DORSAL AXD LUMBAR FASCI.^. 299 



the latissimus dorsi, and its aponeurotic part is firmly united for some 

 distance with the tendon of that muscle. 



Actions. — The serratus posticus superior elevates the upper ribs, and is there- 

 fore to be regarded as a muscle of inspiration. The serratus inferior acts directly 

 as a depressor of the lower ribs, and may aid either in expiration or inspiration ; 

 in expu-ation by acting in concert with the muscles which depress the higher 

 ribs ; in inspiration by fixing the lower ribs and giving fiminess to the origin of 

 the diaphraigm. 



Tlie vertebral aponeurosis is situated on the same plane as the 

 serratus posticus interior, and consists of a thin lamella which separates 

 the muscles belonging to the shoulder and arm from those which sup- 

 port the spine and head. Its fibres are for the most part transverse ; 

 some however are longitudinal. Above, it passes beneath the superior 

 serratus ; below, it is connected with the tendons of the latissimus and 

 inferior serratus muscles, and in being stretched from the spinous pro- 

 cesses outwards across the vertebral groove, it helps to enclose the 

 angular space in which are lodged the long extensor muscles. 



Dorsal and Lumbar Fasciae. — Under the name of lumbar fascia 

 or aponeurosis it has been customary to describe three layers of strong 

 fibrous substance sheathing the erector spinas and quadratus lumborura 

 muscles. The deeper parts of this structure, to which by some the 

 name of lumbar fascia is restricted, will be described along with the 

 abdominal muscles, with which they are chiefly connected. The super- 

 ficial or posterior layer is that through which the latissimus dorsi and 

 serratus posticus inferior muscles are attached to the spines of the dorsal, 

 lumbar and sacral vertebrae and to the crest of the ilium. This layer, 

 which is of considerable strength, extends outwards beyond the origin 

 of the latissimus and serratus inferior, and being closely united with 

 the middle layer, binds down firmly the erectores spinas muscles : it is 

 by some described as the lower part of the vertebral aponeurosis, with 

 which it is continuous, by others it has been named the aponeurosis of 

 the latissimus dorsi. 



The SPLENius muscle is so named from its having the form of a 

 strap, which binds down the parts lying under it. It is attached supe- 

 riorly in part to the cervical vertebras, in part to the skull, and is 

 described accordingly under two names. 



a. The splenius colli is attached inferiorly to the spinous processes 

 of the third, fourth, fiith, and sixth dorsal vertebrae, and superiorly along 

 with the slips of the levator anguli scapulae to the transverse processes 

 of the first two or three cervical vertebras. 



h. The splenius capitis, broader and thicker than the preceding, 

 arises from the spines of the seventh cervical and two upper dorsal 

 vertebrae, and from the ligamentum nuchfe as high as the third cervical 

 vertebrae. It is inserted into the lower and back part of the mastoid 

 process, and into the outer part of the superior curved line of the 

 occipital bone. 



lidatlonn. — The splenius is covered by the trapezius, the rhomboid, and the 

 sen-atus posticus superior ; and at its attachment to the occipital bone by the 

 stemo-mastoid. It conceals, in part, the complexus and trachelo-mastoid. 



Erector Spin^. — This muscle may either be regarded as one large 

 composite muscle, or as consisting of seven distinct muscles. Viewed 

 as one muscle it may be conveniently considered as formed of three 



