206 Mammalia. 



should be carefully followed with the point of the scalpel ; and 

 at a little depth below the surface he will come upon a white 

 cord. This is the cord of the Sympathetic Nerve, which lies 

 just ventrad of the bodies of the Yertebrae : its fibres may 

 be traced forwards dorsad of the Azygos Yein, to about the 

 level of the second rib, and backwards to the diaphragm. 

 In such a small subject, the Sympathetic is not easily traced, 

 except by a practised hand, through the anterior aperture of 

 the Thoracic cavity ; and should the Student attempt to trace 

 the right Sympathetic cord, he must follow it up dorsad of 

 the subclavian artery, about one eighth of an inch from its 

 origin at the Aorta ; and then along the side of the carotid 

 artery. Under a lens the ganglia on this cord should be 

 noted : especially opposite to the cut ends of the first and 

 second ribs. There may also be noted branching from it, 

 about an inch anterior to its perforation of the diaphragm, a 

 smaller nerve, the great Splanchnic, which perforates a cms 

 of the Diaphragm. On the left side of the body, the left 

 Azygos Yein, the entrance of which into the vena cava 

 descendens was noted above, should be traced back alongside 

 of, but slightly dorsad of, the Aorta ; on its dorsal aspect will 

 be found the corresponding cord of Sympathetic Nerve. 



The Aorta and Oesophagus should both be cleaned, and the 

 Pneumo- gastric nerves left in situ, one on each side of the 

 (Esophagus. 



In the neck, the Phrenic nerve being very fine is not easily 

 traced to its origin ; but the Sympathetic and Pneumo- 

 gastric should be traced up to the Head, closely adhering to 

 the Carotid artery. The common Carotids should be followed 

 up on either side to the point of their bifurcation into the 

 internal and external Carotids, which will be found to take 

 place on the level of the anterior termination of the Trachea, 

 viz.^ opposite the Larynx. 



Dissection of Salivary Glands. The Student should 



