of Edinburgh, Session 1868 - 69 . 
457 
into the vein would have been very considerably impeded by its 
presence; for there is reason to believe that the fenestrated state, 
not only of this, but of the other valves at the mouths of the great 
veins, is due to atrophy taking place after birth. As the muscular 
coat of the superior cava possessed its usual thickness, the valve 
was obviously not developed to compensate for any deficiency in 
that portion of the wall of the great vein. 
As the Eustachian valve at the mouth of the inferior cava serves 
in the foetus to direct the current of blood passing upwards along 
that vein through the foramen ovale, it is possible that the valve 
at the mouth of the superior cava may have exercised some direct- 
ing effect on the blood which entered the auricle by the latter 
vessel. From its position it would, I think, have directed the 
blood of the superior cava away from the auricular septum, and 
thus have aided in preventing, during the foetal condition, the 
mingling of the blood of the two cavse in the auricular cavity. 
The occurrence of such a valve is not, however, of interest 
merely in its physiological relations : it possesses also a morpholo- 
gical value. For it may be regarded as presenting in the human 
heart a rudimentary example of an arrangement which is met with 
in the heart of the bird. If the heart of a large bird, e,g., the 
ostrich ( Struthio camelus ), be examined, it may be seen that the 
sinus, into which the venee cavas open, is separated from the auricle 
proper by a large double muscular valve. The right segment of this 
valve is related not only to the mouth of the right superior cava, 
but extends down the wall of the auricle to the mouth of the inferior 
cava, and is then prolonged as far as the mouth of the left supe- 
rior cava, which may be regarded as representing in position the 
coronary vein in the human heart. Now, in this specimen it will 
be remembered that the valve at the mouth of the superior cava 
was continued, through the intermediation of a fibrous cord (*), into 
the Eustachian valve, and that the latter again was directly united 
with the valve at the mouth of the coronary sinus. 
As additional illustrations of the tendency to the development 
of rudimental structures in this individual, it is of interest also to 
mention that he had in each upper arm a processus supra-condy- 
loideus humeri internus , the relations of which to the supra-condy- 
loid foramen of various of the mammalia, more especially of the 
