ANATOMY. 
590 
ling arteries of the (kin, through which it freely paffes. 
Thefe exhaling veirels or arteries, are eaiily demonftrated 
by an injection of water or ifinglafs into the arteries, which 
fw eat out from all parts of the (kin, in an infinite number 
of (mail drops; and thefe fubftances being transfufed un¬ 
der the cuticle, rendered impervious by death, raife it up 
into a blifter. In a living perfon, this exhalation is many 
ways demonftrable. A clean looking-glafs placed againft 
the warm and naked fkin, is quickly obfcured by the moift 
vapour. In fubterraneous caverns, where the air is more 
denfe, it is evidently feen to fly off from the whole fur- 
face of the body, like a thick cloud. 
Whenever the motion of the blood is encreafed, while 
at the fame time the fkin is hot and relaxed, the fmall cu¬ 
taneous pores, inflead of an invifible vapour, difcharge 
fweat, confifling of minute but vifible drops, which run 
together into larger drops by joining with others of the 
fame kind. The hottefi parts are mod fubject to fweat, 
as the head, bread, and foldings of the fkin. The expe¬ 
riment before-mentioned, of injecting the arteries, the 
fimplicity of nature, and the apparent cutaneous and pul¬ 
monary exhalation, diffidently perfuade 11s, that the per- 
fpirable matter and fweat are difcharged through one and 
the fame kind of veflels, and that they differ only by the 
quantity and celerity of the matter. The humour of the 
febaceous glands and the fubcutaneous oil, which being 
more plentifully fecreted, and diluted with the arterial 
juice difcharged with the fweat, are of an oily and yel¬ 
low confidence, and chiefly give fmell and colour to the 
fweat. Hence we find the fweat more fetid in the arm- 
pits, groins, and other parts, where thofe glandules are 
mod numerous or abundant. Both blood and fmall fand 
have been known to proceed from the fkin along with the 
fweat. 
The nature and quantity of the perfpirable matter may 
be invedigated by experiments, and by coniidering its ana¬ 
logy to the pulmonary exhalation. What flies off from 
the lungs in this exhalation is chiefly water, as appears 
from experiments, by which the breath, being condenfed 
in large veffels, forms into watery drops. That the per¬ 
fpirable matter is alfo chiefly water, is demonfirated by 
its obfcuring a glafs on which it is received; by obftrmfted 
perfpiration producing a diurefis or diarrhoea; by the 
fpeedy palfage of liquors, drunk warm, through the (kin if 
the body be kept warm, or through the kidneys if the bo¬ 
dy be cold; and by feveral other phenomena. The water 
of thefe vapours is chiefly from what we drink, but is in 
part fupplied from what is inhaled by the fkin. The par¬ 
ticular fmell of the aliments may be fometimes plainly 
perceived in the perfpiration. That there are, befides 
water, fome volatile alkaline particles, is evident, as well 
from the nature of our blood, as from the confiderable 
mifchiefs which follow an obftrudted perfpiration. This 
volatile alkaline matter ariles from the finer particles of 
blood, attenuated by perpetual heat and triture, and chan¬ 
ged into an acrimonious nature. Thefe afford the fcent 
which is clofely followed by dogs, who would not know 
their mafters unlefs fomething of a peculiar nature perfpi- 
red from each perfon. 
The quantity of our perfpiring moifture is very large, 
whether w e confider the extent of the organ by which it is 
feparated; the abundance of vapours derived from the 
lungs only; or barely take a review of the experiments 
made by Sandlorius. This indefatigable man concluded, 
that five pounds out of eight of the aliment was difcharged 
in a healthy perfon by the infallible perfpiration alone, in¬ 
dependent of the vifible fweat, and other excretions. In 
colder climates, the quantity perfpired was found to be 41- 
out of 8. But the cutaneous exhalation is even much lar¬ 
ger than this; fince it not only throws oft' a quantity of the 
aliment, but likewife what is added to the blood by inha¬ 
lation, which entering, often in a very confiderable quan¬ 
tity, is thus again expelled. But different difpofitions of 
the air, and of the human body, caufe great variations in 
thefe proportions. In warm countries, in the fummer 
months, and in young perfons ttfing much exercife, more 
goes off from the body by perfpiration, and lefs by the 
urine; while in cold climates, during the temperate or 
winter feafons, in aged or inactive perfons, more goes off 
by the urine than by the infenfible difcharge. In tempe¬ 
rate countries, making a computation throughout the 
w hole year, fomething more is perfpired than what paffes 
off' by urine ; and, joining together all the experiments 
made in different countries, both excretions are almoft 
alike, d lie difference ot time after feeding alfo in fome 
meafure varies the quantity perfpired ; but in general it is 
mod copious when the greater part of the digefted nourifh- 
ment is conveyed into the blood, and there attenuated fo 
as to be fit for exhalation. It is naturally diminiftied in 
deep, even in the warmer climates; but it is increafed by 
the heat of bed-clothes. 
