_Instruments._--Laennec’s discovery in 1819 of auscultation, and the stethoscope, for determining internal conditions by sound, was a great step in diagnosing diseases. The binaural stethoscope was invented by Cammann in 1854, and a later improvement is the phonendoscope, by Bianchi. The opthalmoscope is an instrument for inspecting the interior of the eye, which was invented by Prof. Helmholtz, and described by him in 1851. The laryngoscope, for obtaining a view of the larynx, was said to have been constructed by Mr. John Avery, of London, as early as 1846. The opthalmometer, Fig. 174, is a comparatively recent invention. It is designed to ascertain variations in corneal curvature for the correction of corneal astigmatism. Electric lights with reflectors are arranged on each side of the patient’s head, while the operator looks into the eye with a telescope. The sphygmograph, a little instrument to be strapped on to the wrist to record the action of the pulse, was first reduced to a practically useful form by Marey in 1860. A later development of these devices, by Verdin, known as the sphygmometrograph, is shown in Fig. 175. The endoscope, for looking into the urethra, and the cystoscope, for looking into the bladder, are other useful instruments of the modern practitioner. Greater than them all, however, is the modern X-ray apparatus, for locating foreign substances in the body and making visible the bones through the flesh, for which see special chapter. The use of the thermometer in recording the progress of fevers is also a valuable modern application, and the list of instruments and small tools is beyond enumeration. There are series of obstetrical appliances, instruments relating to bone surgery, to the taking up of arteries, cupping instruments, trepanning instruments, speculums, hypodermic syringes, electric cauteries, fracture appliances, instruments for lithotrity, bandages for varicose veins, atomizers, breast pumps, inhalers, nasal douches, trusses, pessaries, catheters, abdominal supporters, and an endless variety of proprietary articles, such as electric baths and belts, plasters, chest protectors, liver pads, and so forth, all of which are practically the products of the Nineteenth Century. The surgeon of to-day can straighten the eyes of a cross-eyed man, or take the bow out of his bandy legs, can make him a new nose of his own flesh, patch his skull with a silver plate, remove the stone from his bladder, supply him with a wind-pipe, wash out his stomach, and perform many other operations even more difficult. Among such more important operations may be mentioned ovariotomy, which was first performed by Dr. Ephraim McDowell, of Danville, Kentucky, in 1809, and the tying of the great arteries. The operation of lithotrity, for removing stone from the bladder by crushing the stone, was introduced by Civiale, 1817-1824, who devised successful instruments and modes of using them.