192

ELEMENTS QF MATERIA MEDICA.

without acting primitively on the brain; but when more is injectedthan the blood can dissolve, it produces death by distending the heart, aswhen air is injected into the veins (see p. 23). Applied to the skin ofanimals, free access of common air to the lungs being preserved, it pro-duces, if the experiment be continued long enough, death.

(d.) On man. —If an attempt be made to inhale pure carbonic acid gas,the glottis spasmodically closes, so as to prevent the smallest portionsfrom entering the lungs (Davy, Researches, p. 472). When mixed withmore than twice its volume of air, this gas ceases to provoke spasm ofthe glottis, and may be taken into the lungs. In this case it gives rise tosymptoms resembling those of apoplexy. It usually causes a sensationof tightness at the chest, uneasiness, giddiness, loss of muscular power,insensibility, and stertorous breathing, sometimes accompanied by con-vulsions or delirium. These symptoms are succeeded by asphyxia anddeath.

Applied to the conjunctiva it acts as an irritant, and excites pain, redness,and a flow of tears. Applied to the skin (care being taken that it is notinhaled) it produces a sensation of warmth and pricking or tingling,sometimes accompanied by' pain, increased frequency of the pulse,sweating, and excitement of the nervous system. M. Collard de Mar-tigny (quoted by Dr. Christison) experienced weight in the head, obscu-rity of sight, pain in the temples, ringing in the ears, giddiness, and anundefinable feeling of terror. Taken into the stomach, dissolved in water,or in the form of effervescing draughts, it allays thirst, and diminishespreternatural heat, thus acting like the other dilute acids. If it beevolved in the stomach, it distends this viscus, excites eructations, andchecks both nausea and vomiting. It appears to promote the secretionsof the alimentary tube, to assist the digestive process, to allay irritation,and to act as a refreshing and exhilirating substance. It is said to bediuretic and diaphoretic. Wohler and Stehberger expressly state, thatthe use of carbonic acid did not increase the quantity of this substancein the urine (Duncan, Supplement to the Edinb. Disp. p. 223). Whendrunk too quickly, and in large quantity, water impregnated with thisgas has been known to excite giddiness and intoxication (Fodere, Med.Legale ); and it is probable that champagne is indebted to this substancefor part of its intoxicating powers. Applied to ulcers and suppuratingsurfaces, carbonic acid gas acts as a stimulant, improves the quality ofthe discharge in ill-conditioned and indolent ulcers, retards the putrefac-tion of the secreted matters, diminishes the unpleasant odour of ‘foul andgangrenous sores, and promotes the separation of the dead and mortifiedparts.

Uses — [a.) When inhaled. —In some diseases of the lungs, particularlyphthisis, it has been proposed to mix carbonic acid gas with, thf atmos-pheric air breathed by the patient, with the view of lessening thtnkimu-lant influence of the oxygen, to diminish the quantity, and improvfrthequality of the matter expectorated, and at the same time to relieve thehectic symptoms. It is not at all unlikely that temporaiy relief mightbe gained by its employment; but difficulty is experienced in the modeof applying it. Of course, to be beneficial, it ought to be constantlyinspired. Temporarily it is readily inhaled, by generating it in a largebottle or jar, and breathing it by means of a tube ; but for its continueduse, the only method that can be employed is to evolve the acid in the