216 MOHR AND REDWOOD'S PRACTICAL PHARMACY. 
with the gum in powder, and lastly the water added gra- 
dually in the manner of making an emulsion. A much 
more permanent and better mixture is obtained by triturat- 
ing the camphor to a uniform paste by the addition of half 
its weight of olive or almond oil, then adding twice its 
weight, or more, of powdered gum-arabic, mixing inti- 
mately, and adding the water gradually, triturating con- 
stantly till the whole is mixed. 
" One of the best ways to make a camphor mixture, 
when the addition is not contraindicated, is by means of 
myrrh. One part of that gum-resin will suspend four parts 
of camphor. The tears richest in volatile oil should be 
chosen, as in making an emulsion of myrrh, the camphor 
should be powdered by the addition of a little alcohol, and 
added to the myrrh previously reduced to a milky paste 
with water, the two then triturated until uniformly mixed, 
after which the water is gradually added. 
" When a few drops of croton oil are directed to be sus- 
pended in mucilage, it is well to admix a little olive oil, so 
as to increase its quantity and render the emulsion moro 
permanent. 
"Scammony mixes very readily into an emulsion with a 
little milk ; and resin of jalap, which will not mix with milk, 
may be diffused through emulsion of almonds by triturating 
it with the almonds and water." 
A few instances will now be specified in illustration of 
the foregoing principles, and with the view of more fully 
explaining the mode of proceeding in the preparation of 
pills. The principal substances which enter into the compo- 
sition of pills will here be divided into classes which will be 
considered separately. 
Rhubarb may be taken as the type of a class of substances 
frequently administered in the form of pill. Jalap, ipeca- 
cuanha, ginger, conium, digitalis, and other vegetable 
powders belong to this class. Now, taking these substances 
as a class, syrup is perhaps the best excipient to use for 
