456 
Proceedings of the Royal Society 
the auricle. There did not appear to be any deficiency in the thick- 
ness of the muscular coat of the superior cava. 
The Eustachian valve projected for upwards of an inch into the 
auricular cavity, and presented in a remarkable degree the fenes- 
trated character which that valve occasionally exhibits in the 
adult heart. At its left extremity it subdivided into two parts, 
one of which passed in the usual way to the auricular septum, 
and became continuous with the annulus ovalis, whilst the other 
was blended with the valve at the mouth of the coronary sinus, 
which also exhibited a fenestrated appearance. 
A. Aorta. P. Pulmonary artery. SC. Superior, and IC. Inferior cava. 
* The fibrous cord connecting the two valves. C Coronary sinus, — From a 
drawing of the specimen by Mr T. D. Nicholson. 
Owing to its fenestrated condition, and small size, when com- 
pared with the orifice of the superior cava, it is obvious that the 
valve situated at the mouth of that great vein could have had 
but little influence in preventing the regurgitation of blood during 
the contraction of the auricle in the adult heart. But it is 
probable that in the foetal stage of this heart the backward flow 
wall of the auricle, almost as far as the orifice of the superior cava, but no 
valve existed at the mouth of the superior cava. 
