Meyer1) claimed that " chondroitinsulfuric acid B " is stably linked to proteins in skin because it is separated by strong alkali from the tissue but not by neutral salts contrary to the chondroitinsulfuric acid in carti lage, which is readily extracted with 10% CaCl2. Whether or not the skin itinsulfuric acids (Cf. Aizawa2)) are firmly fixed in the tissue through normal co-valency in distinction from mucoitin, chondro-and limacoitin sulfuric acid and heparin is an important problem (Cf.

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... e3)). As a matter of fact, the writer could not extract the itinsulfuric acids from pig skin with 10% CaCl2 and the half-saturated NaCl nor even by the for malin method of Masamune and Osaki4) which is processed at pH 8.0 and with the half-saturated lime water (pH 9.8). However, as is dealt with in this account, 10% CaCl2 releases from the skin a mixture of the itinsulfuric acids of similar composition as those obtainable by the aid of alkali2) and that in similar yield, when the tissue is preliminarily treated with 50% urea in order to eliminate collagen present in an abundant quantity. Many years ago, Masamune5) put forward the opinion that the linkage between a hexuronic acidcontaining mucopolysaccharide and proteins in tissues is chiefly ionic and subsidiarily coordinate. The present result is another affirmative evidence for his view, because basic groups of collagen must be considered to take a great part in binding the itinsulfuric acids in skin. EXPERIMENTAL Fresh and shaved pig skin was freed from fatty tissue, ground in a masticator and dried in a Faust apparatus. 130 g. of the dry tissue (corresponding to 300 g. of the fresh pulp) were shaken with 7 volumes of 50% urea for 24 hours at room temperature, and percolated. The residual tissue was submitted to the same treatment over again. The filtrates 383