364 EXPERIMENTAL INOCULATION OF ANIMALS 



thetic must be administered to the animal. In the 

 monkey or the dog, the internal saphenous vein is the 

 most convenient and before puncturing should be dis- 

 tended or rendered prominent by compressing the vein 

 above the selected site.) 



Preparation of the Inoculum. Care must be taken 

 in preparing the inoculum, as the injection of even 

 small fragments may cause fatal embolism. To obviate 

 this risk the fluid should, if possible, be filtered through 

 sterile filter paper before filling into the syringe. 



Air bubbles, when injected into a vein, frequently 

 cause immediate death. To prevent this, the syringe 

 after being filled should be held in the vertical posi- 

 tion, needle uppermost. A piece of sterile filter paper 

 is then impaled on the needle and the piston of the 

 syringe pressed upward until all the air is expelled from 

 the barrel and needle. Should any drops of the inocu- 

 lum be forced out, they will fall on the filter paper, 

 which should be immediately burned. 



1. Have the animal firmly held by an assistant. 

 The selected ear is grasped at its root and stretched 

 forward toward the operator. 



2. Shave the posterior border of the dorsum of the 

 ear. 



3. Disinfect the skin over the vein, rubbing it 

 vigourously with cotton- wool soaked in lysol. The 

 friction will make the vein more conspicuous. Wash 

 the lysol off with ether and allow the latter to evaporate. 



4. Direct the assistant to compress the vein at the 

 root of the ear. This will cause its peripheral portion 

 to swell up and increase in calibre. 



5. Hold the syringe as one would a pen and thrust 

 the point of the needle through the skin and the wall 

 of the vein till it enters the lumen of the vein (Fig. 189) . 

 Now press it onward in the direction of the blood 

 stream i. e., toward the body of the animal. 



6. Direct the assistant to cease compressing the 



