THE DISSECTION OF THE BACK 59 



ligament of the scapula and the adjacent part of the superior 

 border of the bone. The transverse scapular artery (O.T. 

 suprascapular) will be noticed passing over the upper trans- 

 verse ligament, whilst the suprascapular nerve traverses the 

 notch below it. 



Dissection. The second day's work is now completed, and 

 on the same day the dissector of the upper limb must finish his 

 share of the dissection of the back, so as to allow the dissector 

 of the head and neck to begin the examination of the deeper 

 structures on the dorsal aspect of the trunk. 



Three days are allowed for the dissection of the deeper 

 structures of the back. The work may be arranged in the 

 following manner : On the first day, all the muscles, fasciae, 

 nerves, and blood vessels of the back, with the exception of those 

 in connection with the sub-occipital triangle, should be studied ; 

 on the second day, the sub-occipital triangle may be examined ; 

 and on the third day the medulla spinalis (O.T. spinal cord) must 

 be displayed. 



Commence work on the third day after the body has been 

 placed on its face by cleaning the posterior serrate muscles. 

 They are two in number, superior and inferior. The superior 

 has been exposed by the removal of the trapezius, and the 

 rhomboids and the inferior by the removal of the latissimus 

 dorsi. Both pass from the spines of the vertebras to the ribs, 

 the superior in a downward and lateral direction to some of the 

 upper ribs, and the inferior in an upward and lateral direction 

 to the lower four ribs. 



Musculi Serrati Posteriores. The posterior serrate muscles 

 are two thin sheets of fleshy fibres, which are placed upon 

 the posterior aspect of the thoracic wall. The serratus posterior 

 superior is much the smaller of the two ; it arises by a thin 

 aponeurotic tendon from the lower part of the ligamentum 

 nuchae ; from the spinous process of the seventh cervical 

 vertebra ; and from the spinous processes of the upper two or 

 three thoracic vertebrae. It passes obliquely downwards and 

 laterally, and is inserted into the outer surfaces of the second, 

 third, fourth, and fifth ribs, a short distance anterior to their 

 angles. 



The serratus posterior inferior takes origin from the spinous 

 processes of the last two thoracic and upper two lumbar 

 vertebrae, and the supraspinous ligaments between them. 

 The dissector will note, however, that this is not an indepen- 

 dent and distinct attachment, but that it is effected through 

 the medium of the lumbo- dorsal fascia, with which the 

 aponeurotic tendon of the muscle blends. The muscle 

 passes upwards and laterally and is inserted into the outer 



