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ELEMENTS OF MATERIA MEMCA.

as if sulphuric acid had been swallowed. The symptoms are analogousto those produced by sulphuric acid (see Sulphuric Acid ). The yellow',citron, or orange spots, sometimes observed on the lips, chin, or head,will, when present, at once indicate the kind of acid swallowed. Some-times the binoxide of nitrogen is evolved by the mouth.

Properly diluted, nitric acid produces effects similar to those of theother dilute acids (see pp. 81 and 84: also Hydrochloric and SulphuricAcids). It is said, however, to act less evidently as a tonic, and to bemore apt to disagree with the stomach, so that it cannot be employed forso long a period. In some cases it has excited ptyalism, and from thiscircumstance, as w'ell as from the occasional benefit derived from its use inthe venereal disease, it has by some writers been compared, in its operation,to mercury; a comparison founded rather on theoretical than practicalconsiderations.

Uses.— (a.) Internal. —As nitric acid produces certain effects, incommon with other mineral acids, it may be used as a substitute for thelatter in various diseases. Thus, it is administered in conjunction withthe bitter infusions, in those conditions admitting of, or requiring, the useof tonics. Properly diluted, it is employed as a refrigerant in febriledisorders. In litliiasis, attended with phosphatic deposits in the urine,it may be used instead of the sulphuric or hydrochloric acid. In someobstinate cutaneous diseases, as impetigo, it is given to the extent of halfa drachm daily in barley water (Rayer, Treatise on the Diseases of theSkin, p. 502). It may be employed also to relieve heartburn.

In 1793 this acid was used by Mr. Scott, a surgeon at Bombay, as asubstitute for mercurial preparations, which Girtanner erroneously fanciedowed their efficacy to the quantity of oxygen which they contained.Mr. Scott first tried it in chronic hepatitis, and wdth considerable suc-cess. He then extended its use to venereal diseases, and obtained thehappiest results from it.

Subsequently, it has been most extensively employed in the last-mentioned diseases; but the success attending its use has been veryvariable. That it has been, and is frequently serviceable, no one candoubt who reads the immense body of evidence offered in its favour byScott, Kellie, Albers, Prioleau, Rollo, Cruickshank, Beddoes, Ferriar ,and others. But on the other hand it is equally certain that on verymany occasions it has been useless. The same remark, indeed, may bemade of mercury, or of any other remedy: but as an antivenereal medi-cine it does not admit of comparison wdth this metal. However, wefrequently meet with syphilitic cases in which the employment ofmercury is either useless or hurtful. Thus it can rarely be employedwith advantage in scrofulous subjects ; or in persons whose idiosyn-crasies render them peculiarly susceptible to the influence of this metal;and in sloughing sores it is inadmissible. Now these are the cases inwhich nitric acid may be employed with benefit; and I believe the bestmode of administering it is in conjunction with the compound decoctionof sarsaparilla.

For further information respecting its employment, I must refer to theworks of Holst (De Acidi Nitrici usu Medico Dissertatio, Christiana;1818) and Mr. Samuel Cooper [Diet, of Practical Surgery).

{h .) External. —In the concentrated state, nitric acid has been em-ployed as a powerful caustic to destroy warts, and as an application to