The act of solution, in which solid substances assume the fluid state through the agency of liquids, is one of the most important operations of practical pharmacy. The process has received a variety of names, according to the mode of applying the menstruum and the degree of heat employed; as maceration, infusion, digestion, decoction, displacement, or percolation and circulatory displacement.

Two classes of substances are the subject of solution; those which dissolve in the menstruum, as salts, gum, etc., and those which consist of soluble and insoluble matter, as roots, leaves, barks, etc. The former yield simple solutions; the latter infusions, decoctions, tinctures, wines, etc.†

It is our province here, to consider the subject in a different light, that is, the solubility of substances in their transition through the system as medicinal agents.

We know that the presence of acids, of alkalies, of albuminoid substances, and of fatty matter, is, if not indispensable, at least of use in aiding the solution and absorption of a large number of medicaments of themselves rather difficult of dissolution. It suffices to know this general law - the necessity of the presence of modifying substances - to understand that, according as they are in abundance, in small proportion, or not at all present, there will be facility or difficulty of absorption, or no absorption at all. Thus, the acid of the stomach will favor the introduction of all the substances which are in need of acid to penetrate into the economy; such as the metals and very insoluble acid salts. And thus again, the opposite condition will prevent absorption. Alkalinity of the intestines is favorable to the absorption of a certain number of substances, and, in particular, of arsenious acid, as also of salts having an alkaline, or an earthy base, and which have acids rendering them insoluble. Thus, the tartrates and the oxalates of lime, of potash, and of soda, are little soluble when they are acid, and if they are easily soluble, then they are alkaline and basic; consequently, they can penetrate with more facility when the amount of alkali which they meet in the intestines is more considerable.*

*Prof. A. Gubler. †U. S. Dispensatory.

There is within the intestines, with the exception of the caecum, which is said to be acid, great scope to effect the solubility of medicines, owing to the alkalinity of the secretions. It is in those parts that a chemical reconstruction often takes place with many substances. Medicines that become soluble under the reaction of acids of the stomach, in reaching the intestines are precipitated, and then redissolved by the alkaline albuminous fluids of the intestines, and taken into the circulation. Not only res-inates are thus dissolved, but metals; gold, silver, calomel, zinc, lead, sulphur, phosphorus and platinum. We have reason to think there are circumstances where substances pass through a triple and quadruple chemical change in their passage through the system, as affected by the acidity of the stomach, the alkalinity of the intestines, the albuminoids in the blood, and finally the acidity of the emuuctories.

Albuminoid substances which are found in the intestines, and throughout the whole of the digestive duct, as well as in the blood, are not only emulsive agents, but perform the office of real solvents to facilitate the penetration of different substances into the circulation.* In the digestive duct they are able to dissolve calomel, which penetrates into the organism as an albuminate of protochloride of mercury, and behaves like calomel. This likewise applies to proto-iodide of mercury, to sulphur, phosphorus, and to all substances that are soluble in mucus and albuminoid substances. * It is said that calomel likewise may be dissolved in mucilaginous sub-stances.†

It is a general law that albumen modifies remedial agents in a certain manner, to render their introduction into the economy more facile; but once introduced, this same albumen opposes in the blood the effects, whether chemical or physiological, which these remedies usually exercise on the organ with which they come in contact.*

Medicines Changed in the Blood, and their Effects on the Blood.

Some drugs have an immediate effect on the blood, either to impoverish it, or to improve it by oxidation. Mercury and the salines belong to the former; and nitrate, permanganate and chlorate of potassium, iron, etc., to the latter. The hemostatics, although directly intended for the blood, make no chemical impression on it, as is generally supposed - their power is in contracting the arterioles. Ergot fully reveals this physiological action. So does turpentine through its stimulating properties, and its extraordinary penetrability, forcing its way through the protective albuminoids of the blood vessels, and acting as a direct stimulant to the capillary vessels, causing them to contract to resist its influence, and to keep it from invading routes not its own. The constitutional use of iron acts as an indirect hemostatic, so modifying the blood by oxidation that by its own normal force it will impart its tonicity to the blood vessels.

*Prof. Adolph Gubler. †Personne.

It is supposed by giving mercury, that it is found in the blood as a double albuminate,* and therefore contra-indicated in albuminuria and adynamic affections. It is evidently highly destructive to the fibrin of the blood.

