Practical Course, . 95 
Open up the muscular wall, a little on one side of the middle line, 
taking great care not to cut into the organs which lie below. Cut 
through the coracoid bone behind and the clavicle in front, which connect 
the breast-bone (sternum) with the shoulder joint. By clearing away 
the muscular wall on either side you will be sble to make out ;— in the 
middle line, the sternum, which terminates above and below in wide 
cartilaginous flaps ; and on the side the shoulder joint, where the humerus 
bone terminates in the glenoidal fossa formed by the junction of the 
clavicle and the coracoid bones in front and the scapula behind. 
Cut out the sternum altogether, taking care not to injure the heart 
which lies below. Now pia back the flaps of muscular tissue on either 
side, taking care not to damage the large central vein (anterior abdo- 
minal), which lies in the middle line. Notice also the large vein 
(muscular cutaneous) which leaves the myscle and joivs the sub-clavian 
vein on either side. You will now have exposed— , 
(1) In the middle line in front, the large heart, invested ina 
transparent membrane (pericardium). 
(2) On either side bebind the heart, the large reddish flaps of 
the liver. 
(3) Below the liver, you will see the stomach and part of the 
intestine coiled up in the lower part of the body cavity. 
Move the intestine carefully to one side, without cutting anything, 
and see the delicate urinary bladder, which lies in the hinder part of 
the body cavity. Also notice the two dark-reddish elongated kidneys 
that lie behind, and the yellow finger-like processes of the fat body. 
Now dissect off the pericardial membrane, so as to expose the vessels 
of the heart and make out — 
(1) The thick muscular chamber (ventricle), which occupies the 
apex of the heart. 
(2) he distended thin-walled auricles which lie at the base of the 
ventricle and from the outside appear to consist of but 
one chamber. 
(3) The thick-walled tube (truncus arteriosus) which arises from 
the right of the base of the ventricle in front of the 
auricles, and almost immediately divides into a right and 
left aortic arch. 
(4) On lifting up the ventricle and carefully bending the heart 
- forward towards the mouth, you wiil be able to make out 
the large thin-walled blood chamber (sinus venosus), 
where the blood collects before passing into the auricle. 
The sinus venosus consists of two chambers, The right 
chamber receives the venous blood from the two vene 
cave superiores and the vena cava inferior, while the left, 
