PHYSIOLOGY. 
propensities, &c. of the human species ; arid 
that these are accompanied by correspond- 
ing irregularities of the skull, discernible by 
external inspection. The whole fabric of his 
speculations is, however, too visionary for 
serious refutation. See Rees’s “ Cyclopae- 
dia, article CrAniology. 
The consideration of the various mental 
powers belongs to the science of metaphy- 
sics, and will be pursuedj under the proper 
articles. 
Sleeping and Watching . — Sleep is the re- 
pose of the organs of sense, and of the vo- 
luntary motions, by means of which the 
communication of the senses with external 
objects is interrupted. It is the result of 
that law which subjects the actions of the 
exterior or animal life to periods of inter- 
mittence. The most perfect sleep is that 
in which all the functions of this class are 
suspended, as the sensations, perception, 
imagination, memory, judgment, locomo- 
tion, and the voice ; the least perfect af- 
fects only a single organ. Between these 
extremes, every gradation may occur ; and, 
from the partial suspension of some func- 
tions, while others are going on, arise 
dreams, and the various phenomena of som- 
nambulism. It is, however, the same prin- 
ciple whether observed in the relaxation 
that follows the contraction of a voluntary 
muscle, or in the entire suspension of the 
animal life. 
Watching may be considered as a state 
of considerable effort and expenditure of 
the sensitive and moving principle by the 
organs of our sensations and motions. This 
principle would soon have been exhausted, 
if its reparation were not facilitated by 
long intervals of rest. Sleep and watching 
therefore call for each other, and are of re- 
ciprocal necessity. 
Sleep, however, only suspends that por- 
tion of life, the design of which is to main- 
tain a commerce with external objects ne- 
cessary to our existence. The interior, 
or assimilating functions, are still carried 
on. Digestion, absorption, circulation, res- 
piration, secretion, and nutrition are con- 
tinued : the two former, indeed, seem to be 
performed with greater energy, while the 
rest are rather diminished. The pulse is 
slower, respiration less frequent, perspira- 
tion and urinary secretion less abundant. 
Numerous causes of excitation constantly 
acting on our senses during the day, keep 
them in a state of activity ; and the absence 
of these at night is favourable to the repose 
of our organs. By multiplying and increas- 
ing stimuli, the period of repose may be put 
off ; but these gradually lose their powers, 
and after a certain time nothing can hinder 
its approach. Exhausted by fatigue and 
watcliing, the soldier sleeps at the side of 
the cannon; the slave reposes under the 
blows of his master ; and the criminal sinks 
to rest amidst the agonies of torture. 
Sympathy. All parts of the living body 
are united by certain relative connections, 
named sympathies, which establish a con- 
cord and harmony between the actions of 
the animal machine. The nature of this 
phenomenon is still obscure : we know not 
why, when one part is irritated, another 
very distant organ should perceive this irri- 
tation, and even contract ; nor are we 
agreed on the peculiar instruments of sym- 
pathy, that is, on the organs which connect 
two parts, one of which perceives or acts 
white the other is affected. That the nerves 
cannot be considered as the exclusive means 
of it is obvious; since muscles supplied from 
the same source do not always sympathise, 
while a close intercourse sometimes subsists 
between parts whose nerves have no imme- 
diate connection. Often also the sympathy 
is not reciprocal. Examples of this prin- 
ciple may be seen in the swelling of the 
breasts from distension of the uterus ; itch- 
ing of the nose from worms in the intes- 
tines, and of the glans penis from stone in 
the bladder; contraction of the diaphragm 
from irritation of the pituitary membrane j 
pain in the shoulder from inflamed liver, 
&c. 
The chief, and perhaps most extensive 
source of sympathy must be referred to tlie 
nerves, and particularly to a reaction of the 
sensorium. When a part is stimulated, and 
the sensorium affected by its stimulation, 
the latter reacts through the nerves on ano- 
ther organ, and incites it to action, although 
there may be no immediate nervous connec- 
tion between them. The motion of the 
iris, arising from the impulse of light on the 
retina; that of the diaphragm in sneez- 
ing, from irritation of the pituitary mem- 
brane, are examples. Other modes of sym- 
patlietic connection, without the immedi- 
ate concurrence of nerves, are pointed out 
by physiologists ; as by blood vessels, in the 
sympathies of the uterus and breasts from 
tlie anastomoses of the epigastric and inter- 
nal mammary arteries ; by lymphatics; by 
analogy of the respective functions, as the 
sympathy of the lungs and common integu- 
ments. 
Uabitf or the reiterated repetition of 
