DISSECTION OF THE HEAD AND NECK 231 



the relation of each to the ligamentum transversum scapulae 

 superius. Make a drawing of the part of the posterior triangle 

 dissected and read in your systematic text-book descriptions of 

 the various structures. 



Broad Muscles of the Back (Second Layer). (Fig. 96.) 



The larger and smaller rhomboid muscles (M. rhomboideus 

 major, M. rhomboideus minor) have been worked out by the dis- 

 sector of the arm. and may be conveniently reviewed. 



Broad Muscles of the Back (Third Layer). (Fig. 96.) 



The dissector of the head and neck now proceeds with the 

 dissection of the muscles of the back, and permits the dissector 

 of the upper extremity to study the parts. Observe the fascia 

 nuchae. 



(a) Superior posterior serratus muscle (M. serratus posterior superior). 



Note its form and position. Establish its exact origin and inser- 

 tion. Test its action. Is it concerned in inspiration or expiration? 

 Find the nerves supplying it. What are they called? Is it a 

 monomeric or a polymeric muscle ? Divide it close to its attachment 

 to the vertebral spines and reflect it lateralward. 



(b) Inferior posterior serratus muscle (M. serratus posterior inferior). 



(c) Splenius ("bandage") muscle of head (M. splenius capitis). 



(d) Splenius muscle of neck (M. splenius cervicis) (0. T. splenius colli). 



Lumbodorsal Fascia (Fascia lumbodorsalis). (Vide Figs. 5 and 6.) 



The posterior layer of this fascia is now visible. That por- 

 tion which corresponds to the thoracic spine is often spoken of as 

 the " vertebral aponeurosis"; that portion corresponding to 

 the small of the back is often called the ' ' lumbar fascia. ' ' 



Examine the posterior layer of the fascia lumbodorsalis. 

 What are its medial and inferior attachments? How is it at- 

 tached lateralward? What becomes of it above? These ques- 

 tions may be answered (1) by making an incision through it in 

 the middle of the thoracic region and passing the handle of the 

 scalpel medialward and lateralward, and (2) by dividing the 

 lumbar portion by a vertical cut made two or three centimetres 

 from the median line and raising it from the subjacent M. sacro- 

 spinalis. Then displace the M. sacrospinalis medialward and 

 expose the anterior layer of the fascia lumbodorsalis. How is 

 the anterior layer attached medialward? Note the fusion of the 

 anterior and posterior layers lateralward. Cut through the 

 anterior layer close to its medial attachment and lift it from the 



