EXPERIMENTS UPON ANIMALS 85 



more than absolutely necessary, avoiding much blood. The 

 material is placed upon a platinum needle and introduced into 

 the pocket; solid bodies, with a forceps. 



To hold the mouse still while the operation is going on a 

 little cone made of metal is used. The mouse just fits in 

 here. There is a slit along the top in which the tail can be 

 fastened, and thus the animal is secure and immobile. 



Intravenous Injections. Rabbits are very easily injected 

 through the veins. Mice are too small. 



Fig. 45. Method of making an intravenous injection into a rabbit. 

 Observe that the needle enters the posterior vein from the hairy surface 

 (McFarland). 



The ear of the rabbit is usually taken. It is first washed 

 with T : 2000 bichlorid, which not only disinfects, but .also 

 makes the vessels appear more distinct. The base of the ear is 

 compressed to swell the veins. Then a syringe, like the one 

 used for the injection of " tuberculin," a Koch syringe, which 

 can be easily sterilized, is filled with the desired amount of 

 virus and slowly injected into any one of the more prominent 

 veins present (Fig. 45). 



