MUSCLES OF THE BODY. 151 



(Fig. 68, /), latissimus dorsi (Fig. 68, ;//), serratus posterior 

 inferior (Fig. 73, w) and superior (Fig. 73, /), serratus anterior 

 (Fig. 73, z), scalenus (Fig. 73,/), and iliocostal (Fig. 69, //). 

 Inner surface with the internal intercostals (Fig. 69, /). 



Action. Protractors of the ribs. 



Mm. intercostales intern! (Fig. 69, k). The internal 

 intercostals are similar to the external intercostals, beneath 

 which they lie. Their fibres pass between the ribs at nearly 

 right angles to those of the external intercostals and have nearly 

 the direction of the fibres of the internal oblique. They occupy 

 all the intercostal spaces from the first to the thirteenth ribs. 



Relations. Quter surface with the external intercostals 

 (Fig. 69, 2), and ventrad with the scalenus (Fig. 73,/;, trans- 

 versus costarum (Fig. 73, _/), and rectus abdominis (Fig. 

 73, k}. Inner surface with the pleura and the transversus 

 thoracis. 



Action. Retractors of the ribs. 



M. transversus thoracis (triangularis sterni ; sternocostalis 

 internus). This represents a thoracic portion of the transversus 

 abdominis. It consists of five or six flat muscular bands lying 

 on the inner surface of the thoracic wall. 



Origin on the lateral borders of the dorsal face of the 

 sternum, opposite the attachments of the cartilages of the third 

 to the eighth ribs. The six bands thus formed, each about one 

 centimeter wide, pass laterad and are inserted into the cartilages 

 of the ribs near their junction with the ribs, and into the fascia 

 which covers the inner surface of the internal intercostals in this 

 region. 



Relations. Outer surface with the internal intercostals and 

 the cartilages of the ribs. Inner surface with the pleura. 



Diaphragma (Fig. 74). The diaphragm consists of a cen- 

 tral so-called semilunar tendon (e) and of muscular fibres which 

 pass radially from the body wall to the tendon. It forms a 

 complete oblique partition between the abdominal and thoracic 

 cavities. The dorsal end is farther caudad than the ventral. 



The central tendon (e] is thin and irregularly crescent- 

 shaped, with the convexity ventrad and the horns of the cres- 

 cent prolonged as two tendinous bands (/) which end in two 



