700 BLOOD-VASCULAR SYSTEM OF THE HORSE 



superficiales) lie on the anterior border of the anterior deep pectoral muscle, in 

 relation to the omo-hyoideus medially and the brachiocephalicus laterally (Figs. 

 556, 566, 590). They are on the course of the ascending branch of the inferior 

 cervical artery, and may form an elongated series which is continuous ventrally 

 •ndth the posterior cervical group. They receive afferents from the neck, breast, 

 shoulder, and arm. Their efferents pass to the posterior cervical glands. 



The tracheal ducts, right and left (Ductus trachealis dexter, sinister), are col- 

 lecting trunks for the lymph of the head and neck. They lie on the trachea in 

 relation to the carotid arteries. The right one goes to the posterior cervical glands 

 or to the right lymphatic duct, the left one to the terminal part of the thoracic duct. 



THE LYMPH GLANDS AND VESSELS OF THE THORAX 



The thoracic lymph glands (Lgg. thoracales) are in general of small size, but 

 are numerous. They comprise the following: 



1. The intercostal lymph glands (Lg. intercostales) are small and are situated 

 at the sides of the bodies of the thoracic vertebrae, in series corresponding to the 

 intercostal spaces; others are between the aorta and the vertebree. They receive 

 afferents from the vertebral canal, the spinal muscles, the diaphragm, intercostal 

 muscles, and pleura. The efferent vessels go to the thoracic duct.'- 



2. The anterior mediastinal lymph glands (Lgg. mediastinales craniales) 

 are numerous. Some are situated on the course of the brachial arteries and 

 their branches; on the right side they are related deeply to the trachea, on the left 

 to the oesophagus also. They are variable in size and disposition and are continuous 

 in front with the posterior cervical glands. Other glands lie along the ventral face of 

 the trachea on the anterior vena cava and the right atrium of the heart; these are 

 continuous behind with the bronchial glands. A few glands usually occur along the 

 dorsal surface of the trachea, and there is often one at the angle of divergence of 

 the brachiocephalic trunk. The afferent vessels come chiefly from the pleura, 

 the pericardium, the heart, the thymus or its remains, the trachea, the oesophagus, 

 and the bronchial lymph glands. Their efferent vessels pass to the posterior 

 cervical glands and the thoracic duct. 



The glands along the ventral face of the trachea are frequently enlarged and commonly pig- 

 mented in dissecting-room subjects. The left recurrent nerve hes above them on the ventral 

 face of the trachea. 



3. The bronchial lymph glands (Lgg. bronchiales) are grouped around the 

 terminal part of the trachea and the bronchi. One group lies on the dorsal surface 

 of the bifurcation of the trachea, and is continued a short distance backward under 

 the oesophagus. Others lie below the trachea and bronchi and also occupy 

 the angle between the aortic arch and the pulmonary artery, concealing the 

 left recurrent nerve and often covering the vagus in this part of its course. 

 Small glands occur along the chief bronchi in the substance of the lungs (Lg. pul- 

 monales). They receive the deep and most of the superficial lymph vessels of the 

 lungs, and the efferents from the posterior mediastinal glands. Their efferent 

 vessels go to the thoracic duct and the anterior mediastinal glands. The deep 

 lymph vessels of the lung arise in plexuses which surround the terminal bronchi 

 and accompany the bronchi to the root of the lung. The superficial vessels form 

 a rich network under the pleura; most of them pass to the bronchial glands, but 

 some go to the posterior mediastinal glands. 



The bronchial glands are commonly pigmented (except in young subjects) and are often 

 enlarged and indurated. 



4. The posterior mediastinal lymph glands (Lgg. mediastinales caudales) are 

 ' These glands appear to be more numerous in the young subject than they are later in life. 



