THE DISSECTION OF THE BACK 61 



the thoracic region it dips beneath the serratus posterior 

 superior into the neck, and at the lower end it blends with 

 the aponeurosis of origin of the serratus posterior inferior, 

 and, through that, becomes continuous with the posterior 

 layer of the lumbar portion. 



Dissection. To display the lumbar part of the lumbo-dorsal 

 fascia, take away the remains of the origin of the latissimus 

 dorsi, which springs from its posterior surface, and then reflect 

 the serratus posterior inferior by cutting through it at right 

 angles to its fibres and turning it medially and laterally towards 

 its origin and insertion. As the lateral part is turned aside 

 secure its nerves of supply ; they are derived from the ower 

 intercostal nerves, and enter its deep surface. Next, remove the 

 remains of the origin of the serratus posterior inferior, and then 

 the posterior layer of the lumbar part of the lumbo-dorsal fascia 

 will be completely exposed. 



The Lumbar Part of the Lumbo-dorsal Fascia is separable 

 into three lamellae, a posterior, a middle, and an anterior. 

 All three fuse together laterally, where they become connected 

 with the internal oblique and the transversus abdominis 

 muscles. The posterior layer, which is the strongest of the 

 three, is a dense tendinous aponeurosis. It is continuous 

 above with the thoracic part. Below^ it is attached to the 

 posterior part of the outer lip of the iliac crest, and to the 

 dorsum of the sacrum and the coccyx. Medially^ it is attached 

 to the tips of the spines of the lumbar and sacral vertebrae ; 

 and laterally it blends with the posterior surface of the middle 

 lamella (Fig. 18). The aponeurosis of origin of the latissimus 

 dorsi and the serratus posterior inferior arise from its posterior 

 surface. 



Dissection. Make a longitudinal incision through the 

 posterior layer of the lumbar part of the lumbo-dorsal fascia, 

 midway between its medial and its lateral borders. At each 

 end of the longitudinal incision make a transverse incision, 

 extending from the spines medially to the lateral border of the 

 rounded mass of spinal muscles lying under cover of the fascia. 

 Turn the medial part of the divided fascia towards the median 

 plane, and verify its attachment to the vertebral spines and the 

 supraspinous ligaments. Pull the lateral part aside, and at the 

 lateral border of the mass of posterior spinal muscles note that 

 it blends with a deeper middle lamella. Push the mass of 

 posterior spinal muscles towards the median plane, and follow 

 the middle lamella of the fascia to its attachment. 



The middle lamella is attached, medially, to the tips of the 

 transverse processes of the lumbar vertebrae; below, to the 

 iliac crest, and, above, to the last rib. Laterally, it blends 



