different. That which alone can give to a particular fact in the treatment of disease the stamp of genuine value, is the wide and uncontradicted assertion of its truth by competent observers. A true experience in medicine, T would define as the result which is arrived at through the observation of numerous fitting observers; wlho, after due investigation, arrive each at a like concltusion-the conclusion not being contradicted by the observation of other equially capable observers. Whenever

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... us discordance of opinion exists concerning the influence of a remedy over disease, wisdom would lead us to infer that its actual influence in such case has yet to be demotnstrated. The pathology, then, of modern days, however little it may have helped us to a knowledge of the nature of the essential and original provoker of diseases, has been of immense service in directin,g us rightly and logically to their treatment. It does not tell us how or why tubercle is deposited in the organs of the body; buit it does teach us how to ward off and provide for the local injuries inflicted on the organs by its presence. When we would learn how to counteract the depositing of the tuibercle, then we must turn to the lessons of experimental therapeutics. And it is from the results of expelience alone that we can, in any case, arrive at a knowledge of the treatment of disease, so long as pathology is unable to disclose to us its nature. I need not here refer to the extraordinary changes which lhave passed into the treatment of diseases in consequence of the recognition of these sort of facts. No class of diseases illustrates this fact more remarkably than the diseases which I am about to speak of here. We no longer look upon en docarditis, or pericarditis, simply as local, so-ctalled, idiopathic itflammations; for we now know them to be the expression of some general disordered condition of the body; and we recognise the fact that the successful treatment of these diseases implies the application of a remedy which shlall, so to say, neutralise the agent which produces the disordered condition. We do not now regard the local inflammation as the sole element to be provided against in treatment; and consequently have discovered that those prime agents, bleeding and mercury, which were once thought to be intensely efficacious in cardiac inflammations, are actually baneful when used as then recommended. The physical diagnosis of diseases is founded on pathological anatomy. It, in fact, premlises a knowledge of the pathological states of the different parts of the body, such as they are displayed to us by the anatomist. In the case of the heart, our knowledge of its diseased conditions, so far as they are explained to us by physical diagnosis, is derived-from alterations in the natural character of its sounds; from the presence of sounds, wvhich are heard over the heart coincidentally with its movements, anid where none such exist in health; from alterations in the natural extenit of the precordial dulness, as ascertainied by percussion; and from changed conditions-changes in extent, position, an(d force-of the healthy impulse of the heart. It is unnecessary to dwell upon the advantages which medicine lhas gained through the discovery of the diagnosis of internal diseases. The study has naturally become an essential part of the physician's education. But it has been thought, and with reason, that the stuidy may be too minutely prosecuted; and that, relying thereon, the practitioner sometimes pretends to a greater accuracy in diagnosis than the nature of the subject adnmits of. And, also, that through over estimation of the value of the physical signs, he is apt to fall into the error, when applying his remedies, of unduly subordinating the general symptoms to the local signs. In practice, indeed, we may safely put aside all fiue drawn discrinminations in the physical diagnosis of cardiac diseases; and may rest well assured that great skill in the practice of the art is not requisite in order that the observer mav be enabled to arrive at a sufficient knowledge of the affection of the heart. That degree of acute observation, whichi pretends so nicely to discriminate, during life, all the minuite differences of diseased structure, the exact position and relations of them, such as patlology discovers them after death, is certainly not necessary to guide the practitioner to their treatmetnt. Few people, indeed, possess those pbysical qualities-that nicety of tact, that fine sense of hearing-which are necessary to serve the observer in such minute differences as the subject may offer. I have seen enough of stethoscopy to satisfv me that over refining in its practice is oftener fraught with mischief than with good for the patient; and apt to lead the observer into erroneous conclusions and practices. Experience has satisfied me that when the auscultatory signs, in any given case, are such as not to present, to any ordinarily coo skilled person, clear and distinct indications of deviations from health, they are worth nothing as indications for treatment. It surely, indeed, would be wiser to abandon the stethoscope altogether, than to submit to the conclusion that only one man in a thousand is able to use it effectually. I have thus endeavoured to state, shortlv, the uses of a knowledge of pathology to the physician; and how intimately connected with the treatment and diagnosis of diseases is a correct knowledge of their pathology. I shall, in the next paper, proceed to detail the pathological anatomy of pericarditis.