INTRODUCTION 



II 



just mediae! of the jugular, as indicated by the line d (Fig. 2). 



Having cut through the muscle, two white cords are seen along 



either side of the trachea. The 



medial one may be red, as it is 



the carotid artery. The lateral 



one, lying in the same sheath 



with the preceding, is the vagus 



or tenth cranial nerve. Sepa- 

 rate the artery from the nerve 



and tie two cords loosely 



around the vessel as in the 



case of the jugular. Lift up the 



artery with the index finger 



(Fig. 3), and make an oblique 



incision with the scissors. The 



cannula with the connecting tube 



attached should then be inserted 



caudad in the oblique cut of 



the artery (Fig. 4), and the string 



^ drawn tight so as to hold the 



cannula in place. The string 



st should then be tightened to 



prevent the injection mass from running out where the cannula 



is inserted. After stirring the red mass, filling the syringe, and 



slipping the nozzle into the con- 

 necting tube the operator should 

 press slowly but continuously on 

 the plunger until that portion of 

 the carotid craniad of the string 

 st is well distended. In a large 



Fig. 3.-METHOD OP Making ^^\ this will not OCCUr Until the 



Incision IN THE Carotid Artery Syringe is nearly or quite empty. 



NjECTioN. When the vessels are full, the 



cannula is withdrawn while the string s is tightened. The 



syringe is washed out, after which the blue mass is well stirred 



Fig. 2. — Diagrammatic View of 

 Operation for Injection. 

 d. Broken line showing course of 

 the carotid artery beneath; h, string 

 loosely tied; c, transverse vein unit- 

 ing external jugulars; a, points of 

 curved forceps containing string. 



