128 EQUINE ANATOMY. 



with the trachea, scalenus muscle, blood vessels and 

 nerves of the neck ; and on the left side with the jug- 

 ular vein ; in the tliorax with the inferior cervical gan- 

 glion and its branches ; the vertebral, superior cervical, 

 and dorsal arteries and veins, with the left bronchia, 

 aorta, lung, oesophageal arterj and nerves. Structure : 

 Two coats of muscular fibres, a mucous membrane with 

 longitudinal folds, oesophageal arteries and branches of 

 the pneumo-gastric nerve. 



Thyroid Gland.— Composed of two ovoid lobes, one 

 on each side of the lirst two rings of the trachea, united 

 by a small band running in front of the trachea. Struc- 

 ture : A fibrous envelope, parenchymtous mass, branches 

 of the thyro-laryngeal and thyroid accessorius arteries 

 and nerves from the first and second cervical pairs. 



AXGEJOLOGY. 



Arteries. — Fsimitive carotid. — Branches of the 

 cephalic trunk : E-unning along the trachea to the gut- 

 tural pouches and the larynx, where it terminates in 

 the arteries of the head. (See page 102.) Collateral 

 brandies: Innominated to the oesophagus, the trachea 

 and the cervical muscles ; the thyro-laryngeal, whicli 

 runs downwards to the thyroid gland and sends branches 

 to the larynx, and the thyroid accessorius to the thyroid 

 body by its posterior extremity. 



