30. =Apex of lung in the neck.=--The extent to which the apex of the lung rises into the neck is greater than is generally supposed. Many observations in reference to this point lead to the conclusion that the lung rises behind the sterno-mastoid, on an average, one inch and a half above the clavicle; in persons with long necks, as much as two inches. The apex of the lung and pleura is covered by the clavicular origin of the sterno-mastoid, the sterno-thyroid, and a part of the scalenus anticus. It is also crossed by the subclavian vessels in the first part of their course. As this cervical portion of lung is peculiarly liable to tubercular disease, it 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-clavicular 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. _THE CHEST._