DISSECTION OF THE HEAD AND NECK 233 



surface of the M. quadratus lumborum. Displace the latter 

 medialward and the fascia covering the anterior surface of the 

 latter will be brought into view. (This fascia was formerly 

 called the anterior layer of the lumbar fascia.) Make a drawing 

 of the structures in your cadaver corresponding to Spalteholz, 

 Fig. 334. 



Long Muscles of the Back (First and Second Layers) (O. T. Third 

 Layer of the Back). (Vide Fig. 4, p. 47.) 



Cut through the attachments of the M. splenius capitis and 

 M. splenius cervicis, close to the spines of the vertebrae, and 

 reflect the muscles upward and lateralward. Turn the whole of 

 the posterior layer of the fascia lumbodorsalis with the M. ser- 

 ratus posterior inferior lateralward. 



(a) Sacrospinal muscle (M. sacrospinalis) (0. T. erector spinae). What 

 are the names given to the three main divisions of this 

 muscle? Which is the largest of the three, and which the 

 smallest? Pull the M. iliocostalis lateralward on the right 

 side; reflect it on the left. Blood-vessels and nerves 

 emerge between the M. iliocostalis and the M. longissimus 

 dorsi and are the guide in dissection. (Vide Spalteholz, 

 Fig. 336.) 



(aa) Lateral subdivision: iliocostal muscle (M. iliocostalis). 



(aaa) Iliocostal muscle of loins (M. iliocostalis lumborum) 



(0. T. sacrolumbalis). 



(aab) Iliocostal muscle of back (M. iliocostalis dorsi) (0. 



T. musculus accessorius). 



(aac) Iliocostal muscle of neck (M. iliocostalis cervicis) 



(0. T. cervicalis ascendens). 



Establish the exact origin and insertion of each. Test 

 action. Find innervation. 



(ab) Middle subdivision: longest muscle (M. longissimus). 



(aba) Longest muscle of back (M. longissimus dorsi). 



(abb) Longest muscle of neck (M. longissimus cervicis) 



(0. T. transversalis cervicis). 



(abc) Longest muscle of head (M. longissimus capitis) (0. 



T. trachelomastoid). 



Establish exact origin and insertion of each. Test action. 

 Find innervation. 



(ac) Medial subdivision: spinal muscle (M. spinalis). 



(aca) Spinal muscle of back (M. spinalis dorsi). 



(acb) Spinal muscle of neck (M. spinalis cervicis) (0. T. 



spinalis colli). 

 (ace) Spinal muscle of head (M. spinalis capiti*). 



Establish exact origin and insertion of each. Test action. 

 Find innervation. 



