STANDARDIZATION OF SERUMS. 185 



Any other high-grade serum would have answered 

 equally well. 



The institute keeps in stock a large number of 

 vials, each containing 2 grains of this dried 

 serum. The air and moisture are exhausted from 

 each vial and the latter is then sealed in the flame. 

 Once in three months one of these vials is broken 

 open carefully and the serum dissolved in 200 c.c. 

 of a solution made up of equal parts of glycerin 

 and 10 per cent, salt solution; hence each cubic 

 centimeter of the solution contains 17 units. Dur- 

 ing the succeeding three months this antitoxic 

 solution is used in the comparative valuation of 

 new antitoxins; the solution retains its strength 

 unaltered for this period. For individual tests 

 the serum-solution just described is again diluted 

 seven teenf old, so that each cubic centimeter con- 

 tains one unit. This adds to convenience and ac- 

 curacy. 



The first step in the process is to standardize 

 some diphtheria toxin in which the degenerative 

 changes (toxoid formation) have come to a stand- 

 still. This is done by adding so much of the toxin 

 to 1 unit (1 c.c.) of the test serum that an excess 

 of one fatal dose of the toxin remains unbound by 

 the antitoxin. 



The quantity of the toxin which gives this re- 

 sult is called the L+dose. 6 The LO dose of the 



the serum of one of his horses has a high value he may 

 draw a small amount of blood from the animal and send 

 the serum to Frankfurt for a preliminary test. If the 

 serum is sufficiently strong he may then bleed the horse 

 freely ; if it is weak he will be advised to continue the 

 immunization for a time. 



6. L=Limes (Limit) : -f is commonly used to indicate 

 a fatal result. 



