Among the laboratories which I mentioned, one of the most important is that of pathology and morbid anatomy, or the study of diseased tissues and organs. The first work on pathology written in this country was by one of our best-known surgeons, the late Samuel D. Gross, and one of his most important contributions to surgical progress consisted in his persistent advocacy of the need for the study of pathology as a basis for all our means of cure. This is evident, if we consider the illustration I used a moment ago of a steam-engine. Unless he knows precisely the defects of such a machine, the influence of fresh or salt water on a boiler, the influence of rust, the effect of oils, entirely apart from the mere mechanism of the engine, an engineer might make the most serious mistake, resulting in fatal damage, both to the machine and probably to life. So, surgical pathology is the study of the processes of disease, the alterations in the minute structure of tissues and organs, without which no surgeon can be fitted for his task, much less can he be called an accomplished surgeon. All of these laboratories mark the difference between the scientific and the empirical method. The old student of medicine went from case to case, heard many a good maxim, and learned many a useful trick; but, after all, it was only an empirical knowledge which he obtained. It did not go to the foundation of things, it was not scientific, as is the collegiate instruction of to-day. Having now glanced rapidly at the improvement in medical instruction, let me turn next to a few of the principal discoveries which have made the surgery of to-day so much superior to the surgery of a hundred years ago. ANÆSTHESIA After vaccination, the most important medical event of the century is the discovery of anæsthesia. While there were some prior attempts at anæsthesia, practically it dates from October 16, 1846, when Dr. John C. Warren, in the Massachusetts General Hospital, first performed a major surgical operation, without inflicting the slightest pain. I cannot enter into the merits of the various claimants for the credit of first using an anæsthetic, but ether was then for the first time publicly administered by Morton, and the very sponge which was then used is now a precious trophy of the Massachusetts General Hospital. I may, perhaps, quote from an address which I delivered before the Medical and Chirurgical Faculty of the State of Maryland, at their centennial anniversary, in April, 1899, the following in relation to anæsthesia: