THE HEART. 



317 



were injected with red and blue plaster respectively. After the plas- 

 ter had hardened, a small hole was made in the left ventricle and a 

 long canula inserted and pushed through the auricula-ventricular 

 opening into the left auricle. Red plaster was then injected so as 

 to fill the pulmonary veins. Finally, the pericardium was removed 

 together with the fat and connective tissue covering the cardiac 

 vessels. 



825. Description. This, the dorsal or " posterior " aspect of the heart, is less famil- 

 iar to most persons and less frequently represented. It is, however, much more compre- 

 hensive and instructive than the ventral aspect, 

 and is given in the following works : Quain, A, 

 II, Fig. 166 ; Smith, E. N., A, PI. 55 ; McAl- 

 pine, B, PI. XXIII, Fig. 3 (rabbit) ; Gegenbaur 

 (Lankester), A, Fig. 336 (pig). 



The present figure fairly represents the size 

 of a somewhat large heart, and its form when 

 injected. As stated, however, in 829, it is 

 probable that the less thickness of the lateral 

 wall of the right ventricle has permitted it to 

 yield to the force of the injection so that the 

 right side is unduly convex. 



The word ventriculi is written across the 

 apex of the ventricular portion, and the abbre- 

 viation V. crd. is just below the furrow between 

 that and the auricular portion. 



For the sake of showing certain parts more 

 distinctly, the figure represents the organ as if 

 rotated slightly upon its longer axis so as to ex- 

 pose more of the right than of the left side. 

 The line of demarcation between the right and 

 left auricles (Aur. dxt., Aur. sin.) coincides 

 nearly with a line connecting the V. of V. crd. 

 with the left border of the prcecava. The duatus 

 arteriosus ( 867) is not shown. 



826. General Description of the Heart. 

 The heart is a hollow, quadrilocular (four cham- 

 bered) muscular organ situated in the thorax. 

 It is the anatomical and physiological center of 

 the vascular system, simultaneously receiving 

 blood from the lungs and from all other parts of the body, and distributing it thereto. 



827. Location. As seen in Fig. 77, 99, 101, the heart is on the meson, but extends 

 a little farther to the left than to the right. In Fig. 101 it appears at a considerable dis- 

 tance from the diaphragm, but of the latter only the dorsal portion remains, and its 

 cephalic convexity is really very clos'j to or in contact with the heart. 



828. Pericardium. The heart proper is enveloped in a nbro-membraneous sac, the 

 pericardium, which is attached about the rootsof the great vessels, but elsewhere is uncou- 

 nsctsd with the heart, which thus moves freely within it. The pericardium is best studied 



FIG. 91. THE DORSAL ASPECT OP THE 

 HEART WITH THE CENTRAL Pou- 

 TIONS OP THE LARGER VESSELS; 

 from a Maltese cat ; x 1. 



