VII 



HALOGEN-ALBUMINS 233 



diminished in egg-albumin. lodo-albumins are affected very slightly 

 by acids. When working with haemoglobin, Kurajeff noticed that 

 haematin is also iodised. 



By peptic and tryptic digestion a portion of the iodine is split off, 

 according to Hofmeister and Kurajeff, and there are formed iodo- 

 albumoses and iodo-peptones. Oswald succeeded in iodising all the 

 albumoses of Pick, and in addition peptones and an abiuretic body, 

 which was probably a peptid. 



Hetero-albumose contains 10'27 per cent iodine, and prot-albumose 

 12 '4 8 per cent. This slight difference is very remarkable, as the 

 prot-albumose contains the whole of the tyrosin and tryptophane, 

 while the hetero-albumose contains only phenylalaniii. Amongst the 

 products of tryptic digestion, besides tyrosin, yet another substance 

 could be iodised. 



During metabolism the iodine is completely split off and excreted 

 as alkali-iodides. Only if very large amounts of iodised proteid are 

 administered, does some pass unchanged into the urine. 



From the physiological standpoint iodised albumins are indifferent 

 inasmuch as they produce only such effects as can be obtained with 

 the salts of iodine, but iqdised albumins 'are metabolised more slowly 

 than are simple albumins, according to Falta. 1 Dissociation with 

 acids liberates iodine as does ferment action ; on dissociating a 

 chlorine-casein compound by means of fuming nitric acid, Panzer 2 

 observed chlorinated fatty acids besides and in place of the usual 

 amino-acids. There is also formed according to Hofmeister and 

 Oswald an iodised body with the properties of a peptone, which could 

 not however be obtained in a pure form. Liebrecht has prepared 

 caseo-iodine from iodised casein ; both resemble one another in their 

 reactions. The 'iodalbacid' of Blum belongs, according to Oswald, 

 also to this group of substances. 



Amongst the iodo-albumins occurring in nature, the one of the 

 greatest importance to us is the thyro-globulin of the thyroid gland, 

 which was discovered by Baumann, and more fully studied by 

 Oswald 3 in Hofmeister's Institute. It contains only 1'75 per cent 

 of iodine, therefore much less than do the artificial iodine-proteids, 

 but it is capable of being still further iodised according to Blum. 

 Being less iodised it is less acid than are the completely iodised 

 albumins, but otherwise it has the same reactions. The peculiar 

 physiological action of the thyroid gland is connected with the thyro- 



1 W. Falta, Naturf. Ges. zu Basel, XV., No. 2 (1903). 



2 T. Panzer, Z&itschr. f. physiol. Chem. 33. 131 (1901). 



3 A. Oswald, ibid. 27. 14 (1899), 32. 121 (1901) ; (here also the literatxire). 



