258 JAMES W. PAPEZ 
The septal raphe (figs. 1 and 2, R) is the portion of the atrial 
septum in front of the oval fossa in which most of the large muscle 
bundles of both of the atria commence. I have designated it 
the septal raphe because the term suggests that this is the seam 
along which the atria are knitted together. It is best seen on 
the internal surface of the atria when the endocardium has been 
removed, but its anterior margin appears in a vertical groove 
on the anterior surface of the atria below the interatrial band 
as shown in figure 5. 
The septal raphe, as shown in figures 1 and 2, R, forms an 
irregular line in the septum that extends from the front of the 
atrioventricular node of Tawara to the front of the superior 
vena cava where it turns to the right to join the head of the sino- 
auricular node. This continuity is along the external or anterior 
surface of the right posterior crest (4). On the right surface of 
the septum (fig. 1) the principal portion of the raphe is about 
1.5 em. above and in front of the atrioventricular node region 
and is covered by superficial strata of right posterior crest (4) 
and right leaf of the septum secundum (7), which have a lower 
and variable origin. These strata have a variable origin in 
different hearts and obscure the raphe. From the right side 
of the raphe arise the right anterior crest (3), right posterior 
crest (4), right leaf of the septum secundum (7), right leaf of 
the septum primum (8), septocoronary bundle, intercaval bundle 
(5), and the left radiate bundles of the superior vena cava (6b). 
On the left surface of the septum (fig. 2) the raphe, as seen from 
the inner surface, extends along a long s-shaped line. The upper 
end of it is situated just behind the interatrial band, which is 
on the anterior surface of the atrial junction. This portion of 
the raphe gives origin to the septopulmonary bundles (12) and 
the upper portion of the intercaval bundle (5) and the left leaf 
of the septum secundum (13). The middle portion of it is 
situated in front of the oval fossa adjacent to the principal 
portion on the right side and gives origin to the large left septo- 
atrial bundle (14). The lower portion of it is situated below 
the oval fossa opposite the region of the atrioventricular node 
close to the junction of the atrial and ventricular septa and gives 
origin to the large left leaf of the septum primum (14). 
