270 Experimentation upon Animals 



be injected. This is, however, really disadvantageous, 

 inasmuch as the cushion of compressed air that drives out 

 the contents is elastic, and unless carefully watched will 

 follow the injection into the body of the animal. In making 

 subcutaneous injections there is no disadvantage or danger 

 from the entrance of air, but in intravenous injections it is 

 extremely dangerous. 



Syringes with metal or glass pistons are excellent, though 

 not very durable. All syringes should be disinfected with 5 

 per cent, carbolic acid solutions before and after using, the 

 carbolic acid being allowed to act for some time and then 

 washed out with sterile water. Syringes should not often be 



Fig. 74. Method of making an intravenous injection into a rabbit. 

 Observe that the needle enters the posterior vein from the hairy 

 surface. 



boiled, as it ruins the packings, whether of asbestos, leather, 

 or rubber. 



The intravenous injections differ only in that the needle 

 of the syringe is introduced into a vein. This is easy to 

 achieve in a large animal, like a horse, but is very difficult 

 in a small animal, and well-nigh impossible in anything 

 smaller than a rabbit. Such injections, when given to rab- 

 bits, are usually made into the ear-veins, which are most 



