+55. Bosworth's theory.+--By a very recent work of L. L. Van Slyke and A. W. Bosworth (Van Slyke and Bosworth, 1912, 1913; and Bosworth and Van Slyke, 1913), in which ash-free casein and paracasein were compared as to their elementary composition, and as to the salts they form with bases, and the properties of these salts, it is indicated that the two compounds are alike in percentage composition and in combining equivalent, the paracasein molecule being one-half of the casein molecule. Moreover, Bosworth (1913) has shown that, if the rennin cleavage be carried out under conditions which avoid autohydrolysis, no other protein is formed; also that, if the calcium caseinate present be one containing four equivalents of calcium, the paracaseinate does not precipitate, save in the presence of a soluble calcium salt, while, if the calcium caseinate be one of two equivalents of base, rennin does cause immediate coagulation. Bosworth concludes that the rennin action is a cleavage (probably hydrolytic) of a molecule of caseinate into two molecules of paracaseinate, the coagulation being a secondary effect due to a change in solubilities, dicalcium paracaseinate being soluble in pure water but not in water containing more than a trace of calcium salt, and the monocalcium caseinate being insoluble in water. The alkali paracaseinates, as well as caseinates, are soluble. This explanation seems to promise to harmonize the observations with regard to acidity and the effects of the presence of soluble salts. This theory represents, therefore, many years of continuous work at the New York Experiment Station centered primarily on American Cheddar cheese. Disputed points remain for further study but these workers have contributed much toward a clear description of the chemical constitution of casein as affected by rennet action and bacterial activity. The investigations of these authors and of Hart with regard to the changes which the paracasein, the calcium and the phosphorus undergo during the ripening of cheese (Van Slyke and Hart, 1902, 1905; Van Slyke and Bosworth, 1907, 1913; Bosworth, 1907) contributed to this interpretation. BANG, IVAR, Ueber die chemische Vorgang bei der Milchgerinnung durch Lab, Skand. Arch. Physiol. 25, pages 105-144; through Jahresb. u. d. Fortsch. d. Thierchem. 41, pages 221-222, 1911. BOSWORTH, A. W., The action of rennin on casein, N. Y. Exp. Sta. Tech. Bul. 31, 1913. BOSWORTH, A. W., Chemical studies of Camembert cheese, N. Y. Exp. Sta. Tech. Bul. 5, 1907. BOSWORTH, A. W., and L. L. VAN SLYKE, Preparation and composition of basic calcium caseinate and paracaseinate, Jour. Biol. Chem. Vol. 14, pages 207-210, 1913. DUCLAUX, ÉMILE, Action de la présure sur le lait, Compt. Rend. Acad. Sci. 98, pages 526-528, 1884.