DIGESTIVE AND CIECULATOEY SYSTEMS 397 



each other, to open close together into the distal lirah of the 

 duodenum, about the middle of its length, and close to the 

 right bile-duct. 



The third pancreatic duct is longer than the others. It 

 leaves the gland near its anterior end, and runs forwards to 

 open into the distal limb of the duodenum, close to its junction 

 ■with the small intestine. 



Pin out the duodenum on a dissecting-ioard, and dissect 

 the bile-ducts and pancreatic dv^ts. The dissection is best 

 performed under water, and from the dorsal surface, j 



V. DISSECTION OF THE CIECULATOEY SYSTEM. 



A. The Heart. 



The heart of the bird is of large size, and is divided into four 

 cavities, those of the right and left sides being completely 

 separated from each other. The right side of the heart 

 receives the blood which is brought back by the veins from all 

 parts of the body, and drives it to the lungs to be aerated : from 

 the lungs it is returned to the left side of the heart, and thence 

 driven all over the body through the arteries. The right side 

 of the heart therefore contains venous blood, and the left side 

 arterial blood. 



Open the pericardial cavity so as to expose the heart fully ; 

 and dissect away the connective tissue and fat from the vessels 

 at the base of the heart. 



The heart is conical in shape, with the apex directed back- 

 wards and slightly to the left side. A line of fat, which en- 

 circles it, marks externally the division into auricular and 

 ventricular portions. 



1. The auricular portion is anterior in position, and forms 

 the base of the cone. It is thin-walled, dark in 

 colour, and distinctly divided into right and left 

 auricles, the division being indicated externally by a 

 line of fat. 



