SUBCLAVIAN. 



395 



objection to the operation. If, however, it has been determined upon to perform the operation 

 in this situation, it should be remembered that it occasionally happens, that the artery passes in 

 front of the Scalenus anticus, or through the fibres of that muscle ; or that the vein sometimes 

 passes with the artery behind the Scalenus anticus. 



In those cases of aneurism of the axillary or subclavian artery which encroach upon the outer 

 portion of the Scalenus muscle to such an extent that a ligature cannot be applied in that situa- 

 tion, it may be deemed advisable, as a last resource, to tie the first portion of the subclavian 

 artery. On the left side, this operation is quite impracticable ; the great depth of the artery 

 from the surface, its intimate relation with the pleura, and its close proximity with so many im- 

 portant veins and nerves, present a series of difficulties which it is impossible to overcome. On 

 the right side, the operation is practicable, and has been performed, though not with success. 

 The main objection to the operation in this situation is the smallness of the interval which usu- 

 ally exists between the commencement of the vessel, and the origin of the nearest branch. 

 This operation may be performed in the following manner. The patient being placed on a 

 table in the horizontal position, with the neck extended, an incision should be made parallel with 

 the inner part of the clavicle, and a second along the inner border of the Sterno-mastoid, meet- 

 ing it at right angles. The sternal attachment of the Sterno-mastoid may now be divided on a 

 director, and turned outwards ; a few small arteries and veins, and occasionally the anterior 

 jugular, must be avoided, and the Sterno-hyoid and Sterno-thyroid muscles divided in the same 

 manner as the preceding muscle. After tearing through the deep fascia with the finger-nail, the 

 internal jugular vein will be seen crossing the artery ; this should be pressed aside, and the artery 

 secured by passing the needle from below upwards, by which the pleura is more effectually avoided. 

 The exact position of the vagus nerve, the recurrent laryngeal, the phrenic and sympathetic 

 nerves, should be remembered, and the ligature should be applied near the origin of the vertebral, 

 in order to afford as much room as possible for the formation of a coagulum between the ligature 

 and the origin of the vessel. It should be remembered, that the right subclavian artery is occa- 

 sionally deeply placed in the first part of its course, when it arises from the left side of the aortic 

 arch, and passes in such cases behind the oesophagus, or between it and the trachea. 



Collateral Circulation. After ligation of the third part of the subclavian artery, the collate- 

 ral circulation is mainly established by three sets of vessels, as was described in a case of axillary 

 aneurism, in which Mr. Aston Key had tied the subclavian artery on the outer edge of the 

 Scalenus muscle, twelve years previously. 1 



" L. A posterior set, consisting of the suprascapular and posterior scapular branches of the 

 subclavian, which anastomosed with the infrascapular from the axillary. 



" 2. An internal set, produced by the connection of the internal mammary on the one hand, 

 with the short and long thoracic arteries, and the infrascapular, on the other. 



" 3. A middle or axillary set, which consisted of a number of small vessels derived from 

 branches of the subclavian, above ; and passing through the axilla, to terminate either in the 

 main trunk, or some of the branches of the axillary, below. This last set presented most con- 

 spicuously the peculiar character of newly-formed, or, rather, dilated arteries," being excessively 

 tortuous, and forming a complete plexus. 



" The chief agent in the restoration of the axillary artery below the tumor, was the infra- 

 scapular artery, which communicated most freely with the internal mammary, suprascapular, and 

 posterior scapular branches of the subclavian, from all of which it received so great an influx 

 of blood as to dilate it to three times its natural size." 



BRANCHES OF THE SUBCLAVIAN ARTERY. 



These are four in number. Three 

 arising from the first portion of the vessel, 

 the vertebral, the internal mammary, and 

 the thyroid axis ; and one from the second 

 portion, the superior intercostal. The 

 vertebral arises from the upper and back 

 part of the first portion of the artery ; the 

 thyroid axis from the front, and the in- 

 ternal mammary from the under part of 

 this vessel. The superior intercostal is 

 given off from the upper and back part 

 of the second portion of the artery. On 

 the left side, the second portion usually 

 gives off no branch, the superior inter- 



Fig. 215. Plan of the Branches of the Right 

 Subclavian Artery. 



Guy's Hospital Reports, vol. i. 1836. 



