928 ANTIBACTERIAL SERA 



the only method which seems to have any relation to its therapeutic value. Since virulent 

 strains must be employed, this test can be done only in isolated laboratories by experts and 

 cannot be employed as routine in the usual laboratory. 



ANTI-PNEUMOCOCCIC SERA 



The pneumococci of the three fixed types, I, II, and III, are highly specific in 

 their immune reactions, so that a serum effective against one type has little or no 

 value against the others or against the miscellaneous group IV. Sera have been pro- 

 duced against type I and type II pneumococci, both as monovalent and as poly- 

 valent sera. Of these, type I serum is the easier to prepare in high potency, and is the 

 one with which most clinical work has been done. The type I serum was the original 

 serum prepared at the Rockefeller Institute. Because of the difficulties in preparing 

 type II and type III sera, it has been advised that typing be done in each case and 

 that the serum be administered only in type I cases. Later, Park, of the Bureau of 

 Laboratories, Department of Health of New York City, produced a potent type II 

 serum which, in a series of clinical tests, has shown definite therapeutic value. Up to 

 the present, no one has succeeded in preparing a therapeutically effective type III 

 serum. 



Preparation. — The methods of immunization are the same for the monovalent fixed type 

 of sera and for the polyvalent serum. The procedure for all may be described under one 

 heading, with the understanding that the end-product depends upon the antigen used. 



The usual method is to inject horses intravenously with small doses of killed organisms, 

 followed later by emulsions with living organisms. It is thought necessary to start with 

 virulent strains, but it is unwise to grow the organisms in media which retain the virulence, 

 since this is unnecessary and destructive to the horses. The method of one of us (F.M.H.) 

 is to grow the organisms eighteen hours in hormone gelatin broth, centrifuge, re-emulsify the 

 organisms in salt solution, and kill by heating to 55° C. for thirty minutes. Sodium bicar- 

 bonate to the amount of 0.25 per cent is added to the emulsion before heating. It has been 

 found that after this addition the horses tolerate the injections much better and that the 

 immunity rises faster. After treatment with killed organisms for two weeks, living organisms 

 are employed, giving from one to three injections per week, gradually increasing the dosage 

 until the animals receive 3, 5, and 10 cc. of an emulsion containing 50,000 million organ- 

 isms per cubic centimeter. At the end of six weeks, trial bleedings are made and the serum 

 is tested for potency according to the method specified by the Hygienic Laboratory. 



Method of testing. — The protection test, prescribed by the Hygienic Laboratory of 

 the United States Public Health Service, is described in chapter Ixxii of this volume 

 (see pp. 958, 959). 



When type I serum has reached a point where 0.2 cc. protects white mice 

 against o.oi-o.i cc, of a culture of type I pneumococcus, of which o.oooooooi cc. 

 will kill a white mouse in forty-eight hours, the serum is then regarded as potent. In 

 the production of type II serum, the usual potency found is a serum of which 0,2 cc, 

 protects a white mouse against 0,01 cc. of a type II culture which kills in 0.00000001 

 cc. Park has produced a serum protecting against 0,1 cc, and the authors have recently 

 produced a similar serum. The type III potency is that of a serum of which 0.2 cc. 

 protects against o.oi cc. of a culture which kills in o.ooooooi cc. 



In the authors' opinion, however, a more reliable criterion of the value of an 



