INTRODUCTORY. 
109 
depends upon the care of the individual, and need not 
receive attention here. 
The adulterations, substitutions and sophistications 
will be considered under the respective drugs. 
The Valuation of Drugs. — In the identification of 
vegetable drugs certain characteristics are taken into 
account, such as color, odor, general appearance, struc- 
ture, texture, etc., these at the same time indicating in 
a greater or less degree the qualitative value of the 
drug. While these characteristics may enable the ex- 
pert to detect very slight variations in quality, and to 
estimate approximately the value of a given drug, still 
the true value is based upon the amount of the medici- 
nal principles or so-called active constituents. The 
methods employed in the valuation of drugs may be 
grouped as follows: (1) Chemical, (2) Physical, (3) 
Microscopical, and (4) Biological. 
(1) Chemical methods are more generally employed 
and usually involve the isolation and estimation of 
the active principles. 
(2) Physical methods involve such processes as the 
determination of specific gravity of the drug, as of 
jalap, or the determination of the elasticity or measure- 
ment of the fibers, as of cotton, and still other special 
methods which apply to individual drugs, giving in- 
directly their valuation. 
(3) Microscopical methods of valuation may often- 
times be employed when other methods fail, as, for 
example, when foreign starches are added to starchy 
products, as in the cereals and spices. Microchemical 
reactions may also be depended upon in some instances 
to indicate the value of a drug, as in strophanthus 
where the value of the drug depends directly upon the 
number of seeds giving a green coloration with sul- 
phuric acid. 
