OF THE DIFFERENT MUSCLES. 147 



MUSCLES OF THE TRUNK. 

 PECTORAL REGION. 



The pectoral muscles constitute the breast. 



They are named — Pectoralis transversus, 

 Pectoralis magnus, 



Pectoralis parvus, (or Depressor scapu- 

 lar.) 



The first is inserted into the fascia of the arm, extending 

 from the elbow nearly half way down to the knee. It con- 

 fines the arm to the side in its motions. 



The magnus originates from the sternum, is inserted into 

 the os humeri, and serves to pull the point of the shoulder 

 backwards. 



The parvus, or depressor, originates from the inferior part 

 of the sternum, is inserted into the muscles covering the 

 shoulder joint, and assists the last named muscle. 



COSTAL REGION. SERRATUS MAGNUS. 



Origin. — From the bodies and transverse processes of the 

 fourth, fifth, sixth, and seventh cervical vertebras j and from 

 the eight anterior true ribs, as low down as their cartilage. 



Insertion. — By strong fascicula, into the upper and inward 

 part of the scapula. 



Use. — It constitutes the main attachment of the scapula 

 to the trunk, and is more or less concerned in all the motions 

 of the shoulder blade. 



The costal muscles are — Superficial costarum, 



Transversalis costarum, 

 Intercostalis externi, 

 " interni. 



They are all, more or less, concerned in dilating the thorax. 



STERNAL REGION 



Comprehends two small muscles that are employed in the 

 contraction of the chest, or raising the sternum, and con- 

 tracting the cartilages. 



They are named lateralis sterni, and sterno-costalis externi. 



