liv PROCEEDINGS OF THE 



The following tributaries open into this brachio-cephalic trunk : — 



(a) Inferior thyroid vein. 



(b) a vein receiving the blood from the 1st and 2nd intercostal 

 -spaces. 



(c) A large vessel which commences in the ascending lumbar vein 

 of the left side, and runs upwards on the left side of the bodies of the 

 dorsal vertebrae, receiving the intercostal veins of the lower eight 

 spaces. This vein apparently represents the vena azygos major 

 transposed to the left side, and it receives tributaries across the 

 middle line, which correspond to the vente azygos minores, superior 

 and inferior. That resembling the vena azygos minor superior is 

 a large vessel which receives the third to the eighth intercostal veins 

 of the right side. Above, this vein arches forwards over the root of 

 the right lung to join the superior vena cava of the right side, in the 

 same way as the normal vena azygos major; but below, it crosses the 

 middle line over the body of the eighth dorsal vertebra to join the 

 transposed vena azygos major. 



The vena azygos minor inferior commences in the ascending lumbar 

 vein of the right side, and after receiving the intercostal veins of the 

 lower three spaces, crosses the body of the tenth dorsal vertebra to 

 join the vena azygos major. 



The veins from the upper two intercostal spaces on the right side 

 join together to form a single trunk, which passes upwards, behind 

 the subclavian vessels, to open into the termination of the internal 

 jugular vein. 



ii. Arteries. — The abnormalities of the arteries, which are con- 

 fined to the thoracic region, would appear to have reference to a 

 marked constriction which is present in the descending thoracic aorta, 

 immediately below the attachment of the ductus arteriosus. It is to 

 be noticed that this constriction does not correspond to that which is 

 usually described as the aortic isthmus, for it is situated below the 

 opening of the ductus arteriosus, and therefore in the position usually 

 occupied by the aortic spindle. Arising from the descending thoracic 

 aorta, about a half inch below this constriction, and opposite the head 

 of the 6th rib, is a large arterial trunk which runs upwards and 

 backwards over the heads of the 5th and 4th ribs, and behind the 

 necks of the 3rd and 2nd ribs, to terminate by joining the left sub- 

 clavian artery. This vessel, which becomes remarkably convoluted 

 as it nears the subclavian, supplies the arteries to the upper three 

 intercostal spaces, and in addition gives of!" a large branch which 

 passes upwards and backwards, through a foramen in what appears 

 to be a fusion of two ribs. Counting this double-headed rib as one, 

 there are only eleven ribs on the left side as compared with twelve on 

 the right ; so it probably represents both the first and the second on 

 this side. 



The remaining seven intercostal spaces are supplied in the usual 

 manner from the descending thoracic aorta. 



Though the above description has special reference to the arteries 

 of the left side, it would apply equally well to those of the right, 



