body, or they effect trans- 
 itory changes in the relative positions of parts of the body, or 
 they tend towards the continuance of the species. Even those 
 manifestations of intellect, of feeling, and of will, which Ave 
 riffhtlv name the hiirher faculties, are not excluded from tliis 
 
7 
 
 classification, iiiasmucli as to every one but tlie subject of tliem, 
 they are known only as transitory changes in the relative posi- 
 tions of parts of the body. Speech, gesture, and every other 
 form of human action are, in the long run, resolvable into muscu- 
 lar contraction, and muscular contraction is but a transitory change 
 in the relative positions of the parts of a muscle. But the scheme, 
 which is large enough to embrace the activities of the highest 
 form of life, covers all those of the lower creatures. The lowest 
 plant, or animalcule, feeds, grows and reproduces its kind. In 
 addition, all animals manifest those transitory changes of form 
 which we class under irritability and contractility ; and it is more 
 than probable, that when the veget^ifo^fi^ld is thoroughly ex- 
 plored, we shall find all plants in poJR^^s^^^f the same powers, 
 at one time or other of their existei]^H 'Pam not now alluding 
 to such phenomena, at once rare and conspicuous, as those ex- 
 hibited by the leaflets of the sensitive plant, or the stamens of 
 the barberry, but to much more widely-spread, and, at the same 
 time, more subtle and hidden, manifestations of vegetable con- 
 tractility. You are doubtless aware that the common nettle owes 
 its stinghig property to tlie innumerable stifl" and needle-like, 
 though exquisitely delicate, hairs which cover its surface. Each 
 stinging-needle tapers from a broad base to a slender summit, 
 which, though rounded at the end, is of such microscopic fineness 
 that it readily penetrates, and breaks ofii" in, the skin. The wliole 
 hair consists of a very delicate outer case of wood, closely applied 
 to the inner surface of which is a layer of semi-fluid matter, full of 
 innumerable granules of extreme minuteness. This semi-fluid 
 lining is protoplasm, which thus constitutes a kind of bag, full of 
 a limpid liquid, and roughly corresponding in form with the inte- 
 rior of tlie hair which it fills. When viewed with a sufiiciently 
 liigh magnifying power, the protoplasmic layer of the nettle hair 
 is seen to be in a condition of unceasing activity. Local con- 
 tractions of the whole thickness of its substance pass slowly and 
 gradually from point to point, and give rise to the appearance of 
 progressive waves, just as the bending of successive stalks of 
 corn by a breeze produces the apparent billows of a corn-field. 
 But, in addition to these movements, and independently of them, 
 the granules are driven, in relatively rapid streams, through 
 channels in the protoplasm which seem to have a considerable 
 amount of persistence. Most commonly, the currents in adjacent 
 parts of the protoplasm take similar directions ; and, thus, there 
 
is a general stream up one side of the hair anxl down the otlier. 
 But this does not prevent the existence of partial currents which 
 take different routes; and, sometimes, trains of granules niav be 
 seen coursing swiftly in opposite directions, Avithin a twenty- 
 thousandth of an inch of one another; while, occasionally, oppo- 
 site streams come into direct collision, and, after a longer or 
 shorter struggle, one predominates. The cause of these currents 
 seem to lie in contractions of the protoplasm wliicli bounds the 
 channels in which they flow, but wdiicli are so minute that the 
 best microscopes show only their effects, and not themselves. 
 
 The spectacle afforded by the wonderful energies prisoned 
 within the compass of the jnicroscopic hair of a plant, which we 
 commonly regard as^ mei^y passive organism, is not easily for- 
 gotten by one who has watched its display continued hour after 
 hour, without pause or sign of w^eakening. The possible com- 
 plexity of many other organic forms, seemingly as simple as the 
 protaplasm of the nettle, dawns upon one ; and the comparison of 
 such a protoplasm to a body with an internal circulation, which 
 has been put forward by an eminent physiologist, loses much of 
 its startling character. Currents similar to those of tlie hairs of 
 the nettle have been observed in a great midtitude of very dif- 
 ferent plants, and weighty authorities have suggested that they 
 probably occur, in more or less perfection, in all young vegetable 
 cells. If such be the case, the wonderful noonday silence of a 
 tropical forest is, after all, due only to tlie dullness of our hear- 
 ing ; and could our ears catch the murmur of these tiny mael- 
 stroms, as they whirl in the innumerable myriads of living cells 
 which constitute each tree, wo should be stunned, as with the roar 
 of a great city. 
 
 Among the lower plants, it is the rule rather than tlie ex- 
 ception, that contractility should be still more openly manifested 
 at some periods of their existence. The protoplasm of Algce and 
 Fungi becomes, mider nniny circumstances, partially, or com- 
 pletely, freed from its woody case, and exhibits movements of its 
 whole mass, or is proju'lled by the contractility of one, or more, 
 hair-like prolongations of its body, Avliich are called vibratile cilia. 
 And, so far as the conditions of the manifestation of the phenom- 
 ena of contractility have yet been studied, they are the sani^ Jbr 
 the plant as for the animal. Heat .md electric shocks influence 
 both, and in the same Avay, though it ma) be in different degrees. 
 It is by no means my intention to suggest that there is no differ- 
 
