At a recent meeting of the Physiological Society of Berlin, Prof.
Zuntz spoke on heat regulation in man, basing his remarks on
experiments made by Dr. Loewy. The store of heat in the human body at
any one time is very large, equal, in fact, to nearly all the heat
produced by the body during twenty hours, hence the heat given off to
a calorimeter during a given period cannot be taken as a measure of
the heat production. This determination must be based rather upon the
amount of oxygen consumed and of carbonic acid gas given off. The
purpose of the experiments was to ascertain what alteration the
gaseous interchange of the body undergoes by the application of cold,
inasmuch as existing data on this point are largely contradictory.
The observations were made on a number of men whose respiratory gases
were compared, during complete rest, when they were at one time
clothed, at another time naked, at temperatures from 12° to 15° C.,
and in warm and cold baths. Each experiment lasted from half an hour
to an hour, during which period the gases were repeatedly analyzed. As
a result of fifty-five experiments, twenty showed no alteration of
oxygen consumption as the result of cooling, nine gave a lessened
consumption, while the remaining twenty-six showed an increased using
up of oxygen. This diversity of result is explicable on the basis of
observations made by Prof. Zuntz, who was himself experimented upon,
as to his subjective heat sensations during the experiments. He found
that after the first impression due to the application of cold is
overcome, it was quite easy to maintain himself in a perfectly passive
condition; subsequently it required a distinct effort of the will to
refrain from shivering and throwing the muscles into activity, and
finally even this became no longer possible, and involuntary shivering
and muscular contraction supervened, as soon as the body temperature
(_in ano_) had fallen ½° to 1° C. During the first stage of cooling,
Zuntz's oxygen consumption showed a uniform diminution; during the
period also in which shivering was repressed by an effort of the will,
cooling led to no increased consumption of oxygen, but as soon as
shivering became involuntary there was at once an increased using up
of oxygen and excretion of carbonic acid.
This explains the differences in the results of Dr. Loewy's
experiments, and may be taken to show that in man, and presumably in
_large_ animals, heat regulation as directly dependent upon alteration
(fall) in temperature of the surrounding medium does not exist; the
increased heat production is rather the outcome of the movements
resulting from the application of cold to the body. In _small_
animals, on the other hand, there undoubtedly exists a heat regulation
dependent upon an increased activity of chemical changes in the
tissues set up by the application of cold to the surface of the body,
and in this case the thermotaxic centers in the brain most probably
play some part.--Dr. Herter gave an account of experiments made by Dr.
Popoff on the artificial digestion of various and variously cooked
meats. Lean beef and the flesh of eels and flounders were digested in
artificial gastric juice; the amount of raw flesh thus peptonized was
in all cases greater than that of cooked meat similarly treated. The
flesh was shredded and heated by steam to 100° C. The result was the
same for beef as for fish. When compared with each other, beef was, on
the whole, the most digestible, but the amount of fish flesh which was
peptonized was sufficiently great to do away with the evil repute
which fish still has in Germany as a proteid food. Smoked meat
differed in no essential extent from raw meat as regards its
digestibility.
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