UNSOLVED PROBLEMS 621 



from the immunologically inert and frequently undesirable com- 

 ponents of serum without at the same time denaturing or unduly 

 destroying the wanted immune substances. The economical concen- 

 tration of the unimpaired curative principles of serum in small 

 bulk in a solution of bland physiological action is the goal to be 

 striven for. From a purely practical standpoint, if antipneumococ- 

 cic serum is to render its greatest service, aside from an appre- 

 ciable lowering of the cost of the product, the elimination of super- 

 fluous protein and of antagonistic or chill-producing substances 

 constitutes a step of more immediate need. 



POTENCY TESTS ON THERAPEUTIC SERUM 



The early proximal or presumptive tests employed for estimat- 

 ing the curative value of antipneumococcic serums have gradually 

 been supplanted by methods that ensure a greater degree of accu- 

 racy in measuring the antibody content of the product. Great as 

 has been the effort expended in devising a technique that will at the 

 same time be simple and exact and afford a reliable index of the 

 curative value of the product, no method so far devised can be 

 looked upon as ideal. The principles involved are discouragingly 

 more complex than those met in the titration of antitoxic serums. 

 The direction that further endeavors should take is toward econ- 

 omy of means and time and a closer correlation between antibody 

 titer and therapeutic strength. It is now generally taken for 

 granted that precipitin and protective titer are the only factors 

 to be considered, but the possible importance of allied antibodies 

 should not be overlooked. 



The fairly successful production of specific serum for Type I 

 infections encourages efforts to prepare a product of enhanced 

 potency for Type II pneumonia and to attack from new angles the 

 baffling puzzle presented by Type III Pneumococcus. The devel- 

 opment of monovalent immune rabbit serums for these types and 

 for the types of relatively low incidence holds promising possi- 

 bilities. 



