A contribution to the chemistry of proteids

IN the first part of this communication we described the separation from the tryptic digestion products of casein of a substance capable of giving the glyoxylic (Adamkiewicz) reaction. This substance was found to yield also the tryptophane reaction with halogens. Since Tiedemann and Gmelin2 in 1831 first described the colour reaction given by pancreatic juice when treated with chlorine water, and Claude Bernard3 in 1856 showed that the same reaction could be obtained from the tryptic digestion products of casein and from the products of putrefaction, many workers, beginning with Kiihne4, have concerned themselves with the phenomenon. The literature of the subject comprises, however, chiefly accounts of work upon the coloured halogen derivatives themselves. As regards isolating the parent substance most observers have contented themselves with reporting their failure in the attempt. Neumeister5, though he did not follow up the matter, suggested that amyl alcohol might prove a solvent capable of extracting the suibstance from digestion mixtures, but Stadelmann6 immediately afterwards showed that success was not to be attained by the use of this solvent. So far as we know no other suggestion had been made until we described the use of mercuric sulphate as a precipitant. [Reference must be made however to the observations of Ferd. Klug published in 1901. This author isolated from the products of the self-digestion of the pancreas an amorphous pigment, and his analyses of the product correspond with the formula C4H8NO2. This pigment