Some medicines will run the gauntlet of the acidity of the stomach, and the alkalinity of the intestines, as well as of the blood, and are eliminated with little or no alteration. Ordinarily, this takes place in substances of a homogeneous nature, and when introduced into the body in excess. Sugar, albumen, chlorate of potash, chloride of sodium, pyrogallic acid, cantharadin, quinine, chloride of barium, iodine, etc., will be found unchanged in the urine. Volatile or gaseous substances taken into the system are eliminated with little or no change through the lungs, and at times through the skin. The carbonates, the nitrates, the sulphates, the silicates of potassa and soda, that is the alkaline salts, the sulphate of protoxide of iron, yellow ferrocyanide of potassium, alum, the chlorides, the bromides and the iodides may likewise be placed under this classification; and of organic substances: indigo, rhubarb, gamboge, the resins of the coniferae, terebinthenaceae, the leguminous plants, as the copaiva, and sulphuric, nitric, chlorhydric, and phosphoric acids. The essential oil of cajaput and the essence of eucalyptus will pass almost intact the respiratory organs. Aloes is partly absorbed, since children have been purged by the milk of a nurse using it. Pyridine can be traced in the urine almost immediately after the commencement of an inhalation,† Cane sugar injected into the veins of a living animal is not assimilated by the system, but is immediately rejected by the kidneys,‡ The inorganic salts are always combined with nitrogenized matter, and seem to pass through the organism without undergoing any considerable change, and there is no evidence that they have any connection of themselves with the production of heat.

Boric and gallic acids are eliminated by the urine; the latter has been detected an hour after it has been taken. || Chloride of ammonium is eliminated almost entirely unchanged by the urine. The carbonate of potassium passes through the kidneys unchanged.* The chlorate of potassium is eliminated unchanged in all the secretions.* It may be found in tears, the nasal mucus, the perspiration, and in the milk of nursing women.¶ It appears in the saliva sooner than in the urine.** The iodide of potassium may be detected unaltered in the blood, urine, or other secretions. It is rapidly eliminated from the animal fluids. Atropine, hyoscyamin, are eliminated by the kidneys, and have been detected in the urine twenty-two minutes after the hypodermic injection of gr. 115 of the alkalo'id.††

*Prof. R. T. Edes. ‡Bernard. ||Parker. **Laboide.

tGermain. §Flint. ¶Byasson. ††Waring.

Naphthaline is excreted by the kidneys chemically unchanged,* and so is cinchonidine.† Apparently, readily oxidizable substances, such as grape sugar, are not consumed in the system.; Saccharin passes unchanged through the organism to be eliminated by the kidneys, as do benzoic acid and resorcin, imparting their antiseptic properties to the urine.§ Corrosive sublimate in large doses, causing gastrointestinal irritation, shows prominent symptoms which indicate that the bichlorate is eliminated unchanged from the alimentarycanal.|| Salicin is rapidly absorbed, probably as salicin, but once in the blood it seems to be quickly decomposed, the products of its change appearing in the urine fifteen to thirty minutes after the ingestion of a single dose. This change does not appear to be complete, according to Husemann: in the urine of man after the ingestion of salicin not only saligenin, and salicylic acid occur, but also unchanged salicin. Further, Falck injecting salicin into the blood of the dog, found that it escaped chiefly from the kidneys u faltered. The elimination seems to go on slowly, as Senator has detected salicylic acid in the urine sixty hours after the injection of a single dose of salicin.

Muscarina produces very marked and exhilarating effects upon the human subject. It is stated that the poisoning through the body increases in power, so that the urine of a person partially intoxicated with muscarina, is capable of rendering other persons very drunk.**

Many substances which have made the rounds of the circulation, do not become permanently active, and do not suffer any modifications before they become free, and this does not happen until they arrive in organs which do not contain albumen; then these substances become free, as in the urine, in the cerebrospinal fluid, in the fluid contained in the internal ear, and in the aqueous humor of the eye, and here in these liquids there is a recurrence of symptoms due to the activity of the drug, which had first induced notable effects on the surface to which it had been applied. It is on this account that cantharadin circulates in the blood without manifesting its noxious properties; however, on its arrival in the kidneys, the urine not being albuminous, it acts on the organs like a veritable blister, renewing the effects it had produced on the skin.††

Substances that pass through the system without mutation nevertheless may render a portion to the economy, provided its elective organs are in a condition to receive the storage. Under a protective physiology, heterogenous substances are usually eliminated under chemical dissolution. Homogeneous substances can be removed intact without the liability of producing a histogenic or organic lesion; therefore their chemical dissolution in passing through the system is not an absolute necessity.

There are special benefits to be derived by the unchanged condition of some medicines elinfinated, as exemplified in the use of copaiva, and in the acids and alkalies in urinary affections, in the resinous expectorants in some forms of diseases of the lungs, while others may inflict damage either to the emunctory through which they pass, or some organ in close sympathy with it. Thus, cantharadine is apt to cause a serious hyperaemia of the kidneys, and turpentine, strangury. Therefore, in prescribing the Spanish fly internally, an adjuvant is a matter of importance to protect the kidneys. Camphor will serve this purpose.

*Prof. E. R. Palmer. †Prof. L. Hermann. ||Dr. J. Rosenbach. **Waring.

†Byasson.

§Br. Chas. W. Purdy. ¶Prof. H. C. Wood. ††Prof. Adolph Gubler.

There are substances that may exercise their power in the blood without undergoing any change. Hydrogen, carbonate (carburetted) hydrogen, carbonic acid, and oxide of carbon, protoxide or binoxide of nitrogen, sulphuretted hydrogen and hyponitrous acid, prussic acid, nitrites of amyl, and ethyl, and all the volatile and gaseous substances belong to this class, and it appears they have a special tendency to be eliminated by the lungs.

Wood charcoal, and madder have been discovered in the blood of the mesenteric veins, and of the vena porta, and in the liver, and the lungs of animals which had been fed on food containing them.

Deposit of Drugs in the System through Assimilation.

The normal tissues are formed of solid and fluid elements, of which the former undergo a more gradual transformation than the latter: A foreign body, therefore, will have a tendency to remain longer in the system when it becomes a part of a formed tissue than when associated with one of the fluid elements; and if the part in which it is deposited is comparatively inactive in function (such as the bone), it may remain in the system indefinitely without producing any symptom as a result of its presence. It is only lately that examples of this form of assimilation of poisonous substances, which are always inorganic, have attracted any attention. In such instances it has been found that the inorganic principles in the animal economy may be replaced by other isomorphic elements. As examples of this, may be mentioned the substitution of lead and baryta salts for the lime salts of the bones; the substitution for the phosphates of the isomorphic salts of arsenious acid; and probably also the deposits of copper in the various organs are governed by the same rule. As regards the ultimate fate of such foreign ingredients of the tissues, it is probable that they are finally replaced by the normal constituents when the supply of the poison is interrupted.*