264 



BACTERIOLOGY. 



Fig-. 42 is made use of. This apparatus can be readily im- 

 provised out of an ordinary 250 c.c. measuring cylinder. 



Usually, bouillon cultures are employed for the pur- 

 pose of injection. Occasionally, however, the bacterial 

 growth is on a solid medium, like agar or potato. In that 

 case, bouillon or sterile water should be introduced into the 

 tube by means of a drawn out tube pipette (Fig. 61). The 



growth is then thoroughly 

 stirred up in the liquid by 

 means of the end of the 

 pipette. The suspension is 

 then drawn up into the tube, 

 and transferred to a sterile 

 Esmarch dish, or to a small 

 sterile conical test-glass (Fig. 

 43). In the case of a bouillon 

 culture, this is transferred 

 directly to the sterile vessel. 

 The neck of the tube, after 

 withdrawal of the cotton 



Fig. 42. Apparatus for injecting large quantities of liquid. 



plug, must, of course, be heated in the flame before pouring 

 out the culture. 



When injecting small animals care must be taken that 

 the needle does not pass through the abdominal wall into 

 the peritoneal cavity. A fold of the skin should be raised, 

 and the needle inserted while the syringe is held in a 

 position almost parallel to that of the body. A success- 

 ful subcutaneous injection will show a swelling over the 

 place of inoculation. 



The injection is made most conveniently over the abdominal 

 wall, inasmuch as the skin is softer there than elsewhere. The rabbit 



