various conditions, by the unaided senses of sight and touch, has taught us a vast deal. Percussion has been of use within its own limits. Obviously auscultation has revealed what could not otherwise have been ascertained or demonstrated. Harvey appears to have been acquainted with the practice of "direct auscultation"; but the invention of the stethoscope by Laennec, and the publication of his first memoir on "mediate auscultation" in 1818, gave a marked impetus to the examination of the heart by this method; and I need scarcely remind you of the advances which subsequently took place as regards the recognition and interpretation of the phenomena associated with the action of this organ, both in health and disease. Although there are some points which are still matter of controversy, it may be affirmed that our knowledge of these phenomena is now, speaking generally, established on a firm basis. Auscultation has also been of conspicuous service in relation to the arteries and veins. The introduction of the phonendoscope is regarded by some as an advance in the study of cardiac auscultation, but its claims have not been generally accepted, and in my opinion have certainly been exaggerated.
3. The cardio-vascular system naturally lends itself to the invention and employment of various kinds of special instruments and apparatus, either for the purpose of demonstrating or recording more definitely