9 
 
 eiice ill faculty between the lowest plant and tlie highest, or be- 
 tween plants and animals. But the difference between the pow- 
 ers of the lowest plant, or animal, and those of the highest is 
 one of degree, not of kind, and dejjends, as Milne-Edwards long 
 ago so well pointed out, upon the extent to which the principle 
 of the division of labor is carried out in the livhig economy. In 
 the lowest organism all parts are competent to perform all func- 
 tions, and one and the same portion of protoplasm may succes- 
 sively take on the function of feeding, moving, or reproducing 
 apparatus. In the highest, on the contrary, a great number of 
 parts combine to perform each function, each part doing its allot- 
 ted share of the work with great accuracy and efficiency, but 
 being useless for any other purpose. On the other hand, not- 
 withstanding all the fundamental resemblances which exist be- 
 tween the powers of the protoplasm in plants and in animals, 
 they present a striking difference (to which I shall advert more 
 at length presently,) in the fact that plants can manufacture fresh 
 protoplasm out of mineral compounds, whereas animals are 
 obliged to procure it ready made, and hence, in the long run, de- 
 pend upon plants. Upon what condition this difference in the 
 powers of the two great divisions of the world of life depends 
 nothing is at present known. 
 
 With such qualification as arises out of the last-mentioned 
 fact, it may be truly said that the acts of all living things are 
 fundamentally one. Is any such unity predicable of their forms? 
 Let us seek in easily verified facts for a rejjly to this question. 
 If a drop of blood be drawn by pricking one's finger, and viewed 
 with proper precautions and under a sufficiently high microscopic 
 power, tliere will be seen, among the innumerable multitude of 
 little, circular, discoidal bodies, or corpuscles, which float in it 
 and give it its color, a comparatively small number of colorless 
 corpuscles, of somewhat larger size and very irregular shape. If 
 the drop of blood be kept at the temperature of the body, these 
 colorless corpuscles will be seen to exhibit a marvelous activity, 
 changing their forms with great rapidity, drawing in and thrust- 
 ing out prolongations of their substance, and creeping about as 
 if they were independent organisms. The substance which is 
 thus active is a mass of protoplasm, and its activity differs in de- 
 tail, rather than in principle, from that of the protoplasm of the 
 nettle. Under sundry circumstances the corpuscle dies and be- 
 comes distended into a round mass, in the midst of which is seen 
 
10 
 
 a smaller splierical body, which existed, but was more or less 
 hidden, in the living corpuscle, and is called its nucleics. Cor- 
 puscles of essentially similar structure are to be found in the 
 skin, in the lining of the mouth, and scattered through the whole 
 framework of the body, ^^'ay, more; in the earliest condition 
 of the human organism, in that state in which it has just become 
 distinguishable from the Qg^ in which it arises, it is nothing but 
 an aggregation of such corpuscles, and every organ of the body 
 -was, once, no more than such an aggregation. Thus a nucleated ( 
 .mass of protoplasm turns out to be what may be termed the . 
 structural unit of the human body. As a matter of fact, the 
 body, in its earliest state, is a mere multiple of such units ; and, 
 in its perfect condition, it is a multiple of such units, variously 
 modified. But does the formula which expresses the essential 
 structural character of the highest animal cover all the rest, as 
 the statement of its powers and faculties covered that of all 
 others ? Very nearly. Beast and fowl, reptile and fish, mollusk, 
 worm, and polype, ai-e all composed of structui-al units of the 
 same character, namely, masses of protoplasm with a nucleus. 
 There are sundry ver}^ low animals, each of which, structurally^ 
 is a mere colorless blood-corpuscle, leading an independent life. 
 But, at the very bottom of the animal scale, even this simplicity 
 becomes simplified, and all the phenomena of life are manifested 
 by a particle of protoplasm without a nucleus. Xor are such 
 organisms insignificant by reason of their want of complexity 
 It is a fair question whether the protoplasm of those simplest 
 forms of life, which people an immense extent of the bottom of 
 the sea, would not outweigh that of all the higher living beings 
 which inhabit the land put together. .Vnd in ancient times, no 
 less than at the present day, such living beings as these have 
 been the greatest of rock builders. 
 
 What has been said of the animal world is no less true of 
 plants. Imbedded in the protoplasm at the broad, or attached, 
 end of the nettle hair, there lies a spheroidal nucleus. Careful 
 examination further proves that the whole substance of the nettle 
 is made up of a repetition of such masses of nucleated proto- 
 plasm, each contained in a wooden case, which is modified in 
 form, sometimes into a woody fibre, somethnes into a duct or 
 spiral vessel, sometimes into a i:>ollen grain, or an ovule. Traced 
 back to its earliest state, the nettle arises as the man does, in a 
 particle of nucleated protoplasm. And in the lowest plants, as in 
 
11 
 
 the lowest animals, a single mass of such protoplasm may consti- 
 tute the whole plant, or the protoplasm may exist without a 
 nucleus. Under these circumstances it may well be asked, how 
 is one mass of non-nucleated protoplasm to be distinguished from 
 another? why call one " plant," and the other "animal ?" The 
 only reply is that, so far as formSs concerned, plants and animals 
 are not separable, and that, in many cases, it is a mere matter of 
 convention whether we call a given organism an animal or a plant. 
 
