VIII.] 



THE MUSCLES. 



299 



the other side only by a narrow interval which is occupied 

 by a tendinous cord the linea alba. 



The fibres of the rectus are interrupted at intervals by 

 transverse tendinous intersections. 



A small pyramidalis muscle arises on each side of the 

 pelvis, and extends from the pubis to the linea alba. 



Quadratus lumborum. This is a mass of muscle situate 

 close to the vertebral column, and extending upwards from 

 the ilium to the last rib. 



Layers of fibres between adjacent ribs are called the ex- 

 ternal and internal intercostal muscles. The former extend 

 from the tubercles of the ribs to their cartilages. The latter 

 extend from the sternum to the angles of the ribs. The 

 intercostal nerves and vessels are interposed between them. 



The levatores costarum are small groups of fibres passing 

 obliquely downwards from the transverse processes to the 

 respective ribs at their proximal parts. 



Triangularis sterni is the name given to a layer of muscle 

 which diverges upwards to the cartilages of the ribs from the 

 deep surface of the lower part of the sternum. 



1 1. The DIAPHRAGM is a very important muscle for respira- 



VCJ 



-OB 



FIG. 275. THE DIAPHRAGM, viewed from the lower or abdominal side. 



V.C.I., the vena cava inferior ; CE, the oesophagus ; Ao, the aorta ; Th. D., the 

 thoracic duct, cut where they pass through the diaphragm, the broad white 

 tendinous middle of which is easily distinguished from the radiating muscular 

 fibres which pass down to the ribs and into the pillars in front of the vertebra;. 



