156 SURGICAL APPLIED ANATOMY, ich.ip. ix. 



only gives the surgeon increased room for the opera- 

 tion, but also brings the trachea nearer to the surface, 

 and by stretching the tube renders it much less 

 mobile. 



In cutting down upon the trachea in the middle 

 line of the neck from the cricoid cartilage to the 

 sternum the following parts are met with. Beneath 

 the integument lie the anterior jugular veins. As 

 a rule these veins lie some little way apart on either 

 side of the median line, and do not communicate 

 except by a large transverse bi-anch which lies in the 

 interfascial space at the upper border of the sternum. 

 Sometimes there are many communicating branches 

 right in front of the tracheotomy district, or the veins 

 may form almost a plexus in front of the trachea, or 

 there may be a single vein which will follow the 

 middle line. Then comes the cervical fascia, enclos- 

 ing the sterno-hyoid and sterno-thyroid muscles. The 

 gap between the muscles of opposite sides is lozenge- 

 shaped, and is such that the trachea can be exposed 

 without dividing muscle fibres. The isthmus of the 

 thyroid usually crosses the 2nd, 3rd, and 4th rings of 

 the trachea. Above it a transverse communicating 

 branch between the superior thyroid veins is sometimes 

 found. Over the isthmus is a venous plexus, from 

 which the inferior thyroid veins arise, while below the 

 isthmus these veins lie in front of the trachea together 

 with the thyroidea ima artery (when it exists). The 

 inferior thyroid vein may be represented by a single 

 trunk occupying the middle line. In the infant before 

 the age of two years the thymus extends up for 

 a variable distance in front of the trachea. At 

 the very root of the neck the trachea is crossed by the 

 innominate and left carotid arteries and by the left in- 

 nominate vein ; and lastly, abnormal branches of the 

 superior thyroid artery may cross the upper rings of 

 the windpipe. 



