IN THE VENTRICLES OE THE VERTEBRATE HEART. 
493 
Fig. 20. Right and left ventricles of the sheep’s heart, seen anteriorly. Shows the direc- 
tion of the fibres of the superficial or first external layer of both ventricles, 
the track for the anterior coronary artery, &c. See page 468. 
Fig. 21. Right and left ventricles of the sheep’s heart, seen posteriorly. Shows the direc- 
tion of the fibres of the second layer of the right and left ventricles. See 
pages 475 & 476. 
Fig. 22. Right and left ventricles of the sheep’s heart with the septum exposed, seen 
posteriorly. Shows how the fibres of the second layer of the septum corre- 
spond in direction with those of the second layer of the right and left ventricles 
generally. See page 476. 
Fig. 24. Right and left ventricles of the sheep’s heart, seen posteriorly. Shows the 
direction of the fibres of the third layer of the right and left ventricles. See 
pages 476 & 477. 
Fig. 25. Right and left ventricles of the sheep’s heart with the septum exposed, seen 
posteriorly. Shows how the direction of the fibres of the third layer of the 
septum corresponds with the direction of the fibres of the third layer of the 
right and left ventricles generally. See pages 476 & 477. 
Fig. 27. Right and left ventricles of the sheep’s heart, seen posteriorly. Shows the 
fourth or central layer of the left ventricle, and the fifth layer of the right 
one. The fourth layer of the right ventricle is seen at pq of fig. 23. See 
pages 477, 478, & 479. 
Fig. 28. Right and left ventricles of the sheep’s heart with the septum exposed, seen 
posteriorly. Shows that the direction of the fibres on the septum corresponds 
with that of the deeper fibres of the fourth or central layer of the left 
ventricle. See pages 477 & 478. 
Fig. 23. Right and left ventricles of the sheep’s heart, seen anteriorly. Shows the 
direction of the fibres of the fourth or central layer of the right ventricle (p q), 
as compared with the direction of the fibres of the undissected left ventricle 
(dd”). They run at nearly right angles. See pages 477 & 478. 
Fig. 26. Right and left ventricles of the sheep’s heart, seen anteriorly. Shows the 
direction of the fibres of the fifth layer of the right ventricle (pq) as compared 
with the direction of the fibres of the third layer of the left one ( d d'). See 
pages 478 & 479. 
Fig. 29. Right and left ventricles of the sheep’s heart, seen anteriorly. Shows the 
direction of the fibres of the sixth layer of the right ventricle (p q) as com- 
pared with the direction of the fibres of the fourth layer of the left one (d d'). 
See page 479. 
PLATE XIV. 
Fig. 30. Right ventricle of the sheep’s heart. Shows the bone of the heart (c) in situ , 
direction of the fibres of the first layer, &c. See pages 467, 468, 474, & 475. 
mdccclxiv. 3 u 
