250 



ANTITOXINS 



the amount of antihemolysin present in a serum, which is dependent on 

 the amount of serum necessary to protect the red blood-cells of rabbits 

 against a solution of the staphylolysin. 



(a) Staphylolysin. This is prepared by growing a known hemolysin- 

 producing staphylococcus in slightly alkaline broth for three weeks, 

 filtering through a Berkefeld filter, and preserving the filtrate with 0.5 

 per cent, phenol in the refrigerator. 



(6) Rabbit Blood. Remove 2 or 3 c.c. of blood from the ear of a rab- 

 bit and place in 5 c.c. of a 1 per cent, sodium citrate in normal salt solu- 

 tion. Wash the corpuscles three times, and make up in a 1 per cent, 

 suspension (dose 1 c.c.) or up to the original volume of blood (dose, 1 

 drop). 



(c) Patient's Serum. The serum is inactivated by heating to 56 C. 

 for half an hour. 



(d) Control Serum. As every normal serum contains a certain 

 amount of antilysin, it is necessary to use a normal control serum. 

 Normal horse serum, dried in vacuo to prevent deterioration, and freshly 

 dissolved for each test in 10 volumes of sterile distilled water or salt 

 solution, has been advocated by Bruck, Michaelis, and Schulze. 



(e) The Test. It is first necessary to titrate the staphylococcus fil- 

 trate, to ascertain the amount of lysin present. This is accomplished 

 according to the following scheme: 



TABLE 5. METHOD OF TITRATING STAPHYLOLYSIN 



In this test 0.1 c.c. is the smallest amount of lysin that can completely 

 hemolyze the given quantity of erythrocytes, and is taken as the unit 

 for the second part of the test. 



The lytic dose of filtrate just determined is now placed in a series of 

 small test-tubes, with increasing doses of serum to be tested and a con- 

 stant dose of corpuscles. 



