84 



APPLIED IMMUNOLOGY 



travenous injections of human blood-serum are made 

 into the rabbit in quantities of 1-2 c.c. every five or 

 six days. The strength of the antihuman serum thus 

 formed may be tested after three or four injections. 

 This is obtained by piercing a vein in the ear of the 

 rabbit, collecting a few cubic centimetres of blood, al- 

 lowing the clear serum to separate, and titrating it 

 with different dilutions of human serum. The dilu- 

 tions are to be made with normal salt solution. The 

 antiserum may be regarded as of sufficient strength 

 when 0.1 c.c will produce distinct cloudiness when 

 mixed with 1 c.c. of human serum in 1-1000 dilution 

 after incubation for five minutes at 37° C. The anti- 

 serum, moreover, must give no cloudiness with plain 

 salt solution, nor with the serum of any other animal 

 in 1-200 dilution after half an hour at 37° C. The fol- 

 lowing table illustrates the titration of a suitable anti- 

 human serum : 



Antihuman 

 rabbit serum 



Human 

 serum 1 c.c. 



Controls 



Result after incuba- 

 tion for y^ hour at 

 37° C. 



0.1 



0.1 

 0.1 

 0.1 

 0.1 

 0.1 



0.1 



1-10 



l-IOO 



1-1000 



1-5000 



1-10000 



1 c.c. normal salt 

 solution 



1 c.c. normal 

 guinea-pig ser- 

 um (1-200) 



Marked turbidity- 

 Marked turbidity- 

 Marked turbidity- 

 Turbidity 

 Slight turbidity- 

 Clear 



Clear 



