pular branch, abundantly restore the circulation. Should the carotid have been tied, its mesial communications, already mentioned, especially those within the skull, and about the thyroid gland,—assisted at those places and elsewhere by anastomoses with the subclavian,—adequately fulfil their vicarious duty. So abundant are these various communications, that the ligature of a main trunk, in the dead subject, in no degree interferes with the distension of its branches by fine injection: if we inject water, or any equally fluid material, through one carotid artery, it freely returns by the other. Under these circumstances, it excites our surprise that the cure of aneurism by ligature should be so certain; for the amount of circulation through the affected vessel can at first be little affected, and the arrest and ultimate cure of the disease must be referred rather to the withdrawal of a distensive impulse than to any considerable derivation of current. It seems to have been considered, in operating for aneurism, that, so long as no large branch arose from the vessel closely on the cardiac side of the ligature, it mattered not what branches might arise on its distal side,—how large, or how near. In many instances secondary hæmorrhage, inducing death, has manifestly depended on defective adhesion at the distal side of the ligature, and for an obvious reason. The condition of that part of the artery has been neglected: it has been thought unimportant though a large vessel should arise just beyond the ligature; or, if a great length of artery have been injudiciously denuded, the cardiac portion has had an exclusive preference of security given to it, by the ligature being drawn as high as possible in that direction. If an equal attention were bestowed on both sides of the proposed seat of ligature,—if like care were taken, in both directions, to avoid the likelihood of disturbance to the adhesive process by side currents,—if, where the artery has been much denuded, (instead of a single thread being applied at the cardiac extremity of that isolated portion, by which plan the succeeding part of the tube,—though separated from its connexions, and likely to ulcerate or slough,—is yet left open to the stream of recurrent blood,) a second ligature were placed at the distal limit of the endangered part, there would seem no greater reason to anticipate the occurrence of secondary hæmorrhage than when arteries are tied after an amputation.
3. Anomalous arrangement of the cervical vessels is a contingency which the surgeon must bear in mind. Most of these are comprehended in the abnormalities of the arch already described. (See Aorta.) The existence of a median inferior thyroid artery, derived from the arch, or from the arteria innominata;—the irregular passage of the right subclavian artery from the left side, behind the œsophagus, or between that tube and the trachea;—an early division of the carotid, even to nearly the level of the sternum, or so late a one, that the common trunk furnishes many, or most, of the branches normally originating from the external;—the absence of an arteria innominata, its branches arising separately from the arch, or in irregular combination with those of the left side; the occasional origin of the vertebral from the common carotid,[1] are the deviations which it most behoves the practitioner to remember.
4. Certain veins in the neck have an anatomical disposition, rendering them liable, when opened in surgical operations, to become channels for inspiration of air to the cavities of the heart, the fatal tendency of which is well known. The internal jugular, innominatæ, and subclavian veins are, as M. Bérard notices, "at the root of the neck, so firmly united by fascial laminæ and cords to the adjacent bones and muscles, that they do not collapse on division, but gape and it is obvious that this circumstance (but for which they would be flattened, and rendered impervious, by the atmospheric pressure on their outward surface) must expose them remarkably (perhaps alone) to a dangerous participation in the inhaustive movements of breathing. M. Velpeau (who has written a paper of excellent critical research on the subject[2]) recommends the following precautions in approaching veins of the nature described (veines canalisées): studiously to avoid wounding them,—to detach no deeply fixed tumour from its adhesions, without having previously commanded the vessels at its base,—and to maintain no unnecessary tension on the fasciæ, by forced positions of the shoulder.
- ↑ A single instance has occurred to me in the dissecting-room, of an arrangement, which I believe to be very rare. An innominata (for so its origin and course entitled it to be named) divided at the sterno-clavicular joint into common carotid and vertebral: the right subclavian arose from the descending part of the arch, and directed itself to the scalene space by passing behind the œsophagus.
- ↑ Médecine Opératoire; and Lettre sur l'Introduction de l'Air dans les Veines. Paris, 1838.
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