492 
DR. PETTIGREW ON THE ARRANGEMENT OE THE FIBRES 
v. Posterior and inner segment of the bicuspid valve, attached by its chord® 
tendine® to the musculi papillares. 
y y The anterior musculus papillaris, consisting in this instance of two 
portions, from the fibres composing it never having fully united. 
x. Posterior musculus papillaris, likewise terminating in muscular processes. 
z. Carnese column®, forming a rich network which lines the interior of the 
ventricle. 
s s'. Vertical section of the ventricular wall, showing how it tapers towards 
the base and the apex. 
Fig. 16. Wax cast of the interior of the right ventricle of a deer’s heart, seen anteriorly. 
Shows the spiral nature of the cavity. See page 482. 
l. Eight auriculo-ventricular opening. 
7c. Conical-shaped spiral infundibulum or conus arteriosus, with the spiral 
grooves occasioned by the projection of the carnese column® into it. 
These grooves facilitate the passage of the blood towards the pulmonary 
artery during the systole. 
h. Depression caused by the head of the right anterior musculus papillaris. 
m. Eight apex, the peculiarity of which consists in its being more blunted, 
and less distinctly spiral, than that of the left apex. 
Fig. 17. Wax cast of the interior of the left ventricle of a deer’s heart. Shows the 
peculiar spiral twist of the left ventricular cavity, and how, like the wall, it 
tapers towards the base and the apex. See pages 462 & 482. 
b. Left auriculo-ventricular opening. 
x. Spiral track of the posterior musculus papillaris. 
y. Spiral track of the anterior musculus papillaris. 
z w b. Projecting spiral ridge, corresponding to one of the spiral grooves or 
hollows found between the spiral musculi papillares. 
z . Left apex, twisting rapidly upon itself and terminating in a point. The 
left ventricular cavity is widest at the upper part of its middle third (w), 
and the amount of spiral made by it rather exceeds a turn and a half. 
Note. — Figs. 16 & 17 give the exact shape of the ventricular cavities, and 
consequently the precise form assumed by the blood, prior to the systole. 
PLATE XIII. 
Fig. 18. Eight and left ventricles of the sheep’s heart, seen posteriorly. Shows the 
superficial or first external layer of both ventricles. See pages 467 & 468. 
Fig. 19. Eight and left ventricles of the sheep’s heart, seen posteriorly, the right ventri- 
cular wall being divided and separated to expose the septum. Shows how 
the direction of the fibres of the first layer of the septum corresponds with 
the direction of the fibres of the first layer of the right and left ventricles. 
See pages 468 & 469. 
