There is, very rarely, any considerable effect produced on the arterial system by iodine, if it be given with propriety and caution. Sometimes it accelerates the pulse in a slight degree; it frequently occasions a little mucous expectoration from the chest, and it often raises nervous symptoms in delicate subjects, which are very distressing. I saw it given to a young woman in one of the public hospitals in Paris, in whom it produced such a state of insomnia that she told me she had not slept at all for a whole week, though she had been a very good sleeper before. I have said that it affects the pulse but a little, yet it sometimes stimulates very powerfully the arterial vessels of the tumor. This is mentioned by all the authors who have written on iodine, and is one of the most singular circumstances in its medical history! This irritation of arterial vessels frequently becomes active inflammation, requiring the use of bloodletting for its relief. Topical bleeding will, in general, be found fully competent to remove it. Indeed, it sometimes happens that when the iodine has lighted up smart inflammation in the tumor, the arterial system generally is unaffected. To what is this effect on the vessels of the part to be attributed, from which the constitution generally is free? The same is occasionally true of the absorbent vessels. I have seen some very large tumors discussed, while there was no evidence whatever of the absorbent vessels in other parts of the body having felt the influence of the medicine. It is a curious question, to determine by what law the constitution remains impassive to the action of a medicine, which affects remote and distant parts through the constitution. Certain tumors are of so irritable a nature, that a stimulus, which only serves to rouse the healthy energies of the body, excites the process of destruction in them. In the quaint language of a celebrated modern lecturer, “they are irritable beings, if you touch them they’ll kick.” But this is not the case with many of the tumors which are dissipated by iodine. Bronchocele, for instance, is of a slow growth; all the operations which go forward in its structure are of a very indolent and chronic kind. Such, also, is the case with the greater number of scrophulous tumors. Yet all of them have been dissipated, like a charm, by the agency of iodine.