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"A living being, considered as an object of chemical research, is a laboratory, within which a number of chemical operations are con. ducted; of these operations, one chief object is to produce all those phenomena which, taken collectively, are denominated · Life ;' while another chief object is to develope gradually the corporeal machine or laboratory itself, from its existence in the condition of an atom, as it were, to its utmost state of perfection. From this point of utmost perfection, the whole begins to decline as gradually as it had been deve. loped; the operations are performed in a manner less and less perfect, till at length the being ceases to live; and the elements of which it is composed, again set free, obey the general laws of inorganic nature.”
But although it is true that chemical compounds are formed in the living being, and that these compounds may be resolved into the elements which we find in brute matter, still by no means whatever can the chemist work backwards, and again form those organic compounds from the elements which he has set free. Elementary principles, such as carbon, oxygen, hydrogen and azote, may be liberated from fibrine or soluble albumen, and, moreover, the exact proportion of each be ascertained, and yet all the art of all the chemists has never yet been able to make them enter again into combination, so as to reproduce fibrine or albumen. How is this?
Without occupying our time with the “ Moving Principle” of Aris. totle; the “ Anima” of Stahl; the “Archæus" of Van Helmont; the “ vis medicatrix naturæ,” and a thousand other vagaries of the imagina. tion, let us come at once to the state of physiological science at the present day.
On this subject, physiologists are divided into two sects.
The first of these maintain, that the phenomena of life must be referred to the agency of a force or power, distinct from, and opposed to, the general affinities of brute matter.
The other sect maintain, that the existence of any such force is a pure hypothesis ; that there is no necessity, or even good reason for its introduction; and that all vital phenomena, so far from being opposed to the general laws which regulate the operations of matter, are in reality but so many various manifestations of those laws.
The first support their tenets in this way :
It is admitted that those compound substances which are formed in living bodies cannot be imitated by the chemist. Let him bring carbon and oxygen and hydrogen together as he please, he cannot, with his greatest skill and all his agents, produce one single compound such as is produced in living beings. He can neither form starch nor sugar, nor lignine, all of which are organic compounds formed of these ele. ments in different proportions. Now, what is the art of the chemist? In forming compounds from elementary substances, what does he do, what can he do, but bring those substances in contact with each other? If they have affinities for each other, he can no longer control them; they must, of necessity, obey those affinities ;- he can neither limit, nor increase, nor diminish their play after it has once commenced.* Those
* Traité de Chimie, tom. v.
† Ad opera nil aliud potest homo, quam ut corpora naturalia admoveat et amoveat reliqua, natura intus transigit.--Nov. Organum.-Aph. iv.
elements, then (carbon, oxygen and hydrogen), will not combine, of their own natural affinities, one to another, so as to produce an organic Compound. We are, therefore, obliged to refer the formation of these compounds to another force, more powerful than the affinities of their elements, one to another. This force we term the “ Vital Force;" and we use the phrase to designate some unknown power which we infer to be in operation, from the results we see. In truth, so far from framing an hypothesis, we are, in reality, only adhering more closely to phenomena. And the case is precisely the same with all other subjects of inquiry in physics. There are, in every direction, ultimate facts beyond which we cannot proceed. The word " attraction” is used to designate that tendency which one mass of matter has to approach another mass;
- the word “affinity,” to distinguish the approach of the particles of a substance to those of another. But in either of these instances, is it possible to go beyond the visible phenomena? Has the unknown cause why bodies approach each other ever been revealed ? Assuredly not. The words attraction and affinity are used merely to represent certain actions in matter, the efficient causes of which are unknown. In like manner we use the words “vital force.” We employ the term to distinguish certain other actions in matter, which we see, in their results, to be different from those actions represented by the word affinity.
Concerning the intimate nature of this force or power, we feel it to be useless to speculate ; just as it is useless in the case of attraction or affinity. Vital actions are ultimate facts, in the same way as chemical combinations, or the revolution of the planets, are ultimate and inexplicable.
Again, we see every day that organic compounds may or may not possess life. Sugar and starch are organic products, and they may exist in the living vegetable or out of it; that is, they may be endowed with life or not. Fibrine or albumen may exist in the vital state, or in that of brute matter : therefore, life must be a principle superadded to common matter; for if it were not, there would be no difference between fibrine and albumen in the living body, and fibrine and albumen out of it.
