The striking relationship existing between pulse rate and general
metabolism, noted in the fasting experiments made with the earlier
apparatus, has impressed upon us the desirability of obtaining records
of the pulse rate as frequently as possible during an experiment.
Records of the respiration rate also have an interest, though not of as
great importance. In order to obtain the pulse rate, we attach a Bowles
stethoscope over the apex beat of the heart and hold it in place with a
light canvas harness. Through a long transmission-tube passing through
an air-tight closure in the walls of the calorimeter it is possible to
count the beats of the heart without difficulty. The respiration rate is
determined by attaching a Fitz pneumograph about the trunk, midway
between the nipples and the umbilicus. The excursions of the tambour
pointer as recorded on the smoked paper of the kymograph give a true
picture of the respiration rate.
Of still more importance, however, is the fact that the expansion and
contraction of the pneumograph afford an excellent means for noting the
minor muscular activity of a subject, otherwise considered at complete
rest. The slightest movement of the arm or the contraction or relaxation
of any of the muscles of the body-trunk results in a movement of the
tambour quite distinct from the respiratory movements of the thorax or
abdomen. These movements form a very true picture of the muscular
movements of the subject, and these graphic records have been of very
great value in interpreting the results of many of the experiments.