the unfortunate individual; he was removed to shelter, the parts were washed with spirits and vinegar, and the loathsome objects removed, as far as was possible. Cordials were poured down his throat, but he swallowed with difficulty; and in a very short time spasms took place which prevented him from swallowing altogether. The putrescence advanced; in a short time he became insensible; and about noon the following day he died, in a state of total _putrisolution_.” AERIAL POISONS. Under this division we include all those deleterious substances which can be administered through the medium of the atmosphere. Those gases, the respiration of which occasions death by the negative operation of excluding oxygen, are not ranked under the class of poisons, for the history of such bodies involves physiological views peculiar to themselves, and belongs more correctly to the subject of suffocation, under which head it has already met with full consideration, _vol._ 2, _p._ 48. _Aërial poisons_ are of very undefined extent, and their history is involved in considerable obscurity. Every poison, capable of volatilization, may be admitted into the division; and even those substances which are generally regarded as fixed, may be mechanically suspended in the air, and thus produce their effects on the living system, through the medium of the lungs, stomach, or nerves. In the present state of our knowledge, we have, perhaps, only an imperfect idea of the distinction between a fixed and a volatile body. A very interesting paper on this subject was read before the Royal Academy of Berlin, by _Professor Hermbstaed_,[497] in which he observes that, generally speaking, we might consider all bodies as volatile, as it is most probable that, could we produce a sufficient degree of heat, no substance could resist it. The professor also states that many bodies, hitherto considered as fixed, are actually volatilized at the temperature of boiling water; such he found to be _lime_, _baryta_, _strontia_, and _potass_. We apprehend, however, that the professor has, in these instances, mistaken a phenomenon for _volatility_, which it is highly important to distinguish from it, viz. _the elevation of a certain portion of a fixed body, by the carrying power of a vapour_; thus, fixed oil may, in a minute proportion, be carried up with the steam of water. Certain bodies, however, which have been long considered as perfectly fixed at the ordinary temperature of the atmosphere, have been lately discovered to undergo a slow and almost imperceptible evaporation under such circumstances; and the discovery has led to a very satisfactory solution of several problems which were previously unintelligible. We shall adduce a striking exemplification of this truth, under the consideration of mercurial vapours. The substances, included under the head of _Aërial poisons_, may be conveniently arranged in two orders, viz.