24 
ACACIA. 
soul. From its brittleness it is easily injured, 
especially when grafted above the surface of the 
ground: a preferable mode, therefore, for dwarfs, 
is to graft them on the root, or under the soil, 
or to train them to a wall.—Loudon’s Gardener’s 
Magazine, vol. xvi-——Hunter’s Georgical Essays, 
vol. iv.i— Miller's Gardener’s Dictionary — Marshall 
on Planting —The Penny Cyclopedia.—Johnson’s 
Farmer's Encyclopedia—Dictionnaire D’ Histoire 
Naturelle. Paris, 1816, Tome [.—Maund’s Bo- 
tanic Garden. 
ACACIA (Turuz THornep). See GreprrcHta. 
ACALYPHA. A numerous genus of uninter- 
esting plants of the euphorbia tribe. The species 
amount to upwards of forty; they are natives 
variously of North America, Jamaica, the Carac- 
cas, the East Indies, and China; some are stove 
plants, and several are hardy annuals; and those 
best known have a considerable resemblance to 
the common nettle. 
ACANTHA. The prickle of a thorny plant ; 
and, by a figure of speech, anything pointed in 
the manner of a thorn. 
ACANTHACEHOUS PLANTS. Thistles, haw- 
thorns, briers, and all other plants which are 
armed with prickles, thorns, or spikes. But the 
Acanthacez, in the systematic er botanic sense, 
are merely one natural order of plants with one- 
petalled flowers; they are almost all herbaceous, 
or only in a slight degree shrubby; and most of 
them are found only within the tropics, and may 
be regarded as there corresponding to the mints, 
| sages, thymes, and deadnettles of Hurope. 
ACANTHUS. An herb with broad, prickly 
leaves, which gives both name and form to the 
imitation-foliage or architectural decoration on 
the capital of a Corinthian pillar. Both this 
plant, which is botanically called Acanthus spi- 
nosus, and another, which is called Acanthus mol- 
lis, and which has sometimes been regarded also 
as the model of the Corinthian capital, are culti- 
vated in the gardens of Great Britain, but require 
protection from severe frost. The acanthus is a 
genus of plants, having these two as its best 
known species, but including about a dozen other 
species, and serving as the type of the acantha- 
ceous order. The generic name is derived from 
the Greek, and signifies a spine. The Acanthus 
mollis is named in old pharmacopceias Brankur- 
sine. Its leaves and roots have emollient and de- 
mulcent qualities. It should remain undisturbed 
in the shrubbery for several years, when it will 
throw up strong undivided stems of flowers. 
A/CARI. Minute insects which form, feed upon, 
and propagate scab in sheep and mange in horses, 
and of which one or other species are known to 
infest almost every tribe of the animal kingdom. 
Though no larger than the hole formed by the 
point of a fine pin, they burrow under the skin, 
irritate the flesh below it, and travel from place to 
place on the body, extending their devastations. 
“ Tf one or more female acari,” says M. Walz, “are 
placed on the wool of a sound sheep, they quickly 
ACARI. 
travel to the root of it, and bury themselves in | 
the skin, the place at which they penetrate being 
scarcely visible,yor only distinguished by a minute 
red point. On the tenth or twelfth day, a little 
swelling may be detected with the finger, and the 
skin changes its colour, and has a greenish blue 
tint. The pustule is now rapidly formed, and 
about the sixteenth day breaks, and the mothers 
again appear, with-their little ones attached to 
their feet, and covered by a portion of the shell 
of the egg—from which they have just escaped. 
These little ones immediately set to work, and 
penetrate the neighbouring skin, and bury them- 
selves beneath it, and find their proper-nourish- 
ment, and grow and propagate, until the poor 
animal has myriads of them to prey on him and 
to torment him, and it is not wonderful that he 
should speedily sink. Some of the male acari 
were placed on the sound skin of a sheep, and 
they, too, burrowed their way, and disappeared 
for a while, and the pustule in due time arose; 
but the itching and the scab soon disappeared 
without the employment of any remedy.” Both 
sexes of the insect are present when the disease 
is propagated. The female appears to be very 
prolific, producing from eight to fifteen in a litter. 
Though most of the insects perish before the 
severity of winter, yet some survive it, and occa- 
sionally recommence their devastations in spring. 
See article Scas. 
The Acarus scabiei, or Sarcoptes hominis, gener- 
ally exists on all persons affected with itch who 
have not commenced a course of medicine. It is 
almost entirely confined to the hands, where it is 
found beneath the epidermis, but is also some- 
times met with on the feet, in the arm-pits, and 
other places. It is never found on persons af- 
fected with any other cutaneous disease than 
itch. The insects are all destroyed after the sul- 
phuro-alkaline ointment has been applied; but the 
patient may not be still cured, for the eruption 
may remain, unless it be properly treated. In- | 
sects removed from an affected to a sound person, 
multiply on the skin of the latter, when presently | 
the eruption appears. M. Gras several times com- 
municated the disease in this manner; once, at 
the desire of Dr. Pariset, secretary of the Aca- 
demie de Medicine, when it produced a sanatory 
revulsion in a young girl who had fallen into a | 
state of stupor. On the other hand, he several 
times tried to inoculate himself with the serum 
of the itch vesicles, but without success. He 
therefore concludes that the sarcopites is the sole 
agent in producing the contagion of itch, which 
is not contracted unless that animal or its eggs 
adhere to the skin or clothes of persons coming 
into contact with those having the disease. The 
number of insects on a person has no relation to 
the extent and intensity of the eruption; for 
sometimes not more than five or six are found on 
individuals covered with vesicles and pustules ; 
and again, a hundred have been taken from the | 
hands of a person, who yet had only a few vesicles. 
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