146 
MR. MARSHALL ON THE DEVELOPMENT 
d. Changes which tahe place at Bh'th. 
The shrinking of the ductus arteriosus, and the simultaneous enlargement of the 
pulmonary artery and veins and of the left auricle, are accompanied by changes in 
the intrapericardial remnants of the left primitive vein. The pericardial fold is, as it 
were, invaded by the enlarging pulmonary vessels, and becomes relatively shorter, 
and more deeply concealed between the left pulmonary artery and the subjacent vein. 
The narrow opake streak running around the root of the pulmonary vein and along 
the back of the left auricle, pursues a longer course, and becomes attenuated of 
broken up. Lastly, as the left auricle expands, the oblique vein is less evident, and 
the true coronary vein and the coronary sinus become more alike to each other in 
direction and diameter. 
Vestiges in the Adult Condition (Plate I. fig. 1, Plate V.). — The relation of the left 
superior intercostal vein to the primitive vessel in different cases has been already 
noticed. Commencing from the trunk of this vein (Plate V. i), there may frequently 
be traced a few vertical Jibrous hands {f) lying beneath the pleura, posterior to the 
phrenic nerve, and usually accompanied by small blood-vessels and by a fine branch 
of the vagus nerve (13). Generally one of these bands may be actually followed 
to the left superior intercostal vein ; and in most cases they are continued downwards 
through the pericardium into the pericardial fold. 
This fold (Plate I. fig. 1, and Plate V. v), which might be named the vestigial fold of 
the pericardium, maybe compared to the broad ligament of the liver, after the closure 
of the umbilical vein. As far as I know, it has hitherto escaped attention, though it is 
probably always present in the ordinary condition, as I have found it in twenty-two 
adult hearts*. In one instance, it could not be distinguished in consequence of com- 
plete adhesion of the pericardial surfaces, and in another, adventitious bands of mem- 
brane occupied its usual position. Sometimes it is obscured by fat, deposited within or 
near it. To demonstrate this vestigial fold and the opake streak continuous with it 
below (which are almost unavoidably injured by dividing the great vessels within the 
pericardial sac), the heart, great vessels and pericardium, should be removed in con- 
nection with the root of the left lung ; after which, on opening the pericardium and 
drawing asunder the left pulmonary artery and the subjacent pulmonary vein, the 
fold will be seen passing nearly vertically across the deep interval between those 
vessels (Plate V. v). Besides a duplicature of the serous layer of the pericardium, 
including cellular and fatty tissue, the vestigial fold contains some fibrous bands, 
small blood-vessels and nervous filaments. Its opake well-defined and curved mar- 
gin is commonly from half to three quarters of an inch in length, but I have once 
found it measure upwards of an inch and a half. It varies in thickness in different 
* Senac states (Traite du Mouvement du Cosur, &c. Paris 1749, p. 14) that Hallek, in his account of the 
reflections and cornua of the pericardium, following Eustachius and Lancisi, has described, amongst many 
others, a falciform process (J^aulx) between the left pulmonary artery and veins ; hut I can only find in Haller 
a description of a “ saccus ”■ or depression between those vessels. 
