UPPER EXTREMITY AND THORAX, POSTERIOR, 373 



The Vertebral Aponeurosis. Fig. 76. 



This aponeurosis starts in the cervical region as a very 

 thin layer, but gradually becomes thicker as it descends, 

 until in the lower dorsal and lumbar regions it is somewhat 

 thicker. In the last region it receives the tendons of the 

 latissimus dorsi and serratus posticus inferior muscles. It 

 is attached in the median line to the spines and supraspi- 

 nous ligaments of the vertebrae extending from the sacrum 

 to the base of the skull ; laterally it passes in the cervical 

 region to the tips of the transverse processes, in the dorsal 

 region to the angles of the ribs, and in the lumbar region 

 to the crest of the ilium, and becomes continuous with the 

 lumbar fascia. From the lumbar portion of the aponeurosis 

 arises the latissimus dorsi and the serratus posticus inferior 



muscles. 



DISSECTION. 



Remove the fascia and expose the muscles beneath. Separate them care- 

 fully and make out the limits of each. 



NOTE. The person dissecting the lower extremity removes the fascia 

 from the lumbar region, the one on the thorax the portion there, and the one 

 on the head and neck the cervical portion. 



The Extensor Muscles of the Spine. Fig. 76. 



The spinal gutter alongside of the spinous processes is 

 filled up by a muscular mass extending from the sacrum to 

 the base of the skull. 



This muscular mass, though really continuous and con- 

 stituting one muscle, in action is divided into separate por- 

 tions for convenience of reference. 



Below, the mass is found blended together to form the 

 erector spinae, which fills in the lumbar portion of the spinal 

 gutter. Above, the continuation of the erector spinae is 

 represented by three columns. The inner column, repre- 

 sented by the spinalis dorsi ; the middle column, by the 

 longissimus dorsi, transversalis cervicis, and trachelomas- 



