234 CHEMISTRY OF THE PROTEIDS CHAP. 



globulin, but Koos l has shown, in opposition to Blum, 2 that the 

 physiological activity is independent of the iodine-content of the 

 thyroid gland. 



lodothyrin is a dissociation -product of the thy ro- globulin, and 

 is comparable to the caseo-iodine mentioned above. It was prepared 

 by Baumann directly from the thyroid gland, and by Oswald by 

 dissociating thyro-globulin by means of acids; it contains 14' 2 per 

 cent iodine, is insoluble in water and acids, but soluble in alkalies. 

 It still possesses the physiological properties of thyro-globulin. 



Drechsel 3 found in the framework of a coral, the Gorgonia carolinii, 

 an iodised keratin, the gorgonin. Mendell 4 has found iodine also in 

 other West Indian species of corals. Gorgonin possesses the properties 

 of keratin, but contains nearly 8 per cent of organically bound iodine, 

 while probably an even much higher percentage will be found in the 

 older, firmer portions of the framework. The crystalline dissociation- 

 products of gorgonin are given in the table on p. 73; besides these 

 there is also formed, when gorgonin is dissociated with acids, the 

 iodo-gorgonic acid, which Drechsel believed to be iodo-amino-butyric 

 acid, a view which, however, is not confirmed by Henze. 5 



Sponges also contain an iodo- albumin according to Baumann, 6 

 Harnack, 6 and Hundeshagen. 7 From this iodo -albumin Harnack pre- 

 pared iodo-spongin having this percentage composition : 



C H N S I 



47-66 6-17 9-93 4'54 9'01 22'69 



It is not a proper iodo -albumin, but a product split off from 

 the original substance, which explains the, even for a keratin, high 

 percentage of sulphur, the low N- value, and the absence of the 

 biuret-reaction. The lead sulphide reaction is positive, but no other 

 albumin reactions are obtainable. It is worthy of notice that the 

 ratio I : S is the same for the whole sponge as it is for the iodo- 

 spongin " that therefore in sponges the iodine is only absorbed by 

 the sulphur containing radicals of the organic matter." By weight 

 iodo-spongin forms about one-sixth of the total unaltered molecule. 



1 E. Roos, Zeitschr. f. physiol. Chem. 28. 40 (1899). 



8 F. Blum, Pflugers Arch. f. d. ges. Phys. 77. 70 (1899) ; [see also A. Oswald, ibid. 

 79. 450 (1900)]. 



3 E. Drechsel, Zeitschr. f. Biol. 33. 84 (1896). 



4 L. B. Mendel, Amor. Journ. of Physiol. 4. 243 (1900). 



5 M. Henze, Zeitschr. f. physiol. Chem. 38. 60 (1903). 



6 E. Harnack, ibid. 24. 412 (1898). 



7 F. Hundeshagen, Zeitschr. f. angew. Chem. 1895, p. 473 ; according to Chem. 

 ZentraM. 1895, p. 570. 



