PREFACE BACK in the 70s of the last century-not so many years ago, after all-photography was in its infancy and but little practiced by the general public. The few professionals who made it their regular business prepared most of their own materials, plates, papers, etc., and the results were frequently very uncertain, as they depended largely upon local conditions, and on the skill and knowledge of the operator. Photography as applied today to the arts and sciences was unheard of. Now, there is hardly a science, industry, or enterprise of any account undertaken that photography, in some fom or other, does not enter into. It is invaluable as an aid to research, study, and to the diffusion of knowledge. It has extended its influence far beyand the limits of a popular science, into a world-embracing industry. It is an Art it is a part of every science. It has revolutionized the art of printing. The magazine and book illustrations, the depicting of current events in the newspapers, the beautiful half-tones, photogravures and three cdor reproductions that have brought the worlds master pieces of Art into our homes, are all the result of photographic process as applied to printing. Its products are the only universal language, understood by all the people of the earth. It has preserved, in facsimile, the wodds most valuable manuscripts. In Medicine and Surgery, a