Of the less active antiseptic agents, _boric acid_ is considered absolutely innocuous, yet is known sometimes to cause intestinal disturbance, while in one instance serious toxic effects followed its use. _Naphthalin_ will sometimes produce vertigo or vasomotor symptoms, especially when administered internally. Many of the antiseptic materials used are more or less irritating to the skin, and such local expressions as _eczema_, etc., provoke little comment. _Iodine_ is a drug whose activity should be borne in mind. Applied upon the surface, it tans the skin and does no good. Injected in solutions of varying strength into serous cavities (for example, hydroceles, etc.) it gives rise to symptoms which may be alarming. Fatal poisoning following its injection into an ovarian cyst has been reported, and alarming symptoms have been produced by injection of the ordinary solution into a hydrocele sac. Much of the virtue ascribed to _iodoform_ is credited to the liberation of free iodine by its decomposition. Whether or not this be true, iodoform is one of the most frequently toxic of the antiseptic agents in ordinary use. In mild cases it produces headache, restlessness, wakefulness, and often a distinct taste of iodoform in the mouth. In more pronounced degrees of poisoning there is fever, often with mental derangement which may amount to delirium or even to acute mania, and may cause well-founded suspicion of meningitis. Death after its use has repeatedly occurred from syncope or in coma. _Carbolic acid_ produces unpleasant effects, both upon patient and operator, or with whoever it may come in contact. Aside from its local effect upon the skin, which is most unpleasant, but which usually passes away within a few hours, it seems to affect especially the kidneys, causing often temporary albuminuria with discolored urine, deranged secretion, and sometimes more acute forms of disturbance, similar to those met with after its internal use. Carbolic poisoning was observed most frequently during the era when Lister’s original directions were scrupulously followed, and at a time before it was learned that it is much better to remove dirt than to try to antagonize its action. Eminent surgeons were compelled to discontinue its use because of its unpleasant effect upon themselves as well as upon their patients.