SLEEP. 
is more liable to dream than the bull. Accord- 
ing to Chabert, this phenomenon among cattle 
is only observed in the bull, the ram, or in cows 
which are suckling. | 
It is possible to protract the usual period of 
sleep by an unusual excitement; but if the 
stimulus be long continued its effect goes off, 
and then nothing can prevent sleep as long as 
the health continues good. In fact, sleep, once 
in the twenty-four hours, is as essential to the 
existence of the mammalia as the momentary 
respiration of fresh air. The most unfavourable 
conditions for sleep cannot prevent its approach. 
Coachmen slumber on their coaches and couriers 
on their horses, while soldiers fall asleep on the 
field of battle, amidst all the noise of artillery 
and the tumult of war. During the retreat of 
Sir John Moore, several of the British soldiers 
were reported to have fallen asleep upon the 
march, and yet they continued walking onwards. 
The most violent passions and excitement of the 
mind cannot preserve even powerful minds from 
sleep; thus Alexander the Great slept on the 
field of Arbela, and Napoleon upon that of 
Austerlitz. Even stripes and torture cannot 
keep off sleep, as criminals have been known to 
slumber on the rack. Noises which serve at 
first to drive away sleep, soon become indispensa- 
ble to its existence; thus a stage-coach stopping 
to change horses, wakes all the passengers. The 
proprietor of an iron forge, who slept close to 
the din of hammers, forges, and blast furnaces, 
would awake if there was any interruption to 
them during the night; and a sick miller, who 
had his mill stopped on this account, passed 
sleepless nights until the mill resumed its usual 
noise. Homer, in the Iliad, elegantly represents 
sleep as overcoming all men, and even the gods, 
excepting Jupiter alone. 
The length of time passed in sleep is not the 
same for all men; it varies in different indivi- 
duals and at different ages; but nothing can be 
determined from the time past in sleep, relative 
to the strength or energy of the functions of the 
body or mind. From six to nine hours is the 
average proportion, yet the Roman Emperor 
Caligula slept only three hours, Frederic of 
Prussia and Dr. John Hunter consumed only 
four or five hours in repose, while the great 
Scipio slept during eight. A rich and lazy 
citizen will slumber from ten to twelve hours 
daily. It is during infancy that sleep is longest 
and most profound. Women also sleep longer 
than men, and young men longer than old. 
Sleep is driven away during convalescence after 
a long sickness, by a continued fasting, and the 
abuse of coffee. The sleepless nights of old age 
are almost proverbial. It would appear that 
carnivorous animals sleep in general longer than 
the herbivorous, as the superior activity of the 
muscles and senses of the former seem more 
especially to require repair. Satiated with their 
prey, they are obliged to seek repose to digest 
SLUG. 
those very substantial matters which compose 
their aliment. 
In general, it may be stated, that during sleep 
the internal functions predominate over those 
relating to the exterior of the body. Every thing 
which tends to interrupt the relaxations of the ex- 
ternal with surrounding objects serves to induce 
sleep. On the contrary, the existence of external 
stimuli tend to expel it, until at length they lose 
their effect by long-continued exercise. From 
this it ought to follow that excessive cold, which 
benumbs the external powers, ought to occasion 
sleep. When exposed to the action of a low tem- | 
perature, animals experience an irresistible de- | 
sire to sleep which soon terminates in death. Of 
this there are frequent examples in the inhospi- 
table climates of the north, Siberia, Lapland, and 
Kamtschatka, or on the tops of high mountains, 
as the glaciers of Switzerland. Dr. Solander and 
party nearly lost their lives from this cause 
among the hills of Terra del Fuego. Surprised 
by an excessive cold, he was with difficulty pre- 
vented by his companions from yielding to this 
impulse of nature, although knowing well the | 
consequences of sleeping. Travellers on horse- 
back are peculiarly liable to be overcome by this 
propensity to sleep, when the cold is very intense, 
in which case they are sure to be frozen to death. 
There prevails among many mammaliaa singu- | 
lar internal modification, which cannot be ex- 
plained by any cause more general than itself, 
but must be referred to some unknown original 
constitution. We refer to that state of torpidity 
commonly called Hypernation. See that article. 
SLIPPER-PLANT,—botanically Pedilanthus. 
A genus of curious, South-American, evergreen 
undershrubs, of the spurge order. Six or seven 
species, all about 20 inches high and apetalous, 
have been introduced to the dry stoves of British 
gardens. They thrive in any common soil, and 
are propagated from cuttings. The name alludes 
to the flower. 
SLIPPERWORT. See Cancronarra. 
SLIPPING. See Azorrion. 
SLIT-PLANTING. See Puantine. 
SLOANHA. A genus of tropical ligneous 
plants, of the lime-tree order. The tooth-leaved 
species, S. dentata, is a South-American ever- 
green timber-tree, of commonly about 40 feet 
high, and was long ago introduced to the bota- 
nical collections of Britain. Seven other species 
are known. 
SLOE-TREE. See BuacktHorn. 
SLOUGH-HEAL. See Surr-Heat. 
SLOUGH-IN-THE-EYE. See Inrzammarion. 
SLUG,—scientifically Zomax. A group of small, 
creeping, soft-bodied animals, constituting, to- 
gether with the snail or helix group, the terres- 
trial, pulmonious, gasteropodous family of mol- 
luscs. Both groups, or at least some very abun- 
dant species of them, are well known to gardeners 
and farmers for their extensive depredations on | 
herbaceous cultivated crops. The most common 
