THE CHEMISTRY OF THE ANIMAL BODY. 953 



BROMINE, Br = 80. 



Salts of bromine are found in marine plants and animals, but their physiological im- 

 portance has not been established. Bromine is a fluid of intensely disagreeable odor, 

 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 5 + 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 



IODINE, I = 127. 



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

 cially in the algce. 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. 2 



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 for 

 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.* 

 A similar explanation avails in the case of Drechsel's* 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.) Baumann 5 has recently announced the dis- 

 covery of an organic compound of iodine occurring in the thyroid gland and containing as 

 much as 9. 3 per cent, of iodine. This thyro-iodin is the effective principle, or at least one 

 of the effective principles, of the thyroid gland. 6 Whether free iodine or hydriodic acid 



is liberated in the tissues from ingested iodides is a disputed point, 

 t 



FLUORINE, F = 19. 



Fluorine is found in the bones and teeth, in muscle, brain, blood, and in 

 all investigated tissues of the body, though in small quantities. In one liter 

 of milk 0.0003 gram of fluorine have been detected. 7 Fluorine is found in 

 plants, and in soil without fluorine plants do not flourish. It seems to be a 

 necessary constituent of protoplasm. Free fluorine is a gas which cannot be 

 preserved, as it unites with any vessel in which it is prepared. 



1 Nencki and Schonmow-Simanowski : Archiv fur exper. Pathologie und Pharmakologie, 1895, 

 Bd. 34, p. 320. * Nencki and Schoumow-Simanowski, loc. eit. 



1 Schmiedeberg : Grundriss der Arzneimittellehre, 2d ed., 1888, p. 197. 

 Centralblatt fur Physiologic, 1896, Bd. 9, p. 704. 

 5 Zeitschrift fur physiologische Chemie, 1895, Bd. 21, p. 319. 

 8 See Drechsel : Centralblatl filr Physiologic, 1896, Bd. 9, p. 705. 

 1 G. Tammann: Zeitschrift fur physiologische Chemie, 1888, Bd. 12, p. 322. 



