THE HEAD, ANTERIOR. 69 



In the median line recognize from above downward the 

 (i) hyoid bone. (2) The thyroid cartilage and its forward 

 projection, called Adam's apple, and the angle left between 

 the alae of the cartilage. (3) The cricoid cartilage, just 

 below (and connected to the thyroid cartilage by a stout 

 membrane ; see page 146) ; the cricoid cartilage is in front 

 of the fifth intervertebral disc. (4) The trachea, (5) ob- 

 scured by the thyroid gland, which lies upon either side 

 of, and is connected by its isthmus across the front of the 

 trachea. (6) Lastly, the depression just above the ster- 

 num fonticulus gutturis, and between the anterior ends 

 of the clavicles the suprasternal, or interclavicular notch. 



Laterally, from above downward, identify superior curved 

 line of the occipital bone and the mastoid process, its base 

 and tip ; the sternomastoid muscle, which forms a broad 

 elevation, extending from the mastoid process to the 

 sternum and inner end of the clavicle (when it is put upon 

 the stretch). 



As the arteries (subclavian, outer portion, and the 

 carotids) are injected, their position can be recognized by 

 touch, and their course sketched upon the skin by an 

 aniline pencil. The superficial jugular veins usually show 

 through the integument, and their course can be similarly 

 indicated. 



The position of the sternoclavicular articulation should be 

 carefully noted, as it marks so many important structures. 



Consult page 262 for the distance to which the lung 

 extends into the base of the neck. 



DISSECTION. 



Incisions. I. Carry the median incision to the top of the sternum. 



2. Make a transverse incision outward along the clavicle to the point of 

 the shoulder. (If the upper extremity is being dissected this incision has 

 already been made. See page 264.) 



