Page 374 - Anatomy and Physiology of Farm Animals, 8th Edition

The Respiratory System / 359

left, plus a middle lobe between these and the body wall to sample fluid from the
pericardial sac).
a ventrocaudal accessory lobe near the
VetBooks.ir midline (Fig. 19‐8). Horses lack the mid- After an animal has taken the first
dle lobe. A more or less distinct gap
between lobes along the ventral margin of breath at birth, the lungs always retain
a significant volume of air, even in
the lungs is usually identifiable. This is the pathologic conditions of collapsed
cardiac notch, and it tends to be larger on lung. In the fetus, however, the lungs
the right side (Fig. 19‐10). At the cardiac are nearly the consistency of liver, con-
notch, the heart makes contact with the tain no air, and sink in water. Whether
thoracic wall, a fact that is exploited for the lungs will sink or float in water is a
echocardiogram imaging (wherein the standard test to determine whether a
ultrasound device is applied to the tho- newborn animal was born dead, in
racic wall, where no lung tissue intervenes which case the lungs sink, or drew at
between it and the heart) and pericardio- least one breath, in which case the
centesis (introducing a needle through lungs float.

Ox
13th rib
c

a’ d
1st rib b

e

Cardiac notch

Horse 18th rib

c
1st rib a d

e

Cardiac notch

Figure 19-10. Disposition of the left lung in the ox (above) and horse (below), shown in a cutaway view
of the thorax. a, cranial lobe; a’, cranial part of cranial lobe (ox only); b, caudal part of cranial lobe (ox only);
c, caudal lobe; d, diaphragm; e, heart.