Re: Brains size and sweat

Bill Frix (
Wed, 8 Jan 1997 08:18:45 GMT-5

A couple of points regarding Glenn Morton's comments:

> A human supplied with sufficient water and salt can theoretically sweat up to
> 24 liters over a 12 hour period. This shows the difference between our
> sweating efficiency and the eland.

Perhaps this is the maximum limit of sweating by humans. According
to Gray's Anatomy (28th Ed, 1969, p. 1114), "the average quantity of
sweat secreted in 24 hours varies from 700-900 grams (milliliters)." I
would expect the 48 liters per 24 hour period represents extreme
physical activity in extreme temperatures. Is the data on the Oryx
and Eland based on maximum limits or average production?

I would also like to inquire about swine sweat apparatus. From what
I remember, swine are highly desirable in sweat research because
their skin/sweat system is similar to ours. Not having a comparative
anatomy/physiology of the pig, I cannot check this point.

Additionally, it would seem logical to me (from a heat loss
evaluation) that the sweat glands would be located nearest the area
of maximum heat loss requirements. Arguing for sweat glands being
the result of increased brain capacity, this would place the
greatest density in the scalp region. Such is not the case.
According to Gray's anatomy, their are 370 sweat glands per square
cm on the palm (which would be eccrine glands, according to your
report), 200 per sq cm on the back of the hand, 175 on the forehead,
155 on the breast, abdomen and forearm, and 60-80 per sq cm on the
back and leg. In terms of size, the largest occur in the axillae
(arm pits) and groin regions. These glands are apocrine glands,
secreting the reddish fluid discussed in your transmission.

Finally, their is a drastic difference in sweat capacity (almost
2:1) on a racial basis. According to Gray's Anatomy, white Americans
have the smallest gland density at 558.2 glands per sq cm while
Negrito youth (sic) have the greatest at 950.0 glands per sq cm.
Make of it what you will.

In summary, the majority of sweat apparatus in humans appears to be
apocrine, in spite of what Britannica says. I would like to see more
on this issue.

By the way, my wife thinks the idea that the majority of pain in
childbirth being due to the large head is poppycock. She thinks this
is just some male's opinion.
William M. Frix
Assistant Professor, Electrical Engineering
Box 3021
John Brown University
Siloam Springs, AR 72761
Phone: (501) 524-7466
FAX: (501) 524-9548