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that perhaps there never was a writer whom it would be a greater severity of justice to make strictly accountable for all the natural inferences from what he says.
We have been drawn on to a length of observation far beyond our intention, by a solicitude to combine with that impartial justice which is the duty of our office, the most favourable representation, which the sincerest candour could give, of the work of an Author whose moral temperament and whose attainments, are adapted to excite a friendly disposition even in veteran critics.
In the Notes there is a very curious illustration of the compatibility of great mental powers and exercise with long life, in a very ample list of eminent men of genius, learning, and science, who have attained a great age. Art. IV. An Experimental Inquiry into the Effects of Tonics and
other medical Substances on the Cohesion of the Animal Fibre. By the late Adair Crawford, M.D. F.R.S. Edited by Alexander
Crawford, M.D. 8vo. pp. 124. Callow, London, 1816. IT T is a curious fact connected with the consideration of the
laws and susceptibilities of animate existence, that a minute portion of matter taken into the stomach of a living animal, shall in some instances produce upon a distant part of the frame, an operation similar to what shall be produced by a larger portion of the same material, applied directly and without intervention to the part itself. This principle of agency is especially shewn in the case of astringents. Astriogency, as acting upon dead animal matter, would seem to be a something which causes the particles of such matter to take a different form and arrangement from that in which they existed prior to the subjection of the material to this kind of agency. This is familiarly illustrated in the instance of tanning the skins of particular animals, and thereby forming different kinds of leather. When substances of similar quality are applied externally and directly to a part of the living body, the analogy of their operation is, to a certain extent, sufficiently obvious. Thus it is easy to conceive, that the principle by which styptics contract the diameter of bleeding vessels, and so arrest hæmorrhage, is the same as that which contracts the fibres of skin, and hardens it into a new substance. But when, in order to stop the flow of blood from large and distant vessels, recourse is had to the internal administration of a comparatively minute portion of matter possessed of styptic qualities, and thereby a result similar to that which attends upon a more bulky and direct introduction of the same substance, is produced, it is not so easy to trace in this latter instance the actual similarity of agency.
Certain preparations of lead, for example, when applied outwardly in a given quantity, most unequivocally evince a constringing and styptic power; and the same effect is shewo when such preparations are taken into the stomach ; but then, in this latter case, the quantity made use of, must, in order to ensure either safety or efficacy, be much less than in the former instance. And so in respect of several other mineral as well as vegetable substances, which, either diffused through the mass of circulating blood, or communicating their influence through the nervous system in some way that is at present inscrutable, convey as it were their virtues in this remarkable manner, to distant portions of the animate machine.
But further, there are some medical substances which operate with the same effect upon the living body, without possessing a similar property in any degree, when applied to dead matter, or even to the surface of the organized frame. An author who was much more in repute, about twenty years since, than he is at present, has ventured boldly to deny that there is even the most distant analogy, between the impulse given to living actions, and the astringent or tonic effect operated upon dead matter. Density and tone, Dr. John Brown tells us, are regulated by laws essentially different, in the living system and in dead matter; and he has expressed this doctrine by the following axiom : 'Incitatio densitatis (in vivo corpore) causa.' Density, in the living system, is the effect solely of excitement. But this axiom is at variance with unprejudiced and faithful observation, and cannot therefore stand the test of truth. The hypothesis, however, from which it was engendered, has had an extensive influence upon the whole system of medical science, and a kind of sceptical generalization has insensibly become fashionable in the practice of physic, even among many who would be anxious to repel the slightest imputation of Brunonian faith.
Under these circumstances we cannot but regard the present performance as exceedingly well-timed, and calculated to bring back into estimation and into use many important agents in medicinal operation, of the actual virtues and beneficial qualities of which practitioners were sliding into an unwarrantable disregard.
Dr. Adair Crawford's name is well known to every one who has the most slender acquaintance with physiological science. The doctrines of animal heat first promulgated by this physician, notwithstanding the several material modifications they have undergone since his time, are in their great outlines still received. A posthumous work, therefore, from an individual of his great fame and real professional merit, cannot fail of being received with some avidity; and, as the subject of the present inquiry is interesting to the philosopher as well as to the physician, we have judged it not inconsistent with our general plan to introduce it to the attention of our readers.
The following is the Editor's statement of the circumstances connected with the publication before us.
It is upwards of twenty years since the following treatise was prepared for the press by the author ; but the publication was prevented by his death, which happened immediately after. It is unnecessary to trouble the public with all the reasons that have delayed the publication since: only for the last six years, the time it has been in my possession, a very infirm state of health prevented my at. tending to any serious pursuit. The copy from which this is printed, is in my brother's hand-writing ; and, however it may be received by those who are most interested in such investigations, I believe it will not be thought presumption to allege that it bears marks of that industry, ingenuity, and just reasoning, which, in the opinion of the philosophic world, distinguished the former writings of the author,
The experiments and investigations, an analytical view of which we are now about to present to the reader, are founded upon the analogical principles just referred to; and, indisposed as we are to urge any thing in the way of cavilling objection to the reasonings and inferences of such a man as the late Dr. Crawford, we must just premise, that it seems to us that this analogy is pursued to an extent beyond the warranty of truth. We wish to be understood as saying, that his deductions from experiments on small portions of exanimate matter, are, in our judgement, too readily transferred to the phenomena of the organized body.
