191-4.] NATURAL SCIENCES OF PHILADELPHIA. 421 



ra^ and ulnar, uP, arteries, fig. 4, A. The radial artery, in the 

 car]:>al region, divides in a complicated way into five main vessels 

 that extend into the digits. The ulnar artery gives off several 

 branches, to the forearm, but apparently does not connect directly 

 • with the branches to the digits. 



The primary carotid, capr. After leaving the heart, this very 

 largo vessel passes cephalad and laterad for some distance on the 

 left side of the body and then gives off, from its anterior side, the 

 large left subclavian artery, sc.s., to be described later. After 

 giving off the subclavian artery, it makes a short loop, still further 

 to the left, and then turns sharply mecliad to pass to the head in the 

 median plane directly dorsal to the oesophagus. Its distribution 

 in the cervical and cephalic region will be described later. The 

 mate to the oesophageal branch, oe (near heart), of the right sub- 

 clavian which was mentioned above is apparently sometimes given 

 off from the primary carotid near its base (as shown in fig. 4) and 

 sometimes as a branch of the left pleural artery. 



The left subclavian artery, sc.s., although it has a different origin, 

 has the same branches as described in connection with the right 

 subclavian. The exact order in which the first of these (the thyroid, 

 th; the internal mammary, im' ; the coUateralis colli, cc; the pleural, 

 plu, and the vertebral, v^) are given off is, as might be expected, 

 subject to some variation. 



The coUateralis colli, cc (following Bronn's nomenclature), whose 

 origin was noted above, will now be discussed; since the two are 

 alike only one need be described. After leaving the subclavian, it 

 passes cephalad, at the side of the trachea and oesophagus, in com- 

 pany with the internal jugular vein, so that in this part of its course 

 it would seem to be the internal carotid artery. It gives numerous 

 small twigs to the trachea and oesophagus, oe. In the region of 

 the posterior part of the huge jaw muscle it is connected directly, x, 

 with the adjacent branch, cm-, (called by Bronn the common carotid) 

 of the primary carotid, and indirectly, x^, with a complicated group 

 of branches from the common carotid. Cephalad to the connective 

 x^, which extends dorsad and is hence foreshortened in the figure, 

 the coUateralis colli gives off a small vessel, y (too large in fig 4), 

 to the shoulder and skin; it then sends a fairly large branch, jm, 

 into the large jaw muscle, close to which it now lies. Next a small 

 branch, Ig, is sent to the larynx. Continuing cephalad and laterad 

 (in figure 4 it is drawn further to the side than it actually lies) for a 

 short distance further, it divides into three branches: (1) a short 