Moreover, it is idle to talk of Life as the result of organization. Attentive observation of phenomena warrant no such conclusion, but, indeed, rather the reverse. It is true that life is never met with, and cannot be conceived of, apart from organization ; but is organization ever met with, which, at one time or other, has not been endowed with life? Is not, in fact, the organization built up by what we call the vital force? What two things on earth more dissimilar than the human being in the flush of manhood, and the embryo a week old? Where a greater difference than between the full-grown oak and the acorn ? And yet the embryo and the acorn were the primitive forms of these two beings, man and the oak. And what has thus built them up, but the vital force ? Abstract this force, or principle, or whatever you choose to term it, from the acorn or the embryo, and what is the con. sequence? The acorn will never become an oak, nor the embryo a man. Then it is, that the usual, the ordinary affinities of matter come in play; — after the removal of this controlling power, the vital force.
The chemical elements, no longer subjected to a superior power, obey the general laws of brute matter : particle obeys the call of particle, and the organic fabric is resolved into its elements, or moulded into new compounds.
Such are the arguments used by one class of physiologists. The reasons urged are unquestionally specious, nay, convincing to those who are not accustomed to close and abstract reasoning. But let us look a little more closely at the matter.
Life, in the other view of the case, is a general term, employed to express a great variety of phenomena, which have agreement in certain points, but may be altogether different in others; just as the word * quadruped” is used to designate certain animals, which may resemble each other only so far as they all have four legs: for that this is really the case, one may satisfy himself by solving the question, what are those phenomena common to both a bird and a plant? It will be found that they agree only in possessing an areolar tissue, in which certain actions are constantly going on. The results of these actions being different from what is observed to occur in brute matter, it has been thence inferred, that the chemical elements which enter into organic compounds are forced into combination by a distinct power superior to those general affinities wherewith, observation informs us, all matter is endowed. The reasons advanced we think inconclusive and unsatis. factory.
Because (to commence this subject with a criticism) this thing which has been a force, a principle, an agent, &c., just as happened to suit the fancy of the employer, must necessarily be in one of three categories. It must be either a substance, the property of a substance or substances, or it must be merely expressive of a condition or state of things, which condition may be one either of repose or action of rest or motion-static or dynamic.
Were life a material substance, it must of necessity possess the general properties of matter, and so be cognizable by the senses; and that such is not the case, it is scarcely necessary to mention. Nor can life, with logical strictness, be assimilated to the imponderables. Of the existence of light, heat and electricity, we have the same evidence that we have for the existence of any thing external to us, viz., that of our senses. For the existence of life as an entity per se, we have no such evidence. Moreover, we are acquainted with many of the properties of these imponderables ; they are the subjects of extensive sciences;but what properties of life are we acquainted with? Those properties, termed vital, such as sensibility and contractility, are the properties of certain tissues and organs existing under certain circumstances, not of a particular substance called “ life.” *
* Bichat has no less than five of these vital properties. Later authors have reduced them to two, contractility and sensibility.
Now, what is contraction? It is but a closer approximation of particles, so that the volume of the whole mass is diminished. If cold be applied to the skin, it contracts ;- if we prick or galvanize a muscle, or if we exert our will, it contracts. We know, in the last case, that if the nerve leading to the muscle be divided, no contraction will ensue. Hence, in all cases, there is some material cause (whether we have discovered it or not) producing the effect.
Those who would make life an immaterial principle, are surely guilty of framing a very vague hypothesis, which, indeed, may be very conve. nient, as it puts a stop to all further inquiry, and may be acceptable to those who suppose they learn any thing from admitting it, but which we have just as much reason to frame for the solution of any other phenomenon, and just as much reason to insist upon. But, in truth, this is one of those hypotheses which can neither be maintained nor refuted, since it is impossible for the human mind to frame any distinct notion of such a principle. It is a sound, and nothing more.
Admitting, however, for the nonce, that it is possible to attain a clear conception of it, have we escaped our difficulties ? Review the great variety of living beings; observe the innumerable diversities of form, and the multitude of organic productions. Has each species of living beings a vital principle peculiar to itself? If the answer be yes, the difficulty is by no means got over: the admission must extend far beyond this. A separate vital principle must be framed for every tissue and organ, the functions of which are different.* Now, there is a time when the embryo exists without any of the organs being yet formed: where, during this period are their peculiar vital principles?
