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PHYSIOLOGY. 
made many experiments on this subject, 
and concluded that there is always an exer- 
tion or expense of animal power in resisting 
cold, proportioned to the necessity of the 
case ; that tliis exertion is in proportion to 
the perfection of the animal, and to the de- 
gree of heat natural to the species, and 
that it is independent of circulation, voli- 
tion, and sensation. 
The power of resisting heat arises from 
the evaporation that is constantly going on 
from the surface of the skin, and which be- 
comes extremely abundant when the tem- 
perature of the air is much raised. See the 
account of the organ of touching. This is 
a very powerful means of diminishing ani- 
mat temperature, and consequently, when 
long continued, has a very weakening ef- 
fect. Of fourteen persons shipwrecked in 
December, three sat on the deck, out of 
water, but exposed to sleet, snow, and 
wind; the evaporation from their surface 
must have been immense, and they died. 
All the others were up to the middle or 
shoulders in the water for twenty- three 
hours, yet survived. 
Animal heat may be altered from its 
standard by external applications or disease ; 
but the change can be carried much further 
below the standard than above it. A man 
could bear to have his penis cooled to 50" ; 
but it could not be heated beyond lOOi" ; 
although the heat employed raised a dead 
penis to 114". 
Secretim. The blood, circulated in the 
manner we have just mentioned, and pre- 
pared by the organs of respiration, is the 
source from which the various fluids of the 
animal body are formed in the process of 
secretion. 
The various arrangements of these pro- 
ducts are, in a great measure, arbitrary. 
Milk seems to be formed by the most easy 
process, as it resembles so strongly the na- 
ture of chyle. Next come the watery 
fluids; (so called from their appearance, 
although in composition they differ con- 
siderably from water, chiefly in containing 
albumen). The humours of the eye, tlie 
tears, sweat, lymph of the cellular sub- 
stance, vapour of the thorax, abdomen, 
and pericardium, and the water of the ventri- 
cles belong to this class. The urine seems 
to come under the same head, although it 
is of ajpeculiar and compound nature ; next 
follow the salivary and pancreatic juices ; 
and then the mucous fluids poured into the 
alimentary, respiratory, and generative or- 
gans. The fat, marrow, grease of the skin, 
ear-wax, sebaceous matter of the eye-lids, 
and of the external organs of generation in 
both sexes, constitute the class of adipous 
fluids. The liquor of the amnion, the syno- 
via of the joints, and the prostatic fluid, arc 
of a gelatinous kind. The male semen, and 
the bile, are both of a very peculiar nature. 
The chemical analysis of these fluids will be 
considered under their proper articles. 
These very various products are separated 
from the blood by very different organs. 
The most simple mode of secretion is that 
performed by the arteries of a part without 
any glandular apparatus; as the fluids of 
circumscribed cavities, the lymph of the 
cellular substance, and the fat and mar- 
row. 
Secretion is more complicated when per- 
formed by means of certain organs called 
glands. The most simple of these are the 
mucous follicles, found in various parts of 
the alimentary and respiratory canals ; con- 
sisting' of a small bag receiving the secreted 
fluid from the arteries, and expelling it 
through a short excretory duct. But the 
name of gland is applied more properly to 
the larger organs of complicated structure, 
as the pancreas, breast, salivary glands, &c. 
These, consisting of an aggregation of minute 
particles, are called conglomerate, to dis- 
tinguish them from the lymphatic or conglo- 
bate glands. Each of them possesses an 
excretory duct, made up by the union of 
branches from the various component por- 
tions of the gland. The larger portions, 
into which each gland is resolved, may be 
divided into smaller and smaller particles, 
and ultimately into very minute portions j 
concerning the structure of which, anato- 
mists have warmly disputed. Some de- 
scribed them as being hollow, and called 
them acini, or cryptae ; while others assert- 
ed that they consist merely of convoluted 
blood-vessels : the latter opinion is the 
most prevalent at present. The structure 
of the liver and kidney is analogous to this, 
in its minute parts: both these organs, and 
particularly the latter, exhibit the acinous 
appearance. The ultimate blood-vessels 
are arranged in very different ways in various 
glands ; coiled up in roundish masses, as in 
the kidney, arranged like stars in the liver, 
and forming an appearance like a camel’s 
hair pencil in the spleen. 
The various properties of secreted fluids 
depend, no doubt, more on the interior tex- 
ture and vital powers of the secreting organs, 
than on their external habit and conforma- 
tion. For comparative anatomy shows us 
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