930 A MANVAL OF ANATOMY 



The aortic intercostal and collateral intercostal arteries give 

 branches to the intercostal muscles and ribs. Those of the third, 

 fourth, and fifth spaces, at least, furnish branches to the mammary 

 gland and pectoral muscles, which anastomose with the thoracic 

 branches of the acromio-thoracic artery from the first part of the 

 axillary, and with the long thoracic from the second part of that 

 vessel. The first aortic intercostal artery, as it enters the third 

 intercostal space, gives off a branch which ascends to the back part 

 of the second intercostal space, and anastomoses with the branch 

 of the superior intercostal artery to that space. 



Anterior Series, — The internal mammary artery furnishes two 

 anterior intercostal arteries to each of the upper six intercostal 

 spaceSy and the musculo-phrenic branch of the internal mammary 

 furnishes two anterior intercostal arteries to each of the seventh, 

 eighth, and ninth in tercostar spaces. The arteries of the upper six 

 spaces lie at first upon the triangularis sterni muscle, and then 

 upon the parietal pleura, being under cover of the internal inter- 

 costal muscle. Afterwards all the anterior intercostal arteries pass 

 between the external and internal intercostal muscles. In each space 

 they anastomose with the aortic intercostal and collateral intercostal 

 arteries, and also with the corresponding intercostal arteries of the 

 upper two spaces. 



Branches. — ^These are distributed to the intercostal muscles, ribs, 

 mammary gland, and pectoral muscles. 



The lower two intercostal spaces are not furnished with anterior 

 intercostal arteries. The aortic intercostal arteries of these spaces, 

 after leaving them, enter the abdominal wall, and pass forwards 

 between the internal oblique and transversalis muscles to the rectus 

 abdominis, in which they anastomose with the superior epigastric 

 and deep epigastric arteries. 



Intercostal Veins. — ^These veins accompany the corresponding 

 arteries. 



The chief intercostal vein passes backwards in the subcostal groove 

 of the upper rib, in company with the aortic intercostal artery, 

 above which it lies. In the region of the angle of the rib it is joined 

 by the collateral intercostal vein, which accompanies the correspond- 

 ing artery. Close to the vertebral column the chief intercostal vein 

 receives a large dorsal branch, which returns blood from the muscles 

 and integument of the back, the dorsal spinal venous plexus, and 

 the spinal canal. The mode of termination of the chief intercostal 

 veins differ on each side, and will be described in connection with 

 the dissection of the posterior wall of the thorax. 



The anterior intercostal veins accompany the anterior intercostal 

 arteries. Those of the upper six intercostal spaces pass to the 

 internal mammary, and those of the succeeding three spaces pass 

 to the musculo-phrenic, veins. 



Intercostal Lymphatics. — ^The lym]:)hatic vessels of the intercostal 

 spaces pass partly to the posterior intercostal glands, which lie at 

 the back parts of the intercostal spaces, and partly to the anterior 



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