carbonate from the action of free carbonic acid in the stomach and other parts of animals, or because the salt is decomposed by double decomposition from the accidental presence of alkaline carbonates. It does not appear to me, however, that the researches of Dr. Thomson, taken along with the prior inquiries of other physiologists, will bear out this conclusion. The experiments of Wibmer in particular would seem to show that the carbonate is at least not more active than the acetate; nor does it appear probable that the small doses of acetate given by him, seldom exceeding two or three grains at a time, could yield any carbonate in the alimentary canal of a dog, where there is commonly much free muriatic acid. Farther, in many of the instances of lead colic related above as produced by cider, wine, and other acid substances acting on lead or its oxide, the acid must have been so greatly in excess, that it was scarcely possible that carbonate of lead could have been formed afterwards by any ordinary accident. And even supposing the carbonate to be more active than other compounds in occasioning colic and palsy, as Dr. Thomson's inquiries would tend to show, the fact may be admitted without necessarily leading to the inference, that it is the only active compound of lead, or that other preparations must be converted into the carbonate before they can act as slow poisons. For the superior activity of the carbonate may be owing to the great obstinacy with which its impalpable powder adheres to moist membranous surfaces, and the consequent greater certainty of its ultimate absorption. It certainly appears at least but consistent with a general law, to which hitherto no undoubted exception has been found, that the carbonate must be dissolved before it can act constitutionally.
The symptoms observed in man from the preparations of lead are of three kinds. One class of symptoms indicate inflammation of the alimentary canal: another spasm of its muscles: and a third injury of the nervous system, sometimes apoplexy, more commonly palsy, and that almost always partial and incomplete. Each of these classes of symptoms may exist independently of the other two; but the last two are more commonly combined.
The irritant effects of large doses of the soluble salts of lead come first under consideration. Of these the acetate, or sugar of lead may be taken as an example.
Here it will, in the first instance, be observed that, according to the experiments mentioned above, the acetate of lead, though certainly an irritant poison, is not very energetic,—being much less so than the vulgar generally believe, and far inferior to most of the metallic poisons hitherto treated of. This farther appears from the experience of physicians as to its effects in medicinal doses. The acetate has been often given in pretty large doses in medical practice; and although it has sometimes excited colic when continued too long, ordinary irritation of the stomach seems to have been rarely observed. Mr. Daniell, in a paper on its effects as a remedy for mercurial salivation, states that he gave it in doses of ten grains three times a day, and that he never observed it to excite any other un-