 There is a living body called uTJthaliwm sejyticum^ which 
 appears upon decaying vegetable substances,and in one of its forms, 
 is common upon the surface of tan pits. In this condition it iF> 
 to all intents and purposes, a fungus, and formerly was always 
 regarded as such ; but the remarkable investigations of De Bary 
 have shown that, in another condition, the ^thallum is an ac- 
 tively locomotive creature, and takes in solid matters, upon 
 which, apparently, it feeds, thus exhibiting the most characteris- 
 tic feature of auimality. Is this a plant, or is it an animal? Is 
 it both, or is it neither? Some decide in favor of the last suppo- 
 sition, and establish an intermediate kingdom, a sort of biologi- 
 cal No Man's Land for all these questionable forms. But, as it 
 is admittedly impossible to draw any distinct boundary line 
 between this no man's land and the vegetable world on the one 
 hand, or the animal, on the other, it appears to me that this pro- 
 ceeding merely doubles the difficulty which, before, was single. 
 Protoplasm, simple or nucleated, is the formal basis of all life. 
 It is the clay of the potter: which, bake it and paint it as he 
 will, remains clay, separated by artifice, and not by nature, from 
 the commonest brick or sun-dried clod. Thus it becomes clear 
 that all living powers are cognate, and that all living forms are 
 fundamentally of one character. .^ -^ ^ ^^^^^^^ c^^^^^^^^^^.. ; 
 
 The researches of the chemist have revealed a no less strik- 
 ing uniformity of material composition in living matter. In per- 
 fect strictness, it is true that chemical investigation can tell us lit- 
 tle or nothing, directly, of the composition of living matter, inas- 
 much as such matter must needs die in the act of analysis, and 
 upon this very obvious ground, objections, which I confess seem 
 to me to be somewhat frivolous, have been raised to the drawing 
 of any conclusions whatever respecting the composition of actu- 
 ally living matter from that of the dead matter of life, which 
 alone is accessible to us. But objectors of this class do not seem 
 to reflect that it is also, in strictness, true that we know nothing 
 
about the composition of any body whatever, as it is. Tlie state- 
 ment that a crystal of calc-spar consists of carbonate of lime, is 
 quite true, if we only mean tliat, by appropriate processes, it may 
 be resolved into carbonic acid and quicklime. If you pass the 
 same carbonic acid over the very quicklime tlnis obtained, you 
 will obtain carbonate of lime again ; but it will not be calc-spar, 
 nor anything like it. Can it, therefore, be said that cliemical 
 analysis teaches nothing about the chemical composition of calc- 
 spar ? Such a statement would be absurd; but is is hardlv 
 more so than the talk one occasionally hears about tlie uselessness 
 of applying the results of chemical analysis to the living bodies 
 which have yielded them. One fact, at any rate, is out of reach 
 of such refinements, and this is, that all the forms of protoplasm 
 which have yet been examined contain the four elements, carbon, 
 hydrogen, oxygen, and nitrogen, in very complex union," and 
 that they behave similarly towards several reagents. To this 
 complex combination, the nature of which has never been deter- 
 mined Tvith exactness, the name of Protein lias been appliec!. 
 And if we use this term with such caution as may properly arise 
 out of our comparative ignorance of the things for which it stands, 
 it may be truly said, that all protoplasm is proteinaceous ; or, as 
 the white, or albumen, of an egg is one of the commonest exam- 
 ples of a nearly pure proteine matter, we may say that all living 
 matter is more or less albuminoid. Perhaps it would not yet l>e 
 safe to say that all forms of j)rotoplasm are affected by the direct 
 action of electric shocks ; and yet the number of cases in whicli 
 the contraction of protoplasm sliown to be effected by this agency 
 increases every day. Nor can it be affirmed with perfect confi- 
 dence that all forms of protoplasm are liable to uiidergo that pecu- 
 liar coagulation at the temperature of 40 degrees — 50 degrees 
 centigrade,which has been called "heat-stiffening," though Ktlhue''s 
 beautiful rescarclies have |»roved this occurrence to take place in 
 so many and such diverse living beings, that it is hardly rash to 
 expect that the law holds good for all. Enough has, perhaps, 
 been said to prove the existence of a general uniformity in tlu^ 
 character of the protoplasm, or physical basis of life, in whatever 
 group of living beings it may be studied. But it will be under- 
 Btood that this general iiniformity by no means excludes any 
 amount of special modifications of the fundamental substance. 
 The mineral, carbonate of lime, assumes an immense diversity of 
 characters, though no one doubts that under all these Protean 
 changes it is one and the same thing. 
 
13 
 
 And now, wliat is the ultimate fate, and what the origin, of the 
 matter of life ? Is_it, as some of the older naturalists supposed, 
 difluLised throughout the universe in molecules, Avhich are inde- 
 structible and unchangeable in themselves ; but, in endless trans- 
 migration, unite in innumerable permutations, into the diversified 
 forms of life we know ? Or, is the matter of life com^posed of ordi- 
 nary matter, differing from it only in the manner in which its 
 atoms are aggregated. Is it built up of ordinary matter, and 
 again resolved into ordinary matter Avhcn its work is done? 
 Modern science does not hesitate a moment between these alter- 
 natives. Physiology writes over the portals of life 
 
