404 THE MUSCLES AND FASCIA 



of ligation of the common carotid artery and in some other operations. Between the sternal 

 and clavicular heads is a slight depression, most marked when the muscle is in action. This 

 is bounded below by the prominent sternal extremity of the clavicle. Between the sternal origins 

 of the two muscles is a V-shaped space, the suprasternal notch, more pronounced below, and 

 becoming toned down above, where the Sternohyoid and Sternoth \ roid muscles, lying upon 

 the trachea, become more prominent. Above the hyoid bone, in the middle line, the anterior 

 belly of the Digastric to a certain extent influences surface form. It corresponds to a line drawn 

 from the symphysis of the mandible to the side of the body of the hyoid bone, and renders convex 

 this part of the hyomental region. In the posterior triangle of the neck, the posterior belly of 

 the Omohyoid, when in action, forms a conspicuous object, especially in thin necks, presenting 

 a cord-like form running across this region, almost parallel with, and a little above, the clavicle. 



MUSCLES AND FASCLffi OF THE TRUNK. 



The muscles of the Trunk may be arranged in four groups, corresponding 

 with the region in which they are situated. 



I. The Back. III. The Abdomen. 



II. The Thorax. IV. The Perineum. 



I. MUSCLES OF THE BACK. 



The muscles of the back are very numerous, and may be subdivided into five 

 layers: 



FIRST LAYER. Longissimus dorsi. 



m . Spinalis dorsi. 



1 rapezms. 



Latissimus dorsi. 



Cervical Region. 



SECOND LAYER. Cervicalis ascendens. 



Levator anguli scapulae. Transversalis cervicis. 



Rhomboideus minor. Trachelomastoid. 



Rhomboideus major. Complexus. 



rJiventer cervicis. 

 Spinalis colli. 



THIRD LAYER. 



Serratus posticus superior. 



Serratus posticus inferior. FIFTH LAYER. 



Splenius capitis. 



Splenius colli. Semispmahs dorsi. 



- t Semispinalis colli. 



Multifidus spinae. 

 FOURTH LAYER. Rotatores spinae. 



Supraspinales. 

 Sacral and Lumbar Regions. Interspinales. 



Erector spinae Extensor coccygis. 



Intertransversahs. 



Dorsal Region. ? ectus ^P*! 8 P ost ! cus ma J or " 



Kectus capitis posticus minor. 



Iliocostalis. Obliquus capitis inferior. 



Musculus accessorius ad iliocostalem Obliquus capitis superior. 



