SANGUIFEROUS SYSTEM. 505 



but two branches sent from the arch of the aorta, for the 

 nourishment of the anterior parts of the body, and this 

 structure has been observed among species the most dissi- 

 milar of nearly all the orders of this class. In some of the 

 cetacea, pachyderma, and edentata, and in most of the 

 rodentia, masupialia, and carnivora, the first trunk from the 

 arch of the aorta is the great brachio-cephalic or innominata 

 which gives off the right subclavian and the two common 

 carotids, and the second or left trunk from the aortic arch 

 is the left subclavian, which arises separately as in man. 

 In some of the cheiroptera and insectivora, as vespertilio and 

 talpa, the two aortic trunks consist, as in most of the feathered 

 tribes, of two similar brachio-cephalic arteries which divide 

 each into a subclavian and a common carotid. In the lowest 

 herbivorous quadrupeds, the ruminantia and the allied solid- 

 ungulous pachyderma, one trunk only arises from the arch 

 of the aorta as in the chelonian reptiles, but this single great 

 brachio-cephalic trunk here divides into two unequal branches, 

 the larger on the right side giving off the right subclavian 

 and the united trunk of both common carotid arteries, and 

 the smaller branch being the subclavian artery of the left 

 side. In the elephant, however, the right as well as the left 

 subclavian has a separate origin, making thus three branches 

 from the arch of the aorta, the middle one of which is the 

 united trunk of the two common carotid arteries. 



In the higher quadrumana and in man, as seen in the an- 

 nexed figure (142) of the adult and foetalhuman vascular trunks, 

 there are three branches from the arch of the aorta, for the 

 anterior parts of the body, the first being the right brachio- 

 cephalic or arteria innominata (142. A. g. h.) which divides 

 into the subclavian and common carotid of the right side, the 

 second forming the left common carotid (142. A. i.), and the 

 third branch being the subclavian (142. A. k.) of the left 

 side. The same structure is seen in some insectivorous and 

 carnivorous quadrupeds, as the hedgehog and seal, and in 

 some of the lower orders of mammalia, as in the beaver, the 

 hamster, the rat, the sloth, the armadillo, the ant-eater, and 

 the ornithorynchus ; and most of the other normal forms of 

 these aortic trunks met with in inferior tribes, occasionally 

 present themselves as abnormal varieties in the human body. 

 So that the arterial trunks which most generally come off 



