666 ORD. XL. Oleracce; RHEUM PALMATUM. 
first is in oblong pieces, flattish on one side, and convex on the 
other; compact, hard, heavy, mternally of a dull red coloug, 
variegated with yellow and white, and when recently powdered 
appears yellow, but on being kept becomes gradually redder. 
The second is the most valuable, and is brought to us in roundish 
pieces, with a large hole through the middle of each; it is more 
soft and friable than the former sort, and exhibits, when broken, 
many streaks of a bright red colour. ‘‘ The marks of the goodness 
of rhubarb are, the liveliness of its colour when cut; its being 
firm and solid, but not flinty or hard; its being easily pulverable, 
and appearing when powdered of a fine bright yellow colour; its 
imparting to the spittle, on being chewed, a deep saffron tinge, and 
not proving slimy or mucilaginous in the mouth; its taste is sub- 
acrid, bitterish, and somewhat styptic; the smell lightly aromatic.” | 
The purgative qualities of rhubarb are extracted more perfectly 
by water than by rectified spirit: the root remaining after the 
action of water is almost if not wholly inactive; whereas after 
repeated digestion in spirit, it proves still very considerably pur- 
gative. The virtue of the watery infusion, on being inspissated 
by a gentle heat, is so much diminished, that a dram of the extract 
is said to have scarcely any greater effect than a scruple of the 
root in substance; the spirituous tincture loses less; half a dram 
of this extract proving moderately purgative. “ The qualities of 
* this root are that of a gentle purgative, and so gentle that it is 
often inconvenient by reason of the bulk of the dose required, 
“‘ which in.adults must be from half a dram to a dram. — When 
“given in a large dose;it will-eccasion some 2 griping, as other 
** purgatives ae? but it is hardly ever heating to the system, or 
« shews the other effects of the more 7 purgatives. The 
“ purgative quality is accompanied with a bitterness, which is 
‘© often useful in restoring the tone of the stomach when it has 
« been lost; and for the most part its bitterness makes it sit“better 
“* on the stomach than many other purgatives do. Its operation 
joins well with that of neutral laxatives; and both together 
“ operate in a lesser dose than either of them would do singly. 
