To return from this digression. The influence of a recognition of the principles to which I was referring is apparent equally in the diagnosis and treatment of disease: in diagnosis, by the enlarged view which is taken of all the particulars of the individual case, meting out a due value and proportion to each; and by comparison with others, similar in all or some of their features; but most conspicuously so in instances where no precedent for comparison exists, and where an opinion must he

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... ed by the observation of remote analogies, from the history of the case, the hereditary tendencies of the patient, and a variety of incidental circumstances which have only an indirect bearing on the questions at issue. In surgical treatnment, still more will simple general principles be found efficient guides in practice. But, whether in diagnosis or treatment, the accomplished surgeon brings to the task an accurate acquaintance with the structure and functions of the human frame, and, as far as our knowledge extends, a clear perception of the various relations of sympathy and vicarious action in different organs; so that he may read aright the pointing of the hands upon the dial, and know with confidence where and how to give assistance. But selfreliance is not the only attainment which familiarity in the treatment of disease brings with it. Trust in Nature's unaided efforts seems a simple lesson to learn; yet, I apprehend, there are few of my elder hearers who will not echo the remark, that it is only as years pass by that this apparently rudimental knowledge is acquired. The readiness to interfere yields only to the conviction which is gradually forced upon us, that it is safer and wiser in this respect to follow than to lead; more judicious to withhold interference until we see clearly the necessity for action, and then to act promptly and decidedly;-taking, in short, for our guidance, those principles which were so ably enforced and exeniplified by yourself, Sir, when you fulfilled the duties of the office I now occupy. It would serve to abate our exaggerated reliance on our own resources, and to enhance our faith in those of Nature, if we could more familiarise our minds with the true character of the phenomena which we are accustomed to regard and to treat as disease. These phenomena find their expression especially in the nervous and vascular systems; yet how rarely can they be interpreted as other than essentially curative in their nature. The excitement, both local and general, which attends the introduction of a poison into the system, and the train of symptoms which accompanies the eliminative effort, are so many steps in the direction of reparation; and such is likewise the case in severe mechanical injuries to the frame. The ulcer, slough, or abscess, are necessary preliminaries to, or accompaniments of, repair, though often destructive in their excess. And the surgeon, who has been conversant with such cases will watch anxiously for the reaction which follows the shock of an injury or operation, and estimate thereby the reparative power of his patient. I shall have frequent opportunity, in the succeeding lectures, of illustrating this remark, and of showing that Nature's resentment of an injury is the measure of her ability and purpose to repair it; that the tranquil, unruffled state of the nervous and vascular systems is often a deceitful calm-the index of feeble power, the precursor of inaction, and the harbinger of death. The intimate alliance which exists between the vascular and nervous systems, their interdependence and mutual reaction, are the sources of numberless complications, which, whilst they often perplex the scientific practitioner, are unintelligible to him who expects to find in the records of the past an exact rehearsal of the present. This remark applies with peculiar force to the class of injuries which I propose to consider. In many visceral lesions, the nervous and vascular systems are immediately implicated; in all, they are necessarily more or less involved; and the numberless sympathies which result demand both sagacity and patient research to unravel, and to refer them to their several sources. And it is often upon the just interpretation of the phenomena springing from these sympathies, that the correctness of the surgeon's opinions and the fitness of his treatment much depend. But the subject of diagnosis has a far wider basis than this. The etymology of the word implies breadtl and penetration; and these are qualities which are especially required in studying the signs and symptoms by which diseases are distinguished and identified. This single word includes a moiety, and a large moiety, of scientific medicine and surgery. Even with it, much of medical practice is empirical; without it, medicine could have no claim to be classed as a science; and surgery could scarcely be said to have existence, except, as was the case in barbarous ages, as a blind and cruel handicraft, rarely benefiting those it pretended to relieve, but mutilating and sacrihcing many at the shrine of its ignorance. Happily, the qualifications for surgical diagnosis are within the reach of all who have the opportunity of study, and bring an earnestness to their work; though it must be admitted that natural endowments are not without their influence in assisting their possessor to a rapid and precise judgment regarding the disease of which he may have to determine the character. Yet, as I just now remarked, I am disposed to regard the discernment, popularly attributed to sagacity or an intuitive perception of that which escapes common notice, as really the fruit of patient study and accurate observation, conducted by a well-balanced and educated intellect, of which the conscientious love of truth is a predominant characteristic. A bold and shrewd conjecture of the charlatan may be occasionally correct, and may dazzle the ignorant; whilst the many failures are kept out of sight, or accounted for by explanations or excuses which impose too readily on the uninitiated, who are singularly incompetent to appreciate the long and tedious process by which the scientific practitioner attains that tact and aptitude in the diagnosis of disease, which expresses itself with the modesty and misgiving often appropriate even in the most experienced-appropriate, because he knows, as others cannot imagine, how many sources of error surround him; how many accidental circumstances may influence a conclusion which, to the superficial inquirer, appears inevitable. The special education of the senses-the agents in observing-has its import, in common with the calm and dispassionate consideration of the information they convey to the mind. Yet, with all the acquired preliminary knowledge which physiology and pathology supply, with all the penetration in observing, and all the delicate tact and distinguishing refinement of eye and ear, whichexperience alone can impart, thediagnosis of disease and injury is often rendered obscure and perplexing by some novel circumstance, or by some accidental peculiarity which taxes the sagacity of the surgeon to the utmost. The concurrence of two forms of injury in the same locality, such as a fracture and a dislocation; the distortion or unsymmetrical development of limb consequent on occupation or habit; the modified expression of disease dependent upon temperament or excess,-these are conditions which illustrate my remark, and which meet the surgeon at every turn in his daily practice. Again, deformity, or other consequence resulting from pre-existent disease or injury, often masks a present malady. These cases are so frequently brought under the observation of the hospital surgeon, that scarcely a week passes without examples being offered to his notice. But they are not therefore the less perplexing, especially as patients are often unwilling to admit a relation between circumstances which they cannot themselves appreciate; and thus, sometimes in ignorance, sometimes wilfully, they mislead the surgeon. In other instances, a misapprehension of the true nature of the case may lead to an incorrect history being given; or, again, the history may be true, but perverted by some preconceived opinion transmitted to the surgeon. In illustration of this source of complexity, I may refer to necrosis of bone; not so much because it may mislead, as to exemplify, in a striking class of cases, the difficulties which are sometimes thrown in the way of diagnosis. The history of necrosis from acute ostitis is generally intelligible enoug,h; but the recognition of the original inflammation of the bone or periosteum would appear to be less simple, if we mayjudge by the frequency of its being overlooked, or rather masked, by the attendant symptoms. Exposure to cold and wet is a rife source of ostitis and periostitis, and so it is of rheumatism. Both are attended with suffering, more or less localised, and likewise with febrile disturbance. Hence, these cases of recognised necrosis are transmitted to us, sometimes as the sequel of rheumatism, at others as consequent on fever.: Whereas, the acute suffering, not infrequently of the severest kind, and the corresponding constitutional or febrile disturbance, are both due to the inflammation of the bone or its investing membrane. Thus-to give one or two typical cases-a young sailor was hurt on the thigh, and this injury was followed by an attack of so-called rheumatic fever, and subquently an abscess formed. When admitted into the hospital, the shaft of the femur was the subject of necrosis. A lad, after repeated exposure to cold and wet, was attacked with fever; the right knee and shoulder being, at the same time, much swelled and very painful. His medical attendant appears to have at first regarded this attack as rheumatic 25