THE DISTRIBUTION OF ARTERIES. 129 



The anterior aorta is continued single unto between the 

 second and third rib ; where it divides into its right and left 

 branches, called arteri(B mnominatfE (Fig 9.2). The left 

 division supplies the dorsal to the back ; and (Fig 9 . 4) 

 one branch, which penetrates between the first and second 

 ribs, under the name of posterior cervical, to afford nur- 

 ture to the neck {Fig 9.5): afterwards, passing towards 

 the first rib, it gives off the left vertebral. The vertehrals 

 (Fig 9 . 6) are two important arteries : they are given off 

 opposite the first ribs ; and pass under the transverse process 

 of the last cervical vertebra ; and are continued upwards 

 through the foramina at the base of the transverse processes 

 of the remaining six of these vertebrae. As they pass, they 

 send off small branches through the lateral notches in the 

 vertebrae to the spinal marrow ; likewise to the muscles 

 of the neck. Approaching the head, they give a branch, 

 wdiich usually passes through a foramen in the wing of the 

 atlas to communicate with the external carotid {Fig 11 . 4) . 

 After they have made a number of inflections, apparently 

 to retard the circulation, they join branches, and form 

 the basillary artery, that runs along the base of the medulla 

 oblongata {Plate V. Fig 2). 



After the vertebrals the innominatae, give off the internal 

 and external pectorals, which go to the breast {Fig 9 . 10, 11): 

 w^hen, bending its course over this rib, it takes the name 

 of axillary {Fig 9.7). The right division of the anterior 

 aorta is much larger, as well as longer, than the left. In 

 its course, having furnished some considerable branches 

 w^hich mainly correspond with those given off to the left 

 side, it becomes the common carotid {Fig 9.8); which 

 directing itself forwards divides into the right and left caro- 

 tids {Fig 9 . a, b. Plate VIII. h). 



The axillary artery {Fig 10 . a), as furnishing the whole 

 of the fore extremities with blood, must be deemed very 

 important. The trunk of the vessel curves over the first rib, 

 to reach the innermost side of the fore limb. After having 

 pursued its course for a short distance it gives branches to 

 the scapula, and becomes the humeral. The humeral artery 

 descending along the internal surface of the humerus, gives a 

 considerable branch to the flexor brachii ; as well as others to 

 the scapula {Fig \0 . b,c, d, e, g, i, i, i) : here also it often 



K 



