This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
From the above discrepant results, it becomes difficult to theorize concerning the action of iodine on nutrition, and further reliable analyses of the excretion under its use are highly desirable. The French physiologists concluded that its influence resembled that of arsenic, i.e., was more of alterative, modifying character, than absorbent and eliminant. My own observations lead me to place more stress upon the latter. Although the medicinal use of iodides in certain disorders may bring about an improved state of the nutrition (Wallace found, for instance, that his syphilitic patients gained flesh under its use); yet, when given continuously to persons of average health, these medicines usually impair nutrition and induce more or less emaciation. This affects the periglandular and fatty tissues rather than the true glandular structures, and it may be connected either with disturbance of digestion, or with certain important physical effects recently traced to iodide of potassium. One of these is the increased rate of circulation produced in capillary tubes when that salt is added to the circulating fluid (Poiseuille), and the other is its dissolving the central substance of starch-granules with great expansion of peripheral layers, so that the grains become twenty-five to thirty times larger than normal (Payem). We may suppose that, introduced into the human economy, the drug both quickens capillary circulation and dissolves glycogenic material.