Lewis [Footnote: Lewis: Brit. Med. Jour., 1909, ii, 1528.] believes
that 50 percent of cardiac arrhythmia originates in muscle
disturbance or incoordination in the auricle. These stimuli are
irregular in intensity, and the contractions caused are irregular in
degree. If the wave lengths of the pulse tracing show no regularity-
-if, in fact, hardly two adjacent wave lengths are alike--the
disturbance is auricular fibrillation. Injury to the auricle, or
pressure for any reason on the auricle, may so disturb the
transmission of stimuli and contractions that the contractions of
the ventricle are very much fewer than the stimuli proceeding from
the auricle. In other words, a form of heart block may occur.
Various stimuli coming through the pneumogastric nerves, either from
above or from the peripheral endings in the stomach or intestines,
may inhibit or slow the ventricular contractions. It seems to have
been again shown, as was earlier understood, that there are
inhibitory and accelerator ganglia in the heart itself, each subject
to various kinds of stimulation and various kinds of depression.

Both auricular fibrillation and auricular flutter are best shown by
the polygraph and the electrocardiograph. The former is more exact
as to details. Auricular flutter, which has also been called
auricular tachysystole, is more common that is supposed. It consists
of rapid coordinate auricular contractions, varying from 200 to 300
per minute. Fulton [Footnote: Fulton, F. T.: "Auricular Flutter,"
with a Report of Two Cases, Arch. Int. Med., October, 1913, p. 475.]
finds in this condition that the initial stimulus arises in some
part of the auricular musculature other than the sinus node. It is
different from paroxysmal tachycardia, in which the heart rate
rarely exceeds 180 per minute. In auricular flutter there is always