COLUMBA. 367 
heart. Here it bends into the middle line and proceeds to 
the hind-end of the body as the dorsal adrta. Its main 
branches are celiac, anterior mesenteric, paired renals, 
Jemorals, sciatics and internal tlacs, and it terminates in 
the tail as the caudal artery. 
Fig. 259.—VENTRAL VIEW OF THE ARTERIAL SYSTEM 
OF THE PIGEON. (Ad nat.) 
GH 
Systemic Arch.-—~ 
\ Innominate (left). 
LS. 
Hire 
Dorsal Aorta. Anterior 
Mesenteric. 
re Renal. 
A Femoral 
Renal. 
Sciatic. 
Renal. 
Internal Iliac. Internal Iliac. 
Posterior . 
Caudal. Mesenteric. 
The anterior arterial system is peculiar in lying super- 
ficially to the venous system. Apart from the four- 
chambered heart, which is shared by mammals, the blood- 
vascular system of the pigeon is chiefly remarkable for 
the very high temperature of the blood, the systemic arch 
persisting only on the right, and the large size of the 
pectoral arteries and veins. 
If the heart be now removed, the trachea can be traced 
throughout its length till it bifurcates into the two bronchi. 
At its front-end is a /axynx which, however, is not an organ 
for producing sounds in the bird. The trachea is distended 