With regard to the different tissues and organs, and the functions they perform, it may be argued, that though the vital principle is identical in all, yet different effects are produced, because the materials on which it operates are different.t But this very argument carries with it the admission, that there are other causes besides the existence of a vital principle, why gastric juice is secreted from one organ, and urine from another; why muscular fibre is deposited in one place, and bone, &c., in another. Afier such an admission, the vital principle may be rejected entirely; it is no longer necessary to explain vital phenomena.
Again, plants and whole tribes of the inferior animals are capable of propagation by division. By cutting to pieces a single individual, we may make hundreds, each of which will possess an independent life. Have we, in this case, divided the vital principle? How can we ima. gine the division of a thing which is not material ?
Contractility is inseparably connected with the peculiar structure and chemical constitution of the tissue which contracts, and is, therefore, as much a physical property as any other.
Contraction, moreover, is not a phenomenon peculiar to living beings: it occurs also in dead substances. Metals expand by heat, and contract from cold; wood expands by absorbing moisture, and contracts when robbed of it. (a)
Sensibility, also, can only be termed a rital property, in the sense that none but living beings manifest it. But neither do all living beings possess it; nor all parts of the living system of sentient animals. It is, therefore, not essential to life.
* It is considered by many, and perhaps truly, that we are not yet prepared for a generalization of so high a kind, (that is, the hypothesis of life, being a simple principle,) or, at least, that it would be more convenient for the analysis of vital phenomena to consider life as made up of several principles differing in their nature."--Notes to John Hunter's Principles of Surgery, by JAMES F. PALMER.
† Such was the opinion of John Hunter.
(a) The difference betwoen this species of contraction, and that of the muscles, has been pointed out in the Essay on the Nervous System.-See Chapter 10.
If life be made a separate and distinct property of matter, the enormous difficulty presents itself, for us to conceive how matter can possess a property that is moveable,-tbat may reside in a certain substance to-day, and, without the occurrence of any change in its structure or che. mical constitution, be gone to-morrow,—which must occur if death can take place without disorganization, as the vitalists contend.* That the properties of a substance may be dormant, it is easy to conceive, because it may have never been placed under those circumstances necessary for their revelation ; but that matter, without a change of form, or of the disposition of its molecules, can take on and put off again a property, is, we humbly think, an impossibility-a proposition irre. concileable with the notions of matter that our minds are constituted to entertain; for, (to come to the pith of the matter,) what is the real meaning of the words, force, power, property, &c. ?
In strict philosophy, observation is the only admitted means we possess of obtaining knowledge. Observation, and reflection upon what we observe, are the limits which bound in all human science, and beyond which the human mind cannot advance. “Homo, naturæ minister et interpres, tantum facit et intelligit, quantum de naturæ ordine, re vel mente observaverit; nec amplius scit aut potest.” To this aphorism of Bacon, our reason gives assent at once, for it requires no great expendi. ture of logic to prove that a dream is to be valued but as a dream; that an hypothesis, until proved to be true, is but an assumption ; in short, that in leaving the path pointed out, we turn aside from nature, to pursue the meteors of the imagination.
Keeping, then, our senses intent upon facts, what do they reveal to the mind? The existence of unremitting activity; of change-inces. sant change; of phenomena succeeding phenomena in endless rotation! But for any of these phenomena, where shall we find an ultimate reason? True, we may often take to pieces, as it were, some particular fact, and show that it is made up of a series of more general phenomena. But for any one of these general or ultimate facts, as they are called, who shall give a reason? Why may it not have happened otherwise ? or exactly the reverse ?
* " I have observed that animal matter may be in two states; in one, it is endowed with the living principle, in the other it is deprived of it. From this it appears, that the principle called life cannot arise froin the peculiar modifications of matter, because the same modification exists when this principle is no more. The matter abstracted from life appears at all times to be the same, as far as our senses and experiments carry us.”—John Hunter, Principles of Surgery, chap. ii.
“ Our ideas of life have been so much connected with organic bodies, and principally those endowed with visible action, that it requires a new bent to the mind, to make it conceive that these circumstances are not inseparable. I shall endeavor to show, that organization and life do not depend in the least on each other; that organization may arise out of living parts, and produce action, but that life can never rise out of, or depend on, organization. An organ is a peculiar conformation of matter (let that matter be what it may) to answer some purpose, the operation of which is mechanical : but mere organization can do nothing, even in mechanics, it must still have something corresponding to a living principle, namely, some power.”—HUNIER, On the Blood, fe., chap. i., sec. vi.