Blood before the exhibition of nitre is cupped and buffed, but loses much of this character after its administration in quantity.† It communicates a bright arterial tint to venous blood, and when added to fresh drawn blood it impedes coagulation.‡ Why it fails as a hemostatic is evidently owing to the rapid elimination of the solids, under its diuretic effects.

Chloral coagulates blood as powerfully as is the effect of phenic acid. Therefore, when you introduce a solution of chloral, it must be a massive dose; because if over diluted it would produce a commotion of the heart. Thus you risk causing a coagulation of the blood, and giving rise to emboli to infarets and a suspension of life in some of the essential organs.§

Chlorate of potassium, rich in oxygen, has without decomposition the valuable property by its mere presence to oxygenate or aerate the the blood, and so by restoring or exerting this* vital character of the circulating fluid, influencing 1o a corresponding degree the nutrition and functional activity of the various tissues and organs of the body.||

There are substances which act while present in the blood, but they are gaseous or volatile bodies, which act in the same manner as the air in respiration, directly on the blood corpuscles, and which accomplish their destiny, it might be said, in the blood itself; these substances are hydrogen, carbonated (carburetted) hydrogen, carbonic acid and oxide of carbon, which spend their activity on the globules. The same is true of protoxide or binoxide of nitrogen - substances which act on the circulation, as do also nitrous and hypo-nitrous acid; and prussic acid, too, acts in the blood, as do the nitrites of amyl and of ethyl, and all the volatile and gaseous substances which induce anaesthesia. These all induce phenomena which really pass into the blood, and no more striking proof of this is needed than their instantaneous and often fugacious action in the great proportion of cases.§ In the human organism, and in the circulation, albumen will exercise its suspending properties on substances introduced into the blood and circulating in the serum of that fluid; thus preventing the manifestation of a certain number of chemical phenomena which would have occurred if it were not present.*

*Prof. R. T. Edes.

‡Stevens.

||Dr. J. S. Sinclair Coghill.

† Waring. § Gubler.

The albuminoids in the system supply an environment of protection to animal life in a thousand ways; not only as far as the ingesta of chemicals are concerned, but of food itself. If it were not for this wonderful protection, many a thing we daily partake of would prove a deadly poison. One drink of rum would kill as if it were prussic acid. It is an element variously developed in different living beings, and, therefore, what may be food to one, may be poison to another. But this substance, tenacious as it is in its function to render systemic protection, may assume a pathological relation perhaps with all zymotic diseases. We are led to think so, as it has failed to render the usual protection. It is exceedingly interesting to investigate the relation the albuminoids may have as an etiological factor to two very formidable diseases, one not of a zymotic nature, namely: diabetes, the other, Asiatic cholera. There is only one resemblance between the two diseases, that is, the loss of an enormous amount of fluid in some mysterious way, and in the renal symptomatology of the two they diverge to the utmost extreme. Do these two diseases betray two different morbid conditions of the albumi noids? Without going into details, we incline to think they do. In accordance with this view, might not a plan of treatment of these diseases be called for?

If there are remedies that change the chemical properties of blood, it is well to remember that it is usually the blood of the veins. When medicinal substances are introduced into an organ distant from the arterial system, the digestive tract, for instance, they cannot enter the arterial system, because they are stored up or expelled before reaching it. They must pass through the portal system, the hepatic vein, and the pulmonary texture, there to be exhaled, or they can be expelled from the liver with the bile.† This is the route a medicated gas would take when administered by enema. If the same were administered by inhalation, and accepted by absorption, it evidently would seek the same route, but may not reach it, being carried out of the system by more active emumctones than the lungs. This question has an important bearing in the gaseous medication for pulmo nary diseases, either by inhalation or by en-emata. Both make their impression on the blood, but not by the same process, nor with the same advantage, nor are always indicated for the same malady. Medicated inhalations are indicated for superficial lesions of the pulmonary mucous membrane, but where the parenchyma is involved a gaseous enemata may at times serve a better purpose, for the reason the lungs would be its immediate emunctory, where by inhalation the medicine would be more systemic, and apt to seek its outlet not from the source of its admission.

Another item for consideration in gaseous enemata is, what seems may be harmless as an enema would prove disastrous by inhalation. The security lies in the gradual absorption of the poison by the veins; the danger by its sudden admission into the arterial system.

*Prof. Adolph Gubler. †Ch. Bernard.