THE BACK. 183 



PART yi.— SPECIAL ANATOMY. 

 The Back. 



By dissecting the skin from the lateral thoracic incision 

 to the middle line of the back the panniculus is first ex- 

 posed, and then the manner in which, by uniting with the 

 combined ajDoneurotic exjDansions of latissimus dorsi, the 

 two small serrati (or superficialis costarum), and the dorsal 

 trapezius, it forms the lumbar faschia, which extends along 

 the whole length of the back, from the shoulders to the 

 quarters, where it blends with the gluteal investing layer. 

 It is attached to the superior spinous ligament and extends 

 about six inches on either side of the sj^ine. 



Having divided panniculus and thrown it back, leaving 

 it attached to the lumbar faschia, we expose latissimus 

 dorsi, running from about the centre of the mass of muscle 

 forming the shoulder. Its muscular portion terminates 

 about opposite the eighth rib, where it blends with the 

 lumbar faschia. Superiorly situated to this is trapezius, a 

 triangular muscle, the apex of which is fixed to the tubercle 

 on the spine of the scapula, its base to the superspinous 

 ligament blending with the lumbar faschia posteriorly, an- 

 teriorly covered by levator humeri, and with it attached to 

 the cordiform upper portion of ligamentum nuchse. Its 

 tendinous portion extends from its apex to its base at the 

 withers, thus dividing the muscular portion into two 

 parts. 



The posterior small serratus is exposed to view by re- 

 moval of panniculus. It presents a serrated margin infe- 

 riorly, its fibres runnmg in an upward direction from the 

 posterior margins of the seven posterior ribs to the lumbar 

 faschia. 



Below this we see the external intercostals running in a 

 downward and backward direction from the posterior 

 .margin of one rib to the anterior margin of the next. Still 



