PRELIMINARY OPERATIONS 



93 



get a cannula into a vessel. The cannula is now tied in 

 the artery (Fig. 93). (If desired for injections the right 

 external jugular vein may also be dissected out just be- 

 neath the skin and fascia of the neck Fig. 93.) 



In a similar manner isolate and ligate loosely the left 

 vagus nerve. 



(c) Insertion of Femoral Injecting Cannula; Dissection 

 of Femoral Artery and Vein and Saphenous Nerve. Ob- 



Fig. 94. Burette, tubing, clips and cannula arranged for connecting with a vein for 



injection of drugs. 



serve with great care the arrangement of the apparatus 

 shown in Fig. 94. Solutions to be injected into the veins 

 are placed in the burette. The cannula is tied in the vein, 

 a bull-dog clamp being ahvays left on the vein just prox- 

 imal to the cannula. When injections are made the bull- 

 dog is loosened and the dose is measured by opening cau- 

 tiously the clip on the tube leading from the burette. As 

 soon as the drug is injected the spring clip is closed and the 

 bull-dog is replaced on the vein. This is a double check 



