All the decoctions are prepared from vegetable substances.

Extracta. Extracts. Many different kinds of extracts are to be found in the British Pharmacopoeia.

1. Some consist of the fresh juice, reduced to the state of solid extract by evaporation: these are commonly termed fresh or green extracts, and are ordered to be prepared in the following manner. The juice obtained from the fruits of the plant, leaves and flowering tops, etc, is first heated to 130°, in order to coagulate the green colouring matter, filtered and heated to 200°, at which temperature the albumen is coagulated. After being again filtered to remove the albumen, the juice is evaporated at a temperature not exceeding 140° to the consistence of a thin syrup, and the colouring matter, previously separated by the first coagulation, is added, and the whole evaporated to the proper consistence of an extract.

It will be observed, if the details of the process be examined, that the colour of a green extract is no test of its goodness, for the evaporation of the bulk of the juice may have been carried on at too high a temperature, and yet the product may preserve its green appearance, provide the last part of the process be carefully conducted.

The green extracts of the Pharmacopoeia are Extractum Aconiti, Extractum Belladonnas, Extractum Conii, and Extractum Hyos-cyami. Extractum Colchici, Extractum Colchici Aceticum, and Extractum Taraxaci, are formed in a similar manner, with the exception that in the preparation of these extracts the temperature of the juice is at once raised to 212° to coagulate the albuminous matters, and the filtered juice afterwards reduced to the proper consistence at a temperature of 160°.

2. A second group of extracts is formed from the drugs in a dry state, by the action of cold or boiling distilled water, by which means all the matters soluble in this menstruum are dissolved, and the fluid afterwards reduced by evaporation to the proper consistence. In this manner the following extracts are prepared:-

Extractum Aloes Barbadensis, Extractum Aloes Socotrinae, Extractum Anthemidis, Extractum Gentianae, Extractum Glycyrrhizae, Extractum Haematoxyli, Extractum Krameriae, Extractum Opii, and Extractum Quassiae.

3. A third group is formed in a similar manner, except that the active matters are extracted by means of rectified or of dilute spirit, in place of water. This group consists of Extractum Calumbse (proof-spirit), Extractum Cannabis Indicae (rectified spirit), Extractum Colocynthidis Compositum (proof-spirit), Extractum Jalapae (first spirit, then cold water), Extractum Humuli (spirit, then by boiling in water), Extractum Nucis Vomicae (rectified spirit), Extractum Rhei (spirit and water), and Extractum Stra-monii (proof-spirit).

4. In the British Pharmacopoeia liquid extracts are introduced; these preparations are made for the most part by macerating the drug in a large quantity of cold water, and extracting by this means such of the active matter as is soluble in this menstruum; afterwards evaporating the watery infusion, and, lastly, adding sufficient spirit to prevent decomposition.

In the Pharmacopoeia the following liquid extracts are found: Extractum Cinchonae Flavae Liquidum, Extractum Ergotae Liquidum, Extractum Filicis Liquidum, Extractum Opii Liquidum, Extractum Pareirae Liquidum, Extractum Sarzae Liquidum.

In the case of the liquid extracts of Bael, Ergot, and Pareira, each fluid part represents a solid part of the drug employed.

5. Ether is occasionally employed in lieu of water in the formation of the liquid extracts, especially when the drug contains much oleaginous matter. In the case of Extractum Ergotse Li-quidum it is used to free the preparation from the oil; in that of Extractum Filicis Liquidum it is employed as the solvent of the active matter.

Infusa. Infusions. There are a few points to be noticed under Infusions.

In the preparation of the majority of them, boiling distilled water is ordered, the time of infusing varying from ten minutes to two hours, according to the solubility of the active ingredients of the drugs; in some few cases, as in those of the infusions of Chiretta and Cusparia, water at 120° Fah. is made use of; and in others, as the infusions of Calumba, Gentian, and Quassia, cold distilled water is employed. In the case of calumba the use of cold water is of advantage, as the starch is not dissolved, and hence the infusion will keep much longer, and will not strike a blue colour in the presence of free iodine.

In making Infusum Gentianae Compositum, a different method of procedure is adopted. A little proof-spirit is first poured upon the dry ingredients, and, after maceration, cold water is added, and the process continued as with other infusions.

Linimenta. Liniments, Embrocations. A liniment, derived from linio, I anoint, implies strictly a preparation capable of being used in anointing, and therefore of an oily or soapy nature. In the British Pharmacopoeia the word is employed in a more extended sense, and includes most of the liquid pharmaceutic preparations which are employed as external remedies, and either rubbed or painted upon the part.

The majority of the liniments contain either a fixed or volatile oil or soap, camphor being regarded as a concrete volatile oil; the exceptions are Linimentum Cantharidis and Linimentum Iodi; both of which, unless united with other liniments or oily substances, are best used as paints, for producing blistering or powerful counter-irritation.

Liquores. Solutions. These preparations are watery solutions, either of inorganic substances or of certain definite active organic principles, and should not be confused either with juices of plants (succi), or with liquid extracts: this error is frequently made.

It is important to remember certain points in regard to these preparations.

When made by the solution of a salt or alkaloid, the strength is such that four grains of the active principle are contained in one fluid ounce of the preparation; this is the case with Liquor Arsenicalis, Liquor Atropinae, Liquor Morphiae Hydrochloratis, Liquor Potasses Permanganatis, Liquor Sodas Arseniatis, and Liquor Strychniae. It must be remembered that Liquor Morphiae Hydrochloratis is only half the strength of the preparation in the London Pharmacopoeia; also, that Liquor Ammoniae Acetatis is five times stronger.