546 POPULAR SCIENCE MONTHLY. 



made tlie not unimportant discovery that gypsum, heated with 

 sodium chloride to 130° C, was converted into the crystalline anhy- 

 dride, and in 18T5 he published a series of researches on the forma- 

 tion 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 dis- 

 coveries, but also for the great number of ingenious methods of re- 

 search devised by him. Our methods of examining pathological 

 transudations, pus, the blood, are derived in large part from him. 

 He was quick to jDerceive the value of the spectroscope in the study 

 of the chemical changes in the pigments of blood, urine, bile, exu- 

 dations, 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 im- 

 proved 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 - sub- 

 stances contained in gall, together with their decomposition prod- 

 ucts. 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 Kolliker'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 Yirchow. 



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 com- 

 position. 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- 



