THE HEAD AND NECK and of the subdivision of the by fold^ in the skin, which are primarily caused by some fibres of the platysma muscle (Fig. 25) crossing to the other side, and by the movement of the head upon the neck but they are secondarily perpetuated by the formation of fascial, or fibrous, bands fat in large quantities,
fat
;
under the skin. Note that in the case of a well-marked double chin
Fig.
69.— Furrows aronnd Moutli.
TMn lips.
Double
cliln.
the intervening furrow is prolonged on to the lower part of the side of the face. Immediately under cover of the lower jaw, never visible, and but very rarely even palpable until the head is bent backwards, is the slight median body of the hyoid hone. So small is this that it would hardly be Tvorth noticing in a study of surface form were it not for the fact that from the hyoid many muscles pass to the lower jaw and tongue, and to the thyroid 182