James,
This really frustrates me. And this note is rather blunt.
We did indeed go around twice on this issue. Both
times you have accused me of not knowing the data. The
first (in 1997) was after the PSCF article was published but our discussion
wasn't about the PSCF article. It was about a post I had made to the ASA.
You had interpreted my comments as saying that there was no sweating except
in humans, which is absolutely false,and was never advocated by me. No where
can you find me saying that there is no sweating in any other animal. Our
1997
discussion was about the post which had been turned into a web page. I made
some corrections we discussed and now you are saying things haven't changed.
You can't say that I haven't listened to you as I noted your objection in
the
parenthesis on my web page
http://www.glenn.morton.btinternet.co.uk/sweat.htm
--you are the biologist referred to there. You told me in one of these
rounds
that camels sweat more than humans but never provided any DATA to back up
that
assertion. Below I will perform a calculation to show how silly such an idea
is.
The next discussion we had was in 1999 and was about a comment I made about
the reversal of blood flow into the cranium when humans are under heat
streass. You were quite adamant that this couldn't be the case and said it
didn't happen like that. You accused me of not knowing biology and indeed of
not knowing that blood flowed in a circle. I documented the FACT that
during
heat stress the blood in the emissary veins of the head do reverse direction
and you agreed that it was a phenomenon of which you were
unfamiliar. See the very end of this for what I wrote you at that time.
I provide this so that we don't have to go around again about that issue.
This topic seems to bug you. Why, I don't know but every time I say
something
on this topic you seem to imply that I don't believe that ungulates
sweat. There appears to be something theological rather than scientific in
your
constantly raising the same issues over and over. The fact that the web page
I referred
everyone to discusses sweating in ungulates should dispell that notion
(implicit in the title of this thread) but it doesn't seem to work in your
case! Elands sweat 5.5 liters of water per 100 kg of body weight; Oryx's
sweat 1.87 liters per 100 kg body weight. But humans can sweat 48 liters of
water per 100 kg of body weight! That certainly is 'unique' in my
perspective. If you have DATA, not opinion, that would correct this please
let me know but unless you can come up with an animal that beats that rate
of sweating then I don't think your comments are worthy of much
consideration especially given what is ON MY WEB PAGE. more comments below.
>-----Original Message-----
>From: Glenn Morton [mailto:glenn.morton@btinternet.com]
>Sent: Sunday, November 18, 2001 1:39 PM
>To: Glenn Morton
>Subject: sweat
>
>
>Folks,
>
>
>May I suggest that the Glen's page on sweating, while reflecting some of
>the anthropological literature does not entirely agree with some of the
>biologic research on heat removal in mammals.
>
>
>Glenn seems to think that "the human sweating system is uniquely capable
>of performing that function (cooling not only the face and the rest of
>the body and blood." p. 91 of his ASA article He seems to think
>following Bernard Campell that primates and almost all mammals sweat
>very little.
Of course there is sweating in ungulates and in primates. Compared to man,
they sweat very little. ONCE AGAIN, IF YOU CAN COME UP WITH *****DATA*****
WHICH SHOWS THAT ANIMALS SWEAT AS MUCH AS MAN THEN YOU HAVE A POINT. But
until then the above is mere quantitatively vacuus opinion! I document on
the web page the quantitiative rates of sweating, which you continue to
ignore and offer no data to back up your assertions.
Campbell is NOT saying that they don't sweat at all but that they sweat
little. To claim that they sweat little presumes that they CAN sweat! But
it is a lot less than in humans. Humans are capable of moving more water
through their system via sweat than any other animal--about 2 liters per
hour at max. Please provide documentation that any other animal can move
water through their system at this rate compared to their body weight! If
you can't, then you should cease claiming that I am wrong about the biology
here.
As to chimps sweating, they sweat little (compared to man) because they live
in a rain forest, and the high humidity there makes sweating less efficient.
YES JAMES, THEY SWEAT BUT NOT A LOT. I stand by that until you can produce
DATA to contradict it.
And I suppose you would think that the Encycloped Britannica is wrong as
well. It says primate sweat glands aren't very effective at cooling:
"Sweat glands on the hairy skin of subhuman primates probably function
subliminally or not at all, although they are structurally similar to those
of man. The skin of monkeys and apes remains dry even in a hot environment.
Profuse thermal sweating in man, then, seems to be a new function." ~ "Skin,
Human", Encyclopedia Britannica,16, (Chicaco: Encyl. Brit., 1982), p. 843
NOTE THAT THEIR SKIN REMAINS DRY IN THE ABOVE SITUATION.
