In all healthy animals two distinct sounds are heard over the chest:—the
=tubal= or =bronchial= sound, and the =vesicular= or =respiratory
murmur=. The =bronchial sound= caused by the air sucking through the
larger bronchi is best heard by applying the ear to the breast over the
lower end of the windpipe or to the upper third of the chest immediately
behind the shoulder. The respiratory murmur is clear and full in the
middle third of the chest immediately behind the shoulder. It is louder
and more prolonged in inspiration than in expiration and in the right
lung than the left especially in cattle and sheep in which the former is
more capacious. It is louder in young animals than in old, hence the
name of =juvenile= respiration applied by Leblanc. In thin animals it is
better heard than in fat ones, the chest walls being thinner, firmer,
and more conducting. In animals of a nervous temperament like the
English racer it is more distinct than in the Norman, Clydesdale and
other heavier breeds. Deep, broad capacious chests emit a stronger sound
than such as are shallow, narrow and short. Exercise, fear or any
excitement accelerating the respiratory act increases the sound. A full
stomach, certain narcotics and other depressing influences lessen it.
Other things being equal the sound is lower in cattle and sheep than in
other domestic animals.
=Horse.= The ear pressed strongly upon the breast where the windpipe
enters detects a strong blowing sound referable to the lower end of the
trachea and the bronchi. In young foals a respiratory murmur is heard
when the stethoscope is applied in front of the shoulder, the limb being
meanwhile drawn backward. A similar murmur may be heard, but less
distinctly over the shoulder blade at this age.
=Left Side.= _Behind the shoulder_ in the _upper third_ of the chest the
sound is loud and somewhat harsh, the respiratory murmur being here
supplemented by the noise of the air rushing through the larger
bronchia. From the 13th rib the respiratory sound is alone heard and
becomes weaker to the second last (17th).
In the _middle third_ the respiratory murmur is moderately clear from
the 4th to the 6th rib, it becomes louder and clearer to the 9th from
which its force gradually diminishes and is lost over the 16th. In the
_lower third_ over the 4th, 5th, and 6th ribs the respiratory sound is
replaced by the sounds of the heart, each beat being distinctly divided
into two sounds, the first dull and prolonged, the second short and
quick. The respiratory murmur is heard over the 7th and 8th ribs, is
weaker on the 9th and lost over the 10th. In the middle and lower thirds
but especially towards the posterior part of the chest, abdominal sounds
are often heard. They consist chiefly in gurgling or in a noise like
that caused by the air rushing into a bottle which has been turned upon
its side when full of water. Such sounds are easily distinguishable from
those occurring in a diseased chest as they bear no relation to the
rhythmical action of breathing.
=Right Side.= In the _upper and middle thirds_ the sounds do not differ
from those of the left side. In the _lower third_ the respiratory sound
is clear from the 4th to the 7th ribs; from this it decreases and is
lost at the 10th.
=Ox.= In very lean cattle the respiratory murmur heard in front of the
shoulder and over the scapula is more distinct than in the same region
of the horse.
=Left Side.= In the _upper third_ a clear respiratory murmur is heard
over the 8th, 9th and 10th ribs but is lost about the 11th. In the
_middle third_ the vesicular sound is feeble at the lower margin of the
region and immediately behind the shoulder because of the proximity of
the base of the heart. Towards the upper margin it is loud and harsh
being complicated by the _tubal_ sound. It is full and clear over the
7th rib whence it decreases in force to be lost at the 11th above and
the 10th below. In the _lower third_ the double heart beat is alone
heard over the lower part of the 4th rib, the respiratory murmur
reappears over the 5th and 6th whence it becomes weaker and is lost at
the lower and upper margin of the region respectively over the 8th and
9th ribs.
=Right Side.= The sounds of the _upper third_ simply repeat those of the
left side. In the _middle third_ the chief difference is the greater
clearness and strength of the respiratory and tubal sounds immediately
behind the shoulder. In the _lower third_ a moderately strong
respiratory murmur is rendered harsh by a tubal sound due to the
proximity of the large bronchus going to the anterior lobe of the right
lung. The respiratory murmur continues with diminishing force to be lost
over the 8th and 9th ribs.
=Accidental but healthy Sounds.= These are more loud and frequent in the
ox than in the horse. There is the same irregular rumbling and gurgling
especially on the posterior parts of the chest. Gurgling as from a full
bottle inverted is often clearly heard over the last six ribs on the
left side, and appears due to the passage of liquids between the paunch
and honey comb bag. An occasional sound as of water falling into an
empty barrel is heard in the same region in cases of slight tympany and
after saliva has been swallowed. Rumbling sounds are chiefly heard over
the last ribs on the right side where the large and small intestines are
situated. The superadded sounds in the ox are those of _crepitation_ and
_friction_. The _crepitation_ or fine crackling due to a dryness of the
areolar tissue under the skin is frequently present in oxen in average
health. A fine _crepitation_ is also heard on the left side from the
bursting of myriads of minute bubbles of air generated among the
contents of the paunch during the process of digestion. This is
especially marked after the animal has fed on green food or potatoes. A
loud _friction_ or _rubbing_ sound, which may be imitated by placing the
back of one hand upon the ear and rubbing the palm of the opposite hand
upon it, is likewise heard over the left side after eating. It is
produced by the movements of the paunch during contraction and not being
synchronous with the respiratory acts cannot be confounded with the
friction sounds of pleurisy to be hereafter noticed.
=Sheep.= The diaphragm being attached to the last rib as in the horse
the respiratory murmur may be heard to the second last. The shoulders
being more movable than in the ox the anterior part of the chest can be
more satisfactorily examined. The vesicular murmur is heard along the
whole lower third on the left side though the heart sounds are
superadded over the 4th, 5th and 6th ribs. Crepitation from the
subcutaneous areolar tissue is rarely heard. Otherwise the sounds of the
chest and abdomen correspond to those of the ox.
=Goat.= This animal differs from the sheep mainly in the greater force
and clearness of the respiratory murmur.
=Pig.= It seems ridiculous to speak of auscultating the pig, yet he is
sometimes thin enough and quiet enough to permit of one obtaining
satisfactory results. Gentle treatment and scratching the back and
abdomen will often persuade him to be temporarily quiet and docile. The
vesicular murmur is very clear in the middle third of the chest on
either side, but diminishes gradually on the last six ribs, and
disappears on the second last. It is much less intense in the upper and
lower thirds. In the posterior part of the chest rumbling and gurgling
abdominal sounds are frequent.
=Dog.= The respiratory murmur is very clear over the whole chest. It is
most intense along the middle third and becomes less clear on the 4 or 5
last intercostal spaces. The mobility of the shoulder permits an
examination of nearly the entire chest. The respiratory murmur may be
heard over the entire length of the lower third on the left side though
the heart’s sounds are equally heard over the 4th, 5th and 6th ribs.
Rumbling and gurgling abdominal sounds are much less frequent than in
herbivora and omnivora.
=Birds.= The respiratory murmur is loud, clear and almost harsh on the
sides of the thorax, beneath the wings, and considerably softer as heard
on the back.