 " Debemur morti nos nostraque," 
 
 with a profounder meaning tlian the Koman poet attached to 
 that melancholy line. Under whatever disguise it takes refuge, 
 whether fungus or oak, worm or man, the living protoplasm not 
 only ultimately dies and is resolved into its mineral and lifeless 
 constituents, but is always dying, aiid, strange as the jDaradox 
 may sound, could not live unless it died. In the wonderful story 
 of the " Peau de Chagrin," the hero becomes possessed of a magi- 
 cal wild ass's skin, which yields him the means of gratifying all 
 liis wishes. But its surface represents the duration of the propri- 
 etors life ; and for everv satisfied desire the skin shrinls 
 
 s m 
 
 pro- 
 portion to the intensity of fruition, until at length life and the 
 last handbreadth of the "Peau de Chagrin," disappear with the 
 gratification of a last wish. Balzac's studies had led him over a 
 wide range of thought and speculation, and his shadowing forth 
 of physiological truth in this strange story may have been inten- 
 tional. At any rate, the matter of life is a veritable "Peau de 
 Cliagrin," and for every vital act it is somewhat the smaller. All 
 work implies waste, and the Avork of life results, directly or indi- 
 rectly, in the waste of protoplasm. Every vv^ord uttered by a 
 speaker costs liim some physical loss ; and, in the strictest sense, 
 he burns that others may have light — so much eloquence, so much 
 of his body resolved into carbonic acid, water and urea. It is 
 clear that this process of expenditure cannot go on forever. But, 
 happily, the protoplasmic ;:>eaz« de chagrin differs from Balzac's in 
 its capacity of being repaired, and brought back to its full size, 
 after every exertion. For example, this present lecture, what- 
 ever its intellectual worth to you, has a certain j^hysical value to 
 me, which is, conceivably, expressible by the number of grains 
 
14 
 
 of protoplasm and other bodily substance wasted in maintaining 
 my vital processes during its delivery. My peau de chagrin will 
 be distinctly smaller at the end of the discourse than it was as the 
 beginning. By-and-by, I shall probably have recourse to the sub- 
 stance commonly called mutton, for the purpose of stretching it 
 back to its original size. Xow this mutton was once the living 
 protoplasm, more or less modified, of another animal — a sheep. 
 As I shall eat it, it is the same matter altered, not only by death, | 
 but by exposure to sundry artificial operations in the process of 
 cooking. But these changes, whatever be their extent, have not 
 rendered it incompetent to resume its old functions as matter of 
 life. A singular inward laboratory, which I possess, will dissolve 
 a certain portion of the modified protoplasm, the solution so formed 
 will pass into my veins ; and the subtle influences to which it will 
 then be subjected will convert the dead protoplasui into living 
 protoplasm, and transubstantiate sheep into man. Nor is this all. 
 If digestion were a thing to be trifled with, I might sup upon lob- 
 ster, and the matter of life of the crustacean would undergo the 
 same wonderful metamorphosis into humanity. And were I to 
 return to my own place by sea, and undergo shipwreck, the Crus- 
 tacea might, and probably would, return the compliment, and 
 demonstrate our common nature by turning my protoplasm 
 into living lobster. Or, if nothing better were to be had, I might 
 supply my wants with mere bread, and I should find the proto- 
 plasm of the wheat-plant to be convertible into man, with no more 
 trouble than that of the sheep, and with far less, I fancy, than 
 that of the lobster. Hence it appears to be a matter of no gwat 
 moment wliat animal, or what plant, I lay under contributit^i for 
 protoplasm, and the fact speaks volumes for the general identity 
 of that substance in all living beings. T share this catholicity of 
 assimulation with other animals, all of whicli, S(^ far as we know, 
 could thrive equally well on the protoi)lasni of any of their fel- 
 lows, or of any plant ; but here the assimilative [)Owers of the ani- 
 mal world cease. 
 
 A solution of smelling-salts in water, with an infinitesimal 
 proportion of some other saline matters, contains all the elemen- 
 tary bodies which enter into the composition of protoplasm ; but, 
 as I need hardly say, a hogshead of that fluid would not keep a 
 hungry man from starving, nor would it save any animal what- 
 ever, from a like fate. An animal cannot make protoplasm, but 
 must take it ready-made from some othei' animal, or some plant— 
 
15 
 
 the aiiimars highest feat of constructive chemistry behig to con- 
 vert dead protoplasm mto that living matter of life which is 
 appropriate to itself. Therefore, in seeking for the origin of 
 protoplasm, we must eventually turn to the vegetable world. 
 The fluid containing carbonic acid, water, and ammonia, which 
 oiFers such a barmecide feast to the animal, is a table richly 
 spread to multitudes of plants ; and with a due supply of only 
 such materials, many a plant will not only maintain itself in 
 vigor, but grow and multiply until it has increased a million-fold, 
 or a million million-fold, the quantity of protoplasm which it orig- 
 inally possessed ; in this way building up the matter of life, to 
 an indefinite extent, from the common matter of the universe. 
 Thus the animal can only raise the complex substance of dead 
 protoplasm to the higher power, as one may say, of living proto- 
 plasm ; w^hile the plant can raise the less complex substances — car- 
 bonic acid, water, and ammonia — to thesame stage of living pro- 
 toplasm, if not to the same level. But the plant also has its lim- 
 itations. Some of the fungi, for example, appear to need higher 
 compounds to start with ; and no known j^lant can live upon the 
 uncomj)ounded elements of protoplasm, A plant supplied with 
 pure carbon, hydrogen, oxygen, and nitrogen, phosphorus, sul- 
 phur, and the like, would as infallibly die as the animal in his 
 bath of smelling-salts, though it would be surrounded by all the 
 constituents of protoplasm. Nor, indeed, need the process of 
 simplification of vegetable food be carried so lar as this, in order 
 to arrive at the limit of the plant's thaumaturgy. 
 