And note the difference between humans and primates in distribution of the
sweat glands:
"In most non-human primates (again excluding gorillas and chimpanzees)
eccrine glands are only found on surfaces used in locomotion (the soles of
the hands and feet, and among the dermatoglyphics found on places of high
friction, like the tails of prehensile species or the knuckle pads of
knuckle-walkers. There are two phylogenetically distinguishable types of
eccrine glands, those found in the friction areas of most species of
primates and many other mammals, and the ones found in humans, chimpanzees,
and gorillas throughout the entirety of their body. In humans, the eccrine
glands of the volar surfaces of the hands and feet begin to develop around
three-and-a-half months of fetal development, and the remaining eccrine
glands begin forming separately around five-and-a-half months (Montagna
1985; Robertshaw 1985)." http://www.humanevolution.f2s.com/anth501.html
You keep focussing in on the word 'unique'. THat doesn't mean that no other
animal has sweat glands. I have told you this privately before. It means
that ours is unique in the quantity of water that can be expelled in a short
time. Why you can't or won't remember this is something I don't understand.
Our system of sweating is more efficient than any other animal on a per kg
basis. If not, prove me wrong with DATA! I have asked for this before and
not gotten it from you. All I have gotten is a response that you don't have
time to go do the research. And the fact that we continue to go around
about this means that you aren't listening or learning.
I know that is not true of at least the ungulates (horses
>and cows etc) who do sweat well. I checked my memory out with Vaughan's
>Mammology and remember reading about sweating camels in
>Gauthier-Pilthers H. and Dagg A. 1981.
As I said before it does not mean that animals don't sweat. I never said
that. INDEED ON THE VERY WEB PAGE I REFERRED EVERYONE TO I DISCUSSED THE
SWEATING IN ELAND'S AND ORYX'S WHO ARE UNGULATES, YET YOU SEEM TO SAY THAT I
DON'T BELIEVE THAT THEY SWEAT. THIS ALONE SHOULD SUFFICE TO DISPROVE YOUR
CRITICISM. And we have argued over this precise issue before. How many more
times must we go around about it, James?
(The camel, its evolution,
>ecology, behavior, and relationship to man. University of Chicago Press.
>Chicago). I know that many mammals have been shown to have sweat
>glands only in some areas - but I also get the feeling that in many
>cases the skin histology has simply not been done.
Science works on 'feeling'? James, just because you haven't studied this
area, doesn't mean that others haven't. The skin histology has been done but
you haven't read it! How do you think it can be said that lower primates
have
eccrine glands mostly on the volar surfaces if they hadn't done the
histological
work? They ultimately came from histological studies! Do you think
the anthropologists or the Encylopedia Britannica just made the things up?
And here you once again raise the camel issue, which I reference in the
first paragraph of the web page. But once again, you provide no quantitative
data for this. I provided Vaughn's quote to you on Jan. 2, 1997, showing
that mammals are not all alike in sweating..
Terry Vaughn, Mammalogy (Philadelphia: W. B. Saunders Co., 1972) states:
"In man and some ungulates sweat glands are broadly distributed over the
body
surface, but in most mammals they are more restricted. In some
insectivores,
rodents, and carnivores, sweat glands occur only on the feet or on the
venter,
and they are comppletely lacking in the Cetacea and in some bats and
rodents.
hair follicles are supplied with sebaceous glands; their oil secretion
lubricates the hair and the skin. " P. 7
Of course the camel sweats. But he can't sweat at a human rate or he could
not go several days without water in the heat of the Sahara. Camel's allow
their body temperature to rise as much as 11 degrees C to lower the sweating
rate. I checked the Grolier's encyclopedia for the following data. A camel
can be as hefty as 680 kg and can lose 25% of his weight in water. So, a 600
kg camel if he sweated as much as a human would go through 48 liters/100
kg/day * 6= 288 liters of water per day. Since they can go without water for
7-9 days that means that their bodies must store 2592 liters of water. Thus
the camel MUST have a volume which is greater than 1000cc/liter X 2592
liters = 2592000 cc. And since water weighs 1 g/cc the camel must be a
behemoth which weights 2592 kg. Of course the weight of a camel is usually
no more than 700 kg. So, yes a camel sweats, but no where near as great as a
man. Lets look at this another way. If a camel can only lose 25% of his
weight in water, that is 170 kg of water. As we have seen this if a camel
sweated as severely as a human, then he would have to sweat more than that
in a single day. Thus, if a camel sweats like a human, he can only go one
day without water. QED. So, please provide data to back up the assertion
that the camel sweating is as great as man. Man's sweating rate is unique--I
stand by this and any suggestion that our sweating is not unique among the
mammals displays a lack of knowledge of the topic as well as a lack of
actually doing the above calculations which would show how silly the idea
is.
In any case
>ungulates clearly sweat efficiently and do other mammals from certain
>areas of their body. Gunthier-Pilthers even state that camel sweating
>under hair is more efficient and cite research done on shorn camels to
>back it up.
It is Gauthier-Pilters AND Anne Innis Dagg, not Gunthier-Pilthers
(mispelled) alone. It just kills me that you make a reference like this
without actually giving any data. A furred animal which sweats 2 liters of
water is less efficient than one which sweats 3 liters of water. Efficiency
is a rate, quantity per hour per 100 kg. If the purpose is to examine heat
removal, which is what we are talking about here, then the more water which
can evaporate the more heat is removed in a shorter time. So, efficiency in
heat removal is the system that removes more heat. Thus allowing 3 kg of
water to evaporate in a given time is more efficient at heat removal than
allowing only 2 kg of water to evaporate in the same time.
