THE LYMPH GLANDS AND VESSELS OF THE HEAD AND NECK 601 



of the diaphragm at tlie first and second lumbar vertebrae. The duct enters the 

 thorax through the hiatus aorticus and runs forward on the right of the median 

 plane betw(>en the vena azygos and the aorta, covered by the pleura. At the sixth 

 or seventh thoracic vertebra it inclines somewhat ventrally, crosses obliquely over 

 the left face of the oesophagus, and passes forward on the left side of the trachea 

 to the inlet of the thorax. The extrathoracic terminal part passes downward and 

 forward a variable distance (3 to 4 cm.) on the deep face of the left scalenus muscle, 

 bends inward ami backward under the bicarotid trunk, and opens into the upper 

 part of the origin of the anterior vena cava just behind the angle of junction of the 

 jugular veins. The terminal bend is ampullate and sometimes divides into two 

 very short l)ranches which open close together. 



Since the duct develops from a plexus of ducts in the embryo, considerable variation from 

 the more iLsual course occurs. There is often a left duct which arises at the cisterna or at a 

 varialjle point from the right duct, runs across the left intercostal arteries parallel to the latter, 

 and unites with it over the base of the heart or further forward. The two are connected by 

 cross-l)ranches. In some cases the left duct is the larger, and there may indeed be none on the 

 right side. Other variations are conunon. 



The chief tributaries of the thoracic duct are as follows: 



1. The two lumbar trunks (Trunci lumbales) are formed by the confluence 

 of the efferent ducts of the lumbar glands, and commonly unite with each other 

 and with the post(>rior intestinal trunk before opening into the cistern. 



2. The intestinal trunks (Trunci intestinales), two or three in number, receive 

 the effercnts of the lymph glands of the intestine, stomach, liver, and spleen.^ 



In its course throtigh the thorax the thoracic duct receives efferents from the 

 intercostal, mediastinal, and bronchial glands. At the thoracic inlet it is joined by 

 ducts from the prepectoral and right axillary glands, and by the left tracheal duct. 

 The duct is provided with several pairs of valves; the best developed are at its 

 termination. 



THE RIGHT LYMPHATIC DUCT 

 This vessel (Ductus lymphaticus dexter) — when present — collects the lymph 

 from the right side of the head, neck, and thorax, and from the right thoracic limb. 

 It is most frequently absent, being represented by a number of short ducts which 

 terminate in the thoracic duct, the right jugulo-brachial junction, or the origin of 

 the anterior vena cava. When present in its typical form, it results from the 

 confluence of efferent ducts from the right axillary and prepectoral lymph glands 

 with the right tracheal duct. It lies on the deep face of the scalenus muscle above 

 the terminal part of the right jugular vein. It is more or less ampullate and usually 

 opens into the anterior vena cava to the right of the thoracic duct. It may be 

 connected with the latter by considerable anastomoses and may join it. 



The duct is very variable in form and in regard to its afferents. Often it is a very short, 

 irregular, and bulbous trunk; in some cases it is about an inch and a half (ca. 3 to 4 cm.) in length 

 and receives the tracheal duct at its terminal bend. The lymphatico-venous connections here 

 need further study. 



THE LYMPH GLANDS AND VESSELS OF THE HEAD AND NECK 



1. The submaxillary lymph glands (Lg. submaxillares) (Figs. 437, 462) are 

 arranged in two elongated groups in the submaxillary space along each side of the 

 omo-hyoid muscles. The two groups are in apposition in front of the insertion 

 of these muscles and diverge posteriorly in the form of a V, extending backward 

 about four or five inches (ca. 10 to 12 cm.). They are covered by the skin and a 



' The lymph vessels of these organs appear to vary considerably in their mode of termina- 

 tion, and the arrangement needs further study. Some ducts from the stomach, liver, and spleen 

 open directly into the cistern. 



