impulses originating at the apex, at the base or at some point in
the right ventricle.

In the ventricles, Lewis states, the Purkinje fibers act as the
conducting agent, stimuli being conducted to all portions of the
endocardium simultaneously at a rate of from 2,000 to 1,000 mm. per
second. The ventricular muscle also aids in the conduction of the
stimuli, but at a slower rate, 300 mm. per minute. The rate of
conduction, Lewis believes, depends on the glycogen content of the
structures, the Purkinje fibers, where conduction is most rapid,
containing the largest amount of glycogen, the auricular musculature
containing the next largest amount of glycogen, and the ventricular
muscle fibers the least amount of glycogen.

Anatomists and histologists have more perfectly demonstrated the
muscle fibers of the heart and the structure at and around the
valves; the physiologic chemists have shown more clearly the action
of drugs, metals and organic solutions on the heart; and the
physiologists and clinicians with laboratory facilities have
demonstrated by various new apparatus the action of the heart and
the circulatory power under various conditions. It is not now
sufficient to state that the heart is acting irregularly, or that
the pulse is irregular; the endeavor should be to determine whit
causes the irregularity, and what kind of irregularity is present.


CLINICAL INTERPRETATION OF PULSE TRACINGS

A moment may be spent on clinical interpretation of pulse tracings.
It has recently been shown that the permanently irregular pulse is