FIBROIN AND SERICIN. 123 



KRUKENBERG, is nothing but iodine crystals, as shown by MORNER. After 

 DRECHSEL l found nearly 8 per cent iodine in the dry substance of the 

 axial system of the Gorgonia Cavolini, C. MORNER showed that in the 

 Anthozoa in general the organic skeletal substance contains halogens in 

 organic combination. Iodine was found in all varieties, and indeed in 

 amounts from traces up to 7 per cent. Bromine was found, with the 

 exception of two Antipathes, in amounts of 0.25 to 4 per cent, while 

 chlorine, which was never absent, occurred as a few tenths per cent. 

 The halogens occur in the organic skeletal substance as gorgonin and 

 pennatulin. 



DRECHSEL obtained leucine, tyrosine, lysine, ammonia and an iodized 

 .ammo-acid, iodogorgonic acid, as cleavage products of gorgonin. This last 

 is identical with the 3-5 di-iodo-tyrosine, HOI 2 C 6 H 2 .CH2.CHNH2 COOH, 

 synthetically prepared by WHEELER and JAMIESON. 2 On acid 

 cleavage of gorgonin HENZE 3 obtained the three hexone bases, abundant 

 tyrosine and very little leucine. On cleavage with barium hydoxide he 

 obtained only lysine, besides tyrosine and glycocoll in larger amounts. 



Fibroin and sericin are the two chief constituents of raw silk. By 

 the action of boiling water the sericin (silk gelatin) dissolves and can be 

 obtained by a method suggested by BoNDi, 4 while the more difficultly 

 soluble fibroin remains undissolved in the shape of the original fiber. 

 The sericin, whose sufficiently concentrated hot solution gelatinizes on 

 cooling, is precipitated by mineral acids, several metallic salts, and by 

 acetic acid and potassium ferrocyanide. The spider silk investigated 

 by FISCHER 5 yielded fibroin but not sericin. 



Fibroin is soluble in concentrated acids and alkalies and reprecipitable 

 (in a modified form) on neutralization. It gives the biuret test and 

 MILLON'S and ADAMKIEWICZ'S reactions, the last only faintly. Fibroin 

 has an especially great interest because of the hydrolyses performed by 

 FISCHER and his co-workers, and especially by the finding of the pre- 

 viously mentioned poly pep tides by these workers. Of . the cleavage 

 products which characterize fibroin we must mention the large amount 

 of glycocoll, alanine and tyrosine, and the very small amounts of hexone 

 bases, besides the nearly complete absence of monamino-dicarboxylic 

 acids. The quantity of the hydrolytic cleavage products of the three 

 silk substances, in so far as they have been investigated, are given in the 

 following table, which also includes the results for elastin, gelatin, and 

 koilin : 



1 Zeitschr. f . Biol., 33. 



2 Wheeler and Jamieson, Amer. Chem. Journ., 33; Wheeler, ibid., 38. 



3 Henze, Zeitschr. f. physiol. Chern., 38 and 51. 



4 Ibid., 34. 



5 Ibid., 53. 



