in book catalogues, and come from various and wide sources are the legitimate outcome of Avenbrugger's and of Laënncc's pioneer treatises. A versatile French writer who devoted especial attention to medical nomenclature was Piorry (1794-1879), to whom we are{263} indebted for the pleximeter. The double stethoscope, a legitimate extension of Laënnec's simple instrument, was invented by Cammann, of New York, and can justly be claimed for American medicine. Other methods of physical examination--like spirometry, chest measurement, and study of expired air--have been introduced since 1846. The ophthalmoscope, which has been of such sterling service, and is based upon the simplest of principles, was the invention of the famous Helmholtz, but just deceased. The principle of endoscopy,--the illumination and visual examination of the various cavities of the human body,--the various specula, the spectroscope, the sphygmograph, the more accurate record of physical sounds, the application of electricity, and the employment of thermometry represent a few of the strides in the medical science of the present century, thereby aiding and perfecting the art of diagnosis, which, in turn, must ever necessarily form the basis for all rational treatment. Let no one complain that we are still so far from certainty in every case; the wonder is that so much has been discovered in so short a space of time. Wonderful as have been these advances, the greatest achievements have accrued to the department of surgery, which Chamisso terms "the _seeing_ portion of the healing art." The sixteenth century opened the way for checking of haemorrhages; the seventeenth accomplished great simplifications and improvement in the way of dressing wounds; the eighteenth gave a refining and elevating tendency to the study of applied practice, and raised surgery to a level with other branches of science; and now the nineteenth century has, toward its close, made surgery as nearly, perhaps, as it ever can be, an exact science, to which every other branch of science has been made contributory. The chain-saw, invented in 1806 by Jeffery, alone gave an impetus to resection, which was cultivated especially in Germany; to resection was added osteotomy by Heine{264} and Maver; this, in turn, was succeeded by the so-called subcutaneous osteotomy of Langenbeck in 1854; Stromeyer introduced subcutaneous tenotomy in 1831, which was a very pronounced advance on all that had gone before; then came the introduction of anæsthesia, by which were made possible operations that had been beyond human endurance; by the introduction of the rubber bandage by Esmarch in 1873 bloodless methods were made possible. Pain and haemorrhage, the two greatest enemies of the conscientious surgeon, being thus almost annihilated, there was left but an apparently theoretical limit to what the surgeon might accomplish. Orthopaedic surgery, introduced by Delpech, was unknown prior to 1816; it was first practiced