342 THE MUSCLES AND FASCIA 



ternally, to the angles of the ribs ; and below, to the upper border of the Serratus 

 posticus inferior and a portion of the lumbar fascia, which gives origin to the Latis- 

 simus dorsi ; above, it passes beneath the Serratus posticus superior and the Sple- 

 nius, and blends with the deep fascia of the neck. 



The Lumbar fascia or aponeurosis (Fig. 213), which may be regarded as the pos- 

 terior aponeurosis of the Trans versalis abdominis muscle, consists of three laminae, 

 which are attached as follows : the posterior layer, to the spines of the lumbar and 

 sacral vertebrae and their supraspinous ligaments ; the middle, to the tips of the 

 transverse processes of the lumbar vertebrae and their intertransverse ligaments; the 

 anterior, to the roots of the lumbar transverse processes. The posterior layer is 

 continued above as the vertebral aponeurosis, while inferiorily it is fixed to the 

 outer lip of the iliac crest. With this layer are blended the aponeurottc origin 

 of the Serratus posticus inferior and part of that of the Latissimus dorsi. The 

 middle layer is attached above to the last rib, and below to the iliac crest ; the an- 

 terior layer is fixed below to the ilio-lumbar ligament and iliac crest ; while above 

 it is thickened to form the external arcuate ligament of the diaphragm, and stretches 

 from the tip of the last rib to the transverse process of the first or second lumbar 

 vertebra. These three layers, together with the vertebral column, enclose two 

 spaces, the posterior of which is occupied by the Erector spinae muscle, and the 

 anterior by the Quadratus lumborum. 



Now detach the Serratus posticus superior from its origin, and turn it outward, when the 

 Splenius muscle will be brought into view. 



The Splenius is situated at the back of the neck and upper part of the dorsal 

 region. At its origin it is a single muscle, narrow, and pointed in form ; but it 

 soon becomes broader, and divides into two portions, which have separate inser- 

 tions. It arises, by tendinous fibres, from the lower half of the ligamentum nuchae, 

 from the spinous processes of the last cervical and of the six upper dorsal vertebrae, 

 and from the supraspinous ligament. From this origin the fleshy fibres proceed 

 obliquely upward and outward, forming a broad flat muscle, which divides as it 

 ascends into two portions, the Splenius capitis and Splenius colli. 



The Splenius capitis is inserted into the mastoid process of the temporal bone, 

 and into the rough surface on the occipital bone just beneath the superior curved 

 line. 



The Splenius colli is inserted, by tendinous fasciculi, into the posterior tubercles 

 of the transverse processes of the two or three upper cervical vertebras. 



The Splenius is separated from its fellow of the opposite side by a triangular 

 interval, in which is seen the Complexus. 



Relations. By its superficial surface, with the Trapezius, from which it is 

 separated below by the Rhomboidei and the Serratus posticus superior. It is 

 covered at its insertion by the Sterno-mastoid, and at the lower and back part of 

 the neck by the Levator anguli scapulae ; by its deep surface, with the Spinalis 

 dorsi, Longissimus dorsi, Semispinalis colli, Complexus, Trachelo-mastoid, and 

 Transversalis cervicis. 



Nerves. The Splenius is supplied from the external branches of the posterior 

 divisions of the cervical nerves ; the Serratus posticus superior is supplied by the 

 external branches of the posterior divisions of the upper dorsal nerves ; the Serratus 

 posticus inferior by the external branches of the posterior divisions of the lower 

 dorsal nerves. 



Actions. The Serrati are respiratory muscles. The Serratus posticus supe- 

 rior elevates the ribs ; it is therefore an inspiratory muscle ; while the Serratus 

 inferior draws the lower ribs downward and backward, and thus elongates the 

 thorax. It also fixes the lower ribs, thus aiding the downward action of the 

 diaphragm and resisting the tendency which it has to draw the lower ribs upward 

 and forward. It must therefore be regarded as a muscle of inspiration. This muscle 

 is also probably a tensor of the vertebral aponeurosis. The Splenii muscles of the 

 two sides, acting together, draw the head directly backward, assisting the Trapezius 



