346 MUSCLES AND FASCIAE. 



8. LATERAL VERTEBRAL REGION. 



Scalenus Anticus. Scalenus Medius. 



Scalenus Posticus. 



The Scalenus Anticus is a conical-shaped muscle, situated deeply at the side 

 of the neck, behind the Sterno-mastoid. It arises by a narrow, flat tendon from 

 the tubercle on the inner border and upper surface of the first rib.; and, ascend- 

 ing almost vertically, is inserted into the anterior tubercles of the transverse 

 processes of the third, fourth, fifth, and sixth cervical vertebrae. The lower 

 part of this muscle separates the subclavian artery and vein ; the latter being 

 in front, and the former, with the brachial plexus, behind. 



Relations. In front, with the clavicle, the Subclavius, Sterno-mastoid, and 

 Omo-hyoid muscles, the transversalis colli, and ascending cervical arteries, the 

 subclavian vein, and the phrenic nerve. By its posterior surface, with the 

 pleura, the subclavian artery, and brachial plexus of nerves. It is separated 

 from the Longus Colli, on the inner side, by the vertebral artery. 



The Scalenus Medius, the largest and longest of the three Scaleni, arises, by 

 a broad origin, from the upper surface of the first rib, behind the groove for the 

 subclavian artery, as far back as the tubercle ; and, ascending along the side 

 of the vertebral column, is inserted, by separate tendinous slips, into the poste- 

 rior tubercles of the transverse processes of the lower six cervical vertebrae. 

 It is separated from the Scalenus Anticus by the subclaviau artery below, and 

 the cervical nerves above. 



Relations. By its anterior surface, with the Sterno-mastoid ; it is crossed by 

 the clavicle, the Omo-hyoid muscle, and subclavian artery. To its outer side is 

 the Levator Anguli Scapulas, and the Scalenus Posticus muscle. 



The Scalenus Posticus, the smallest of the three Scaleni, arises by a thin 

 tendon from the outer surface of the second rib, behind the attachment of the 

 Serratus Magnus, and, enlarging as it ascends, is inserted, by two or three 

 separate tendons, into the posterior tubercles of the transverse processes of the 

 lower two or three cervical vertebra. This is the most deeply placed of the 

 three Scaleni, and is occasionally blended with the Scalenus Medius. 



Nerves. The Eectus Capitis Antic as Major and Minor are supplied by the 

 suboccipital and deep branches of the cervical plexus ; the Rectus Lateralis, by 

 the suboccipital ; and the Longus Colli and Scaleni, by branches from the lower 

 cervical nerves. 



Actions. The Rectus Anticus Major and Minor are the direct antagonists of 

 the muscles at the back of the neck, serving to restore the head to its natural 

 position after it has been drawn backwards. These muscles also serve to flex 

 the head, and, from their obliquity, rotate it, so as to turn the face to one or 

 the other side. The Longus Colli will flex and slightly rotate the cervical 

 portion of the spine. The Scaleni muscles, taking their fixed point from below, 

 draw down the transverse processes of the cervical vertebrae, bending the spinal 

 column to one or the other side. If the muscles of both sides act, the spine 

 will be kept erect. When they take their fixed point from above, they elevate 

 the first and second ribs, and are, therefore, inspiratory muscles. 



MUSCLES AND FASCIAE OF THE TRUNK. 



The Muscles of the Trunk may be arranged in four groups : the muscles of 

 the Back, of the Abdomen, of the Thorax, and of the Perineum. 



MUSCLES OF THE BACK 



The Muscles of the Back are very numerous, and may be subdivided into 

 five layers : 



