SECTION XVIII 

 SURFACE MARKINGS 



The Head. 



ABOUT the head, the important structures whose positions are 

 required are the nerves ; these have already been indicated in 

 their own section. 



The Neck. 



The neck is divided up into compartments by the fascial pro- 

 cesses dipping in between the muscles. The most important one 

 is the central or visceral compartment, bounded anteriorly by the 

 pretracheal fascia, posteriorly by the pre vertebral fascia, and 

 laterally by the fascia enveloping the vascular compartment 

 which contains the carotid artery, internal jugular vein, vagus 

 nerve, and a chain of lymphatic glands ; they all lie just under- 

 neath the sterno-mastoid. 



The central or visceral compartment lies in the middle line of 

 the neck, and extends from the base of the skull into the medias- 

 tinum ; anteriorly it is divided by the hyoid bone into supra- and 

 infrahyoid portions. Below the hyoid bone can be felt the 

 cartilages of the larynx covered by a thin layer of muscles ; and 

 below them again the thyroid gland, whose middle portion lies 

 over the second, third, and fourth rings of the trachea. 



The trachea starts at the level of the sixth cervical vertebra, 

 and divides at the level of the fourth dorsal vertebra ; it 

 gradually recedes as it passes down, and at the level of the upper 

 border of the sternum is 1^ inches from the surface. 



The Thorax. 



The thorax has been divided up into areas by the use of trans- 

 verse and vertical lines : 



210 



