By J. MORTIMER-GRANVILLE.
Such expressions as a “cool head,” “hot-headed,” and the like, commonly
relate to temperament rather than temperature; but it is essential to
a full comprehension of the subject before us that the _rationale_ of
animal heat should be stated, and the laws that govern the phenomenon of
temperature actual and subjective, at least cursorily, explained.
Heat and the sensation of heat are two widely different states. When, on
a chilly day or after washing in cold water, a man rubs his hands until a
glow of heat seems to suffuse them, there is a very slight rise of actual
temperature caused by the friction; the feeling is principally due to
nerve-excitement, produced mechanically by the rubbing. The blood flows
more freely into, and through, the parts excited immediately afterward,
as shown by the redness, but the first impression of heat is mainly one
of sensation. The feeling and the fact are not even constantly related.
A person may feel hot when not only the surrounding temperature but
that of his body is low; or, he may feel cold when really overheated.
These perverted sensations are occasionally morbid—that is to say,
form part of a state of disease—or they may arise from individual
peculiarities which, perhaps, render perceptions of a particular class
especially acute. On the other hand, there are conditions of the body,
and special sensibilities, in which the sense of heat is dulled, and even
considerable elevations of temperature are not perceived. It is easy to
see how impossible it must be to form a correct judgment of the actual
state of heat either around or within us by simple sensation.
Throughout the world, whether man be placed in tropical heat or arctic
cold, the temperature of his body must, to maintain health, be preserved
at the same point—about 98.4 to .6 degrees of Fahrenheit. A very small
departure from this universal mean standard constitutes or indicates
disease. The external heat is comparatively unimportant, or only of
secondary moment, in the economy of nature; we can not rely upon it for
the compensation of differences in the heat generated within the body by
the organism. Except for the production of a temporary effect, such as
to give time for the reëstablishment of the normal temperature in a body
chilled, as by submersion, external heat is useless for vital purposes.
The only way in which it can act is by preventing the loss of more heat,
and giving a slight aid to recovery by warming the surface of the body.
If when a person is cold he goes into a heated apartment, or sits before
a large fire, he receives with advantage just as much heat as will bring
the skin of his body up to the normal standard; as soon as that point is
reached, the organism will begin to labor to get rid of the superfluous
caloric, and by sweating the heat must be kept from rising above the
standard. All the heat thrust upon the body above 98.6 degrees is waste
and mischievous except in so far as it may promote perspiration, which
probably helps to work off some of the useless and burdensome, possibly
morbid and poisonous, materials that oppress the system. This is how
Turkish baths, and “sweatings” generally, do good, by exciting increased
activity of the skin, and, as it were, opening up new ways of egress for
matters which, if retained, might offend.
So far as the heat of the body is concerned, whether in health or
disease, every degree of external heat which is above the complement
to form 98.6 degrees Fahrenheit with the heat of the body itself at
the time, is useless and may do harm. It follows that in fever the
surrounding atmosphere should be kept cool; in depressing disease, when
the heat-producing powers of the organism are small, the air around
should be warm. These are precisely the conclusions to which experience
and observations conduct us; and the facts now briefly stated explain the
reason why.
There is no warmth in clothes; the heat comes from the body itself,
generated within, or the surrounding atmosphere, or from substances with
which the body may be in contact. Of course clothes, like any other
materials, can be charged with heat, and will take up as much thermic or
heating property as their specific capacity allows. It is this capability
of receiving heat which constitutes the first condition of warmth in the
comparative value of different materials of dress. The second condition
consists in the physical power of any fabric to hold the heat with which
the article has been charged. For example, some materials will become
warmer in a given time and retain their heat longer than others under
the same conditions of exposure, first to heating and then to cooling
influences. The principle of clothing should be to protect the body from
external conditions which tend to abstract heat, when the surrounding
temperature is lower than that of the body; and to strike heat into the
organism, when the temperature of the outside air and of the substances
with which the skin may be brought into contact is higher than that of
the animal body itself.
Local temperature, that is, the heat in the several regions of the body
is determined by conditions which control the circulation of the blood,
and the function of nutrition or food appropriation. If the circulation
is free in a part, its temperature is maintained; if, from any cause,
the flow of blood is retarded, the local heat will be reduced. Any one
may put this to the test by encasing the hands in somewhat tight gloves
when the weather is cold. The pressure prevents the free passage of the
blood through the vessels, and the temperature falls. There is no warmth
of any kind in the gloves; they act simply as non-conductors of heat,
and prevent the heat generated within the body from passing off. For
example—if a piece of lint or rag be dipped in cold water and laid on
the skin, and a sheet of impervious or non-conducting material, such as
india-rubber or thick flannel, is wrapped closely round, the heat of the
body will raise the cold water to a temperature at which it will be given
off as steam the moment the covering is removed. When the extremities
are enclosed in thick or dense coverings, their temperature will depend
on the amount of heat generated within them, and if the flow of blood
through the vessels is arrested or retarded, nothing is gained, but
everything lost, by the measures taken to protect them from the external
cold.
