SERRATI AND SPLENITJS MUSCLES. 361 



Internally it is attached to the spinous processes. Externally it is con- 

 nected to the posterior third of the iliac crest, uniting with the tendon of 

 the latissimus ; between the hip-bone and the ribs, to the fascia Inmborum; 

 and in the dorsal region to the ribs and a fascia over the intercostal mus- 

 cles. Below, between the pelvic and vertebral attachments, it blends with 

 the underlying tendon of the erector spinte and multifidus. 



* Dissection. The upper serratus is to be cut through, and the subja- 

 cent vertebral aponeurosis to be taken away ; and the part of the splenius 

 muscle under the serratus should be cleaned. 



The SPLENIUS muscle (fig. 117) is thin and elongated; it is undivided 

 internally, but is split externally into two parts. It takes origin along the 

 middle line from the six upper dorsal spines, from the seventh cervical, 

 and from the ligamentum nuchae as high as the third cervical vertebra. 

 Some fibres ascend to the head (splenius capitis), and others to the neck 

 (splenius colli). 



The splenius coll/, c, is inserted by tendinous slips into the posterior 

 transverse processes of the upper three cervical vertebra? with, but behind 

 the attachment of the elevator of the angle of the scapula. 



The splenius capitis, B, much the largest, is inserted by a thin tendon 

 into the apex and hinder border of the mastoid process, and into the bone 

 behind it for about an inch and a half. 



This muscle is situate beneath the trapezius, the rhomboidei, and the 

 serratus superior; and the insertion into the occipital bone is beneath the 

 sterno-mastoideus. The complexus muscle projects above the upper border 

 of the splenius capitis. 



Action. The cranial parts of both muscles will carry the head directly 

 back ; and one will turn the face to the same side. 



The splenius colli of both sides will bend back the upper cervical verte- 

 brae ; but one muscle will turn the face to the same side, being able to 

 rotate the head by its attachment to the transverse process of the atlas. 



* FOURTH LAYER. In this layer are included the spinalis dorsi ; the 

 erector spirire, with its divisions, and accessory muscles to the neck ; and 

 the complexus muscle. Most of the vessels and nerves of the Back are to 

 be learnt with this layer of muscles. 



Dissection (fig. 118). To lay bare the complexus muscle in the neck, 

 the splenii must be detached from the spinous processes, and thrown out- 

 wards. 



And whilst the large erector spinte is being displayed in the dorsal and 

 lumbar regions by the dissector of the upper limb, two prolongations from 

 it to the cervical vertebrae and the head are to be defined by the dissector 

 of the neck : One, a thin narrow muscle, the cervicalis ascendens, is con- 

 tinued beyond the ribs from the outer piece of the erector (ilio-costalis), 

 and is to be separated from the muscles around. The other is a larger 

 offset of the inner piece of the erector (longissimus dorsi); blended at first 

 with the fibres of the longissimus, it is divided afterwards, like the sple- 

 nius, into a cranial part (trachelo-mastoid) and a cervical part ^transversalis 

 colli). 



* The serratus inferior is to be detached with the vertebral aponeurosis 

 from the spines in the dorsal region, and the areolar tissue is to be cleaned 

 from the surface of the large mass of the erector spinae which now comes 

 into view. Opposite the last rib is the beginning of an intermuscular in- 

 terval, which divides the erector spime into an outer piece (sacro-lumbalis), 

 and an inner (longissimus dorsi). By sinking the knife into this interval 



