IN THE VENTRICLES OE THE VERTEBRATE HEART. 
483 
Shape of the right and left ventricular cavities , as shown hy casts and transverse sections. 
As it is difficult to obtain a correct idea of the shape of the ventricular cavities, a 
detailed description of them may prove not unacceptable. The left ventricular cavity in 
the fresh heart of the deer, at the extreme base (if the aortic opening is not included), 
is more or less circular in form (Plate XII. fig. 17, h). Half an inch or so from the 
base (Plate XV. fig. 49, h) it changes from the circular to the oval, and is slightly in- 
creased in size from the fact of the left ventricular cavity tapering from its middle 
third towards the base (Plate XII. fig. 17, h). In this portion of the left ventricular 
cavity (Plate XV. fig. 49), the chordae tendineae and the segments of the bicuspid valve 
hang loosely. 
Receding from the base to the extent of fully an inch (Plate XV. fig. 50, h ), the 
appearance of the left ventricular cavity again changes — the change in this instance 
being caused by the projection into it of the flattened oblique heads of the papillary 
muscles (x,y), which convert it from an oval shape into an irregularly triangular one 
(Plate XII. fig. 17, w). 
Proceeding an inch or so nearer the apex, the left ventricular cavity (Plate XV. 
fig. 51, h) becomes smaller and more decidedly triangular, and is, from the prominence 
of the carnese columnse and musculi papillares (Plates XII. &XV. figs. 17 & 51, xy), some- 
what bayonet-shaped. The bayonet- shaped appearance of the cavity becomes better 
defined as the extreme apex is reached (Plate XV. figs. 52 & 53, h ), the cavity itself 
becoming smaller and smaller until it terminates in a point (Plate XII. fig. 17, z ). 
The right ventricular cavity (Plates XII. & XV. figs. 16 & 49, l), which is as it were 
applied to or round the left one (Plates XII. & XV. figs. 17 & 49), is also conical- 
shaped (Plate XII. fig. 16). It agrees with the left in having nearly the same vertical 
measurement, but differs from it in having a considerably greater antero- posterior 
measurement, and a decidedly less transverse one (Plate XV. compare h and l of fig. 49). 
Its shape at the extreme base, owing to the spindle-shaped constriction (fleshy pons) 
which separates it from the opening for the pulmonary artery, is oval * (Plate XV. 
fig. 46, l). Half an inch from the base it is concavo-convex (Plate XV. fig. 49, l), and, 
from the protruding of the carnese columnse and musculi papillares (h) at this point, 
more or less irregular. The chordae tendinese and the segments of the tricuspid valve 
hang loosely in this portion of the right ventricular cavity. 
Receding from the base in the direction of the right apex an inch and a half or so 
(Plate XV. fig. 50), the shape of the right ventricular cavity ( l ) is still concavo-convex ; 
it is moreover slightly diminished in its antero-posterior and transverse diameters, in 
conformity with its conical nature (Plate XII. fig. 16). Proceeding to within a quarter 
of an inch of the right apex, the right ventricular cavity (Plate XII. fig. 12, m, and 
Plate XV. fig. 51, l ) is seen to maintain its concavo-convex shape, and to taper gradually 
until it terminates in a blunted extremity (Plate XII. fig. 16, m ). 
* In this description the infundibulum, or conus arteriosus, is regarded as projecting beyond what is com- 
monly regarded as the base. 
