PERSPIRATION, 
dear; fuch as may not be*feen through; diaphanous; 
tranftucent; jiot opake.—As contrary caufes produce the 
like effefls, fo even the fame proceed from black and 
white; for the clear and perfpicuous body effe&eth white, 
and that white a black. Peacham. —Clear to the under- 
ftanding ; not obfcure ; not ambiguous,—All this is fo 
perfpicuous, fo undeniable, that I need not be over induf- 
trious in the proof of it. Sprat. 
The purpofe is perfpicuous even as fubrtance, 
Whofe grofl'nefs little characters fum up. Shakejpeare. 
PERSPICUOUSLY, adv. Clearly; not .obfcurely.— 
The cafe is no fooner made than refolved; if it be made 
not enwrapped, but plainly and perfpicuoufli/. Bacon. 
PERSPIC'UOUSNESS, f. Clearnefs;' freedom from 
obfcurityj tranfparence; diaphaneity. 
PERSPI'RABLE, udj. [from perfpire.'] Such as may 
be emitted by the cuticular pores.— In an animal under a 
c-ourfe of hard labour, aliment too vapourous or perjpirable 
will fubjedt it to too ftrong a perfpiration, debility, and 
fudden death. Arbuthnot on Aliments.- —Perfpiring; emit¬ 
ting perfpiration. Not proper. —Hair cometh mot upon 
the palms of the hands or foies of the feet, which are 
parts more pcrfpirable: and children are not hairy, for 
that their (kins are mod perfpirable. Bacon. 
. PERSPIR A'TION,/. The office of the (kin, by which it 
forms and difcharges various matters, principally fluids, 
from the blood ; or the matters themfelves fo difcharged. 
It is diftinguiflied into fcnjible and infenfible ; and here fen- 
fible perfpiration is the fame with fweating, and infenfible 
perfpiration that which efcapes the notice of the fenfes.— 
Infenfible perfpiration is theiaft and mod perfect action of 
animal digeftion. Arbuthnot on Aliments. 
To afcertain the quantity of matter perfpired through 
the (kin, various experiments have been made, particu¬ 
larly by Sanftorius, who continued them for thirty years. 
More recently Lavoilier and Seguin inftituted fome very 
ingenious experiments in elucidation of this fubjefh 
Seguin was inclofed in a (ilk bag with a (lit for the mouth, 
to which it was cemented ; fo that every thing was con-' 
fined within the bag, except what paffed off by the lungs. 
By weighing himfelf in a delicate balance at the begin¬ 
ning of the experiment, and again after he had been fome 
time in the bag, he afcertained the lofs by perfpiration. 
By weighing himfelf without the bag, and repeating the 
operation after the fame interval of time had elapfed as in 
the former experiment, he found the lofs of weight by 
perfpiration and refpiration. By fubtra&ing from this 
fum the lofs of weight indicated by the firft experiment, 
he obtained the quantity of matter which made its efcape 
by perfpiration in a given time. The following were the 
fluffs he afcertained. That the greateft average lofs by 
perfpiration in twenty-four hours was 41b. 40Z. or fifty- 
two ounces, Troy. It was increafed by drink, but not by 
folid food ; at its minimum after a repaft, at its maximum 
during digeftion. The quantity perfpired is greatly in¬ 
creafed by heat, whether direftly applied, or induced by 
exercife. The fubftances conftantly perfpired are water, 
carbon, an oily matter, and occafionally phofphoric acid, 
phofphate of lime, and urea. 
Mr. Cruikihank introduced his hand into a glafs jar, 
and tied a bladder, fixed to the mouth of the jar, round 
his wrift. In lefs than a minute the infide of the bottle 
was rendered dim, as if it had been held over the (learn of 
warm water: fmall drops appeared in lefs than ten mi¬ 
nutes, and a tea-fpoonful of tranfparent and perfeflly in- 
fipid fluid, weighing 30 gr. was colleSed in an hour. 
A (Turning that the hand is to the whole body as 1 to 60, 
and that the whole furface perfpires equally, the exhala¬ 
tion at this rate would be 7 lb. 6 oz. in 34 hours. 
When the experiment was repeated after taking exercife, 
48 gr. were collected in an hour, which is at the rate of 
12 lb. in 24 hours. By breathing into a bottle for an 
hour, this gentleman collected 124gr. of infxpid tranfpa¬ 
rent fluid : the produce in 24 hours at this rate would be 
Vol. XIX. No. 1339. 
