DISSECTION OF THE BACK. 



In the 

 dorsal 

 region. 



In the 

 loins. 



Dissection. 



Trapezius 



origin ; 



The student is now concerned with branches of the dorsal and 

 lumbar nerves. See fig. 2. 



DORSAL NERVES (D. 1 12). These are furnished by both 

 the inner and outer branches the upper six or seven from the 



inner, and the lower five or six 

 from the outer. On the surface 

 they are directed outwards in the 

 integument over the trapezius and 

 latissimus dorsi muscles. The upper 

 nerves perforate the trapezius near 

 the spines of the vertebrae ; and 

 the branch of the second, which is 

 larger than the rest, extends out- 

 wards over the scapula. The lower 

 nerves pierce the latissimus dorsi 

 mostly in a line with the angles 

 of the ribs ; the number of the 

 superficial offsets from these nerves 

 often varies. 



LUMBAR NERVES (L. 1 3). 

 In the loins the nerves are derived 

 from the outer branches of the first 

 three lumbar nerve trunks ; they 

 perforate the latissimus dorsi muscle 

 at the outer border of the erector 

 spinae, and crossing the iliac crest 

 of the hip-bone, are distributed in 

 the integuments of the buttock. 



FIRST LAYER OF MUSCLES (fig. 3). 

 Two muscles, the trapezius and the 

 latissimus dorsi, are included in 

 this layer, and are now to be 

 cleaned. 



Dissection. The superficial 

 fatty layer and the unimportant 

 deep fascia are to be removed 

 together from the trapezius and 

 latissimus dorsi in the direction of 

 the fibres of each, viz., from the 

 shoulder to the spinal column ; and 

 the upper limb is to be carried 

 backwards or forwards according 



as it may be necessary to put the different portions of the muscles 



on the stretch. 



Some of the cutaneous nerves and vessels may be left in order 



that they may be afterwards traced through the muscles to their 



origin. 



The TRAPEZIUS MUSCLE (fig. 3, A) is triangular in shape, with 



the base towards the spine, but the two muscles together have a 



trapezoid form. The muscle has an extensive origin, by short 



FIG. 2. CUTANEOUS NERVES 

 THE BACK. 



