122 DISSECTION OF THE PHARYNX. 



The structure of the oesophagus will be examined in the dissection of 

 the thorax. 



Directions. The dissector may learn next the digastric and stylo-hyoid 

 muscles, with the hypoglossal nerve (p. 82). Afterwards .lie may take 

 the trunk of the external carotid, with the following branches superior 

 thyroid, facial, occipital, posterior auricular, and superficial temporal (p. 

 83 to 87). 



The dissector is not to examine now the pterygo-maxillary or sub- 

 maxillary regions on the left side, because such a proceeding would inter- 

 fere with the subsequent dissections. Before learning the pharynx he 

 should lay bare, on this side, the middle and inferior ganglia of the sym- 

 pathetic with their branches. 



Dissection. For the display of the two lower ganglia of the sympathetic 

 and their branches, it will be necessary to take away the great bloodvessels 

 by cutting them across at the lower part of the neck, and near the digastric 

 muscle. In removing the vessels, care must be taken of the sympathetic 

 beneath them. 



The middle ganglion must be sought in the fat and areolar tissue near 

 the inferior thyroid artery ; and the inferior one will be seen on the neck 

 of the first rib, after the subclavian artery has been divided. The upper 

 cardiac nerve may be found descending beneath the carotid sheath. 



The upper end of the sternum with its attached clavicle is to be taken 

 away next, by cutting through the middle of the first rib ; and the piece 

 of bone is to be put aside for the subsequent examination of the sterno- 

 clavicular articulation. 



The middle and inferior cervical ganglia of the sympathetic nerve are 

 so similar to the corresponding ganglia of the right side, that the same 

 description will suffice (p. 117). 



The cardiac nerves are three in number on the left as on the right side, 

 viz., superior, middle, and inferior, but they present some differences. 



The superior cardiac nerve has a similar course in the neck on both 

 sides ; but the left in entering the chest lies between and parallel to the 

 carotid and subclavian arteries. 



The middle cardiac nerve unites frequently with the next, and passes 

 beneath the subclavian artery to the deep cardiac plexus. 



The inferior cardiac nerve is generally a small branch, which enters 

 the thorax conjoined with the preceding, to end in the cardiac plexus. 



SECTION XI. 



DISSECTION OF THE PHARYNX. 



THE pharynx, or the commencement of the alimentary passage, can be 

 examined only when it has been separated from the rest of the head ; and 

 it will therefore be necessary to cut through the base of the skull in the 

 manner mentioned below, so as to have the anterior halt, with the pharynx 

 connected to it, detached from the posterior half. 



Dissection. The block being removed from beneath the neck, the head 

 is to be placed downwards, so that it may stand on the cut edge of the 

 skull. .Next the trachea and oesophagus, together with the vagus and 



