340 THE INNOMINATE ARTERY. 



surface of the heart along the line of the interventricular groove, to 

 the right of the apex. 



The left coronary artery supplies some small branches at its commence- 

 ment to the pulmonary artery, to the coats of the aorta, and to the left 

 auricular appendage ; its two branches also furnish throughout their course 

 smaller offsets, which supply the left auricle, both ventricles, and the 

 inter ventricular septum. 



It has been customary to describe the transverse branches of the coronary arteries 

 as anastomosing in the left auriculo-ventricular sulcus, and the descending branches 

 as anastomosing near the apex of the heart ; and this description was never doubted 

 till it was found by Hyrtl, as the result of separate injection of these vessels, that 

 the branches of one coronary artery cannot be injected with material introduced into 

 the other. (Nat. Hist. Review, 1861, p. 321.) 



PECULIARITIES. The coronary arteries have been observed in a few instances to 

 commence by a common trunk, from which they diverged and proceeded to their 

 usual destination. The existence of three coronary arteries is not a very rare occur- 

 rence, the third being small, and arising close by one of the others. Meckel, in one 

 instance, observed four, the supplementary vessels appearing like branches of one 

 of the coronary arteries transferred to the aorta. 



THE INNOMINATE ARTERY. 



The innominate, or brachio-cephalic, artery, the largest of the vessels 

 which proceed from the arch of the aorta, arises from the commencement of 

 the transverse portion of the arch, before the left carotid artery. From this 

 point the vessel ascends obliquely towards the right, until it arrives opposite 

 the sterno-clavicular articulation of that side, nearly on a level with the 

 upper margin of the clavicle, where it divides into the right subclavian and 

 the right carotid arteries. The place of bifurcation would, in most cases, be 

 reached by a probe passed backwards through the cellular interval between 

 the sternal and clavicular portions of the sterno-mastoid muscle. The 

 length of the innominate artery is very variable, but usually ranges from an 

 inch and a-half to two inches. 



This artery, lying for the most part within the thorax, is placed behind 

 the first bone of the sternum, from which it is separated by the sterno- 

 hyoid and sterno-thyroid muscles, and a little lower down by the left 

 innominate vein, which crosses the artery at its root. The lower part of 

 the innominate artery lies in front of the trachea, which it crosses obliquely : 

 on - its left side is the left carotid artery, with the thymus gland or its 

 remains ; and to the right is the corresponding innominate vein and the 

 pleura. 



No branches usually arise from this vessel. 



PECULIARITIES. The length of the innominate artery sometimes exceeds two 

 inches, and occasionally it measures only one inch or less. Its place of division is a 

 point of surgical interest, inasmuch as upon it in a great measure depends the acces- 

 sibility of the innominate in the neck, and the length of the right subclavian artery. 

 It has sometimes been found dividing at a considerable distance above the clavicle, 

 and sometimes, but less frequently, below it. Though usually destitute of branches, 

 this vessel has been observed to supply a thyroid branch, the thyroidea ima, and 

 sometimes a thymic branch, or a bronchial, which descends in front of the trachea. 



The thyroidea ima is an occasional artery. When present, it usually arises (as 

 already stated) from the innominate trunk, but in rare instances it has been observed 

 to come from the right common carotid artery, or from the aorta itself. It is of very 

 different size in different bodies, and compensates in various degrees for deficiencies 



