44 



A MANUAL OF ANATOMY 



is occupied by the third part of the subclavian artery and the 

 trunks of the brachial plexus of nerves. Behind the posterior 

 groove, and extending as far back as the tubercle, there is a 

 rough impression for the insertion of the scalenus medius. The 

 inferior surface is flat and covered by the costal pleura. Near the 

 external border it gives attachment to the internal intercostal 

 muscle of the first space. The internal border, which is thin and 

 concave, gives attachment to Sibson's fascia. Fully i inch from 



_ Scalenus Posticus 



Groove for Subclavian Artery 

 Scalenus Anticus 

 Serratus Magnus 



Groove for Subclavian 

 Vein 



Sternal Extremity 

 Subclavius 



Fig. 30. — The First and Second Ribs of the Left Side 

 (Superior View). 



the anterior extremity this border presents a projection, called the 

 scalene tubercle or spine {tuhercU of Lisfranc), for the insertion of 

 the scalenus anticus. It encroaches slightly on the adjacent part 

 of the superior surface, and is inclined backwards. The external 

 border is convex. It gives attachment to the external inter- 

 costal muscle of the first space, and a portion of the first serration 

 of the serratus magnus at a point opposite the groove for the sub- 

 clavian artery, where the external border is often prominent. The 



