the Foramina Thehesii of the Heart , 107 
pulmonary vessels, are avoided ; and which I next beg leave 
to explain. 
Having formerly been much surprised to find the heart so 
little affected, when the lungs were greatly diseased, and ob- 
serving, in one or two instances, that the foramen ovale was 
open, I was led to pay more particular attention to the state of 
that part ; and I have found this to be almost a constant occur- 
rence in those subjects where pulmonary consumption had for 
some time existed previous to the person’s decease. I took no- 
tice of this circumstance thirteen times in the course of one year; 
and, in several instances, the aperture was sufficiently large 
to admit of a finger being passed through it. Now, as the 
septum aurj,cularum is almost constantly perfect in subjects 
whose lungs are healthy, I cannot but conclude, that the re- 
newal of the foramen ovale is the effect of disease: nor will the 
* 
opinion appear, on reflection, improbable ; for the opening be- 
comes closed by the membranous fold growing from one edge 
of it, till it overlaps the other, and their smooth surfaces being 
kept in close contact, by the pressure of the blood in the left 
auricle, they gradually grow together. But, should there be a 
deficiency of blood in the left auricle, and a redundance in the 
right, the pressure of the latter on this membranous partition, 
will so stretch and irritate the uniting medium, as to occasion 
its removal ; and thus a renewal of the communication between 
the auricles will again take place. 
From these observations it is natural to suppose, that in 
those men, or animals, who are accustomed to remain long un- 
der water, this opening will either be maintained or renewed : 
yet on this circumstance alone the continuance of their life 
does not depend ; for we now have sufficient proof, that if the 
P 2 
