58 PRACTICAL ANATOMY. 



superior thyroid and the inferior thyroid in the substance of the gland. The 

 inferior thyroid artery is a branch of the thyroid axis of the subclavian. Note 

 the crico-thyroid branch on the crico-thyroid membrane. Note also the superior 

 laryngeal artery, the same artery you found when you removed the thyro-hyoid 

 muscle : it accompanies the superior laryngeal nerve. The thyroid gland belongs 

 to the class of ductless structures, as the spleen, thymus, and suprarenal capsules. 

 An enlargement of this gland is called bronchocele ; in which case the isthmus 

 may be divided or one-half of the gland removed. The nerves to the thyroid 

 are of sympathetic derivation, from the middle and inferior cervical ganglia. The 

 inferior thyroid veins you will trace to the left brachio-cephalic vein. -The 

 superior and middle veins open into the internal jugular vein. These veins take 

 their origin in a plexus of veins especially large on the posterior part of the gland. 



The carotid sheath is situated by the side of the trachea and larynx. In 

 this sheath are the common carotid artery internally, the internal jugular vein 

 externally, and the pneumogastric or vagus nerve between the two. 



The internal jugular vein is formed by the confluence of the dural sinuses. 

 These sinuses receive their blood from the brain. The internal jugular veins are 

 made up at the jugular foramina at the base of the skull. The ninth, tenth, 

 and eleventh cranial nerves leave the cranial cavity with' the veins. In its course 

 down the neck the jugular vein receives the superior and middle thyroid 

 veins; and near their termination, they receive the external jugular veins. 

 Behind the clavicle, you will see the internal jugular vein on each side unite with 

 the subclavian vein. The result of this union is a large vein, called the 

 innominate or brachio-cephalic vein. These latter of each side unite with the 

 vena azygos major to form the descending vena cava. 



The right common carotid artery begins on the right side, at the bifurcation 

 of the innominate artery. (Fig. 36.) This division occurs opposite the upper 

 margin of the thyroid cartilage. The result of the division gives us an internal 

 and an external carotid artery. Find to the inner side of the common carotid 

 artery the larynx, trachea, thyroid gland, inferior thyroid artery, and recurrent 

 laryngeal nerve. 



The left common carotid artery on the left side differs from that on the 

 right as follows : It is given off in the thorax from the highest part of the arch of 

 the aorta. (Fig. 36.) It has the same relations in the neck as the right common 

 carotid. In the thorax the left common carotid artery is behind the manubrium 

 sterni, the origins of the sterno-thyroid and sterno-hyoid muscles, the left brachio- 

 cephalic or innominate vein, and the remains of the thymus gland. Behind the 

 artery are the trachea, oesophagus, and thoracic duct. Internal to the artery are 

 the innominate artery, the inferior thyroid veins, and remains of the thymus gland. 

 External to the artery are the vagus nerve, the left lung, and pleura. 



The Glandulae Concatenatse. If the subject be tubercular, you may find 

 the deep cervical lymphatics enlarged. They lie with the internal jugular vein, 

 and may have contracted firm adhesions to the vein or artery or both. This 

 seems to be the tendency of glandular tissue : (i) to penetrate or (2) to embrace. 

 Instance the deep part of the parotid gland, penetrating the glenoid cavity and 

 embracing the styloid process too ; the anterior part of the same gland embraces. 

 in a V shape, the posterior border of the ramus of the mandible. Likewise, 

 these lymphatics, when enlarged, embrace vessels, a circumstance which makes 

 their removal often a very dangerous procedure. These glands you will find 

 forming a continuous chain from the base of the skull to the apex of the thorax, 

 where they are continuous with the mediastinai gland-chains. 



The pneumogastric nerve, also called the vagus, or par vagum, lies between 

 I lie common carotid artery and internal jugular vein. Separate the connective 

 tissue between the vessels and find the nerve, deeply located. This n r\e gives 



