differentiated during sleep by the fact that if the heart does not
markedly slow, there is cardiac weakness or some general
disturbance. There is also cardiac weakness if there is a tendency
to yawn or to take long breaths after slight exertions or during
exertion, or if there is a feeling of suffocation and the person
suddenly wants the windows open, or cannot work, even for a few
minutes, in a closed room. If these disturbances are purely
functional, exercise not only may be endured, but will relieve some
nervous heart disturbances, while it will aggravate a real heart
disability. If the heart tends to increase in rapidity on lying
down, or the person cannot breathe well or feels suffocated with one
ordinary pillow, the heart shows more or less weakness.
Extrasystoles are due to abnormal irritability of the heart muscle,
and may or may not be noted by the patient. If they are noted, and
he complains of the condition, the prognosis is better than though
he does not note them.

It has long been known that asthma, emphysema, whooping cough, and
prolonged bronchitis with hard coughing will dilate the heart. It
has not been recognized until recently, as shown by Guthrie,
[Footnote: Guthrie, J. B.: Cough Dilatation Time a Measure of Heart
Function, The Journal. A. M. A., Jan. 3, 1914, p. 30.] that even one
attack of more or less hard coughing will temporarily enlarge the
heart. From these slight occurrences, however, the heart quickly
returns to its normal size; but if the coughing is frequently
repeated, the dilatation is more prolonged. This emphasizes the
necessity of supporting the heart in serious pulmonary conditions,
and also the necessity of modifying the intensity of the cough by
necessary drugs.