In the exhibition of solid substances, their mechanical state of division may be capable of modifying their operation, from the influence which this condition must necessarily exert upon their solubilities, although I am by no means disposed to assign to it the importance which Gaubius has ventured to express, “_Sunt quæ ruditer pulverata alvum, subtilius vero urinas, aut alios humores movent_;” and Ray, speaking of the _Asarum_ (Hist. p. 208) has the following remark—“_Quo tenuius est tritum, eo magis urinas movere, minus autem alvum ducere creditur_;” and Linnæus[268] observes that this same plant, when exhibited in the state of _very fine_ powder, uniformly acts as an emetic, but that when _coarsely_ powdered it always passes the stomach, and becomes cathartic. M. Virey has made a similar observation with respect to Hellebore,—“_L’Hellebore pulverisé fait vomiter; concassé il purge; et en decoction prolongée, il en devient sudorifique ou diuretique._” I have endeavoured under the article _Pulveres_ to establish some useful precepts upon this subject, to which I beg to refer the reader. The influence of solubility upon the medicinal energies and specific effects of remedies, may be farther illustrated by a comparative examination of the virtues of the _Acetate_ and _Sub-acetate_ (Goulard’s Extract) _of Lead:_ the former preserves its solubility and integrity under any degree of dilution, while the latter, when slightly diluted with the purest water, in consequence of the carbonic acid diffused through it, gives out a copious precipitate; the acetate therefore is undoubtedly the more immediately active application as a preparation of lead, but it is nevertheless perhaps less adapted to remove inflammation and abate irritation than the turbid mixture of the sub-acetate, since the slow and gradual action which is ensured by the latter is more desirable than the instantaneous operation of the same remedy, applied in a more soluble form: the popular injection for gonorrhæa, consisting of a mixed solution of _Sulphate of Zinc_ and _Acetate of Lead_, probably owes much of its value to the insoluble precipitate of _Sulphate_ of lead which necessarily takes place, and which, from becoming entangled in the mucus of the urethra, produces a more permanent stimulus than what could have happened from a soluble salt: (_Form. 62_) thus again the _Sulphuret of Antimony_, and some other preparations of that metal, of slow solubility, establish a more permanent influence than _Tartarized Antimony_, and may be preferable to it in cases where immediate and active evacuations are not required.