I. Preparation of the fresh tissue. If any parts are to be made conspicuous, as blood-vessels, or the lymphatic system, they must be injected with an insoluble, unbleachable substance. Spalteholz recommended carmine or methylene blue, and carbon. I have found Higgin’s ordinary black carbon ink excellent for this purpose. The system or systems are injected with this substance while the tissue is perfectly fresh. II. Fixation. The tissues are fixed preferably in 10 per cent. formalin. The length of time for fixation depends on the size of the tissue. In formalin it requires from eight hours upward to fix completely. III. Rinsing. Running tap water for five or ten minutes accomplishes the rinsing. If it is impracticable to pass directly into the bleaching fluid, the tissues may be kept temporarily in 60 per cent. or 70 per cent. alcohol. They should then be rinsed again thoroughly in water when ready to bleach. IV. Bleaching. The bleaching fluid used is hydrogen peroxid to which ammonia is added until a white precipitate forms. The proportion is approximately two parts of peroxid and one of ammonia. The material is bleached until all the color is removed and the tissue looks perfectly clear or slightly opaque. It may be quite transparent as the protein coagulate is somewhat white, but all yellow or reddish color should be bleached away. V. Washing. Rinse thoroughly in running tap water or through several changes of water until the odor of ammonia is quite gone. VI. Dehydration. Pass gradually through alcohol solutions, 30 per cent., 50 per cent., 60 per cent., 70 per cent., 80 per cent., 95 per cent., and last through absolute alcohol. The time required for dehydration will vary with the size of the material, but in either 95 per cent. solution or in absolute alcohol the tissue should remain until well hardened, twenty-four hours or more. Dehydration is completed by passing from absolute alcohol, to a fluid one-half absolute alcohol and one-half benzol; thence for a few days to pure benzol. VII. Clarifying. From benzol the material is finally clarified in winter-green oil or any other standard clearer, and put up in its final position in the museum jar. In commenting on this method Dr. A. F. Contant says: “I have found this to work very successfully in the injection of the lymphatics of the human skin, which, as you know, is a rather delicate injection and has been difficult of demonstration by other methods. With this method, however, I have prepared whole portions, as the side of the face, the leg, etc., of small animals and embryos which show clearly the whole course of the lymphatic vessels and nodes, in situ, and their relations to surrounding parts.” EQUIPMENT FOR THE DISSECTION LABORATORY