596 BIOLOGY OF PNEUMOCOCCUS 



PRESERVATIVES, BOTTLING, AND LABELING 



The choice of a preservative for diagnostic serums is not so im- 

 portant as in the case of therapeutic products. A satisfactory pro- 

 cedure is the addition of tricresol to a concentration of 0.3 per 

 cent at the time of the collection of the serum from the clot. Any 

 resulting precipitate or detritus may be removed by centrifugation 

 or filtration prior to filling the serum into final containers. 



Containers of diagnostic serum should be labeled with the lot 

 number, the serological type, the dilution to be used (if any), a 

 notation of any cross-reactions produced, and an expiration date 

 beyond which no reliance can be placed upon the indicated po- 

 tency. Serums should be retested at intervals of three to four 

 months. 



Summary 



The main points developed in this chapter may be summarized 

 as follows. For stimulation of antipneumococcal immune sub- 

 stances in animals, vaccines made from highly virulent, type-spe- 

 cific cultures, killed preferably by heating at 100°, have given 

 satisfactory results. The so-called "three-week" schedule of injec- 

 tions is to be recommended, and the dosage of antigen should be as 

 small as is consistent with satisfactory immunological response as 

 indicated by repeated potency tests on the serum. Concentrated 

 and refined serum is preferable to unconcentrated serum for thera- 

 peutic use ; the method of Felton in which alcohol is used as a pre- 

 cipitant being at present the one most generally employed. Current 

 methods for determining the potency of serums are not wholly sat- 

 isfactory, but as long as the mouse protection test remains the ac- 

 cepted procedure, for the sake of uniformity this method should be 

 used. A standard serum for comparative purposes should be 

 adopted for use in the assay of antipneumococcic serum and, in the 

 event that a precipitin test is substituted for the in vivo method, a 

 standard preparation of type-specific pneumococcal polysaccha- 

 ride should be available. Standard methods for preparing and test- 



