i8 LANDMARKS MEDICAL AND SURGICAL. 



should always be carefully examined. Its condition may be 

 ascertained by percussion near the sternal end of the clavicle. 



31. Supra-clavicular fossa. The hollow above the 

 clavicle, between the sterno-mastoid and the trapezius, is very 

 manifest in emaciation and old age. Notice the termination 

 here of the external jugular vein. In some necks only a small 

 depression is visible, particularly when the trapezius has a broad 

 insertion into the clavicle, and comes well forwards, so that its 

 front border gives a graceful contour to the base of the neck. 



32. Subclavian artery. In the supra-clavicular fossa, 

 near the outer border of the sterno-mastoid, and about one 

 inch above the clavicle, we feel the pulsation of the subclavian 

 artery. Here the artery lies upon the first rib, and can be 

 effectually compressed. A little pressure is sufficient. But 

 the pressure must be made in the right direction, or the 

 artery will be pressed off the rib instead of against it. The 

 plane of the rib is such that the pressure, to be effectual, 

 must be made in a direction downwards and a little inwards. 

 It is best to stand behind the shoulder and make the pressure 

 with one thumb. 



It is worth remembering that the outer border of the 

 sterno-mastoid corresponds pretty nearly with the outer edge 

 of the scalenus anticus, which is the surgical guide to the 

 subclavian artery. 



By pressing deeply at the upper part of the supra-clavi- 

 cular fossa, the transverse process of the seventh cervical 

 vertebra can be distinctly felt. 



In long and thin necks, a thin cord is perceptible, running 

 nearly parallel with and just above the clavicle. It is the 

 posterior belly of the omo-hyoideus. See it rising and falling 

 in breathing, and making tense during inspiration that part 

 of the cervical fascia which lies over the cervical portion of 

 the lung. Thus it may be said to be in all respects a muscle 

 of inspiration, co-operating with the sterno-mastoid and 

 scaleni. In the language of transcendental anatomy, we may 

 say that the central tendon of the omo-hyoid represents a 

 rudimentary cervical rib. Its posterior belly is analogous to 

 a serration of the serratus magnus ; its anterior belly to a 

 sterno-hyoid. 



