600 CHEMICAL PATHOLOGY OF THE DUCTLESS GLANDS 



first discovered by Baumann in 1896, and called by him thyroiodin 

 (or iodothyrein) J^ 



The chemical nature of thyroid colloid has been studied particularly 

 by A. Oswald.--* He found that all the iodin of the thyroid is dissolved 

 out in physiological salt solution, and that none of it is present in an 

 inorganic form. In the salt solution extract are two protein bodies; 

 one, precipitated by half saturation with ammonium sulphate, con- 

 tains all the iodin, and seems to be a globulin; it resembles myosin 

 in being precipitated by weak acids, and it contains an easily separated 

 carbohydrate group. The other, precipitated by saturation with am- 

 monium sulphate (exact limits of precipitation are between 6.4 and 

 8.2 tenths saturation), is a nucleoprotein, containing 0.16 per cent, 

 phosphorus, but no iodin; it is without marked physiological activity 

 as also is the protein-free watery extract of the thyroid.-^ The col- 

 loid seems to contain practically all the iodin present in the gland 

 (Tatum).26 



The iodin-containing protein, called thyreoglohulin, constitutes one- 

 fourth to one-half the dry weight of the gland, and seems to contain 

 the sole active constituent of the colloid; at least, its administration to 

 animals has the same physiological effects as does the entire* colloid 

 (great increase in the urea elimination and decrease in blood pressure 

 in animals, curative effect on myxedematous patients, increased tonus 

 of both sympathetic and peripheral nervous systems.)-'^ Analysis 

 of the thyreoglobulin from various animals has shown it to be of quite 

 constant quantitative composition except for the iodin, which may 

 vary greatly in amount. Normal human thyreoglobulin (from persons 

 living in non-goitrous districts) has the following percentage compo- 

 sition : 



C = 51.85, H = 6.88, N = 15.49, I = 0.34, S = 1.86. 

 Thyreoglobulin from goitrous districts contains . much less iodin 

 (0.18-0.19 per cent.), and from calves born with goiters a thyreo- 

 globulin was obtained that agreed in all respects with normal thrj-reo- 

 globulin, except that it contained no iodin at all. On the other hand, 

 administration of iodides to patients causes the thyreoglobulin to 

 become rich in organically bound iodin. ^** From these facts Oswald 



^' Iodin is present in the thyroid of all species, most in marine forms (Cam- 

 eron, Jour. Biol. Chem., 1914 (16), 465; Biochem. .lour., 1014 (7), 466). 



'^"^ His work is reviewed in his dissertation, "Die chem. Beschaffenheit und die 

 Function der Schilddruse," Strassburg, 1900; also see Vircliow's Arch., 1902 

 (169), 444. 



^^ A. Oswald, Arch. ges. Physiol., 1916 (166), 169. Kocher and his collabo- 

 rators, however, ascribe to the thyreonucleoprotein some slight metabolic olTects 

 antagonistic to the thvreoglobulin (See Mitt. Crenz. Med. Chir., 1916, vol. 29). 



2" Proc. ;Soc. Kxp. Biol. Med., 1919 (17), 28. 



" A. Oswald, Arch. ges. Plivsiol., 1916 (164), 506. 

 _ 2« Nagel and Roos (Arch. f. iVnat. u. Physiol., 1902, p. 297) found tliat ad- 

 ministration of ))roini(les had no effect upon the amount of iodin in the thyroid, 

 and no storage of brornin takes place. Administration of pilocarpine docs not 

 increase the amount of iodin in the thyroid. 



