20 ABVACUATION. 
that the fanatic did not actually swallow some of | 
the fluid. Moisture, darkness, and repose, tend. 
A 
to diminish the usual effects of abstinence. 
dog has remained alive under these circumstances | 
for nearly fifty days without food. Persons of a 
vivid imagination, as well as frantic madmen, 
have in general a digestion extremely energetic, 
and they sometimes consume enormous quantities 
of food. Idiots also are frequently tormented 
with a devouring hunger. Next to sleep, which 
| wholly suppresses this appetite for the time, no- 
| thing tends more to drive away hunger in man 
than the long-continued exercise of deep thought. 
There are some surprising instances of the 
power of animals to survive long under the pri- 
vation of sustenance; and others occur, which 
_ are beyond the possibility of deception, such as a 
decapitated snail, which, though deprived of the 
| very organs for taking food, will not only live 
months, perhaps years, but will acquire a new 
head, similar to that of which it was deprived. 
| The state of an animal, living in the air without 
| sustenance, is, in the general case, very different 
_from one living without it in water. 
fluid, we have seen many of the smaller animals 
survive a long time, without any other support 
In this 
than what the simple element afforded. Hy- 
drachnze have been kept eighteen months with- 
_out any supply of food; and leeches, as well as 
certain species of fishes, above three years. Still 
_ these instances are not to be compared to those 
in which the privation of food is absolute ; because 
it is difficult to ascertain whether imperceptible 
animalcule might not be the food of such ani- 
mals. It has been thought, indeed, that living 
creatures may increase in size, without any nutri- 
ment supplied; and it is certain, though the 
point may probably be explained on different 
| principles, that the animated form will unfold by 
the simple application of heat alone ; and after it 
has burst its integuments, that it will increase its 
size. Thus, the eggs of fishes, snails, and other 
aquatic animals, will be hatched, and their young 
attain considerable size, in nothing but water. 
Vipers also, if taken when just produced by the 
mother, will grow much larger, though supplied 
with nothing butair. See articles HyBERNATION 
and Nurrition.—Redi’s Observazioni a gli Animali 
Viventt, chese trovano negli Animals uvventt.— Buf- 
fon’s Histoire Naturelle— Virey sur les Vers.—Sue 
sur la Vitalite—Muller’s Hydrachne.— Hunter on 
the Animal Economy.—Phil. Trans. vol. xiv. p. 
577.—Id. 1741, vol. xli. p. 725.—Mem. Acad. Par. 
1731.—Oomment. Bonnon. tom. ii. p. 221. 
ABVACUATION. The very copious drawing 
off or evacuation of any fluid, particularly blood, 
from the animal system. 
ACACIA. A very extensive and singularly 
beautiful genus of small trees or shrubby plants 
of the pea tribe. The generic name is supposed 
' to be the Greek name of some plant of the genus, 
| and was first taken by Wildenow, in his revisal 
of the genus Mimosa as the designation of one of 
ACACIA. — 
his new divisions. They inhabit chiefly the tropi- 
cal countries of the old world and of America ; 
yet they extend, in a few instances, within the 
temperate zones,—they abound throughout both 
the mainland and the subordinate islands of Aus- 
tralia,—and, in several instances, they are general’ 
and favourite objects of tender cultivation in 
Great Britain. Some of the species produce gum- 
arabic and catechu; two or three other species 
produce tannin,—or the principle by which skins 
are converted into leather ; and most are remark- 
able for the gracefulness of their form, the ele- 
gance of their foliage, and the surpassing bril- 
liance and beauty of their flowers. Nearly three 
hundred species are known to botanists; but 
only about eighty-five appear to have come 
under the notice of British gardeners. The 
species which at present challenge most atten- 
tion, for their superior beauty, or for the no- 
velty of their introduction, are those bear- 
ing the botanical designations which we shall 
here mention in a note.* About two-thirds of 
the whole genus have true leaves, pinnated, or 
winged with series of leaflets in pairs—some 
twice or thrice pinnated—and all spread out 
horizontally, with leaflets, smooth, small, and in 
multitudes; and the other third, when in a per- 
fect state, have, in lieu of true leaves, enlarged 
and expanded leaf-stalks, which maintain a some- 
what vertical position, and probably perform the 
same functions as leaves. The appearance of the 
two divisions or sub-genera is, in consequence, 
widely different,—that of the greater division 
being distinguished by an absolute profusion of 
leaflets in the pinnate arrangement, and that of 
the lesser division exhibiting the solemn baldness 
and majestic simplicity of long, flattened, up- 
right, leafless pedicles. 
The Acacia catechu—one of the most prominent 
species of the greater division, and that which 
yields one of the kinds of catechu or Terra Ja- 
ponica sold in our shops—is, in the East Indies, 
a tree of rather high and strong stem, with leaves 
in ten divisions, linear and downy leaflets in from 
forty to fifty couples, flowers in cylindrical spikes, 
growing two or three together, and flat, narrow, 
oval pods of from two to three inches in length. 
The Acacia Arabica—another of the best known 
species of the greater division, and that which 
yields the best gum-arabic of commerce—is, in 
the East indies, in Arabia, and in Abyssinia, a 
tree of about fourteen feet in height, inelegant in 
appearance, and carrying long, curved, beaded- 
* Acacie alata, brevifolia, biflora, Cunninghamia, 
dealbata, decora, discolor, glaucescens, diptera-eriop- 
tera, homomalla, Juawara, Julibrissin, longifolia, lon- 
gissima, micracantha, obovata, pendula, pentadenia, 
platyptera, polymorpha, pubescens, rotundifolia, spec- 
tabilis, vestita, affinis, cyclops, dentifera, diffusa, has- 
tulata, pulchella, saligna, subcerulea, cuneata, cyano- 
phylla, Farnesiana, gummifera, latifolia, Libbeck, 
nilotica, Riceana, Segal, Sophora, stricta, armata, 
floribunda, heterophylla, lophantha, curvifolia, decur- 
rens, horrida, linifolia, verticillata, and undulefolia. 
