WESLEY D. ANDERSON 
779 
Bicarotid Tk. 
Cervicothoracic ganglion 
Longissimus thoracis m. 
Middle 
cervica 
gang 
Thoraci 
duct 
Descending thoracic 
aorta 
Ansa 
subclovid' 
Axillary 
Pericordicophrenic a 
Interna 
thoracic a, a v. 
Brachiocept^^c trunk 
Thoracic cardiac n. 
Cranial cardiac brs. 
azygos 
miazygos) v. 
Dorsal and 
ventral vagal 
trunks 
Trachea 
monary v 
Pulmonary a. 
Phrenic nerve 
Coronary sinus 
Circumtlex branch of 
left coronary a. 
g reat cardiac vein and 
^rafi(fri[ant.) interventricular a, 
Epicardiol fat 
Figure 13. — Left surface of heart, great vessels and associated structures, sheep. 
calf, dog and other quadrupeds is similar to the 
well understood internal structure of the hu- 
man heart. All normal (and abnormal) ostia 
found in the heart of man can usually be found 
in the animal heart. Of special significance is 
the marked similarity between valvules and 
cusps of sheep and human hearts (Figures 20 
and 
Pericardial Sinuses 
The two sinuses of the pericardial cavity are 
the transverse and oblique. The latter sinus is 
merely a blind pouch and has no clinical signifi- 
cance while the transverse pericardial sinus 
does as it may be used surgically as a channel 
to exert digital or sutural compression upon 
the pulmonary trunk and ascending aorta to 
temporarily halt blood flow into the systemic 
and pulmonary circuits. When the pericardial 
sac is opened one notes that the visceral layer 
of pericardium (epicardium) is reflected 
around both pulmonary trunk and ascending 
aorta in a manner to completely encircle both 
vessels. This space remaining in the pericardial 
sac behind the two great vessels is the trans- 
verse pericardial sinus. Figures 22 and 23 illus- 
trate the comparative features of the pericar- 
dial sinuses in sheep and man. 
The Azygos and Hemiazygos Venous Systems 
In ruminants and in the pig, small ascending 
lumbar veins course high in the sublumbar re- 
gion and unite with small subcostal veins to 
form the left azygos vein (also called the hemi- 
azygos vein. The left azygos vein continues 
cranially invested in endothoracic fascia deep 
to the parietal pleura, and at each intercostal 
space is joined by dorsal intercostal veins. 
