PRODUCTION OF ANTIPNEUMOCOCCIC SERUM 557 



check on the amount of salt added. No concentration of salt higher 

 than that sufficient to effect complete solution of the antibody pre- 

 cipitate should be used. For the majority of preparations 0.85 per 

 cent suffices ; concentrations higher than one per cent should not be 

 required. 



Reaction of the product. The buffering action of the blood is 

 ordinarily considered sufficient to compensate for minor fluctua- 

 tions in reaction from neutrality of substances introduced intra- 

 venously, but a system already strained by disease should not be 

 required to make any unnecessary adjustment of hydrogen ion 

 concentration in the blood. Antipneumococcic serum and concen- 

 trates used for clinical purposes, therefore, should be approxi- 

 mately neutral in reaction. The usual preparations for therapeutic 

 use show hydrogen ion concentrations ranging from pH 6.0 to 

 7.0, with the average approaching pH 6.5, and hence require no 

 readjustment. 



Preservatives. There is no substitute for sterility in products in- 

 tended for therapeutic use. It is customary, and is required by 

 governmental agencies, to add a preservative to antipneumococcic 

 serum. In some laboratories, the antiseptic is added when the se- 

 rum is drawn from the clot. The precipitate which sometimes 

 forms, sediments during storage in the cold. Other manufacturers 

 prefer to add the preservative at some stage during concentration 

 or final processing. In either case, the preservative should be added 

 prior to final filtration. The purpose of the preservative is not to 

 destroy contaminating organisms but to prevent the growth of any 

 adventitious bacteria. 



The choice of preservative, and the concentration of the bac- 

 tericidal agent, are questions of no small moment. Investigations 

 conducted by Hale (1913) 586 with tricresol when used as a pre- 

 servative in antimeningococcic serum led him to conclude that the 

 agent is dangerous when serum is to be introduced by a route 

 that brings the agent into direct contact with the nervous cen- 

 ters. Leake and Corbitt (1917) 794 attempted to determine the tox- 



