This section is from the book "A Manual Of Practical Therapeutics", by Edward John Waring. Also available from Amazon: A Manual of Practical Therapeutics.
Lugol considers that it acts specifically upon the absorbent system; others, that its action is solely that of a general tonic, improving and strengthening the digestive organs, establishing a healthy tone of the system, and thus retarding the development of tubercular disease. Dr. Glover explains its action thus: - "It is well known," he observes, " to all practical men, that Iodine acts as a diuretic; but it is not equally known, that the urine contains large quantities of urea. Now, urea is the product of albuminous tissues, and, as it has been clearly shown by chemical analysis that the tubercle is composed chiefly of albumen, we can understand how Iodine acts by carrying a large quantity of albumen out of the system, thus retarding the growth and promoting the absorption of tuberculous matter."
1574. In order to ascertain whether Iodine has become absorbed into the system, take a strip of starched paper, moisten it with the saliva or urine of the patient, and then touch it with Nitric Acid. If Iodine be present, a more or less intense blue is produced (Rayer). According to Dr. Rosenthal,§ Iodine may be detected not only in the urine, saliva, and other secretions, but also in the alvine evacuations within from four to seven hours after Iodide of Potassium has been taken. Iodine may be detected in the urine when it is introduced into the system through the skin, by means of frictions or baths.