 Let w^ater, carbonic acid, and all the other needful consti- 
 tuents, be supplied without ammonia, and an ordinary j)lant will 
 still be unable to manufacture protoplasm. } Thus the matter of 
 life, so far as we know it (and we have no right to speculate on 
 any other) breaks up, in consequence of that continual death 
 which is the condition of its manifesting vitality, into carbonic 
 acid, water, and ammonia, which certainly possess no j)roperties 
 but those of ordinary matter. And out of these same forms of 
 ordhiary matter, and from none which are simpler, the vegetable 
 world builds up all the protoplasm which keeps the animal world 
 agoing. Plants are the accumulators of the power which animals 
 distribute and disperse, f ^ ■*^fc^ 
 
 But it wuU be observed, that the exist^|||f the matter of 
 life de pends on the pre-existence of certain compoiui ds. namely, 
 cal'bonic acid, water, and ammonia. Withdraw any one of these 
 
16 
 
 three from the world and ail vital })heiioineiia come to an end. 
 They are related to the protoplasm of the plant, as the protoplasm 
 of the plant is to that of the animal. Carbon, hydrogen, oxygen, 
 and nitrogen are all lifeless bodies. Of these, carbon and oxygen 
 unite in certain proportions and under certain conditions, to give 
 rise to carbonic acid ; hydrogen and oxygen produce water ; 
 nitrogen and hydrogen give rise to ammonia. These new com- 
 pounds, like the elementary bodies of which they are composed, 
 are lifeless. But when they are brought together, under certain 
 conditions they give rise to the still more complex body, proto- 
 plasm, and this protoplasm exhibits the phenomena of life. I see 
 no break in this series of steps in molecular complication, and I 
 am unable to understand why tlie language which is applicable 
 to any one term of the series may not be used to any of the oth- 
 ers. AYe think lit to call different kinds of matter carbon, oxygen, 
 hydrogen, and nitrogen, and to speak of the various powers and 
 activities of these substances as the properties of the matter of 
 which they are composed. When hydrogen and oxygen are 
 mixed in a certain proportion, and the electric spark is passed 
 through them, they disappear, and a quantity of water, equal in 
 weight to the sum of their weights, appears in their place. There 
 is not the slightest parity between the passive and active poAvers 
 of the water and those of the oxygen and hydrogen v.hich haA'e 
 given rise to it. At 32 degrees Fahrenheit, and far below that 
 temperature, oxygen and hydrogen are elastic gaseous bodies, 
 whose particles tend to rush away from one another with great 
 force. Water, at the same temperature, is a strong though brit- 
 tle solid, whose particles tend to cohere into dehnite geometrical 
 shapes, and sometimes build up frosty imitations of the most 
 complex forms of vegetable foliage. Xevcrtheless we call these, 
 and many other strange phenomena, the properties of the water, 
 and we do not hesitate to believe that, in some way or another, 
 they result from the properties of the component elements of the 
 water. We do not assume that a something called " aquosity" 
 entered into and took possession of the oxide of hydrogen as soon 
 as it was formed, and then guided the aqueous ])articles to theii* 
 ])lac('S ill tlu' facets of the crysta], or amongst the leallets of tlie 
 lioar-iVost. On the contrary, we live in the hope and in the faith 
 that, by the adv;vn|^ of molecular })hysics, we shall by-and-by be 
 able to see our v>ny as clearly from the constituents of Avater to 
 the properties of water, as we are now able to deduce the operations 
 
17 
 
 of a wateli fi-om tlio form of its parts and the manner in Avhicli 
 they are pnt touetliei-. Ts the, case in any way changed when 
 carbonic acid, water, and ammonia disappear, and in tlieir place, 
 nn(Un- the intinence of pre-existing living ])rotoplasm, an equiva- 
 K'nt w eiglit of the matti^r (1' life makes its appearance ? It is trne 
 tliat. there is no sort of parity between tlie ])roperties of the com- 
 ponents and the ])ro])erties of tlie resultant, but neither was 
 tlieVe in the case of the water. It is also true tluit what I have 
 s|)ol<en of as the influence of pre-existing li\ing matter is some- 
 thing quite uriintelligible ; l)ut does anybody quite comprehend 
 the modus operandi of an electric S])ark, which traverses a mix- 
 ture of oxygen and hydrogen ? Wliat justification is there, then, 
 for the assnm])tion of the existence in the living matter of a 
 something which has no representative or correlative m the not 
 living matter whicli gave rise to it? What better philosophical 
 status has " vitality" than " aquosity ?" And why should 
 ^' vitality" hope for a ])etter fate than the other " itys" which 
 have disappeared since ]Martinus Scriblerus accounted for the 
 operation of the meat-jack by its inherent " meat roasting qnal- 
 ity," and scorned the "materialism" of those who explained the 
 turning of the s])it by a cei-tain mechanism worked by the 
 draught of the chimney? If scientitic language is to possess a 
 definite and constant signification whenever it is employed, it 
 seems to me that we are logically bound to apply to tlie proto- 
 plasm, or physical ])asis of life, the same conceptions as those 
 which are held to be legitimate elsewhere. If the phenomena 
 exhibited by water are its })roperties, so ai'c tliose presented by 
 ])rotoplasm, living or dead, its properties. If the properties of 
 water may be properly said to result from the nature and disposi- 
 tion of its component molecules, I can find no intelligible ground 
 for refusing to s ay that the properties of proto]) lasm result from 
 the nature aiul ^ dis])osition of j ts^ molecules. But I bid you 
 l)eware that, in accepting these conclusions, you are placing your 
 feet on the first rung of a ladder which, in most people's estima- 
 tion, is the reverse of Jacob's, and leads to the antipodes of 
 heaven. It may seem a small thing to admit that the dull vital 
 actions of a fungus, or a foraminifer, are the properties of their 
 protoplasm, and are the direct results of the nature of the mat- 
 ter of which they are composed. 
 