This is a matter of the highest practical moment, and needs to be
thoroughly understood. The feet can not be kept warm unless the blood
circulates freely in the extremities, and that will not be the case if
the boot, shoes, or stockings are tight. These last-named articles of
clothing are practically the worst offenders. A stocking encircling the
foot and leg closely and enveloping every part, with special pressure
at the instep, around the ankle, and above or below the knees, must
inevitably tend to oppose the circulation and so reduce the natural
heat. The arteries which bring the blood to the extremity are set deeper
than the veins that carry it back, and, as the latter are provided with
valves which open toward the heart, it is too commonly supposed that
the “support” afforded by the stocking will favor the return of blood
more than it can impede the deeper supply-currents, and so help the
circulation; but practically we know this is not the fact, for a tight
stocking ensures a cold foot, and the chilliness of which many persons
complain is mainly caused by the practice of gartering, and wearing
stockings which constrict somewhere or everywhere.
There is a popular notion that if the feet are cold the head must be hot,
and by keeping the extremities warm with wraps the “blood is drawn from
the head,” and its temperature reduced. Those who have on the one hand
studied the phenomenon of fever, and on the other noted the physical
condition of races and individuals who habitually leave the extremities
unclothed, will know that this theory of the distribution of heat is
only partially true. Heat depends on the due supply of nutrient elements
to the tissues. It is the expression or result of the process of local
feeding. If a part is active it will be heated. When the feet are left
bare the complex muscular apparatus of the extremity, which in a stiff
shoe scarcely works, is called into vigorous action, the arch of the
foot plays with every step, and each toe performs its share in the act
of progression. This promotes growth and calls for nutrition, whereby
the heat is maintained; whereas if it be simply packed away as a useless
piece of organism, no amount of external heat will warm it. Work is the
cause and counterpart of heat throughout the body.
The same principle applies to the head. No amount of external cooling
will reduce the temperature, no drawing away of the blood by artificial
expedients will permanently relieve the sense or obviate the fact of
heat if the organ within the cranium is excessively or morbidly active.
The brain is a peculiarly delicate and complicated organ, requiring more
prompt and constant nutrition than any other part of the body, because
the constituent elements of its tissue change more rapidly than those
of any other in proportion to the amount of exercise. Moreover, the
brain is always acting during consciousness, and even in sleep it is
seldom wholly at rest, as we know from the occurrence of dreams. The
faculty of nutrition is highly developed in the organ or it could not so
continuously, and on the whole healthily, discharge its functions, even
when other parts of the body, or the system as a whole, are suffering
from disease. When the head is heated there is nearly always a local
cause for it, and the remedy must be addressed to the seat of the malady.
The temporary expedient of “drawing away the blood” by applying heat to
the extremities is useful as far as it goes, and may suffice to enable
the organ to rid itself by the contraction of its blood-vessels from
a surplus charge of this fluid, but in the absence of special causes
the _reason_ of the “heat of head” is undue exercise or disturbance of
nutrition in the brain itself. Perhaps the seat of the over-work and
consequent heating may have been limited to a particular part of the
head; for example, the apparatus of sight, or hearing, as when the head
becomes heated by reading too long or in a strong light. The point to
understand is that when the head is physically hot it is the seat of
too much or disorderly nutrition, and either the amount of brain or
sense-power exercised must be reduced or the mode of action changed, and
the particular part of the apparatus of perception or thought which has
been too severely taxed relieved.
The true condition of health is that in which the temperature of the body
as a whole and of its several parts is not disturbed by surroundings
either of heat or cold. The preservation of a natural and healthy
temperature is mainly to be secured by the maintenance of a regular and
well distributed circulation of blood charged with the materials of
nutrition.
The first condition of a free and continuous flow of blood is a healthy
heart, not hampered by irritants, mental or physical. Sudden grief or
fright produces cold by arresting the circulation, and the flow may
be permanently retarded by anxiety. The mind has a wondrously direct
influence on the heart and blood-vessels—on the latter through the
nerves, which increase or reduce the calibre of the minute arteries,
as in blushing or blanching at a thought. Instead of loading the body
with clothes, the “chilly” should search out the physical cause of their
coldness. The blood must not only circulate freely; it must be rich in
nourishing materials, and not charged with poison. An excess of any one
element may destroy the value of the whole. It is too much the habit of
valetudinarians and unhealthy people of all kinds, to charge the blood
with substances supposed to be “heating” or “cooling” as they think the
system requires them. This is a mistake. The body does not need to be
pampered with cordials, or refrigerated with cunningly devised potions.
If it be well nourished it will be healthy.
* * * * *
There is something fearful in seeing a man of high character being under
an obligation to a fool.—_Goethe._