606 THE ARTERIES. 



anastomosing vessels: "The principal communications by which the circulation was carried on, 

 WITH Firstly, the internal mammary, anastomosing with the intercostal arteries, with the phrenic 

 of the abdominal aorta by means of the musculo-phrenic and comes nervi phrenici, and largely 

 with the deep epigastric. Secondly, the superior intercostal, 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 transversalis colli, 

 by means of very large communications with the posterior branches of the intercostals. Fifthly, 

 the branches (of the subclavian and axillary) going to the side of the chest 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 expended principally in supplying the abdomen and pelvis, while the sup- 

 ply to the lower extremities had passed through the internal mammary and epigastrics. " 



Surgical 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 spine, producing absorption of the bodies of the vertebrae, with curvature of the spine ; 

 whilst the irritation or pressure on the cord will give rise to pain, either in the chest, 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 spine, 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 compress, the oasophagus, causing pain and 

 difficulty of swallowing, as in stricture of that tube ; and ultimately even open into it by ulcera- 

 tion. producing fatal haemorrhage. 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. 



BRANCHES OF THE THORACIC AORTA. 



Pericardiac. (Esophageal. 



Bronchial. Posterior Mediastinal. 



Intercostal. 



The pericardiac are a few small vessels, irregular in their origin, distributed to 

 the pericardium. 



The bronchial arteries are the nutrient vessels of the lungs, and vary in num- 

 ber, size, and origin. That of the right side arises from the first aortic intercostal, 

 or by a common trunk with the left bronchial from the front of the thoracic aorta. 

 Those of the left side, usually two in number, arise from the thoracic aorta, one a 

 little lower than the other. Each vessel is directed to the back part of the corre- 

 sponding bronchus along which it runs, dividing and subdividing upon the bron- 

 chial tube, supplying them, the cellular tissue of the lungs, the bronchial glands, 

 and the oesophagus. 



The cesophageal arteries, 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 oesophageal branches of the 

 inferior thyroid arteries above, and with ascending branches from the phrenic and 

 gastric arteries below. 



The posterior mediastinal arteries are numerous small vessels which supply the 

 glands and loose areolar tissue in the mediastinum. 



The Intercostal arteries arise from the back part of the aorta. They are usu- 

 ally eleven in number on each side, the superior intercostal space being supplied 

 by the superior intercostal, a branch of the subclavian, and the second intercostal 

 space being supplied by a branch from the superior intercostal joining with the first 

 aortic intercostal. The lowest of these branches, the subcostal artery, underlies 

 the last rib. The right intercostals are longer than the left, on account of the 

 position of the aorta on the left side of the spine : they pass outward, across the 

 bodies of the vertebras, to the intercostal spaces, being covered by the pleura, the 