 l)Ut if, as I have endeavored to prove to you, their proto- 
 plasm is essentially identical with, and most readily converted into, 
 
IS 
 
 that of any animal, I can discover no logical halting place 
 between the admission that snch is the case, and the further con- 
 cession that all vital action may, with equal propriety, he said to 
 be the result of the molecular forces of the pratoplasm which dis- 
 plays it. And if so, it must be true, in the same sense and to 
 the same extent, that the thoughts to which I am noAV giving 
 utterance, and your thoughts regarding them, are the expression 
 of molecidar changes in that matter of life which is the source of 
 our other vital phenomena. Past experience leads me to be tolei'- 
 ably certain that, when the propositions I have just placed before 
 you are accessible to 2:>ublic comment and critieism, they will be 
 condemned by many zealous ]:)ersons, and pertiaps by some few 
 of the wise and thoughtful. I should not wonder if " gross and 
 brutal materialism" Avere the mildest phrase applied to them in 
 certain quarters. And most imdoubtedly the terms of the pro- 
 positions are distinctly materialistic. Nevertheless, two things 
 are certain : the one, that I hold the statements to be substantially 
 true ; the other, that I, individually, am no materialist, but, on 
 the contrary, belicA^e materialism to involve grave philoso]diical 
 error. 
 
 This nnion of materialistic terminology with the repudia- 
 tion of materialistic philosophy I share with some of the most 
 thoughtful men with whom I am acquainted. And, when I first 
 undertook to deliver the present discourse, it appeared to me to 
 be a fitting opportunity to explain how such an union is not only 
 consistent with, but necessitated by sound logic. T pur])0sed to 
 lead you through tlie territory of vital phenomena to the materi- 
 alistic slough in which you find yourselves now plunged, and then 
 to point out to you the sole patli by which, in my judgment, 
 extrication is possible. An occurrence, of which I was unaware 
 until my arrival here last night, renders this line of argument sin- 
 gularly opportune. I found in your papers the eloquent address 
 " On the Limits of Philosophical Inquiry," which a distinguished 
 prelate of the English Church delivered before the members of 
 tlie Philosophical Institution on the ])revious day. My argument, 
 also, turns upon this very point of limits of philosophical inquiry ; 
 and I cannot bring out my own views better than by contrasting 
 them with those so plainly, and, in the main, fairly stated by the 
 Archbishop of York, But I may be permitted to make a prelimi- 
 nary comment upon an occurrence that greatly astonished me. 
 Applying the name of "the Xew Philosophy" to that estimate of 
 
10 
 
 the limits of pliilosopliical inquiry wliich I, iii cOiiiiiion with many 
 other men of science, hohl to be just, the Archbishop opens his 
 address by identifying this " new philosophy^' with the positive 
 philosophy of M. Comte (of whom he speaks as its "founder;") 
 and then proceeds to attack that philosoper and his doctrines 
 vigorously. Now, so far as I am concerned, the most reverend 
 prelate might dialectically hew M. Comte in pieces, as a modern 
 ^Vgag, and I should not attempt to stay his hand. In so far as 
 my study of what specially characterizes tlie Positive Philoso2:>hy 
 has led me, I find therein little or nothing of any scientific value, 
 and a great deal which is as thoroughly antagonistic to the very 
 essence of science as anything in ultramontane Catholicism. In 
 fact, M. Comte's philosophy in practice might be compendiously 
 described as Catholicism onimis Christianity. But what has 
 Comptism to do with the " Xew Philosophy," as the Archbishop) 
 defines it in the fi3llowing passage ? 
 
 " Let me briefly remind you of the leading principles of this 
 new philosophy. 
 
 " All knowledge is experience of facts acquired by the senses. 
 The traditions of older philosophies have obscured our ex2:>erience 
 by mixing with it much that the senses cannot observe, and until 
 these additions are discarded our knowledge is impure. Thus, 
 metaphysics tell us that one fact which we observe is a cause, 
 and another is the efl*ect of that cause ; but upon a rigid analysis 
 we find that our senses observe nothing of cause or effect ; they 
 observe, first, that one fact succeeds another, and, after some op- 
 portunity, that tliis fact has never failed to follow — that for cause 
 and effect Ave should substitute invariable succession. An older 
 philosophy teaches us to define an object by distinguishing its 
 essential from its accidental qualities ; but experience knows 
 nothing of essential and accidental ; she sees only that certain 
 marks attach to an object, and, after many observations, that 
 some of them attach invariably, whilst others may at times be 
 absent. ***** ^\^g .j| knowledge is relative, the not '.on 
 of anythhig being necessary must be banished with other tradi- 
 tions." 
 
