PART 1. 



THE ÏÏEAET AND BLOOD-YESSELS. 



I. THE HEART. 



(The original arrangement of this section has been modified.) 



The heart is situated in the middle line above the central portion 

 of the shoulder-girdle and M. stefnohjoicleus, and below the 

 oesophagus; the apex is directed backwards and lies between the 

 lobes of the liver, the base is directed forwards and lies a short 

 distance behind the larynx. The heart is surrounded by the 

 pericardium. 



A. The Pericardium [is a 

 very thin membranous sac, 

 which completely encloses the 

 heart ; it is attached, at some S'- - 

 distance, to the large vessels P.--'' 

 passing to and from the heart, 

 and has inserted into it some ^^■' 

 fibres of the M. oUiqmis ah- TA.- 

 domhiis internes (see page 70). 

 A fold of the pericardiimi 

 extends from the dorsal sur- 

 face to the truncus arteriosus, 

 and through it courses the 

 vena eardiaca. 



The pericardium is a con- 

 nective-tissue membrane, and 

 is lined on either side with 

 endothelium, which is in part 

 ciliated (Leydig); the endo- 

 thelium of the inner surface 

 is continued on to the heart 



AC. 



LA. 



