656 THE VASCULAR SYSTEMS 



The course of the anastomosing vessels, by which the blood is brought from the upper to the 

 lower part of the artery, will be found well described in an account of two cases in the Patho- 

 logical Transactions, vols. viii and x. In the former (p. 162) Mr. Sydney Jones thus sums up 

 the detailed description of the anastomosing vessels: "The principal communications by which 

 the circulation was carried on were: First, the internal mammary, anastomosing with the 

 intercostal arteries, with the phrenic of the abdominal aorta by means of the musculophrenic 

 and comes nervi phrenici, and largely with the deep epigastic. Secondly, the superior inter- 

 costal, anastomosing anteriorly by means of a large branch with the first aortic intercostal, 

 and posteriorly with the posterior branch of the same artery. Thirdly, the inferior thyroid, 

 by means of a branch about the size of an ordinary radial, formed a communication with the 

 first aortic intercostal. Fourthly, the transverse cervical, by means of very large communi- 

 cations with the posterior branches of the intercostals. Fifthly, the branches (of the subclavian 

 and axillary) going to the side of the thorax were large, and anastomosed freely with the lateral 

 branches of the intercostals." In the second case also (vol. x, p. 97) Mr. Wood describes the 

 anastomoses in a somewhat similar manner, adding the remark that "the blood which was 

 brought into the aorta through the anastomoses of the intercostal arteries appeared to be ex- 

 pended principally in supplying the abdomen and pelvis, while the supply to the lower extremities 

 had passed through the internal mammary and epigastrics." 



Applied Anatomy. The student should now consider the effects likely to be produced by 

 aneurism of the thoracic aorta, a disease of common occurrence. When we consider the great 

 depth of the vessel from the surface and the number of important structures which surround it 

 on every side, it may easily be conceived what a variety of obscure symptoms may arise from dis- 

 ease of this part of the arterial system, and how they may be liable to be mistaken for those of 

 other affections. Aneurism of the thoracic aorta most usually extends backward along the left 

 side of the vertebral column, producing absorption of the bodies of the vertebrae, with curvature 

 of the spine; while the irritation or pressure on the spinal cord will give rise to pain, either in 

 the thorax, back, or loins, with radiating pain in the left upper intercostal spaces, from pressure 

 on the intercostal nerves ; at the same time the tumor may project backward on each side of the 

 vertebral column, beneath the integument, as a pulsating swelling, simulating abscess connected 

 with diseased bone, or it may displace the oesophagus and compress the lung on one or the 

 other side. If the tumor extend forward, it may press upon and displace the heart, giving rise 

 to palpitation and other symptoms of disease of that organ ; or it may displace, or even com- 

 press, the oesophagus, causing pain and difficulty of swallowing, as in stricture of that tube; and 

 ultimately even open into it by ulceration, producing fatal hemorrhage. If the disease extends 

 to the right side, it may press upon the thoracic duct; or it may burst into the pleural cavity 

 or into the trachea or lung; and, lastly, it may open into the posterior mediastinum. The 

 diagnosis of thoracic aneurism is facilitated by the use of the or-rays. 



Branches of the Thoracic Aorta. 



fBronchial. ,-, . 



\rp \ ] \ Intercostal. 



Visceral P ' Parietal < Subcostal. 



iMediastinai. I Superior phrenic. 



The bronchial arteries (aa. bronchioles) are the nutrient vessels of the lungs, 

 and vary in number, size, and origin. There is, as a rule, only one right bronchial 

 artery, which arises from the first aortic intercostal, or from the left bronchial. 

 The left bronchial arteries, usually two in number, arise from the thoracic aorta, 

 one a little lower than the other. Each vessel runs along the back part of the 

 corresponding bronchus, dividing and subdividing along the bronchial tubes, 

 supplying them, the cellular tissue of the lungs, the bronchial nodes, and the 

 oesophagus. 



The oesophageal arteries (aa. oesophageae), usually four or five in number, 

 arise from the front of the aorta, and pass obliquely downward to the oesophagus, 

 forming a chain of anastomoses along that tube, anastomosing with the cesopha- 

 geal branches of the inferior thyroid arteries above, and with ascending branches 

 from the phrenic and gastric arteries below. 



The pericardial (rami pericardiaci) are a few small vessels, irregular in their 

 origin, distributed to the pericardium. 



The mediastinal branches (rami mediastinales) are numerous small vessels 

 which supply the nodes and loose areolar tissue in the posterior mediastinum. 



