The application of a ligature to the sub clavian artery on the tracheal side of the sca leni presents, perhaps, fewer merely mecha nical difficulties than that just described, but involves a disturbance of more important or gans, and requires perfect acquaintance with their anatomy. A separation of the sterno cleido-mastoideus from its inferior attachment, and a division of the sterno-hyoid and stern°. thyroid muscles and of their sheaths (includ ing that deep layer which lies beneath the sterno- thyroideus and immediately covers the vessel) will expose the artery.* The ju gular vein is seen crossing it, close to the scalenus, at the outer part of the wound, be hind which lies the phrenic nerve; at the inner part of the wound the bifurcation of the arteria innominata is brought into view, and the sub clavian is seen diverging from the carotid. Between this point and the border of the ju gular vein, from half an inch to an inch of artery intervenes, about midway on which the nervus vagus crosses at a right angle. If the nerve require to be drawn aside, this ma nceuvre must be executed with the extremest delicacy and gentleness; and the operator should not fail to remember his dangerous prox imity to the pleura. The view of these parts is obscured by considerable venous hremor rhage, which is here especially inconvenient, froin the imperative necessity which exists fur clearly seeing the artery and ascertaining the position of its branches before making any attempt to pass the needle. It is considered desirable to apply the ligature on the inner side of the vertebral branch, and as near to it as possible : yet, even under the most favour able circumstances, the adhesive actions at the seat of lig-,ature must be seriously disturbed, both by the near direct stream of the carotid, and by the recurrent tides of the vertebral, mammary,and thyroid arteries. The single in tance, in which I have seen this rare operation performed, was by my friend, Mr. Partridge, who brought to bear on its execution a per fect familiarity with every actual relation, and with every possible contingency; nor could it have been confidently undertaken, or safely conducted, by one of inferior resources. The case was in so far favourable, that the tumour was small, the position of parts unaltered, the arteries reg,ular and free from disease, and the venous liwmorrhage not so troublesome as in many cases it certainly would be ; the parts were clearly seen, and the artery secured with out the least unnecessary disturbance of con tiguous parts. Yet, I confess the impression, which I derived from this single instance of operation, and from frequent consideration of the parts in a great variety of subjects, to have been, that ligature of the arteria innominata would in all cases be as easy, and, in many, far easier to perform, would (by involving organs of less delicacy and importance, than those interested in the tmeheal ligature of the subclavian) render hmmorrhage a less embar rassing obstacle, and would afford a better prospect of undisturbed adhesion in the artery. The steps, necessary for exposing the one, re quire so little modification, to become equally adapted for the other, that the surgeon might even be determined in his choice of either, by considerations developing themselves during the operation, by greater or smaller branchless extent of the subclavian artery, by the verte bral vein obscuring a large portion of this, or by other circumstances of the kind.
Although the arteria innominata cannot in anatomical strictness be considered as belong ing to the neck, yet, in regard both of disease and of surgical operation, its affinity to that region is so close as to warrant its mention in this place. It rises from the convexity of the arch of the aorta, just as that main vessel, having terminated its ascent, inclines leftward.
This point is in young subjects the highest level to which the aorta attains ; but, as Cruveil bier notices, in old age the extreme part of the arch, which corresponds to the origin of the left subclavian artery, is higher. In early life, too, from incomplete development of the ster num, the convexity of the arch more nearly, approaches the root of the neck than in adult growth, and, as also the branches arising from it, may more easily be endangered in trache otomy and other operations in the neighbour hood. Its length is somewhat above an inch : its direction obliquely upward and outward, toward the sterno-clavicular joint, opposite to which it divides. In this course it corres ponds, behind, to the trachea,—in front to the sternum, from which the remains of the thy mus gland, the origin of the sterno-hyoid and stemo-thyroid muscles, and (close to its origin) the transverse crossing of the left vena inno minata separate it,—extemally, to its accom panying vein, and, mediately, to the pleura,— internally, to the left carotid from which it is separated by a triangular interval in which the thymus, or its remnant, lies upon the trachea.
The frequency of its undue extension be yond the precise limit assigned to it, and con sequent appearance in the sub-hyoid region of the neck, together with the fact of its often furnishing a middle inferior thyroid artery, are contingencies never to be disregarded in ope rations thereabout.
This artery has now been tied for cure of aneurism at least six times; unsuccessfully— it is true—but with such nearness to success as not to forbid cautious repetition.. The mode of procedure adopted by Dr. Mott consisted in a transverse division of the skin, muscles, and fascim along the edge of the clavicle and sternum,—in raising these, and taking the sub clavian and carotid arteries (which he seems to have denuded to some extent) as guides to the innominata, in drawing the jugular vein, the vagus, phrenic and recurrent nerves outwards, in pressing the pleura carefully downwards with the convexity of the needle, while he carried its point from below upwards around the vessel. • 6. The digastric space is bounded below by the curve of the digastric muscle, and extends above within the angle and horizontal ramus of the jaw, so that, if considered as a triangle, it may he described as having its base represented by the internal oblique (or myloid) ridge of the lower jaw, and an imaginary prolongation of this to the root of the mastoid process,—its an terior border formed by the ascending belly of the digastric muscle,—its posterior by the de scending fibres of the same; and its apex will obviously be at the point of their reflexion by the hyoid bone. The skin, the superficial fascia with the platysma, and the cervical aponeurosis, wall it in, and that part of the inferior maxilla which lies beneath the oblique line, to the ba sial edge of which the fascia adheres, overhangs it ; its deep surface is constituted by the mylo hyoid muscle and by the side of the tongue and pharynx in front, by the va,inal and styloid processes of the temporal arm behind. A fibrous slip, reflected outwardly from the sty loid process to the angle of the jaw, arid to the deep suiface of the aponeurosis, distinctly di vides the digastric space into two parts. Of these, the posterior is the smaller ; its vertical extent is to the temporo-maxillary articulation : backwards it is bounded by the auditoiy canal and mastoid process; inwardly, by the vaginal plate, the styloid process and its kuscles. In the anterior direction the border of the jaw, to gether with the septum just described, are its limits: whence it seems, within the neck of the jaw, to prolong itself as an interspace between the attachments of the pterygoid muscles.