THE CHEMISTRY OF THE ANIMAL BODY. 509 



whose vapors strongly attack the skin, turning it brown, and likewise the mucous mem- 

 branes of the respiratory passages. 



Hydrobromic Acid, HBr, may be prepared by the action of water on phosphorus 

 tribromide, 



PBr 3 + 3H 2 - 3HBr + H 3 P0 3 . 



It is a colorless gas of penetrating odor. If sodium bromide be given to a dog in the 

 place of sodium chloride, fifty per cent, and more of the hydrochloric acid may be sup- 

 planted by hydrobromic acid in the gastric juice. 1 The various organs are then found to 

 contain bromine, especially the kidneys' through which it may be eliminated. 



Iodine, I = 127. 



Like bromine, the salts of iodine ai'e found in many marine plants and animals, espe- 

 cially in the algae. It is found in the thyroid gland. Iodine is prepared in metallic-looking 

 plates, almost insoluble in water, but soluble in alcohol (tincture of iodine). Iodine is still 

 more strongly corrosive in its action on animal tissue than is chlorine or bromine, and is an 

 antiseptic and disinfectant. A slight trace of free iodine turns starch blue. 



Hydriodic Acid, HI, is prepared like hydrobromic acid, by the action of water on 

 tri-iodide of phosphorus. An aqueous solution of hydriodic acid introduced into the 

 stomach is absorbed, and shortly afterward iodine, as alkaline iodide, may be detected 

 in the urine. On administration of sodium iodide to a dog with his food, only very 

 little hydriodic acid appears in the gastric juice.* 



Circulation in the Body. — Iodine or iodides given are rapidly eliminated in the 

 urine, in smaller amounts in saliva, gastric juice, sweat, milk, etc. It is noticed that ti »r 

 weeks after the administration of the last dose of potassium iodide, traces of iodine are 

 found in the saliva, and none in the urine. The explanation lies in the presumption that 

 iodine has been united with proteid to a certain extent, and appears in such secretions as 

 saliva, which contains materials derived from proteid through glandular manufacture. 4 

 A similar explanation avails in the case of Drechsel's 5 discovery that, in patients who 

 have been treated with iodides, iodine may be detected in the hair (the keratin of hair 

 being derived from other proteid bodies.) Whether free iodine or hydriodic acid is liber- 

 ated in the tissues from ingested iodides are disputed points. Baumann 6 discovered an 

 organic compound of iodine occurring in the thyroid gland and containing as much as 9.3 

 percent, of iodine. Roos 7 states that this thyroiodine from sheep's thyroid constantly 

 contains about 5 per cent, of iodine. When fed it increases the metabolism of proteid and 

 fat 8 and acts as an antitoxine. According to Blum, 9 the iodine is combined with the pro- 

 teids of the thyroid in varying quantity, and any liberated iodine may act within the thy- 

 roid to destroy toxic bodies, especially nerve toxines. 10 Oswald, 11 on the contrary, states 

 that the effective principle of the thyroid is a thyroglobulin containing L.66 per cent, of 

 iodine. This thyroglobulin treated with acids yields thyroiodine. which contains 14.4 

 per cent, of iodine. Thyroids which contain no iodine have no physiological effect 

 upon metabolism. 12 



1 Nencki and Schoumow-Simanowski : Arehivfiir exper. Pathologie wnd Pharmakologie, 1895, 

 Bd. 34, S. 320. 



2 Rosenthal: Zeitschrift fur physiologische Chemie, 1896, Bd. 22, S. 227. 



3 Nencki and Schoumow-Simanowski : Lor. cit. 



* Schmiedeberg : Qrundriss der Arzeinmittellehre, 2d ed., 1888, S. 197. 



5 Cailralblatt fur Physiologic, 1896, Bd. 9, S. 704. 



6 Zeitschrift fur physiologische Chemie, 1895, Bd. 21, S. 319. 7 Ibid., 1898, Bd. 25, S. 1. 

 8 Voit, F. : Zeitschrift fur Biologie, 1897, Bd. 35, S. 116. 



» Zeitschrift fiir physiologische Chemie, 1898, Bd. 26, S. 160. 



10 Blum: Pfluger'a Archiv, 1899, Bd. 77, S. 70. 



11 Zeitschrift fiir physiologische ('/ionic, 1899, Bd. 27, S. 14. 

 u Boss, E. : Ibid., 1899, Bd. 28, S. 40. 



