OF THE GREAT ANTERIOR VEINS. 
163 
right auricle. The transverse branch in the neck {d) is not half the size of either 
jugular vein. It crosses over the commencement of the great arteries of the head 
and neck, and opens into the lateral venous trunks, somewhat below the point of 
junction of the jugular and subclavian veins of each side. This circumstance (ob- 
served also in Professor Sharpey’s preparation) is interesting when considered in re- 
lation to the position of the cross branch in the embryo, and to the mode of forma- 
tion of the right innominate vein. 
From opposite the left end of this cross branch, the additional superior cava 
(fvlos) descends upon the aorta, to the front of the root of the left lung, and 
crossing the corresponding vessels, reaches the side of the left auricle immediately 
behind the appendix; then turning backwards under the lowermost pulmonary vein 
in close contact with the auricle, it runs obliquely inwards beneath the base of the 
heart along the auriculo-ventricular furrow; and finally opens by a wide orifice into 
the right auricle, to the left of, and somewhat before the inferior cava, i. e. in the 
ordinary situation of the orifice of the coronary sinus. 
The azygos vein exists on the right side, and on the left there is a small vein 
opening into the left cava, about 1^ inch below the cross branch, and close above the 
root of the lung: this small vein is a left azygos formed by the persistence of a part 
of the left cardinal vein : it fulfils the office of the left superior intercostal vein. The 
azygos and this small left azygos are also seen in Pi-ofessor Sharpey’s preparation. 
From the cross branch down to the root of the lung, i. e. outside the pericardium, 
the left cava is rather narrower than the right. It is placed close beneath the pleura, 
and supports upon its outer side the left phrenic nerve (14). It rests first upon the left 
carotid and subclavian arteries, and then on the arch of the aorta. The par vagum 
(13) descends further back than the vein, and gives off a branch, which accompanies 
the vessel to the heart. On a level with the upper border of the pulmonary artery, 
the vein pierces the fibrous layer of the pericardium (11, 11). 
Within the pericardium, as may be noticed in all the cases which have been fully 
described, the left vena cava becomes very much dilated. As it passes from the 
left pulmonary artery to the root of the subjacent pulmonary vein, it is lodged {v) in 
a tube-like fold of the serous membrane, the analogue of the vestigial fold. On the 
side and back of the left auricle (/ o), and afterwards along the course of the auriculo- 
ventrieular groove (a), the vessel is everywhere covered and bound down by the 
serous layer of the pericardium, and has muscular walls. 
In turning horizontally to the right it receives the coronary vein (g), which appears 
small, and courses rather over the left border of the ventricle than comes from 
between the ventricle and the auricle. Further on, a posterior {p) and then the 
middle (m) cardiac vein enter it from below. The large vessel itself (o) occupies the 
place of the short oblique vein usually found on the back of the left auricle. The 
lower dilated part of the left vena cava superior (a), occupying the place of the coro- 
nary sinus, is distinctly muscular, its fibres for the most part being circular and ap- 
Y 2 
