94 EXPERIMENTAL PHARMACOLOGY 



for safety to prevent the unintentional injection of drugs. 

 This cannnla is exactly similar to the one in the carotid 

 artery. Drug solutions in the burette can be changed 

 quickly by running the solution out at the side (wash-out) 

 tube. The burette is then rinsed with water and the sec- 

 ond drug is poured into the burette. To get the air out 

 of the tubing the two clips are opened a little and some 

 of the drug solution is washed out at the side tube. The 

 solution is caught in a beaker and returned to the burette. 



When the burette is to be inserted at first some normal 

 salt solution should be placed in the burette and a little 

 of it run through the cannula. This wets the inside of the 

 cannula (and tubes) and prevents air bubbles from stick- 

 ing inside the cannula later on when the drug is poured in. 

 Just as the cannula is inserted into the vein some of this 

 salt solution is run out and the end of the vein next to the 

 cannula is thus filled with solution and the air is driven 

 out. If air is left in the tubes, cannula or vein, then the 

 animal may die of air embolism when the drug is injected. 

 Always carry out tins technic when putting an injecting 

 cannula into a vein. 



To dissect out the right femoral vein consult Fig. 199. 

 Place the tip of the finger in the inguinal region just at 

 the lower outer edge of the abdomen. The pulsations of 

 the femoral artery will be felt just beneath the skin. With 

 the large forceps pick up a narrow fold of the skin directly 

 over the pulsations and cut this fold away ic'rtli the scissors 

 as shown in the illustration. Do not use a scalpel. When 

 the skin and fascia are thus cut away an opening resem- 

 bling that shown in Fig. 95 will be made. With a blunt- 

 pointed probe dissect away the fascia between the sartorius 

 and adductor muscles. The vessels will be seen in the 

 floor of this triangular space as shown in Fig. 96. Use 

 only the probe or blunt-pointed forceps for the dissection. 

 When about one-half inch of the vein has been freed from 

 the fascia slip an aneurism needle under the vessel and lift 



