VEG 
magnitude in diflferent vegetables, and exist 
in the roots, the bark, leaves, and flowers. 
The trachea, or spiral vessels, which are 
readily detected in succulent plants, appear 
in the form - of fine threads, and may be 
drawn out to a considerable length without 
breaking. These vessels are very nume- 
rous in all plants, especially under the bark, 
where they form a kind of ring, and are 
disposed in distinct bundles, in trees, 
shrubs, and stalks of herbaceous plants. 
Vegetable acids, in chemistry. The 
acids which exist in many vegetables are at 
once recognized by their tastfe. These 
acids were formerly denominated essential 
salts of vegetables, and it was supposed, 
that all essential salts w'ere the same, and 
were composed of tartar, or vinegar. But 
Scheele’s discovery of the citric, malic, and 
gallic acids, which possessing distinct pro- 
perties from those of tartaric and acetic 
acids, proved the contrary. Some vege- 
tables contain only one acid, as oranges 
and lemons, which contain citric acid only. 
In other vegetables two acids are found, 
as in gooseberries and currants, the malic, 
and citric acids; and sometimes three, as 
the tartaric, citric, and malic acids, which 
exist together in the pulp of the tamarind. 
As the acids which exist in vegetables hav? 
been already descotbed, under their res- 
pective heads, it is now only necessary 
to enumerate the vegetable acids, speci- 
fying at the same time some of the plants 
from which they are obtained. 
Acetic acid has been discovered in the 
sap of some trees, and in the acid juice of 
cicer arictinum. Oxalic acid exists in 
combination with potash, in the leaves of 
the oxalis acetosella, or wood-sorrel. In 
other species belonging to the same genus, 
and in some species of rumex, it is in the 
state of acidulous oxalate of potash. Oxa- 
late of lime has been found in the root of 
rhubarb. Citric acid is found in the juice 
of oranges and lemons, in the berries of 
two species of vaccinium, &c. Malic acid 
exists unmixed with other acids, in the ap- 
ple, the barberry, plumb, sloe, elder, &c. 
In the gooseberry, in the cherry, straw- 
berry, currants, and some other fruits, malic 
and citric acids are found nearly in equal 
proportions. Malic acid has been found 
mixed with tartaric acid in the agave Ame- 
ricana, and in the pulp of tamarinds, along 
with citric acid. Vauquelin found it com- 
bined with lime, forming a malate of lime, 
in the sempervivum, tectorum or house-leek . 
Gallic acid is found in a great number of 
VEL 
plants, and in them it exists chiefly in the 
bark. Benzoic acid is found in benzoin, 
balsam of Tolu and Peru, liquid styrax, 
cinnamon, and vanilla. Fourcroy and Vau- 
qnelin suspect that it exists in the anthox- 
anthum odoratum, or sweet-scented grass, 
which communicates the aromatic flavour 
to hay. Prussic acid has been found in the 
leaves of the lauro-cerasus and peach, in 
bitter almonds,, in the kernels of apricots ; 
and it is supposed that it exists also in the 
kernels of peaches, of plums, and cherries. 
It is obtained from the kernels of apricots 
by distilling water off them with a mode- 
rate heat; and if lime be added to the con- 
centrated infusion of bitter almonds, a prus- 
siate of lime is formed. ' Phosphoric acid 
has been found in different parts of plants ; 
but it is generally combined with lime, 
forming a phosphate of lime. 
VEIN, in anatomy, is a vessel which car- 
ries the blood from the several parts of the 
body to the heart. The veins are composed 
principally of a membranaceous, a vasculous, 
and a musculous tunic : but these are vastly 
thinner than in the arteries. See Artery. 
VELEZIA, in botany, so named 'from 
Christoval Velezius, examiner, first physi- 
cian, and demonstrator of botany, in the 
College of Apothecaries at Madrid, a genus 
of the Pentrandria Digynia class and order. 
Natural order of Caryophyllei. Caryo- 
phylleae, Jussieu. Essential character : calyx 
filiform, five-toothed ; corolla five-petal led, 
small; capsule oae-celled; seeds numerous, 
in a single row. There is but one species 
viz. V. rigida, a native of the South of Eu- 
rope. 
VELLA, in botany, a genus of the Tetra- 
dynamia Siliculosa class and order. Natu- 
ral order of Siliquosa or Cruciformes. Cru- 
ciferss, Jussieu. Essential character : silicle 
with a partition twice as large as the valves, 
ovate on the outside. There are two spe- 
cies viz. V. annua, annual vella, or cress 
rocket ; and V. pseudo cytisus, shrubby 
vella. 
VELOCITY, swiftness, or that affection 
of motion whereby a moving body is dis- 
posed to run over a certain space in a cer- 
tain time. 
In the doctrine of fluxions it is usual to" 
consider the velocity with which magni- 
tudes flow, or are generated. Thus, the 
velocity with which a line flows, is the same 
as that of the point, which is supposed to 
describe or generate the line. The velo- 
city with which a surface flows, is the same 
as the velocity of a given light line, that. 
