48 AN ANOMALY OF THE THORACIC DUCT. 



diminishes very gradually until, at a point 22 cm. from the ligament, it is reduced to 

 approximately 2.0 mm. The main continuation anteriorly maintains this diameter of 2.0 

 mm., while the anterior duplicating vessel is about half as large. The cervical portion of 

 the duct again widens until, at a distance of 3 cm. from its junction with the subclavian 

 vein, it has a diameter of approximately 4.0 mm. The terminal portion, for about 1.0 cm., 

 is distended with blood. The origin of the posterior duplicating vessel was not determined, 

 as it was broken off during dissection. From the angle at which it joins the main vessel, 

 and from the fact that, like the main vessel, it has a decided widening to 3.5 mm. at a 

 corresponding place, there is little doubt that it took origin from lymphatic vessels in the 

 inguinal region. All of the vessels were opened, in order to study the valves. In the main 

 duct there is a valve, 1 cm. posterior to the ligamentum inguinale, a second valve 11.5 cm. 

 anterior to the ligament, and a third above the point where the anterior duplicating vessel 

 is given off. All the valves have the flaps directed so as to permit the lymph to run in an 

 anterior direction. Between these three valves the inner wall of the duct is smooth. In 

 the posterior duplicating vessel there are two competent valves, one in the widened region 

 a short distance anterior to the ligamentum inguinale, and the second shortly below its 

 junction with the main duct. The flaps of the valves are directed anteriorly. In addition 

 there are numerous transverse thickenings which project into the lumen. In the anterior 

 duplicating vessel a valve is present shortly beyond its origin from the main duct, its flaps 

 directed anteriorly. 



Unfortunately direct connection between the duct found in the body wall and the upper 

 part, leading through the axilla to the subclavian vein, was, as has been explained, not seen. 

 But, in view of the condition of the visceral lymphatics, to be described, there can be little 

 doubt that they were continuous. 



On dissecting the thoracic and abdominal viscera the following conditions are found: 

 In the mid-thoracic region a miniature thoracic duct is present in its usual position between 

 the azygos vein and the aorta. (Figs. 2 and 3, th. d.) At no part of its course does its diameter 

 exceed three-fourths of a millimeter. On being followed anteriorly it is found to pursue 

 the usual course, crossing to the left and coursing toward the junction of jugular and sub- 

 clavian veins. As already noted, the connection with the vein was lost early in the dissec- 

 tion. Posteriorly it grows smaller, and at the ninth thoracic vertebra it comes to an end 

 by curving sharply to the right behind the azygos vein and by passing out into the ninth 

 intercostal space in company with the ninth intercostal artery and vein. No trace what- 

 ever could be found of a continuation further posteriorly of this miniature duct. Two or 

 three minute tributaries were found joining the duct along its course. Careful dissection 

 ventral, dorsal, and to the left of the aorta failed to reveal a possible left thoracic duct- 

 As to the condition of the deep veins, the azygos vein presents a marked abnormality. 

 First, it should be noted that the azygos and aorta lie rather further to the left than usual, 

 so that the azygos, in the mid-thoracic region, is situated nearly in the midline. The usual 

 one or more tributaries which cross the midline, dorsal to the aorta in the mid-thoracic 

 region, carrying the blood from the hemiazygos, are absent. Instead, the left intercostal 

 spaces, beginning with the fourth, are drained by veins collecting in a common trunk which 

 runs posteriorly as far as the body of the ninth vertebra. This trunk is joined by a vein 

 which runs from the left renal vein (fig. 3, a. l. v.), and receives the upper lumbar and 

 lower intercostal branches. This vein represents a much widened ascending lumbar vein, 

 continuous with the lower part of the hemiazygos vein. The common branch formed by 

 these two veins is a trunk of considerable size, about 5.5 mm. in diameter, which crosses the 



