188 INORGANIC AGENTS 



These more frequent symptoms of iodism occur more often after 

 the administration of potassium iodide than after that of iodine. The 

 physiological action of the iodides is similar to that of iodine, which is 

 transformed into iodides in the body. But the iodides are usually pre- 

 ferred for internal use since they are locally so much less irritating. Both 

 iodine and potassium iodide are readily absorbed from mucous membranes, 

 and are found in all the tissues and fluids of the body. Iodine is absorbed 

 as iodides and, perhaps, in loose combination with albumin (iodoalbumi- 

 nates) — and eliminated as iodides by all the usual channels, as well as 

 by the mucous membranes. The kidneys eliminate the greater amount, 

 but iodine is found in the saliva and gastric juice after it has ceased to 

 be present in the urine. The activating effect of iodine on the thyroid 

 gland probably accounts for much of its influence on the body. Iodine is 

 essential for normal thyroid activity. Glandular hyperplasia (colloid 

 goitre) is a physiological reaction to a deficiency of iodine. The iodine 

 content of the gland varies inversely with the degree of enlargement. 

 Giving iodine in simple goitre in puppies causes reduction of the glandu- 

 lar hyperplasia. An excess of iodine ingested in goitre will produce the 

 same symptoms (hyperthyroidism) as occur in morbid conditions where 

 an excess of thyroid secretion is formed (exophthalmic goitre in man), 

 i.e., rapid heart, tremors, wasting, excitement, etc. 



Uses External. — Iodine is of most value applied externally, or local- 

 ly. In sterilizing the skin for an emergency operation the hair should be 

 clipped and shaved dry and the tincture of iodine applied without wash- 

 ing of the skin. 



For other operations the skin may be scrubbed with soap and shaved 

 and dried before applying the tincture. The tincture should always dry 

 on the skin before the operation is begun. The routine method in human 

 surgery for sterilizing the skin, accepted by leading surgeons, consists in 

 first cleansing the skin with gasoline to remove the grease and then 

 applying the tincture of iodine in full or half strength. Half strength 

 should be used on mucous membranes, as the vagina. Potassium iodide 

 is administered internally because it is not irritating to the digestive 

 organs. Although potassium iodide does not exactly represent the action 

 of iodine, yet it is usually preferable for the reason just stated. Potas- 

 sium iodide renders iodine soluble, and prevents its precipitation in fluids 

 within and without the body; it is therefore combined with iodine, when 

 concentrated solutions are desirable. Six parts of potassium iodide and 

 twelve parts of iodine are added to one hundred parts of water, or oint- 

 ment, to make a suitable counter-irritant preparation for the horse. 



Potassii iodldi 6 



lodi 12 



Cerati 100 



M. 



Sig. External use. 

 A useful tincture for veterinary purposes contains 16 parts of iodine 

 and 18 parts of potassium iodide in 100 parts of alcohol. 



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