ARSENIC. 
ARTERIES. 
247 
it has been much adulterated, and care is re- 
quired in the selection of it. The purest is the 
Jamaica or Bermuda arrow-root. A very cheap 
and tolerable substitute for this article may be 
found in the starch obtained from the potato (see 
Poraro), which cannot be too highly recommend- 
ed. When carefully prepared, it is equally agree- 
able, and probably as nutritious as Bermuda ar- 
row-root. West Indian arrow-root is often coun- 
terfeited by the substitution of an East Indian 
variety prepared from the tubers of the Narrow- 
leaved turmeric, which does not make so fine a 
jelly with boiling water as the West Indian variety. 
When compared with the latter, the East Indian 
arrow-root has a less crepitating feel, and is com- 
posed of larger granules. An article, introduced 
not long ago under the name of ‘ Tous-les-mois,’ 
| is the fecula of the Canna coccinea. It has a 
| slightly satiny appearance, and makes a stiffer 
jelly than the arrow-root. 
ARSENIC. A metal of very common occur- 
rence, being found in combination with nearly 
| all of the metals in their native ores. It is of a 
bluish-white colour, readily becoming tarnished 
on exposure to air, first changing to yellow, and 
finally to black. In hardness, it equals copper, 
is extremely brittle, and is the most volatile of 
all metals, beginning to sublime before it melts. 
Its specific gravity is 5°736. It burns with a blue 
flame and a white smoke, emitting a strong smell 
of garlic. It commonly bears the name of black 
arsenic, and is prepared from the white arsenic 
of commerce, by heating this substance with car- 
bonaceous matter, and allowing the volatile ar- 
senic to condense in anadjoining vessel. Arsenical 
pyrite, a very abundant natural substance, is also 
advantageously used in the preparation of arsenic, 
De eee 
in which case iron filings and lime are added, to 
engage the sulphur, and prevent its sublimation 
along with the arsenic. Native arsenic has been 
found in the veins of primitive rocks in several 
countries, but in small quantities, and generally 
alloyed by the presence of iron, silver, or gold. 
This metal is used in metallic combinations, when 
a white colour is desired. With oxygen, arsenic 
forms two compounds, both of which, from their 
property of combining with alkaline and earthy 
bases, are called acids. The arsenous acid, the 
most important of the two, is the white arsenic of 
the shops. It is usually seen in white, glassy, 
translucent masses, to which form it is reduced 
by fusion from a powdery state. It is one of the 
most virulent poisons known, not only when taken 
into the stomach, but when applied to a wound, 
or even when its vapour is inspired. It is found 
native in small quantities, but is obtained for use 
from the roasting of several ores, particularly 
from that of cobalt and arsenical pyrites. The 
arsenous acid is condensed in long, horizontal 
chimneys, leading from the furnaces where these 
operations are conducted, and usually requires a 
second sublimation, with the addition of a little 
| ii 
potash, to deprive it of any sulphur it may con- 
tain. Its manufacture has been chiefly confined 
to Bohemia and Hungary. Persons brought up 
from their youth in the works live not longer 
than to the age of 30 or 35 years. Knowing the 
deleterious nature of their occupation, they are 
so careless, that we have seen them cleaning their 
plates, &c., in wells, over which a skull was painted, 
to warn every body that the water contained ar- 
senic. Besides its use in medicine, and as a rats- 
bane, it is much employed as a cheap and power- 
ful flux for glass; but when too much is added, 
it is apt to render the glass opaque, and unsafe 
for domestic use. Arsenite of potash, mingled 
with sulphate of copper, affords an apple-green 
precipitate, called Scheele’s green, which, when 
dried and levigated, forms a beautiful pigment. 
With sulphur, arsenic forms likewise two definite 
compounds—the realgar and orpiment. The 
former of these contains the smallest proportion 
of sulphur, and is red; the latter is yellow. They 
are both found native in many countries, but 
their supply in commerce depends upon their 
artificial manufacture. This is done by distilling 
a mixture of arsenical pyrites and iron pyrites, 
or of white arsenic and rough brimstone. Realgar 
or orpiment is obtained as the proportion of sul- 
phur employed is greater or less. These com- 
pounds afford valuable pigments to the painter. 
The various preparations of arsenic are pos- 
sessed of eutrophic or alterative virtues, and when 
continued for a proper length of time, and under || 
judicious management, so alter the functions of 
nutrition as to remove diseased actions. Jn 
chronic cutaneous diseases, for example, arsenic 
has been found a most valuable agent. The ar- 
senical paste sometimes employed in cases of | 
cancer is composed of 70 parts cinnabar, 22 dra- 
gon’s blood, and 8 arsenious acid. In veterinary | 
practice, it has been given in glanders and in 
farcy, but with no markedly beneficial results, 
and a small quantity has not unfrequently pro- 
duced fatal inflammation of the stomach. The 
| 
| 
| 
creed 
antidote to an overdose of arsenic is to drink | 
plentifully of cold lime-water, and after that use 
an emetic of sulphate of zinc, to be followed by 
a copious dose of castor oil, or large draughts of | 
milk. 
ARTEMISIA. See Wormwoop. | 
ARTERIES. That order of vessels which arise 
from the two ventricles of the heart, and have 
valves only at their origin; their use being to 
carry the blood from the heart to the various 
parts of the system. When the blood leaves the 
heart, it is sent with considerable force into the | 
large trunks of the arteries; these vessels soon. | 
begin to ramify in various directions to all parts 
of the body, until at length they are reduced to 
vessels too small to be traced by the eye, or even 
by the microscope. There are in the body two 
distinct sets of arteries, which are distributed to 
different organs, and serve very different pur- 
poses in the animal economy ; one of these is sent 
to the lungs, the other to all the remaining parts 
ee 