Dr. Crawford informs his readers that he was led to the experiments detailed in the tract before us, by having observed that when the fibres of animals were immersed in the poison of cancer, they became tender and flaccid; and that when they were exposed to it in contact with common air, they speedily putrified and lost their cohesion. It appeared to him that the diminution of cohesion, in this instance arose, principally from the action of a peculiar fluid, which he denominates animal hepatic air.
• As this fluid (he says) abounds in nature wherever the putre. faction of animal substances exists, it seemed not improbable that many of the morbid appearances in the human body might be ascribed to its influence. For it is manifest, that whatever has a tendency to destroy the cohesion of fibre, must, if not counteracted, eventually give rise to disease or to death.'
Here, in the onset, we are presented with a theory that is, if we may so say, somewhat too chemical. It is true, that an exposure to the noxious qualities of what our iogenious Author calls animal hepatic air, gives occasion to a softness and
want of due cohesion in the fibre, as is instanced in the flaccidity of muscle, and comparative want of tone, observable in individuals who live in crowded cities, or who are otherwise constantly exposed to the impure atmosphere in question. But this noxious air does not seem directly to influence the fibre by the body being in a manner constantly immersed in it; the effect appears to be produced in a more indirect and circuitous manner.
We have, (to point out just one or two links in the chain of causes,) a want of due stimulas to the lungs, a consequent or connected diminution of appetite and digestion, a torpor of the several secretory organs; all acting in conjunction towards occasioning a diminished tone and consequent flaccidity of flesh. Dr. Crawford could not but be aware of these principles ; but we would suggest whether he may not in some measure have overlooked them in the experimental inquiries now to be noticed.
Our Author premises the following definitions, in order to render his subsequent observations more precise and comprehensible.
* By the term cohesion, I mean to express not only the power in. herent in bodies, which resists the disunion of their particles, but likewise that which prevents the particles from changing their relative positions, and from yielding to such forces as have a tendency to separate them to a greater distance from each other.
• Hence it will appear, that under the cohesion of the fibre I comprehend its firmness, elasticity, and strength; affixing to these terms the following significations.
• By the firmness of the fibre, I mean to express the force with which it resists impression ; by the elasticity, its power of resisting extension, and of restoring itself when the extending cause is removed; by its strength, the force which it is capable of exerting in opposition to such causes as tend to destroy the continuity of its parts.
· The first of these properties is known by the touch ; the second, by the comparative extension which the fibres undergo, when they are stretched by equal small weights; and the third, or the strength of the fibre, is known by the weight which is required to break it.
• Those substances (our experimentalist goes on to say, which diminish the firmness and elasticity of the fibre, I shall call relaxants ; those which increase its elasticity, tonics; and those which increase its strength, corroborants.
* It is proper to observe that in the living animal the tone of the fibre is a compound effect. It depends not only on the elasticity of the simple solid, but likewise, as my learned colleague, Dr. Fordyce, has justly observed, upon the energy of the vital principle; in con sequence of which, the approximation of particles during life is greater than that which would be produced by their elasticity alone. The tendency to approximation which they derive from this cause, may, I think, properly be expressed by the term contractility, And hence, in the living animal, those substances must be considered as
tonics, which increase the contractility, as well as the elastic force of the fibre. *
Although it might seem that the elasticity and strength of a fibre should bear some proportion to its firmness, yet it does not appear that any invariable connexion takes place between these properties in nature. We know, that in many cases great strength is united with much softness. Pure gold, for example, is nearly as soft as tin, but its strength, bulk for bulk, is equal to that of iron. · Now, in the last of these very ingenious, and in the main very important and just distinctions, we again have to remark a tendency to infer too much from dead to living existence. Because softness is compatible with strength in some metallic substances, it does not therefore follow that this is the case with the nervous vascular or muscular organization when under the influence of vital excitement. Under these circumstances, indeed, we should feel disposed to question altogether the compatibility of flaccidity of fibre, with display of power; we allow that hardness is not an absolute measure and indication of strength even in the living body, as in some cases of spasmodic or otherwise inordinate rigidity a proportionate degree of capacity cannot with propriety be predicated ; but we believe in all cases of due and healthy excitation the flesh will give to the feelings the sensation of hardness or firmness in the ratio of fibrous or muscular strength.
Dr. Crawford's series of experiments are detailed in the following order. First, he confines his observations to the effects produced on the fibre by vinous and spirituous liquors ; secondly, he tries the effects of narcotics ; thirdly, the different vegetable bitters; fourthly, acids and alkalies, fifthly, neutral and eurthy salts; and, lastly, he details the effects produced by metallic preparations.
Port, and Sherry wines, are the first materials made use of; and it will be necessary to state in full the experiments with these materials, in order to give the reader an insight into the manner in which the whole series of trials was conducted.
Experiment 1st. * With a view (says Dr. C.) to determine the changes which the fibre might undergo by exposing it to the action of port wine, six portions of the small intestines of a kitten were taken, each of which was two inches and a quarter in length. Three of these were introduced into a phial, which was nearly filled with port wine, and closed with a cork; and the remaining three were immersed in water as a standard. Being placed in a cool situation during three days, the portions in contact with the wine were found to have greater firmness than those that were immersed in the water.