38 



LABORATORY COURSE IN SERUM STUDY 



In measuring 0.05, 0.02 and 0.01 c.c. of complement it is best to use 

 a half c.c., .2 c.c. and .1 c.c. of a 1-10 dilution. Shake each tube 

 thoroughly when all the reagents have been added. Incubate one hour 

 in water bath at 37 C. and record by -f- or signs haemolysis at 15, 

 30 and 60 minutes in the following protocol: 



Indicate what the unit is in this case. 



The tabulation given for final record is the manner in which an 

 experiment of this kind is best recorded by experienced workers. We 

 have inserted the simpler protocols of the three series before this in 

 order to make the purpose of this experiment and its execution a little 

 more easy. 



(On account of the costliness of guinea-pig serum students should 

 divide themselves into groups of 3, of whom each student should set 

 up one series of amboceptor dilutions with one of the complement quan- 

 tities.) 



Individual guinea pigs vary in the complementary activity of 

 their serum. For accurate hsemolytic experiments, however, it 

 is necessary to use a constant amount of complement activity. 

 For this reason the unit of amboceptor (which if carefully pre- 

 served remains constant over long periods) is taken as a standard 

 to which the strength of each fresh complement serum is adjusted. 



Strictly speaking, the unit of complement should be that 

 amount which gives complete laking with one unit of cells and 

 one unit of amboceptor. In practice, however, this turns out to 

 be too large an amount, and for this reason complement is usually 

 titrated with two units of amboceptor. The unit of complement 

 then may be defined as the least amount that completely hemo- 

 lyses 1.0 c.c. of a five per cent emulsion of red cells in the presence 

 of two units of amboceptor in thirty minutes in the water bath. 

 If the test is done with smaller quantities of red cells the unit is 

 correspondingly smaller. Set up titrations with both two and 

 one units as follows: 



