ON DRUG-GRINDING. 25 
maceutical works that colocynth is powdered by mediation, 
in the same way as that above described for the pulveriza- 
tion of agaric ; but in this case the addition of a foreign body 
is certainly unnecessary, and I am informed that no such 
addition is made by the drug-grinders in this country. 
The foregoing is a general outline of the various me- 
thods adopted in effecting the pulverization of drugs. We 
may now return to the question, — how far do these processes 
affect the composition, strength, and general medicinal 
efficacy of the substances operated upon ? 
The operations connected with the process of drug-grind- 
ing do not seem to be calculated to promote chemical change 
in the constituents of the powder; for, although the disin- 
tegration, by exposing a larger surface to the action of the 
air, may be somewhat unfavourable to the permanence of 
the proximate constituents of vegetable substances, yet the 
complete desiccation which forms part of the process will 
exercise a conservative influence to probably an equal ex- 
tent. This, at least, would be the case if the powder, when 
prepared, be put in close bottles, and kept for only a mode- 
rate length of time. 
The principal, if not the only necessary, cause of deterio- 
ration to the products, is the long-continued application of 
the degree of heat to which the drugs are exposed in the 
drying-room. There are some substances which cannot be 
thus dried without having a portion of their active volatile 
ingredients driven off, as well as the water they contained. 
The strong smell which fills the drying-room when opium, 
or myrrh, or cinnamon, are under operation, affords sufficient 
evidence that some volatile matter besides water is escaping, 
and that the resulting powders cannot strictly represent the 
drugs from which they are made. All substances which 
contain volatile principles must lose a portion of these during 
the drying process which precedes, and sometimes accom- 
panies that of pulverization ; and if the efficacy of the medi- 
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