USES OF IODINE 373 



is incompatible 'with water, so should be used only upon dry or de- 

 hydrated surfaces (operating areas) as water precipitates the iodine. 



External and Local Actions. The action of iodine is quite 

 different from that of the previously discussed halogens. Free io- 

 dine is one of the most useful counterirritants. Iodine produces its 

 action in a manner similar to the other halogens ; it precipitates pro- 

 teids and forms easily decomposed compounds with them. For this 

 reason it remains for some time at the point of application, and, since 

 it is volatile, it also penetrates very deeply so that we have an agent 

 of lasting and penetrating properties. Its irritant action, however, 

 is mild, seldom producing more than redness and desquamation to- 

 gether with some smarting at the point of application. Since its 

 action is so mild, and can be graduated by successive coatings, it is 

 valuable to obtain long sensory irritation without deeply injuring 

 the tissues. 



Applied directly to the skin, iodine causes some burning and 

 leaves a yellow stain. This discoloration may be removed by a 

 solution of ammonia or hyposulphite of soda. It is very painful to 

 raw su.rfaces or when injected into serous sacs and causes some in- 

 flammation in the latter case. 



Taken internally, iodine is absorbed quite rapidly, as the iodides, 

 and some is found in practically all the secretions ; it is largely elim- 

 inated by the urine, as the iodide. In small doses it exerts the same 

 symptoms as the iodides (see page 379) and may produce iodism 

 under the same conditions. Toxic doses internally are discussed 

 under general discussion of the halogens. 



Uses. 1. Counterirritant. Iodine is very useful when a mild, 

 persistent action is desired, as in the removal of inflammatory prod- 

 ucts, edema, rheumatism, arthritis, synovitis, bony gTowths, etc. 

 The tincture or stronger solutions may be used for this purpose. 



2. Cysts, Enlarged Bursoe, etc. The tincture or Lugol's solution 

 is used as an injection into cysts, enlarged bursas, etc. to destroy, the 

 cyst wall and produce an adhesive inflammation. This is a very pain- 

 ful procedure and may result in local gangrene. Occasionally, also, 

 sufficient is absorbed to produce general symptoms of poisoning. 



3. Goiter. In simple goiter iodine in the form of Lugol's solu- 

 tion or the tincture h^s been used as an injection directly into the 

 gland. There is some difference of opinion regarding its action but it 

 is most generally believed to produce its action as an irritant and not 

 as iodine or the iodides internally. 



4. To reduce enlarged glands. The tincture or ointment is 

 applied locally. 



5. Parasiticide. Tincture or ointment, particularly for ring- 

 worm. 



6. Ahsorleni. For bony growths, etc., generally discussed un- 

 der counterirritants. (See page 342.) 



