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organ of thought. Other men, like mere ma- 
chines moved by habit, perform the same opera- 
tion a thousand times with their hands, while 
the thinking principle remains. buried in a pro- 
found lethargy. 
At the precise moment when the mind loses 
its consciousness, there results a general relaxa- 
tion of all the muscles. If the body be at rest 
and in health, this sudden change in its state of 
obedience to the will is attended with no marked 
result. But if the body be fatigued, or in an 
uneasy posture, or if the joints or muscles be 
painful, this first result of sleep has the effect of 
removing it entirely. Hence arises the difficulty 
of sleeping in a sitting posture, or during an 
attack of gout or rheumatism. The pain which 
the sudden starting of the muscles occasions is 
often so great in these diseases, that sleep can 
only be induced by strong doses of opium or 
some other narcotic. It also follows from this 
relaxation of the muscles, that the limbs become 
bent during sleep, and that a substance grasped 
firmly in the hand, falls at the instant when con- 
sciousness is lost. During sleep the character of 
the respiration is altered; it becomes less fre- 
quent and deeper. The heart also beats more 
slowly, but the pulse is stronger. The heat of the 
surrounding air, when imperfectly renewed, tends, 
however, to increase its movements. ‘The heat 
of the body is not naturally higher during sleep ; 
on the contrary, a diminished respiration tends 
to lower the temperature. It usually happens, 
however, from external circumstances, that there 
is an apparent rise of temperature, from the body 
being surrounded by imperfect conductors of 
heat, and from the circumambient air being but 
slowly renewed. 
As the stomach is a muscular organ, and as 
the passage of the food through the pylorus de- 
pends upon the rapidity with which the almost 
insensible contractions of the stomach are per- 
formed, it follows that sleep retards digestion, 
while, at the same time, it renders it more com- 
plete. This slowness of digestion is further in- 
creased by the state of rest in which the body 
remains, as nothing tends more to excite a rapid 
digestion than the gentle motion of the limbs, or 
of the entire body. The same phenomena take 
place in the intestines, where the aliments re- 
main almost inert in the several portions of the 
alimentary canal. However, the slowness of this 
movement favours the formation of chyle, and 
renders its absorption more complete. 
Absorption is very active during sleep, and 
the danger of slumbering in noxious air hence 
becomes very great. Travellers are usually ad- 
vised to avoid sleeping in marshy situations, 
such as the Pontine marshes of Italy, especially 
in the warm season of the year. Perspiration 
also is performed more easily, because the pores 
remain open during the state of muscular relaxa- 
tion. “ Une nutrition plus efficace, la réparation 
graduelle des forces qui en résulte, et aussi la 
SLEEP. 
réplétion de la vessie, toutes ces choses réveillent 
en nous, durant le sommeil, des idées de jouis- 
sance et des souvenirs de volupté.” As all the 
senses do not fall asleep at the same time, so they 
differ in the order in which they awake. Taste 
and smell commonly resume their functions last 
of all. The sense of sight is roused with greater 
difficulty than that of hearing. An unexpected 
noise will often awaken a somnambulist from his 
lethargy, upon whom the strongest rays of light 
will have had no previous effect, although his eyes 
continue open. Touch, as it was the last sense 
to become dormant, so it appears to be the most 
easily roused. The same person who cannot be 
awakened by very loud noises, will rise instantly 
on being gently tickled on the soles of the feet. 
Often the mere approach of the respiration of 
another will be sufficient to rouse the soundest 
sleeper. 
The positions which the mammalia assume 
during sleep are very various. The young ani- 
mal sleeps with its limbs gathered together, in a 
posture most resembling that of the foetus in the 
womb. This situation is very favourable to the 
renewal of the animal forces, by permitting the 
relaxation of all the articulations, and in pre- 
serving the heat of the more sensitive parts. 
For the latter reason, the dog and cat sleep with 
their bodies formed into a circle. Some mam- 
malia sleep in the open air, while others retire 
to caves and sheltered places. Many repose 
without any covering, while others prepare a 
bed of some imperfectly-conducting substance, 
to preserve the temperature of their bodies, 
which would otherwise fall during sleep below 
the natural standard. It is usually on the right 
side that man reposes. This posture favours 
the action both of the heart and stomach, as 
the vibrations of the former would reverberate 
through the body from the reaction of the sub- 
stance upon which it reposes, and the latter 
would be compressed by the weight of the liver. 
After sleep, all the organs, being refreshed, 
repaired, and completely nourished, acquire a 
greater size; thus man and other animals which 
commonly hold the spine more or less erect, are 
taller in the morning than in the evening after 
the fatigues of the day. 
Sleep is not always profound; some of the 
animal functions continue to act; ideas succeed 
each other, and the animal is said to dream. 
The power of dreaming is falsely ascribed to man 
alone; other mammalia dream likewise, because 
they are capable of thought, and possess a cer- 
tain degree of intelligence. Sometimes the dog 
is observed to howl, struggle, and perspire copi- 
ously. Moving his tail and limbs rapidly, he 
pursues the hare in imagination, and, on the 
point of seizing it, closes his teeth and lips as if 
in the act of dyeing them in blood. Some birds 
are also known to dream, as the parrots. Those 
animals which are most easily excited dream 
more frequently than the others; thus the horse 
ests 
