The lymphatics are composed of four sets, a superficial set along the anterior border of the sternomastoid muscle, a deep set accompanying the great vessels, a submaxillary set around and on the submaxillary gland, and a set, two or more in number, beneath the chin.

The submaxillary gland itself not infrequently enlarges and is difficult to distinguish from an enlarged lymphatic node. All these glands are at times subjected to operative procedures. Fig. 163 shows the submental, submaxillary, and superficial set of lymphatics enlarged, as well as the submaxillary gland itself. It is taken from a tuberculous subject.

The nodes below and behind the jaw become enlarged from diseases affecting the tongue, mouth, and throat as well as from affections of the face and scalp.

The inferior carotid triangle is limited posteriorly by the lower portion of the sternomastoid muscle, anteriorly by the median line of the neck, and superiorly by the anterior belly of the omohyoid muscle. In this triangle, or reached through it, are the lower portions of the common carotid artery and internal jugular vein, with the pneumogastric nerve between. Anteriorly are the larynx, trachea, thyroid gland, and sternohyoid and sternothyroid muscles. The carotid artery, jugular vein, and pneumogastric nerve lie partly in the triangle but rather under the edge of the sternomastoid muscle. Operations on the air-passages, laryngotomy and tracheotomy; on the thyroid gland, thyroidectomy; and ligation of the common carotid artery and removal of lymph-nodes are all done in this triangle. The superficial and deep lymphatics accompany the vessels; there are also some in Burns's space above the sternum. In children, instead of the innominate artery ceasing at the sternoclavicular articulation, it sometimes rises above it and may be wounded in operation on the trachea. The thyroidea ima artery, if present, will lie on the trachea, coming up from the innominate or directly from the aorta.

Posterior Cervical Triangle. The posterior cervical triangle has as its base the middle third of the clavicle; its anterior side is the posterior edge of the sternomastoid muscle; its posterior side is the anterior edge of the trapezius; its apex is at the point of junction of these two muscles at the superior curved line of the occiput. It is customary to divide it into two triangles by the posterior belly of the omohyoid muscle. The upper triangle is large and is called the occipital triangle. The lower triangle is small and is called the subclavian triangle. This division by the posterior belly of the omohyoid muscle is not always satisfactory. The muscle runs upward and inward in a line from about the junction of the outer and middle thirds of the clavicle to a variable distance, up to 2.5 cm. (1 in.), above the clavicle at the anterior edge of the sterno-mastoid muscle. The omoyhoid muscle has its lower attachment at the posterior edge of the suprascapular notch, which is below the level of the clavicle, and its posterior belly is sometimes concealed behind the clavicle and does not rise above it except at its inner extremity beneath the sternomastoid muscle. It is rare that any distinct triangle is formed, hence as far as the surface markings are concerned there is often no subclavian triangle. Therefore the posterior cervical triangle will be considered as a whole and not divided.

It is covered by the skin, beneath which is the subcutaneous tissue, which at its lower portion contains the fibres of the platysma muscle. Its floor is composed from above downward of the splenitis, levator scapulae, scalemis posticus, scalenus medius, and scalenus anticus muscles. The deep fascia of the neck spans the space and splits anteriorly to enclose the sternomastoid muscle and posteriorly to enclose the trapezius. The space contains important arteries, veins, nerves, and lymphatics.

Fig. 169.   Dissection of the posterior cervical triangle.

Fig. 169. - Dissection of the posterior cervical triangle.