PHYSIOLOGY. 
bones that compose these organs render 
them susceptible of infinitely varied mo- 
tions, and enable them to explore with ac- 
curacy the surfaces of the most unequal 
bodies. The Soft ends of the fingers re- 
ceive large nerves and arteries, and possess 
very numerous and prominent papilte. This 
finely organised skin is formed into a gently 
convex protuberance by an accumulation 
of a soft fat under it, and it is defended and 
supported by the nail; and accordingly 
these pulpy extremities of the fingers are 
endowed with the most refined sense of 
touch. The lips and the glans penis have a 
similar structure, and receive from this or- 
ganization a very exquisite sensibility, which 
is a modification of touch. 
As the cutaneous papillae are covered by 
the epidermis, it follows that the very su- 
perficies of the body is insensible. The cu- 
ticle and its appendages, the nails and hair, 
have neither vessels nor nerves, and possess 
no powers of life or growth in themselves. 
It forms a medium, moderating the impres- 
sions which would he too vivid from an ab- 
solute contact of substances ; when preter- 
naturally thickened, as in the hand of the la- 
bourer, it obstructs sensation ; and when 
entirely removed, as by a blister, the con- 
tact of bodies excites pain. It is also im- 
portant in preventing the action which the 
atmosphere would otherwise exert in drying 
the surface of the body ; when removed in 
the dead subject the skin immediately be- 
comes horny, and the same eft'ect extends 
more or less to the subjacent parts ; in-the 
living body its removal is followed by in- 
crustation or scabbing. 
The skin is also to be considered as an or- 
gan of secretion, and perhaps of absorp- 
tion. Under the former head we view it as 
the means of separating and expelling from 
the body extraneous matters, whose reten- 
tion would be injurious to the system. This 
may be proved by eruptive disorders, by 
the odours of musk, garlic, &c. which 
affect the perspiration ; by the phenomena 
of sweating, &c. by the injurious effects on 
the system at large, which a suppression of 
the cutaneous secretion causes, and the re- 
lief experienced by sudorific remedies in 
various cases. 
The secretion from the skin has been di- 
vided into the sensible and insensible. An 
abundant vapour continually exhales from 
tlie whole surface, and has the name of in- 
sensible transpiration, or perspiration,when 
it is invisible to the naked eye, and passes off 
in the state of gas ; but it is called sweat, 
when, becoming more copious, it flows in 
form of a liquid. The innumerable arte-, 
ries, which pervade every part of the skin, 
are the source of these secretions ; and 
their exhaling orifices are supposed to pe- 
netrate the cuticle in a state far too minute 
for any means of research that we possess. 
If the naked body be placed against a 
white wall in the sun during the svimmer 
season, a shadow produced by the cutaneous 
exhalation may be perceived ; and the fol- 
lowing is also a decisive experiment to the 
same point. Apply the end of the finger 
near a glass or finely polished metallic in- 
strument, and the body will soon have its 
surface tarnished by a vapour which is dissi- 
pated when the finger is removed. 
A great resemblance exists between the 
cutaneous and pulmonary secretions ; both 
are simple arterial exhalations, and the 
mucous membrane of the aerial passages is 
a continuation of the skin. The two secre- 
tions counterbalance each other ; and the 
connection between them is evidenced by 
the remarkable distress of breathing at- 
tendant on extensive burns. There is a si- 
milar connection with the mucous exhala- 
tion of the intestinal canal; and a still 
more remarkable one with the kidneys. 
The quantity of the insensible perspira- 
tion appears by experiments to be very 
great. Sanctorius, a Venetian physician, 
who first noticed its importance and extent 
(whence it has acquired the name of pers- 
pirabile sanctorianum) estimated it at five 
pounds in twenty-four hours, when the solid 
and liquid food amounts to eight pounds. 
In temperate climates it may be from two 
to four pounds daily ; but it varies ac- 
cording to numerous circumstances. 
The chief bulk of insensible transpiration 
and of sweat is water ; it holds several salts 
in solution. Carbonic acid gas is also found 
in considerable quantity; and even ac- 
cording to some experiments, azote and 
hydrogen. An oily or sebaceous matter is 
secreted from the skin, to preserve the cu- 
ticle in a proper condition of suppleness ; 
hence water is repelled from the naked bo- 
dy, when thrown on it. There are also 
some volatile and odorous particles fur- i 
nished from the same source, in which the 
peculiar smell of individuals and of nations 
resides. 
Sweat seems ^o be nothing more than an 
increase of the insensible perspiration pro- 
duced by augmented action of the cutane- 
ous yessels. Increased temperature and 
exercise give rise to it ; and it furnishes the 
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