518 THE ARTERIES 



of the internal nianiniary, between the; su])eriur and inferior anterior intercostals, 

 and, })erforating the internal intereostal nmscles, pass forwards between the costal 

 cartilages to the pectoralis major, which they supply. The terminal twigs perforate 

 that nuisele close to the sternum, and are distributed to the integument. The 

 second, third, and fourth perforating supply the inner and deep surface of the 

 mammary gland, and become greatly enlarged during lactation. They frequently 

 require ligation in excision of the l)reast. 



(7) The lateral infracostal artery (Macalister) is given ofif close to the first 

 rib, and descends behind the ril)s just external to the costal cartilages. It anasto- 

 m(.)ses with the upper intercostal arteries. This vessel is often of insignificant size, 

 or absent. 



(8) The superior epigastric artery (fig. o44), or internal terminal branch of 

 the internal mammary artery, leaves the thorax behind the seventh costal cartilage 

 by passing through the costo-xiphoid space in the diaphragm. It is the direct 

 prolongation of the internal mammary downwards. In the abdomen it descends 

 behind the rectus muscle, between its posterior surface and its sheath, and, lower, 

 entering the substance of the muscle, anastomoses with the deep e})igastric, a 

 branch of the external iliac. It gives off the following small branches: — (ft) The 

 phrenic, to the diaphragm; (h) the xiphoid, which crosses in front of the ensi- 

 form cartilage, and anastomoses with the artery of the opposite side; (c) the cuta- 

 neous, which perforate the anterior layer of the sheath of the rectus and sui>i)ly 

 the integuments; {d) the muscular, to the rectus muscle, some of Avhich perforate 

 the rectus sheath laterally, and are distributed- to the oblique muscles; (e) the 

 hepatic (on the right side only), which pass along the falciform ligament to the 

 liver, and anastomose with the hepatic artery; (/) the peritoneal which perforate 

 the posterior layer of the sheath of the rectus, and ramify on the peritoneum. 



(9) The musculo-phrenic, or external terminal branch of tlie internal mam- 

 mary artery, skirts outwards and downwards behind the costal cartilages of the false 

 ribs along the costal attachments of the diaphragm, which it perforates opposite the 

 ninth rib. It terminates, much reduced in size, at the tenth or eleventh intercostal 

 space by anastomosing with the ascending branch of the deep circumflex iliac artery. 

 It gives off in its course the following small branches: — (a) The phrenic for the 

 supply of the diaphragm; (h) the anterior intercostals, two in number for each 

 of the lower five or six intercostal spaces, are distril)Uted like those to the upper 

 spaces, already described, and anastomose like them with the corresponding branches 

 of the lower aortic intercostals; (c) the muscular for the supply of the obliciue 

 muscles of the abdomen. 



Braxches of the Second Paet of the Subceavian Autery 



THE SUPERIOR INTERCOSTAL ARTERY 



1. The superior intercostal artery (fig. 845) usually arises from the back part 

 (»f the second portion of the subclavian artery, behind the scalenus anticus on the 

 right side, but sometimes just internal to that muscle on the left side. It at first 

 runs backwards and a little upwards above the apex of the pleura, and then turns 

 downwards and enters the thorax in front of the neck of the first rib. It termi- 

 nates in a l)ranch which runs forwards in the first intercostal space. Frequently, 

 and especially on the right side, it is continued in front of the neck of the second 

 rib, and sup])lies a branch to the second intercostal space. This branch may then 

 be reinforced by an intercostal from the aorta, wdiich supplies the space when the 

 branch is not present. As the superior intercostal crosses the neck of the first rib, 

 it lies internal to the anterior branch of the first dorsal nerve, and external to the 

 superior thoracic ganglion of the sympathetic. That part of the superior intercostal 

 which intervenes lietwei'u its origin from the subclavian and its first branch, is 

 sometimes called the costo-cervical artery. 



Branches. — The sujx'rior intercostal gives off: — (1) The deep cervical; (2) 

 the first intercostal; and (3) the arteria aV)errans. 



(1) The deep cervical branch is given off from the sujierior intercostal just 



