ELEMENTS OF MAMMALIAN ANATOMY. 



posing the external jugular veins (Fig. 3). With the 



curved forceps thrust beneath the vein a cord may be pulled 



through and tied in a loose 

 knot. One-half inch from 

 the latter a second cord 

 should be tied around the 

 vein loosely. An oblique 

 cut (Fig. 4) with the point 

 of the scissors directed cau- 

 dad is then made in the veins 

 between the cords. The in- 

 cision should extend about 

 half-way through the vessel. 

 Absorbing the blood with 

 absorbent cotton as it runs 

 from the vessel will prevent 

 clogging. I f too much ether 

 has not been used, the blood 

 will continue running fifteen 

 minutes. When it has nearly 

 ceased flowing, the carotid 

 artery must be found by 



making a slit in the muscle alongside of the trachea just 



mediad of the jugular, as indicated by the line d (Fig. 3). 



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. Separate the artery 



from the nerve and tie two cords loosely around the ves- 



FIG. 3. DIAGRAMMATIC VIEW OF 

 OPERATION FOR INJECTION. 



d, Broken line showing course of 

 the carotid artery beneath; b, 

 string loosely tied ; c, transverse 

 vein uniting external jugulars; 

 a, points of curved forceps con- 

 taining string. 



FIG. 4. METHOD OF MAKING 

 INCISION IN THE CAROTID 

 ARTERY FOR INJECTION. 



