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tuting experiments upon the subject, and 1 am happy in being enabledthrough his liberality, to introduce in this place, an account of the pro-cess which he pursues, and which he considers the only one by whichthe article can be brought into the market at any reasonable price.*

In concluding the history of Inspissated juices, it deserves notice thatthe London College uniformly directs that the feculence should be pre-serevd in the compound ; there can be no doubt of the propriety of suchadvice, but the Colleges of Edinburgh and Dublin reject it. The FrenchCodex gives directions for two extracts from each of these substances,one containiug what they please 10 denominate the fecuta, the other not;thus there is'• Extractum Cicut* absque Fecul:.'' and " Extract: Cicut:cu■nFecula. , '' There is one curious fact re-;/e.cting these narcotic pre-parations, that most, if not all of them, contain nitre, common salt, andmuriate of potass.

Manufacturing chemists, in order to give a smooth and glossy appear-ance to their Extracts, generally add to every lbj, about 3ss of gum, f3j

* " I have the C03 Lettuce planted about eight inches asunder in rows, betweenwhich there is sufficient space to enable persons to pass up and down without injuringthe plants. [ commence my operations just before the plant is about to flower, by cut-ting; off an inch of the stem ; the milky juice iminediab ly exudes, and is collected onpieces of Wove Cotto.i, about half a yard square. As soon as this becomes charged,it is thrown from time to time iuto a vessel containing a small quantity of water, whichwhen sufficiently impregnated is evaporated at the common temperature of the atmos-phere, by exposure in a number of shallow dishes. The Lactucaridm, in a fewhours, is fouud adhering to the vessels in the form of an Extract, but differing fromevery other in all its sensible properties : this method enables me toeollectLACTBCA-iiipm with great facility and dispatch, but it is still attended with considerable ex-pense, as the proportion of milky product is necessarily very small, and the price ofthe medicine consequently high, and therefore not within the reach of general prac-tice. This consideration led me to make farther experim nts, for the purpose of as-certaining whether an Extract might not be obtained from the plant possessing allthe properties of Lactucariurn, when administered in large doses, and which could beintroduced at a companatively trifling cost. In prosecuting this enquiry. 1 found thatthe plants contain most of the milky juice when they have flowered and the leavesare beginning to assume a yellow hue, and I observed that when cut down, the milkyjuice assumes for the most part a concrete form, having subsided in the bark of thestalk and 111 the old leaves, a circumstance which accounts for the extreme bitternessof these parts. 1 was naturally led from these circumstances to choose the above pe-riod for my operations, and to select (hose parts only of the plant for my extract, rejecting the substance of the stalk, and the young sprouts. My method of procuringthe extract is as follows. I first macerate the parts in water, for twenty-four hours,and then boil them for two, after which I allow the clear decoction to drain through asieve, without using any pressure; this is then evaporated, as far as it can be donewith safety, and the process is finished in shallow dishes, in the manner above describ-ed, for obtaining Lactucariurn. This extract, which I have called " ExtractumLactuc* Concestratuji,'' is of course less powerful than Lactucariurn, but it pos-sesses all the properties in larger doses, and it has been found equally useful iu a num-ber and Variety of cases, and is not more than a sixth part of the price."

Mr. Probart has retired from trade, but I have just learnt that the same article isnow prepared, by a similar process, by Mr. Selway, Chemist, of New CavendishStreet, and the specimens which I have received authorise me to recommend it fortrial. A concentrated tincture is also prepared.

The " Succus Spissatus Lactucee sativSB," of the shops, must of necessity be almostinert, since it is commonly prepared at that period, when the plant contains none, orvery little of the milky juice; and even if the Lettuce be employed at a more matureseason, it must still fail to afford an extract of any strength, as it is merely the express-ed juice, and that too of the whole plant indiscriminately, and will be found to containa very minute proportion of Lactucariurn. the great bulk being nothing more than inspissated green juicf 1 .