584 



THE VASCULAR SYSTEMS 



extremities. An aneurismal tumor, taking origin from the posterior part of the vessel, may 

 press upon the trachea, impede the breathing, or produce cough, hemoptysis, or stridulous 

 breathing, or it may ultimately burst into that tube, producing fatal hemorrhage. Again, its 

 pressure on the laryngeal nerves may give rise to symptoms which so accurately resemble those 

 of laryngitis that the operation of tracheotomy has in some cases been resorted to, from the 

 supposition that disease existed in the larynx; or it may press upon the thoracic duct and destroy 

 life by inanition; or it may involve the oesophagus, producing dysphagia; or may burst into 

 the oesophagus, when fatal hemorrhage will occur. Again, the innominate artery, or the sub- 

 clavian, or left carotid, may be so obstructed by clots as to produce a weakness, or even a disap- 

 pearance, of the pulse in one or the other wrist or in the left temporal artery; or the tumor may 

 present itself at or above the manubrium, generally either in the median line or to the right of 

 the sternum, and may simulate an aneurism of one of the arteries of the neck. 



Branches (Figs. 432 and 433). The branches given off from the arch of the 

 aorta are three in number the innominate, the left common carotid, and the left 

 subclavian arteries. 



Eight pulmonary 

 rein. 



Right pulmonary 

 vein. 



Vena azygos 

 major. 



Left subclavian 

 artery. 



Left common 

 carotid artery. 



Left innomi- 

 nate vein. 



Inferior thyroid 

 vein. 



Rwht innomi- 

 nate vein. 



Sight subclai-ian artery. 



Right common carotid artery. 



FIG. 437. Relation of great vessels at base of a fetal heart, seen from above (enlarged), 

 in the Museum of the Royal College of Surgeons of England.) 



(From a preparation 



Peculiarities. Position of the Branches. The branches, instead of arising from the 

 highest part of the arch (their usual position), may be moved more to the right, arising from the 

 commencement of the transverse or upper part of the ascending portion; or the distance from 

 one another at their origin may be increased or diminished, the most frequent change in this 

 respect being the approximation of the left carotid toward the innominate artery. 



The number of the primary branches may be reduced to a single vessel, or more commonly 

 two, the left carotid arising from the innominate artery, or (more rarely) the carotid and sub- 

 clavian arteries of the left side arising from the innominate artery. But the number may be 

 increased to four, from the right carotid and subclavian arteries arising directly from the aorta, 

 the innominate being absent. In most of these latter cases the right subclavian has been found 

 to arise from the left end of the arch ; in other cases it was the second or third branch given off 

 instead of the first. Another common form in which there are four primary branches is that 

 in which the left vertebral artery arises from the arch of the aorta between the left carotid and 

 subclavian arteries. Lastly, the number of trunks from the arch may be increased to five or 

 six; in these instances, the external and internal carotids arise separately from the arch, the 

 common carotid being absent on one or both sides. In some cases six branches have been 

 found, and this condition is associated with the origin of both vertebral arteries from the arch. 



Number Usual, Arrangement Different. When the aorta arches over to the right side, 

 the three branches have an arrangement the reverse of that which is usual, the innominate sup- 



