96 LABORATORY COURSE IN SERUM STUDY 



has formed, the tubes can be shaken up and the ordinary precipitin reac- 

 tion (i.e., turbidity and flocculation) can be observed. Note the results 

 after one half hour and one hour at 37 C. and again after 12 hours in 

 the ice box. Is there a "pro zone"? 



Experiment 2 



EFFECT OF HEAT ON PRECIPITINS 



Heat slowly inactivates precipitins. They cannot be reactivated 

 by fresh serum (alexin, complement), in this regard differing from haemoly- 

 sins and bactericidal antibodies. 



Heat 0.5 c.c. of precipitin serum for two hours at 60 C. Mix 

 0.1 c.c. of the heated serum with 0.1 c.c. of that dilution of the antigen 

 which was found in Experiment 1 to give the optimum precipitation. 



Mix 0.1 c.c. of the heated serum with 0.1 c.c. of fresh normal rabbit 

 serum and test this mixture also with the optimum dilution of antigen. 

 Make observations. after 1 hour at 37 C. and again after 12 hours in ice 

 box. 



For each student: 



2 c.c. Immune serum (rabbit whose preparation was begun in 



Lesson I). 

 1 c.c. Antigen serum (human, sheep or horse serum for half the 



class, other animals' sera for the other half). 

 Salt solution. 



12 Precipitation tubes. Test tube rack. Nipple pipette. 

 6 one-c.c. graduated pipettes. 

 0.1 c.c. normal rabbit serum, fresh, 

 8 f-inch test tubes. 



Precipitins can also be produced against proteins heated to 

 70 or over. For the principles of such experiments see Infection 

 and Resistance, page 260. 



