DISTRIBUTION OF BLOOD-VESSELS, 255 



which these multifarious and complicated opera- 

 tions were so deeply planned, and so harmoniously 

 adjusted ! 



§ 4. Disfrihufion of Blood-vessels. 



In the distribution of the arteries in the animal 

 system, we meet with numberless proofs of wise 

 and provident arrangement. The great trunks of 

 both arteries and veins, which carry on the circu- 

 lation in the limbs, are conducted always on the 

 interior sides, and along the interior angles of the 

 joints, and generally seek the protection of the 

 adjacent bones. Grooves are formed in many of the 

 bones, where arteries are lodged, with the evident 

 intention of affording them a more secure passage. 

 Thus the principal arteries which supply the mus- 

 cles of the chest, proceed along the lower edges of 

 the ribs, in deep furrows formed for their protection. 

 Arteries are often still more effectually guarded 

 against injury or obstruction by passing through 

 complete tubes of solid bone. An instance occurs 

 in the arteries supplying the teeth, which pass 

 along a channel in the lower jaw, excavated 

 through the whole length of the bone. The aorta 

 in fishes, after having supplied arteries to the vis- 

 cera of the abdomen, is continued to the tail, and 

 passes through a channel, formed by bony pro- 

 cesses from the vertebrae ; and the same kind of 

 protection is afforded to the corresponding artery in 

 the Cetacea. In the fore leg of the Lion, which is 

 employed in actions of prodigious strength, the 

 artery, witliout some especial provision, would have 



