I . the Distribution and Origin of Sulphur in Wool

TiH distribution of sulphur in protein has long been a subject of interest, and the work of Osborne and numerous other investigators on the sulphur in vegetable proteins indicated the probable presence of at least two forms of organic sulphur; further, Dakin [1920] in his amino-acid analysis of gelatin found sulphur compounds other than cystine. The isolation of methionine [Mueller, 1921] and its synthesis [Barger and Coyne, 1928] clearly established the existence of at least one other sulphur-containing amino-acid. Pirie [1932] has isolated methionine from caseinogen in 1 % yield, corresponding to approximately 50 % of the total sulphur; generally it may be said that this amino-acid appears to enter into the composition of proteins to a considerable degree and may have farreaching effects in nutritional work. Scleroproteins, particularly wool and hair, contain a large proportion of cystine which accounts for as much as 70 % of the total sulphur [Barritt, 1927]. Subsequently Marston [1928], Rimington [1929, 1, 2] and Barritt and Rimington [1931], using colorimetric methods devised by Sullivan [1926] and Folin and Marenzi [1929], were able to show that substantially all the sulphur in wool and -hair could be accounted for as cystine, though it must be noted that 0-2 % of methionine has been isolated from wool [Mueller, 1923]. The possible non-specificity of the Folin-Marenzi reagent for cystine has been discussed, and the recent experiments of Jones and Gersdorff [1933] on the rate of liberation of amino-acids during the hydrolysis of caseinogen are of interest in that they indicate sources of possible error in the determination. A rapid initial increase in the depth of colour developed, the maximum being reached after 45 minutes corresponding to 0*53 % cystine, then an abrupt drop occurred and finally a gradual falling away to a constant value of 0 33 % after 18 hours. Using the Sullivan [1926] reagent, the cystine rose steadily to a constant value of 0-33 % after 6 hours. It appears that a reasonable time for the hydrolysis is necessary when using the Folin-Marenzi technique. Isolation methods for the quantitative estimation of methionine are difficult and much loss of material occurs. Baernstein [1932, 1] has developed a technique for the estimation of methionine in proteins based on methods described by Kirpal and Buhn [1915] and Pollack and Spitzer [1922] for the determination of methylthiol groups. In this method methyl iodide liberated by digesting the protein with hydriodic acid is estimated by passing into alcoholic silver nitrate and determining the silver iodide. Baernstein assumes that this volatile iodide arises solely from the methylthiol group of the methionine, the assumption being supported by the