I sent this to you January 8, 1997. And you are absolutely bass-akwards
about sweating FOR HEAT REMOVAL under hair being more efficient. The entire
reason mankind lost his hair was because the brain required heat removal and
it was slower and less efficient under fur as Gauthier-Pilters and Anne
Innis Dagg show.
**begin**
A furry animal simply cannot have as efficient a sweating mechanism as a
hairless one. I will agree that a kg of water evaporated will remove the
same
amount of heat whether under fur or not. But fur will seriously hinder
evaporation. I do not have the data for dogs, but I do have it for camels.
Consider this:
"Their total water expenditure per day was 3 liters per 100 kilograms body
weight in the shorn animal and only 2 liters in the unshorn camel. Thus a
shorn camel with fur 0.5-1 centimeters long would evaporate 50 percent more
water than would an animal with unshorn fur. The temperature at the fur
surface was as high as 70-80 C, so the temperature gradient through the fur
was more than 30 C."~Hilde Gauthier-Pilters and Anne Innis Dagg, The Camel,
(Chicago: University of Chicago Press, 1981), p. 73
Think about the physics and you will see why fur hinders the efficiency of
sweating.
1. Fur hinders the free flow of air. The air under the fur becomes
saturated
and must be replaced by dry air for heat to be removed.
2. Water on the skin under the fur is cooler than water would be on the open
skin. Cooler temperature means slower evaporation and less heat removed per
unit time.
3. Some of the sweat under the fur will be stuck to the hair itself. When
it
evaporates, it cools the hair, which does not have the same effect as
cooling
the skin, under which flows the blood. It is the blood which needs to be
cooled so that it can cool the interior of the body.
**end**
The heat removed when a gram of water is evaporated is 600 calories. A
liter is 1000 g. Thus 3 liters on the shorn camel removes 3000*600=1.8
million small calories, or in food calories terms, 1800 calories (these are
the large calories) BUt 2 liters removes only 1200 large calories. The shorn
camel is more efficient at heat removal. And until you can show that a
furred camel sweats more than this, then you haven't shown that he is more
efficient. The furred camel is more efficient AT WATER RETENTION BUT NOT
HEAT REMOVAL.
By the way, a camel sweats only 8.8 liters per 100 kg weight per day
compared to man's 48 liters per 100 kg per day.
>
>
>I have previously corresponded privately and extensively with Glenn in
>the past on this topic and have no desire to get into a long debate.
Yes, and haven't paid a bit of attention to what I have said.
>However, I do not see much change in his position on the current web
>page and still think the anthropological literature differs from some of
>the biological research on heat removal especially in desert animals.
THere is no need to change until you can provide documentation for your
rather baseless assertions. I will add the above camel water calculation to
my web page.
>
Comments to James about the reversal of blood flow INTO the brain.
Sat Jul 24 22:11:01 1999
To: James Mahaffy <mahaffy@mtcnet.net>
From: mortongr@flash.net
Subject: question
Cc:
Bcc:
X-Attachments:
In-Reply-To: <379A04C1.63B2B86A@mtcnet.net>
References:
X-Eudora-Signature: <Standard>
Did you see my documentation on the ASA of the fact that blood flow does
reverse in the emissary veins of the brain? Do you have any counter-data?
Here is data from the original article:
"In both subjects the blood flowed rapidly from skin to brain during
hyperthermia; during hypothermia no flow was detected in one subject, and in
the other blood flow was clearly reversed." M. Cabanac and H. Brinnel,
"Blood flow in the emissary veins of the human head during hyperthermia,"
Eur. J. Applied Physiol. (1985):54:172-176, P. 173
"Because of its relatively large mass the human brain needs to be cooled
more than that of most other species. At rest, this is accomplished by the
carotid blood; when the temperature of the artierial blood is raised, the
brain is in jeopardy and there is need for a mechanism to cool the brain
directly. Caputa et al (1978) have shown that in humans the blood flows in
the opthalmic vein according to a pattern compatible with a cooling of the
brain during hyperthermia. When the subjects were hypothermic, the blood
flowed from brain to face, but when they were hyperthermic from face to
brain. Thus cool blood from the sweating face was directed towards the sinus
cavernosus which therefore appears to be a heat exchanger between venous
blood cooled by peripheral skin and warm arterial blood. The emissary veins
are quite numerous and do not possess valves, and the thermal dependence of
the direction of blood flow in them coupled with the earlier results of
Caputa et al, on the flow in the ophthalmic vein, give clear indication of a
possible mechanism for the cooling of the human brain during hyperthermia."
M. Cabanac and H. Brinnel, "Blood flow in the emissary veins of the human
head during hyperthermia," Eur. J. Applied Physiol. (1985):54:172-176, P.
175
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