26 UNIVERSITY OF MISSOURI STUDIES 



apparently to the right of the midplane. The meas- 

 urements were made to the right and left of a 

 line through the center of the centrum of the ver- 

 tebra and the middle of the interspace between the hyoid 

 muscles. From Plates I, II, and III it is evident that the 

 neck is rotated to the right, hence the deviation from the 

 midplane. Over the second thoracic vertebra the trachea 

 is divided symmetrically by the median line, but 

 deviates to the right in the region of the arch of 

 the aorta (Plate VII). It rests upon the oesophagus 

 posteriorly and to the left. It is in relation an- 

 teriorly, above the sternum, with the isthmus of the 

 thyreoid gland and sternothyreoid muscles. Below the 

 upper border of the sternum the trachea is crossed by the 

 left innominate vein, which receives near the midline the 

 inferior thyreoid veins. At about this same level the in- 

 nominate artery is in contact with the right anterior part 

 of the trachea separating it from the junction of the in- 

 nominate veins. The ascending aorta and vena cava su- 

 perior separate the remainder of the trachea from the 

 sternum. In the region of the seventh cervical and the 

 first thoracic vertebrae, the trachea is covered laterally by 

 the lateral lobes of the thyreoid. At the lower extremity 

 of the thyreoid the trachea comes into relation laterally 

 with the common carotid arteries. The left carotid runs 

 nearly parallel with the trachea down to the arch of the 

 aorta, the right one down to the innominate artery. The 

 lower half of the trachea is in contact laterally with the 

 superior lobe of the right lung but is separated from the 

 left lung by the oesophagus, common carotid and subclav- 

 ian arteries above and the arch of the aorta below. In the 

 upper part of the mediastinum the vagi nerves are separ- 

 ated from the trachea by the carotid arteries. Below, the 



