This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
This is prepared by bruising the fresh leaves, expressing the juice, heating this to the boiling point so as to coagulate the albumen, then straining, and evaporating the clear liquor to the proper consistence. It has a dark-brown colour, a narcotic not disagreeable odour, a bitterish taste, and a soft consistence. As used in this country it is generally imported, and is of unequal strength, sometimes very powerful, sometimes feeble, and therefore requiring to be administered with much caution. Special care must be taken that, in increasing the dose, the same parcel should be employed; and if a new one is to be used, the dose should be reduced so as to test its strength. This is the preparation most employed in the United States. The commencing dose is from one-quarter to one-half a grain, twice or three times a day, gradually increased, if necessary, until some sign of its action is produced, as dryness of the throat, dimness of vision with dilatation of the pupil, or uneasy sensation in the head. I have often known half a grain to act decidedly.
In the way of enema not more than three times as much should be given as by the mouth. For endermic use, three or four grains may be employed, but its effects should be watched. If no effect is produced, the quantity may be increased. For friction on the sound skin, from ton to thirty grains or more may be used, with sufficient water to bring it to the consistence of thick cream, or with twice its weight of lard.