ginal features can hardly be recognized, or its true nature discovered. Thus, reasoning from causes to effects, and from effects to causes, is extremely difficult, and the inquirer who attempts it often finds himself involved in a maze of perplexity, through which the few rays of twilight which he is able to command, are insufficient to enable him to see his way, or extricate him from the midnight darkness by which he is surrounded. His situation resembles that of a traveler in a strange land and in a starless night, who gropes along a narrow, and winding, and dangerous way, rendered almost impassable by every species of ob

struction.

In medicine we are never able in strictness to repeat the same experiment in order to detect our errors, and give certainty to our conclusions; and this happens for the obvious reason that circumstances are without our control and beyond our knowledge. Suppose the warm bath is prescribed, as it appears, successfully in a certain species of disease. This prescription is an experiment, and we wish to repeat it in order to confirm ourselves in the conclusions we have derived from it. Now it is a matter of extreme uncertainty whether we ever meet with a second case of precisely the same kind. Even in what is nosologically the same disease, constitutional predisposition, temperament, age, sex, season, climate, particular locality, the nature of the prevailing diseases, &c. &c., are operating and modifying circumstances which are rarely present in the same combination, and in the same intensity, in two different cases, even in the same individual. In endeavoring to repeat the experiment, we truly make a different one, closely or remotely resembling it, according to our knowledge and sagacity. In physical science, such is the fixedness and order, and such our power of selection, combination and separation among the objects of our inquiry, that we are able to repeat a given process an indefinite number of times, and thus to detect and remove all cause of doubt or fallacy in the result. A single well directed experiment in physical science often proves decisive between the claims of rival and plausible hypotheses. Thus by a single stroke, causes which are simply concurrent or accidental, are distinguished and completely separated from those which are efficient and essential. These experimenta crucis, so satisfactory and decisive, where their application is admitted, are unknown in medicine.

In the phenomena of the material world, causes and their effects are immediately successive, or at any rate, not far separated, so that in general, there is little, or comparatively little, difficulty in detecting their relation. When a moving body comes in contact with one at rest, motion is immediately communicated to the

latter. There is no appreciable interval. Cause and effect are recognized as such without difficulty. Not so in medicine. Here they are separated, and often widely. Their connection is not discovered without diligent search; and in consequence of the intervention of other phenomena, a concatenation is often supposed very different from the true one; hence, fallacy of reasoning. The proper effects of a remedial agent frequently cannot be determined until after the lapse of some time; while the multiplied phenomena which fill up the interval, divert and confound the attention, and sometimes lead to error. For instance, the beneficial influence of any given method of treatment, in the forming stage of fever, cannot be fully appreciated until the arrival of the crisis, or even a later period. Whether a crisis takes place early or late, whether it is complete or incomplete, whether it is followed by convalescence or death, whether the final restoration is perfect or imperfect, depends very much on the nature of the first remedial step which has been taken. Suppose blood has been copiously let by an ignoramus at the onset of some low typhoid fever in which it was contra-indicated. The injurious consequences probably would be only in part developed, perhaps not at all, at the time. Perhaps even a mitigation of symptoms might be the immediate result, (for this sometimes happens in such cases.) The detrimental influence of the measure would be but partially discovered until the arrival of the crisis, when the sudden and irrecoverable sinking of the vital powers, or the giving way of some organ or organs essential to life, would announce the hopelessness of the case and the temerity of the practice. In consequence of this disjunction of cause and effect, the ignorant, the rash, the indiscriminating, the speculative, and those who think and act by rote, instead of turning their blunders to their improvement and gaining knowledge from the light of past experience, trudge blindly on, unconscious of error, too stupid to see and reflect, and too proud and confident to learn. In searching for the causes of death, they rarely look back farther than those of immediate antecedence. They do not perhaps even think of that which is truly and chiefly operative; or if it enters their minds, they attribute to it little importance. Thus a conviction of error is never a part of their experience.

This disjunction of cause and effect is also productive of much unmerited censure to the judicious physician, as well as unmerited praise to the ignorant and unprincipled. Friends who are over anxious are often unwilling to await the final results of measures. They look more to immediate than ultimate consequences, and if they do not see almost instantaneous good from a given course of treatment, soon lose their confidence, and rep

rimand or turn away their medical attendant. So on the other hand, such is the disposition to connect an effect with its immediate cause, that any favorable change in a disease is at once attributed to its immediate antecedent; and the impostor who happens to administer some of his panacea at a critical juncture of this sort, is without hesitation set down as a man of extraodinary knowledge, and almost superhuman medical skill. As these junctures are always happening in the course of disease, there is no one, however wildly he may prescribe, but will occasionally stumble upon one, and thus gain an opportunity of building up a reputation. A straggling empiric, who deals out his specific to a patient in the transition state from sickness to health, very probably has attributed to his interference every subsequent step in the progressive convalescence; and though in his ignorance he might mistake what a sensible nurse would recognize, his wonderful success is most likely appealed to as a silencing argument against the cavils of the gainsaying and sceptical.