In general, a plentiful and uniform perfpiration, with 
ftrength of body, are good figns of health. According to 
writers on this (ubje£t, if the perfpiration be increafed by 
the weaknefs of the body, it is more hurtful than if it were 
altogether obftrinffed. It is a lign of health, becaufe it de¬ 
notes a free pervious difpofition of the veflels throughout 
the w hole body, together wfith a complete digeftion of the 
nourifliment, the greater part of which is perfectly atte¬ 
nuated into a vapour. When it is diminiflied, it indicates 
either a conftritftion of the fkin, a weaknefs of the heart, 
or an imperfefl digeftion of the aliments. Perhaps in too 
great a perfpiration the nervous fpirits themfelves are eva¬ 
porated. This difcharge is, by moderate exercife, increa¬ 
fed to lix times that of an idle perfon, even to an half or 
whole pound in an hour. It is likewife increafed by the 
veflels being ftrong and pervious; by warm, watery, and 
vinous, drinks; by animal food of an eafy digeftion; by a 
heavy, temperate, or moderately-warm, air; andlaftlyby 
joy and a tranquil date of mind. The contrary of thefe 
either leffen or fupprefs the perfpiration; as a thick (kin, 
a moift air, or a cold and dry one; reft; more frequent ba¬ 
thing than ufual; a fupervening diarrhoea; and, laftly, a 
difagreeable nervous affection of the mind. The conti¬ 
nuance of life, however, does not depend on afcrupulous 
exadbiefs in the quantity of this difcharge, which is fo eafily 
increafed or diminiflied by flight cattles. It is (hut up by 
paints in many Indian nations; and it is inconliderable in 
many animals without any fenfible injury. When fup- 
prelfed, it is extremely hurtful, producing fevers of the 
word kind. The mifchiefs arifing from its fuppreflion, de¬ 
pend on the putrefcent quality of the particles which are 
retained along with it. 
The fweat is evidently of a faline nature; as appears 
from the tafte; from the minute cryftallizations on the 
clothes of people who work in glafs-houfes; and from dif- 
tillation, which (hew s the fweat to be of an alkaline nature. 
Hence it is, that by this difcharge the moft malignant mat¬ 
ter of many difeafes is thrown off from the body. But, in 
reality, fweat is always a preternatural or morbid difcharge, 
from which a perfon ought always to be free; unlefs by 
violent exercife, or other accidents, his conduction is for 
a fliort time thrown into a difeafed date. Nor is it unfre- 
quent for fweats to do confiderable mifchief in acute difea- 
(es, by wafting the watery parts, thickening the reft of the 
blood, and at the fame time rendering the falts more acri¬ 
monious. By a too violent motion of the blood, the fweat 
is rendered extremely fetid ; and is fometimes even red, or 
mixed with blood itfelf; and, being electrified, it is fome¬ 
times lucid. The ufes of perfpiration are, to free the 
blood from its redundant water, and throw out thofe par¬ 
ticles, which, by repeated circulations, have become al¬ 
kaline or othenvife acrimonious; and polfibly to exhale- 
therewith an extremely volatile oil, prepared from the 
fame blood. Perfpiration likewife qualifies and foftens the 
cuticle, which is a neceffary medium extended before the 
tender fenlible papillae. 
Befides the exhalent; veflels before-mentioned, the fttin is 
full of fmall veffels, which inhale or abl'orb thin vapours 
from the air, either perpetually, or at leaft when it is not 
very 
