Re: Brains size and sweat

Bill Frix (
Wed, 8 Jan 1997 15:02:48 GMT-5

To continue an on-going discussion:

First, I became fascinated by this proposition so have spent the
morning at the library examining comparative physiology and anatomy

(1) The unanimous consensus of the books (about 12 I read) was that
sweating constitutes on 25% of the cooling system in human beings;
60% of heat loss in humans is from radiation.

(2) According to the authors, _all_ mammals sweat, even dogs (there
are sweat glands in the skin and on the pads of dogs). Skin sweating
in dogs has been observed and can be induced by medication similar to
humans. In addition, according to the authors, the cooling systems
in dogs is "as efficient as in humans." The horse and humans have
more highly developed sweat systems.

(3) In terms of heat rejection (as opposed to mere sweating, see item
#1 above), the human is below the rat and the rabbit in terms of
thermal loss per kg of body weight.

(4) There is a discrepancy between researchers on the amount of fluid
a person sweats per day. Unanimously, the researchers indicate that
an average person sweats from 0.5 - 0.9 liters per day while the
extreme (physical exertion in extremely hot environments) varies
according to the researcher from 3 gallons (13.5 liters) per day to
48 liters per day.

(5) Most texts ignore the distinction between apocrine and eccrine
sweat glands. However, the eccrine glands are much fewer in number
and smaller in size than the apocrine glands (the latter being found
in the arm pits, groin and anal regions), which, in my experience,
are the primary sources of sweat. According to my reading,
"apocrine" basically means the glands empty onto hair follicles,
whereas "eccrine" means the glands empty directly on the skin. This
means the eccrine glands are predominantly found on the palms of the
hands and bottoms of the feet. The argument that we have an
increased capacity of sweat _and_ that we have an essentially unique
type of sweat mechanism (eccrinic) appears to be in conflict. I
repeat an earlier email: the pig is predominantly "naked" (i.e.,
devoid of hair), hence should have mostly eccrinic sweat systems.

(6) Since some have argued that apocrine glands are not, per se,
sweat glands but are special modifications (possibly for sexual
attraction), and since the previous emails are proposed the theory
that "our form of sweating (i.e., eccrinic)" is different from that
of animal (i.e., apocrinic), arguments about the volume of sweat
secreted (?) by humans need to be subdivided into volumes of
apocrinic secretions versus eccrinic secretions. We would probably
find that the volume of eccrinic (or "true sweat") per kg of body
weight is of a more comparable

(7) Regarding camels, according to one study a camel can sweat 30%
of its body weight away without complications. Ten percent loss in
humans results in major complications. This constitutes, to me, a
much greater sweating capacity in camels than humans.

William M. Frix
Assistant Professor, Electrical Engineering
Box 3021
John Brown University
Siloam Springs, AR 72761
Phone: (501) 524-7466
FAX: (501) 524-7499