DISSECTING MANUAL. 



the thorax. The cervical part is from two to two and a half 

 inches long, lies on the oesophagus and is clasped by the thy- 

 roid body. [972] 



Thyroid Body. This vascular structure consists of two 

 lateral lobes connected by an isthmus ; it clasps the upper part 

 of the trachea anteriorly and extends upward on each side 

 of the larynx, being firmly attached. Lateral lobe : Each is 

 conical, with its base at the fifth or sixth tracheal ring, and its 

 apex upon the thyroid ala. The superficial surface is flattened, 

 the deep surface conforms to subjacent structures, and the 

 posterior border overlaps the common carotid. Isthmus: 

 This is a narrow band connecting the bases, crossing the sec- 

 ond, third, and fourth tracheal rings. Middle (pyramidal) lobe : 

 This is an inconstant narrow process from the upper border of 

 the isthmus, at one side, extending upward on the larynx and 

 connected with the hyoid by a fibrous, or muscular, strand 

 (Levator glandulse thyroidese) . Structure : It has a thin cap- 

 sule from which septa project inward and branch, dividing it 

 into numerous alveoli which are lined by epithelial cells and 

 mostly filled with colloid matter. [1216] 



Parathyroid Glands. These are two minute bodies on each 

 side, separated by the inferior thyroid artery. One, the more 

 constant, lies on the back of the resophagus at the level of the 

 lower border of the cricoid cartilage and close to the posterior 

 border of the lateral lobe of the thyroid body. The second lies 

 either close to the lower border of the lateral lobe of the thy- 

 roid body, or on the trachea below it. They consist of epi- 

 thelial cells and closely resemble the anterior lobe of the 

 pituitary body. [1218] 



THE NASAL FOSSAE. 



Each extends from the anterior to the posterior nares. Just 

 above the anterior nares is an expansion (vestibule) which is 

 prolonged (ventricle) toward the tip: the vestibule is divided 

 by a ridge, and is limited above and behind by another ridge 



[94] 



