26 



GENERAL TECHNIC 



piece of fresh cotton should be placed in the oven at the time of steriliza- 

 tion, and when this has turned a light-brown color, sterilization is com- 

 pleted. 



3. After a tube has been used for holding living and infectious or- 

 ganisms, as in making bacteriologic, agglutination, 

 and opsonic tests, etc., the tube and its plug 

 should be boiled in water or a 1 per cent, solution 

 of caustic soda before it is again handled. In 

 making hemolytic experiments, the material is not 

 usually infectious, and it is sufficient to wash the 

 tubes without previous boiling. In every case all 

 traces of acids or alkalis must be removed by copious 

 washing in plain water, as the slightest trace of 

 either may interfere with the accuracy of some 

 of the tests. Cheaper grades of glass may contain 

 relatively large amounts of alkali, which would 

 introduce a disturbing element in the reactions. 



SYRINGES 



A good syringe is indispensable in perform- 

 ing bacteriologic and immunologic work. Various 

 sizes should be at hand, but usually a graduated 

 5 c.c. syringe answers most purposes. 



1. Many kinds of syringes are on the market. 

 Those with rubber or leather plungers and pack- 

 ings are unsatisfactory, as they cannot be sterilized 

 by boiling and soon leak. Nothing is more 

 exasperating than a leaking syringe, as with the 

 feakage unknown quantities of inoculum are lost, 

 not to mention the possible dangers of con- 

 taminating the fingers, the animal, and the labora- 

 tory. 



Syringes with metal or glass plungers are to 

 be preferred, as are also those upon which the 

 needle may be fitted without screwing (Fig. 8) . 

 The old Koch syringe is fitted with a rubber bulb for filling and ex- 

 pelling the fluid. This arrangement is well adapted for making sub- 

 cutaneous injections, but is somewhat dangerous for purposes of mak- 

 ing intravenous injection, on account of the danger of injecting air. 



FIG. 8. A SATISFAC- 

 TORY SYRINGE (Rec- 

 ord). 



This syringe has 

 a glass barrel and met- 

 al plunger. It is easily 

 sterilized, durable, and 

 works smoothly and 

 accurately. 