 There is much here that expresses the sj^irit of the " Xcw 
 Philosophy," if by that term be meant the spirit of modern sci- 
 ence ; but I cannot but marvel that the assembled wisdom and 
 learning of Edinburgh should have uttered no sign of dissent, 
 when Comte was declared to be the founder of these doctrinesi 
 
20 
 
 ISTo one will accuse Scou-hiiicn oi' liabilunlly Ibro-cttiug tlieir 
 great countrymen ; but it was enough to nialvc David ITume tui'u 
 in his grave, that liei'e, almost ^vitliin ear-sliot of liis liouse, an 
 instructed audience sliouhl liave Jisteiied, witliout a murmur, 
 Avhile his most characteristic doctrines were attiibuted to a 
 French writer of fifty yeai-s later date, in whose dreary and ver])ose 
 pages we miss alike the vigor of thought and the exquisite clear- 
 ness of the styhi of the man whonl I make bold to term the most 
 acute thinker of the eighteenth century — even though that cen- 
 tury produced Kant. J>ut I did not come to Scotland to vindi- 
 cate the honor of one of the greatest men she has ever pi'oduced. 
 My business is to point out to you that the only way of escape 
 out of the crass materialism in which we just now hmded is the 
 adoption and strict w^orking out of the very principles which the 
 Archbishop holds up to re})robation. 
 
 Let us suppose that knowledge is absolute, and not relative, 
 and therefore, that our conception of matter represents that 
 which it really is.; Let us suppose, farther, that we do know 
 more of cause and effect than a certain definite order of succes- 
 sion among facts, and that we have a knowledge of the necessity 
 of that succession — and hence, of necessary laws — and I, for my 
 part, do not see what escape there is from utter materialism and 
 necessarianism. For it is obvious that our knowledge of what 
 ■\ve call the material world is, to begin with, at least as certain 
 and definite as that of the spiritual world, and that our ac(piaint- 
 ance with the law is of as old a date as our knowledge of spon- 
 taneity. 
 
 Further, I take it to be demonsti-able that it is uttei-ly 
 impossible to prove that anything whatever may not be the effect 
 of a material and necessary cause, and that human logic is 
 equally incompetent to prove that any act is i-eall}- spontaneous. 
 A really spontaneous act is one whicli, by the assumption, has 
 no cause ; and the attempt to i)rove such a negative as this is, 
 on the face of the matter, absurd. And while it is thus a })hilo- 
 sophical impossibility to demonstrate that any given phenomenon ; 
 is not the effect of a material cause, any one who is acquainted ! 
 with the history of science will admit, that its progi-ess lias, in 
 all ages, meant, and now more than ever, means, the extension : 
 of the province of what avc call matter and causation, and the I 
 concomitant gradual b.-uiislnnent from all regions of human t 
 thought of what we call spirit and spontaneity. .^ 
 
21 
 
 1 luivc endeavored, in the ti^^^t \)[\vt of tliis discourse, to give 
 you ii conception of tlie direction towards wliicli modern physi- 
 ology is tending ; and I ask you, wliat is tlie difference between 
 the conce])tion of life as the 2)roduct of a certain disposition of 
 material molecules, and the old notion of an ArchiBus governing 
 and directing blind matter Avithin each living body, except this 
 — that here, as else^vhere, matter and la^v have devoured spirit 
 and spontaneity? And as surely as every future grows out of 
 past and present, so will the physiology of the future gradually 
 extend the realm of matter and law until it is co-extensive with 
 knowledge, witli feeling, and with action. Tlie consciousness of 
 this great truth weighs like a nightmare, I believe, upon many 
 of the best minds of these days. They watch what they con- 
 ceive to be the progress of materialism, in such fear and power- 
 less anger as a savage feels, when, during an eclipse, the great 
 shadow creeps over the face of the sun. Tlie advancing tide of 
 matter threatens to drown their souls ; the tightening grasp of 
 law imi)edes their freedom ; they are alarmed lest man's moral 
 nature be debased by the increase of his wisdom. 
 
 Tf the " Xev,' Pliilosophy" be worthy of the reprobation 
 with which it is visited, I confess their fears seem to me, to be 
 well founded. While, on the contrary, could David Hume be 
 consulted, I think lie would smile at their perplexities, and chide 
 them for doing even as the heathen, and falling down in terror 
 before the hideous idols their own hands have raised. For, after 
 all, what do we know of this terrible " matter," except as a 
 name for the unknown and hypothetical cause of states of our 
 own consciousness ? And what do we know of that " spirit'' 
 over whose threatened extinction by matter a great lamentation 
 is arising, like that which was heard at the death of Pan, except 
 that it is also a name for an unknown and hypothetical cause, or 
 condition, of states of consciousness ? In other w*ords, matter 
 and spirit are but names for the imaginary substrata of groups of 
 natural phenomena. And what is the dire necessity and " iron" 
 law under which men groan ? Truly, most gratuitously invented 
 bugbears. I suppose if there l)e an " iron" law, it is that of 
 gravitation ; and if there be a physical necessity, it is that a 
 stone, unsuj^ported, must fall to the ground. But Avhat is all we 
 really know and can know about the latter phenomenon ? fSim- 
 ply, that, in all human experience, stones have fallen to the 
 gi'ound under these conditions ; that we have not the smallest 
 
