Page 660 - My FlipBook

670 GENERAL PATHOLOGY.
DiCROTiSM.—Dierotism results from diminished arterial tension, and
is the exaggeration of the normal impulse or shock seemingly given to
the blood-wave by the closure of the aortic valves. Vie\ving the heart
as a pump, and following its motions, we will easily gain an under-
standing of this secondary Avave which the sphygmograph shows us is
present in all forms of the pulse, and which may be seen in all the
charts on page 668. When the ventricle is filled the heart contracts
forcibly and the blood is driven into the aorta. Then there comes the
expansion of the ventricle from which the bl(.)od has just been ex])elled,
and the tend of fact, a portion of the blood now contained in the elastic artery does,
with the cessation of the impulse, return toward the heart ; and in this
act the aortic valves are caught and forcibly closed, causing a sudden
arrest of the returning volume of blood at a time when the artery is in
active contraction upon it. These two forces, acting together at a time
when there is a marked relaxation of the arterial system, cause a second
expansion of the principal blood-wave, which necessarily occurs during
its subsidence, as is seen in the charts. It is probably only in great
arterial relaxation that marked dierotism can occur, and it is usually
associated with weakness of the heart as well. In some instances this
second l)lood-wave is almost as high as that of the true pulsation, and
may be plainly recognized with the finger, so that one not accustomed
to pulse-examinations might mistake its significance and count the beats
as double their real frequency. This form of pulse, however, is very
rare, although it is occasionally met with in fevers.
Intermittent Pulse.—AVhen the rhythm of the pulse is regular,
with the exception that an occasional beat fails, it is said to be an infer-
mittent pulse. The omissions of the beat may take ])lace frequently or a
considerable interval may occur between them (Fig. 370, e). They may
happen regularly after every second or third beat, or even after longer
periods sometimes they are entirely irregular in their occurrence.
;
Intermittence differs entirely from irregularity of ])ulse, and is of much
less serious import. In some persons intermittence of the pulse is a
constitutional peculiarity, lifelong in duration and unattended by evil
consequences ; more frequently it does not a]>pear until midtlle life ; in
other cases its occurrence is only occasional, the attacks being induced
by the use of certain articles of food or by certain extraneous conditions.
Many j^ersons who have a pulse occasionally intermittent are made very
imcomfortable by it, but perhaps the greater number are unconscious of
the condition. It seems in no way to endanger life, and the sphygmo-
gra])h shows that in many cases the ap])arently omitted beat is really a
very feeble ])ulsation not sufficiently pronounced to be felt by the finger.
The Puese in I^esions of the Heart.—The importance which the
subject of lesions of the heart has for the specialist, and jiarticidarly for
those who administer anaesthetics, is such that I do not like to ])ass the
sul)ject without notice, although anything like a sufficient treatment of the
variations of the pulse in these conditions would be beyond the scope of
this article. There is not much doubt that the failure on the part of
dentists to detect these conditions contributes to the number of fatalities
that are continually occurring in that special field of practice. A close