DISSECTION OF THE HEAD AND NK< K 209 



(db) Middle (Nn. supraclaviculares medii) (0. T. supra- 

 clavicular). 



Note that the direction of the six principal branches corresponds 

 to six lines radiating from a point at the middle of the posterior 

 border of the M. sternocleidomastoideus. 

 Branches of facial nerve to neck. 



(a) Branch to front of neck (ramus colli N. facialis). 



Note its anastomosis with a branch of the N. cutaneus colli. 



Deep Cervical Fascia and Aponeuroses. (Figs. 87, 88, and 89.) 



At this stage, before proceeding further with the dissection, 

 the student will do well to read a good description of the deep 

 cervical fascia. One of the best descriptions is that in Poirier et 

 Charpy, t. ii. pp. 409-430. If the student does not read French 

 easily, he will find a brief description in Cunningham's Text- 

 Book of Anatomy, 1902, pp. 373, 374, 1178, 1179. In the descrip- 

 tion, pay attention especially to the following points and verify 

 each as the dissection goes on : 



General subdivision of the deep fascia and aponeuroses of the front of 

 the neck into 



(a) A superficial part (fascia colli, superficial layer), corresponding 



to the sternocleidomastoid muscles. 



(b) A middle part (fascia colli, deep layer) (0. T. pretracheal fascia), 



corresponding to the subhyoid muscles. 



(c) A deep part (fascia praevertebralis) , corresponding to the prever- 



tebral muscles. 



Between (b) and (c) are a large central compartment containing 

 viscera and a small lateral compartment on each side containing the 

 great vessels, each compartment having a sheath. 



The Superficial Part (Fascia colli, superficial layer). 

 Attachments. 



Above, to prominentia occipitalis externa, linea nuchae superior, 

 processus mastoideus, and to the fascia parotideomasseterica and 

 the inferior border of the mandibula. 

 Below, to the spina scapulae, anterior border of clavicle, upper border 



of sternum. 



Behind, to the ligamentum nuchae. 

 In front, to same layer of opposite side. 



Note splitting of layer to enclose sternocleidomastoid muscle 

 (M. sternocleidomastoideus) and again to enclose the trapezius 

 muscle (M. trapezius) ; it does not split above the sternum to 

 make suprasternal compartments, as ordinarily described. 



Observe firm transverse fixation of superficial layer of fascia 

 colli to anterior surface of hyoid bone. This is the true line of 

 demarcation between the head and the neck; the suprahyoid 

 muscles are all innervated by cerebral nerves. The mtermuscu- 



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