22 
 
 reason for believing that any stone so eircnmstaneed will not fall 
 to the ground ; and that we liave, on the contrary, every reason 
 to believe that it will so fall. It is very convenient to indicate 
 that all the conditions of belief have been fnlfilled in this case, 
 by calling the statement that unsupported stones will fall to the 
 ground, " a law of nature." But when, as commonly happens, 
 we change will into must, we introduce an i-dea of necessity 
 which most assuredly does not lie in the ol)served facts, and has 
 no warranty that I can discover elsewhere. For my part, I 
 utterly repudiate and anathematise the intruder. Fact I know ; 
 and Law" I know ; but what is this Xecessity, save an empty 
 shadow of my own mind's throwing ? But, if it is certain that 
 w^e can have no knowledge of the nature of either matter or 
 spirit, and that the notion of necessity is something illegitimately 
 thrust into the perfectly legitimate conception of law, the mate- 
 rialistic position that there is nothing in the world bnt matter, 
 force, and necessity, is as utterly devoid of justiiication as the 
 most baseless of theological dogmas. 
 
 The fundamental doctrines of materialism, like those of 
 spiritualism, and most other " isms," lie outside " the limits of 
 philosophical inquiry," and David Hume's great service to human- 
 ity is his irrefragable demonstration of what these limits are. 
 Hume called himself a sceptic, and therefore others cannot bo 
 blamed if they apply the same title to him; but that does not 
 alter the fact that the name, Avith its existing implicjitions, does 
 him gross injustice. If a man asks me Avhat the 2)olitics of the 
 inhabitants of the moon aiv, and I rej^ly that I do not know; 
 that neither I, noi- any one else have any means of knuv>'iiig ; 
 and that, under tiiese circnir.staiices I decline to trouble myself 
 about the subject at all, 1 do not think he has any right to call 
 me a sceptic. On tlie contrary, in replying thus, I concei\e that 
 I am simidy honest aAd truthful, and show a proi)er regard for 
 the economy of time. So Hume's strong and subtle intellect 
 takes up a great many problems about which we are naturally 
 curious, and shows ns that they are essentially (piestions of lunar 
 politics, in their es;-.enee incapable of being answered, and there- 
 fore not worth the attention of men who have work to do in the 
 world. And thus ends one of his essays : 
 
 " If we take in hand any volume of l)i\lnil \ , -t -riKM.l ;neia- 
 pliysics, for instance, let us ask. Does it contain any ahstract 
 reasoning concernlnr/ quantity or number? No. Does it con- 
 
23 
 
 tain any experimental reasoning concerning matter of fact and 
 existence ? Xo. Commit it tlieii to tlie flames ; for it can con- 
 tain nothing but sophistry and ilhision." 
 
 Permit me to enforce this most wise advice. Why trouble 
 ourselves about matters of wliich, however im])ortant they may 
 be, we do know nothing, and can know nothing? iVYe live in a 
 world which is full of misery and ignorance, and the ]dain duty 
 of each and all of ns is to try to make the little corner lie can 
 influence somewhat less miserable and somewhat less ignorant 
 than it vras before he entered it. J To do this eflectually it is 
 necessary to be fully possessed of only two l^eliefs : the flrst, 
 that the order of nature is ascertainable by our faculties to an 
 extent ^vhich is practicall}^ unlimited ; tlie second, that our voli- 
 tion counts for something as a condition of the course of events. 
 Each of these beliefs can bo verified experimentalh^, as often as 
 we like to try. Each, therefore, stands upon the strongest foun- 
 dation upon wliicli any belief can rest ; and fonns one of our 
 highest truths. 
 
 If we find that the ascertainment of the order of nature is 
 facilitated by using one terminology, or one set of symbols, 
 ratlier than anotlier, it is our clear duty to use tlie former, and 
 no harm can accrue so long as we bear in mind that we are deal- 
 ing merely with terms and symbols. ) In itself it is of little 
 moment whether Ave express the phenomena of matter in terms 
 of spirit, or the phenomena of spirit in terms of matter ; matter 
 may be regarded as a form of thought, thought may be regarded 
 as a property of matter — each statement has a certain relative 
 truth. But witli a view to the progress of science, the material- 
 istic terminology is in every way to be preferred. For it con- 
 nects thought with the other plienomena of the universe, and 
 suggests inquiry into the nature of those physical conditions, or 
 con-comitants of thought, which are more or less accessible to 
 to us, and a knowledge of which may, in future, help us to exer- 
 cise the same kind of control over the world of thought as we 
 already possess in respect of the material world ; whereas, the 
 alternative, or spiritualistic, terminology is utterly barren, and 
 leads to nothing but obscurity and confusion of ideas. ^Tlius 
 there can be little doubt that the further science advances the 
 more extensively and consistently will all the phenomena of 
 nature be represented by materialistic formula? and symbols. 
 But the man of science, who, forgetting tlie limits of philosoj)hi- 
 
24 
 
 oal inquiry, slitlos from these formula^ aiul syial)ol> into what is 
 commonly understood by materialism, seems to me to place hun- 
 self on a level with the mathematician, who should mistake the 
 .v'.s an<l y\v. with which he works his .problems, for real entities — 
 and with this further disadvantai:e, as compared with the math- 
 ematician, that the blunders of the latter are of no practical con- 
 se(pience, Avliile the errors of systenmtic materialism may para- 
 lyze the eneroirs and destroy the beauty of a life. 
 
 T. IT. IirXLEY. 
 
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