From what has been said, let it not be inferred that in medicine there are no principles; that in medical phenomena there is no order, no fixed laws; that in reasoning upon them we are incapable of drawing any probable or rational conclusions. Our object has been to show that great and peculiar difficulties beset the calling of a physician, and to set in a strong light the necessity in his case of a mind well cultivated, and well disciplined, and accustomed to the investigation of obscure and complicated phenomena, and acquainted with the nature and evidence of truth. The very difficulty of the investigation affords an additional reason why the mind of the investigator should be amply furnished and prepared for the work. Though with the best qualifications he is often obliged to act on probabilities, still he has advantages immeasurably greater for arriving at certainty, than the undisciplined and uninformed.

In every department of knowledge, there is the frequent confusion of inferences with facts, which is a source of inconclusive reasoning. What are called facts, and admitted as such, are often only the deductions of fallible reason. When the premises are unsettled, all conclusions founded on their truth, are of course of equivocal soundness. When Cullen spoke of the frequency of false facts, and their prejudicial influence in medicine, he had his eye upon this source of fallacy and error. When a drug is administered in a case of dangerous sickness, and recovery presently follows, the efficiency of the drug in the restoration is taken as a fact by the ignorant, and is considered as such in all future time, whereas it is only an inference-a distinction of the utmost consequence. The administration of the medicine, and the re

covery of the patient, are indeed facts, and all the facts; the agency of the former in bringing about the latter, is only a deduction from these facts, and a probable or improbable one, according to the circumstances of the case. The facts of the mere man of practice are generally no more than these inconsiderate inferences; he is obstinate and incredulous because he does not know their nature and is unable to detect the origin of his errors. His experience, of which he talks so much, is as false as the premises which he takes for granted. It is grounded on nothing better than assumptions and hypotheses. Even the man of philosophic and cultivated mind, with all his discrimination and acuteness, sometimes finds it difficult, in his long and intricate investigations, to distinguish and separate facts from inferences, and to give each their true names, and to estimate their respective claims to importance. Though liable to mistake, a knowledge of this liability and of the source of his danger, induces him to be cautious, and directs him in his attempts to detect fallacy where it is found to exist.

The equivocal nature of language, is a productive cause of confusion in medicine. As much the greatest part of our knowledge on almost every subject is received from others, either immediately from their lips, or mediately from books, and as there is no other mode of communication between one mind and another, except through the medium of signs of conventional use, it becomes of the greatest importance that these should express with the utmost precision the idea intended to be conveyed. Now this is impossible with language in medicine. The application of names to objects, and to the qualities of objects, is entirely arbitrary: they have no resemblance to the things to which they are applied. Every one has felt the difficulty of expressing himself with clearness and precision upon abstract subjects. When we attempt to describe a simple sensation, we all know the erroneous impression which is frequently left on the mind of the hearer. In the mathematical sciences we are not subject to this difficulty. Wherever we can apply the rule and the compass, or use number, weight and measure, or deal with circles, squares and solids, we are not liable to be misunderstood. When we speak of a pound, a gallon, an equilateral or right angled triangle, or a circle of certain dimensions, a cube or a sphere of given size, we are sure that every one who hears us receives our idea perfectly, provided he has once been made to understand the meaning of these several terms; but when we talk of subjects to which we cannot apply instruments of measurement, as of colors, in the absence of the objects of which they were once supposed to be properties, of sounds which cannot be recalled, of tastes and odors of

which we have formerly been sensible, of pain, or any other bod ily sensation, we often convey an imperfect, a distorted, or erroneous idea of what we mean.

In medicine, as in subjects of an abstract nature, language is an important medium of thought. Diseases and medical phenonomena are not the direct objects of sense; they have neither color, nor figure, nor dimensions; nor can they be accurately represented on canvass. Signs, when used to represent them, are of arbitrary application; they have no resemblance to the things they signify, and in using them to express our ideas, we can only approximate to truth in the impression we make on the mind of another. We cannot call up at pleasure the thing signified, by way of illustration, to give precision and certainty to our words. Disease is supposed by people in general to be a real, substantial existence, as distinct in its characters and figure as an oak, a horse, or a whale; but it is only a mode of existence. We only know its presence by the symptoms which indicate it, which are qualiities. Like the cause of gravitation, or of electrical phenomena, we know it by its effects, not in itself. Those symptoms, by which we learn its existence and characterize it in description, are manifestations of an unknown state-mere qualities which language is inadequate accurately to embody and convey in the absence of the cause. For instance, the beat of the arteries, or the pulse, is important in its indications in disease. By its general character, by its force, by its frequency, by its hardness or softness, by its volume, etc. it tells us of the existence of particular morbid states; but all these terms are relative-they want precision. The words force, frequency, hardness, etc. are loose in their signification, for we have no standard of comparison. In attempting to characterize the pulse then, we do it but awkwardly and imperfectly. We are liable to the same uncertainty in describing the state of the tongue, the skin, the countenance. But besides; the pulse often has a feel of which it is impossible to give even this faint representation, though it may give important information, because we have no words in the language to use for the purpose. Circumlocution and comparison are of no avail. Those who attempt to describe it find themselves baffled; or if they think they succeed, the diversity of impression which they make on others' minds, shows their common failure. In order to gain a correct notion of, such a pulse, it must be felt; and in order to recognize it where it exists, we must have had a previous acquaintance with it. Whatever is true of the pulse, is also true of the tongue, the countenance, the skin, etc. They have peculiarities which words cannot embody. If we would know them, we must see and feel them. Any one may discover our meaning by attempting to draw a pic