It was not until many years later, early in the second half of the century, that the clinical thermometer came into general use, but it soon showed most strikingly the superiority of the "instrument of precision" to the unaided senses of man. Who would think now of trying to estimate the height of a fever by laying his hand on the patient's skin, or who, even among the laity, would be satisfied with such a procedure? "Doubtless," said the present writer in a former publication ("New York Medical Journal," Dec. 29, 1900), "the use of the thermometer has occasionally given rise to needless alarm, but almost invariably it may be interpreted with great certainty. Often it dispels unnecessary anxiety as in a twinkling by its negative indication, and surely it is to be credited with being distinctly diagnostic in those diseases of which it has itself established the 'curve.'" By the thermometric "curve" of a disease is understood the general visual impression made by the graphic chart of a temperature record--the course of a zigzag line connecting the points indicated by the various individual observations. Numerous other instruments of precision are now in constant use, among the most wonderful of which perhaps is the ophthalmoscope, whereby we are enabled to subject the retina and the intervening media of the eye to minute visual examination. There is not an organ of the body that is not now interrogated daily in the way of physical diagnosis, and we even examine separately the secretion of each of the two kidneys. In addition, there are multitudinous specific signs of which we were not long ago in complete ignorance. To cite only one of these, there is Widal's agglutination test, by which the bacteriologist can usually make a diagnosis of typhoid fever far in advance of the time at which it could otherwise be distinguished. The use of the Röntgen rays in diagnosis was one of the crowning achievements of the century, and now we seem about to enter upon a course of their successful employment in the treatment of disease--even some forms of cancer--as well as in its detection.