731 
6 oz. 1 dr. 36 gr. If this be added to the former ftatement 
of the cutaneous exhalation, the fum will be 8 lb. 1 dr. 
36 gr. Mr. Abernethy collected from his hand and wrift, 
inclofed in a glafs jar for fix hours, about 3 dr. of fluid. 
He eftimated the furface from which this was collefted at 
•j T th of the whole body: hence, if the perfpiration be 
equal at all times and in all parts, the produce in one day 
would be about 2^lb. This refult is fo different from 
that of Mr. Cruikfliank, that there muff be Come fignal 
error on one fide or the other. 
It appears, fays Mr. Brande, that the fun&ion of the 
(kin is in many refpedls analogous to that of the lungs; 
for in both cafes, carbonic acid and water are evolved ami 
oxygen abforbed. Some have doubted whether the (kin 
does abforb. In favour of it, it is dated, that fometimes 
the quantity of urine paffed is greater than the whole in- 
gefta of folid and liquid food, as in diabetes. ' But it 
(hould be recollected, that in this difeafe the folid matter 
of the body is conftantly confuming, and may be conver¬ 
ted into urine. Captain Bligh ordered his companions, 
when deprived of frefli water, to bathe in the fea, and it 
always allayed their third and cooled their bodies. Here 
we might have prefumed, that abforption mull have taken 
place, as third was allayed by the application of water to 
the (kin ; but this effefl may be accounted for by the col- 
la pfe of the outer veffels of the (kin ; and it (hould be re¬ 
marked, there was no increafe of weight. Dr. Currie had 
a patient with ftrifhire of the oefophagus, which preven¬ 
ted his fwalLowing; and his third was always alleviated 
by bathing; but no increafed weight could be detected 
after coming from the bath. Seguin obferved, that no ef- 
fedt was produced on a perfon that he fubmitted to a bath 
in which fome mercurial fait was diffolved ; but, when a 
part of the fkin was abraded, the eft’edts of mercury on 
his eonftitution were evident. Though thefe experiments 
appear decifive, that the (lein cannot abforb water while 
in the fluid form, yet it does not follow that it may not, 
be abforbed in the form of vapour, or that air may not 
be abforbed. Van Mons kept a patient alive for many 
days, who could not fwallow, from a wound in the throat, 
by applying to different parts of the body with a fpunge, 
ftrong foups, or wine. But Dr. Watfon’s experiment is 
more conclufive of the fadt of abforption. A Newmarket 
jockey, that had been fweated down to a weight to qua¬ 
lify him for riding a race-horfe, was weighed on the morn¬ 
ing that he was to ride; he was weighed alfo an hour 
after the race, and was found to have gained thirty ounces 
of weight. In the interval, he had drank but half a glafs 
of wine. Hence Mr. B. thinks, that the dodlrine of ab¬ 
forption by the (kin was juft, although further experiments 
are required to eftablifti this point upon fatisfadlory evi¬ 
dence. Brande’s Lefture on Digeftion and Perfpiration, 
at Apothecaries’ Hall, March 1814. 
Bichat enquires whether the nerves have any influence 
on the cutaneous difeharge. He obferves, that in palfied 
patients fweat takes place on the difeafed as well as on the 
found fide. “ I lately,” fays he, “ attended at the Hotel 
Dieu a patient, in whom the left fide of the body was ren¬ 
dered perfectly paralytic, in confequence of an apoplectic 
attack: yet he fweated only on this fide. Examples of 
the oppofite phenomenon are adduced; but they cannot 
invalidate the common obfervation, that the difeharge is 
equal on both (ides. Is it not well known, that when the 
nervous adtion is entirely annihilated in a paralytic limb, 
blifters affedt it in the ufual manner ? Do convulfions, in 
which the nervous adtion is increafed, augment the cuta¬ 
neous exhalation ? Have the dates of acute fenfibility, 
where there is in the cutaneous nerves fo great a fufeep- 
tibility of impreffions, any known influence on perfpira¬ 
tion ? Let us then confefs, that in cutaneous exhalation, 
as well as in fecretion, we are entirely ignorant of the na¬ 
ture of the nervous influence, if any fuch exift.” 
The Perfpiration of Plants takes place chiefly from the 
furface of their leaves. In order to colled! the liquor per¬ 
fpired, it is only neceffary to introduce a branch of the 
9 A plant 
