made the not unimportant discovery that gypsum, heated with sodium chloride to 130° C, was converted into the crystalline anhydride, and in 1875 he published a series of researches on the formation of the dolomite masses of Germany, which did much to elucidate the problem, indicating, as they did, the formation.of dolomite by the action of sea water on calcium carbonate. His works on percussion and the pulse were valuable contributions to physical diagnosis.
In biochemistry his work is remarkable not only for his discoveries, but also for the great number of ingenious methods of research devised by him. Our methods of examining pathological transudations, pus, the blood, are derived in large part from him. He was quick to perceive the value of the spectroscope in the study of the chemical changes in the pigments of blood, urine, bile, exudations, and elsewhere in the animal and plant kingdom, and he applied the method with particular success to the study of the blood pigment and chlorophyll. He seized upon the Soleil-Ventzke improved polariscope as a valuable means of estimating the albumin and sugar contents of urine, blood serum, transudations, and milk. He studied the circumpolarizing action of gelatin and the-substances contained in gall, together with their decomposition products. By means of these methods he rendered great service to physiological chemistry.
In the chemistry of the organism he broke ground in a great variety of places, but left the further development of nearly all the paths thus indicated to his students. His earliest work was done upon the chemistry of cartilage and the relation of cartilage to bone, work which bore closely on Kölliker's discoveries on the genesis of bone, and showed the essential similarity, in a chemical way, of the great group of connective tissues, first classified by Virchow.
He made extended analyses of the enamel of teeth, showing its essential identity with the rock apatite, and that the enamel of the teeth of fossil and living animals was identical in chemical composition. During his stay in Berlin he published a number of treatises on the composition of transudates, and later compared the effect on the composition of transudations of frequent drawings off of the fluid. He compared the transudations derived from various parts of the body, and endeavored to refer the differences in chemical composition found to differences in the capillary network and blood pressure. He demonstrated the presence of soaps in the blood and lymph, at that time commonly denied, and studied the presence of indican in the urine, a body the true significance of which as a measure of the putrefaction in the alimentary canal was shown by his pupil Baumann. One of the last most important of his discoveries was that of "chitosan," a decomposition product of chitin, the dis-
