4. Draw off serum with sterilized pipette and run 

 into test-tubes. 



5. Place tubes in blood-serum sterilizer and heat to 

 68 or 70 degrees C. for one hour on five successive days. 



6. Place tubes in the apparatus for solidifying blood- 

 serum and heat to 75 or 80 degrees C, until the serum 

 is coagulated. 



H, BLOOD-SEEUM (QUICK METHOD.) 



(Serum made in tlie following manner is, as a rule, more opaque 

 than that prepared as indicated above; but for all practical purposes 

 it is admirable. Much time and annoyance are saved, and imper- 

 fect sterilization, by means common by the other method, is 

 avoided). 



1-4 See G. 



5. Place the tubes in the serum sterilizer and heat 

 at once to 90 or 95 degrees 0. for one hour or more. 



6. Place the tubes (in an inclined position) in the 

 steam sterilizer for one hour or more. 



(It is advisable not to allow the temperature in the steam sterili- 

 zer to run too high or bubbles may result in the solid serum. 

 With the Arnold steam sterilizer, the inside cover may be left off, 

 or with other sterilizers, full gas pressure need not be used.) 



7. Place the tubes in baskets as usual, and steam for 

 from fifteen to thirty minutes on two successive days. 



57 



