EXPERIMENTA TION UPON ANIMALS. 



159 



of Meyer and Roux resemble ordinary hypodermic 

 syringes; that of Koch is supposed to possess the decided 

 advantage of not having a piston to come into contact 

 with the fluid to be injected. This is, however, some- 

 what disadvantageous inasmuch as the cushion of com- 

 pressed air that drives out the contents is elastic, and un- 

 less 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 



FIG. 40. I, Roux's bacteriological syringe; 2, Koch's syringe; 3, Meyer's 

 bacteriological syringe. 



air beneath the skin, but in intravenous injections it is 

 commonly supposed to be dangerous. 



All syringes should be disinfected with 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 be 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 in a 

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

 animal, and wellnigh impossible in anything smaller than 

 a rabbit. Such injections when given to rabbits are gen- 

 erally made into the ear-veins, as those most conspicuous 

 and accessible (Fig. 41). A peculiar and important fact 

 to remember is, that the less conspicuous posterior vein 



