G. W. McCOY 951 



RABIES VACCINE 



This product is employed in several different forms, none of wh'ch is satisfactorily 

 standardized. Some vaccines are made of killed virus, others of attenuated virus, and 

 still others of diluted "fixed" virus. The following specific requirements are in force: 



Vaccines marketed as killed virus shall be submitted to a test to show the absence of 

 living rabic virus. This is effected by requiring the inoculation subdurally of two rabbits, 

 each with o.i cc. of the finished emulsion, and keeping the animals under observation for 

 fourteen days — long enough to permit the development of the infection if any of the virus 

 may have escaped the killing agent. 



Vaccines prepared by the original Pasteur method and its modifications which utilize 

 living virus are submitted to tests to show that the virus is living in certain of the doses of 

 the preparations as they go on the market. The dried, attenuated virus should be lethal for 

 rabbits when inoculated subdurally with the dose that has been dried three days or less. 



When the dilution method is used, the lower dilutions must be capable of infecting 

 rabbits. 



ANTITOXINS 



The testing of antitoxins is the most satisfactory and accurate of any potency de- 

 termination carried on in the control of biological products. 



The potency of antitoxins is measured usually in standard units. In this connec- 

 tion, a unit may be defined as the amount of antitoxic strength contained in a stated 

 volume of a standard serum or antitoxin and used as a basis of comparison for measur- 

 ing the strength of other lots of the antitoxin. 



Standard units are distributed by central testing laboratories. For very accurate 

 work, standardized glassware for measuring and carefully selected animals must be 

 used for the tests, and in general conditions made uniform — but for routine testing 

 of commercial sera considerable latitude is permissible. 



DIPHTHERIA ANTITOXIN 



In essentials the unit established by Ehrlich (cf. Rosenau)' is employed practi- 

 cally everywhere in the world. 



In preparing to test diphtheria antitoxin, it is necessary to have a well standard- 

 ized specimen of toxin. The minimum lethal dose of the toxin — i.e., the amount nec- 

 essary to kill a 250-gm. guinea pig on the fourth day — is determined by means of a 

 series of trials with varying doses of toxin. This amount will afford a guide to the 

 doses to be used in determining the test dose. 



Wliile the unit of antitoxin is the ultimate basis of standardization, of almost 

 equal importance in practice is the "test dose" of toxin often spoken of as the L+ dose. 

 To determine this test dose, varying amounts of toxin are mixed with the standard 

 unit of antitoxin, the mixture incubated for one hour at room temperature and in- 

 jected into test animals. The result of this test — i.e., the death of the animals after 

 a certain period of time — enables one to select the proper test dose of the toxin for the 

 titration of antitoxins of unknown potency. 



Rosenau gives the determination of a test dose of a toxin shown in Table I. 



■ Rosenau, M. J.: Hygienic Laboratory Bull. No. 21. 1905. 



