420 DORSAL NERVES. 



The CIRCUMFLEX NERVE arises from the posterior part of the brachial 

 plexus by a common trunk with the musculo-spiral nerve. It passes 

 downwards over the border of the subscapularis muscle, winds around 

 the neck of the humerus with the posterior circumflex artery, and ter- 

 minates by dividing into numerous branches, which supply the deltoid 

 muscle. 



The Branches of the circumflex nerve are muscular and cutaneous 

 The Muscular branches are distributed to the subscapularis, teres minor 

 teres major, latissimus dorsi, and deltoid. The Cutaneous branches 

 pierce the deltoid muscle, and are distributed to the integument of the 

 shoulder. One of these cutaneous branches (cutaneus brachii superior), 

 larger than the rest, winds around the posterior border of the deltoid, and 

 divides into filaments w r hich pass in a radiating direction across the 

 shoulder, and are distributed to the integument. 



DORSAL NERVES. 



The dorsal nerves are twelve in number on each side ; the first appears 

 between the first and second dorsal vertebrae, and the last between the 

 twelfth dorsal and first lumbar. They are smaller than the lower cervical 

 nerves, and diminish gradually in size from the first to the tenth, and then 

 increase to the twelfth. Each nerve, as soon as it has escaped from the 

 intervertebral foramen, divides into two branches ; a dorsal branch and 

 the true intercostal nerve. 



The Dorsal branches pass directly backwards between the transverse 

 processes of the vertebra?, lying internally to the anterior costo-transverse 

 ligament, where each nerve divides into an anterior or muscular and a 

 posterior or musculo-cutaneous branch. The muscular branch enters the 

 substance of the muscles in the direction of a line corresponding with the 

 interval of separation between the longissimus dorsi and sacro-lumbalis, 

 and is distributed to the muscles of the back, its terminal filaments reach- 

 ing to the integument. The musculo-cutaneous branch passes inwards, 

 crossing the semispinalis dorsi to the spinous processes of the dorsal verte- 

 bras, giving off muscular branches in its course ; it then pierces the apo- 

 neurosis of origin of the trapezius and latissimus dorsi, and divides into 

 branches which are inclined outwards beneath the integument to w r hich 

 they are distributed. 



The dorsal branch of the first dorsal nerve resembles in its mode of dis- 

 tribution the dorsal branches of the last cervical. The dorsal branches of 

 the last four dorsal nerves pass obliquely downwards and outwards into 

 the substance of the erector spinee in the situation of the interspace between 

 the sacro-lumbalis and longissimus dorsi. After supplying the erector 

 spina? and communicating freely with each other they approach the surface 

 along the outer border of the sacro-lumbalis, where they pierce the apo- 

 neuroses of the transversalis, internal oblique, serratus posticus inferior, 

 and latissimus dorsi, and divide into internal branches which supply the 

 integument in the lumbar region upon the middle line, and external branches 

 wnich are distributed to the integument upon the side of the lumbar and 

 in the gluteal region. 



INTERCOSTAL NERVES. The Intercostal nerves receive one or two fila- 

 ments from the adjoining ganglia of the sympathetic, and pass forwards in 



