20 LABORATORY COURSE IN SERUM STUDY 



render blood useless for hsemolytic purposes, nevertheless the 

 products of haemolysis do affect the hsemolytic reaction and it is 

 best to have an entirely clear alexin for use. 



The technique of bleeding of sheep or other large animals has 

 been described on page 2. 



LESSON II 

 BACTERICIDAL POWER OF NORMAL SERUM 



NORMAL blood plasma or serum possesses the power of killing 

 bacteria. Not all bacteria are equally susceptible to this effect. 

 Some, like the Gram-positive cocci, the anthrax bacillus, and 

 others, are probably killed in the circulation only by the co- 

 operation of serum and leucocytes in phagocytosis. When the 

 serum is heated to 56 C., its bactericidal power is suspended. 



Reagents : 



1. Fresh normal rabbit serum, unheated. 



2. Bacillus typhosus 24-hour broth culture diluted 1-5000 in 

 sterile salt solution. 



3. Sterile salt solution. 



The materials in this experiment must be measured with sterile 

 pipettes and placed in sterile test tubes, with care to avoid con- 

 tamination during the process of the experiment. 



(a) Place 0.5 c.c. of normal rabbit serum in each of two sterile 

 test tubes and heat one tube for half an hour at 56 C. Then 

 set up the following preparations in sterile plugged test tubes : 



1. Normal rabbit serum 0.5 c.c. + Typhoid broth (1-5000) 0.5 c.c. 1 



(fresh) 



2. Normal rabbit serum 0.5 c.c. + Typhoid broth (1-5000) 0.5 c.c. 



(heated) 



3. Salt solution 0.5 c.c. -f Typhoid broth (1-5000) 0.5 c.c. 



1 To make dilutions for this and other purposes proceed as follows : 



1. 1 c.c. of original substance to 9 c.c. of salt solution = 1-10 



2. 1 c.c. of dilution (1.) to 9 c.c. of salt solution = 1-100 



3. 1 c.c. of dilution (2.) to 4 c.c. of salt solution = 1-500 



4. 1 c.e. of dilution (3.) to 1 c.c. of salt solution = 1-1000 



5. 1 c.c. of dilution (4.) to 4 c.c. of salt solution = 1-5000 



This illustrates the general method, which can be shortened or lengthened 

 by longer or smaller intervals as the particular occasion requires. 



