476 INFECTION AND RESISTANCE 



fection or within a very definite period after inoculation. The 

 standardization of streptococcus sera may be accomplished by de- 

 termining its protective value for animals when injected 18 to 20 

 hours before infection. When the sera are produced by immuniza- 

 tion with streptococci obtained from the human body and without 

 pathogenicity for animals the standardization is of course unsatis- 

 factory. 



SERUM TREATMENT IN PNEUMONIA 



Attempts to work out a therapeutically valid method of passive 

 immunization in pneumonia have been many and date from the very 

 beginning of the discovery that pneumonia was a bacterial infection. 

 Sera have even been marketed and used, but until recently no very 

 encouraging results were obtained. Recent studies have revealed 

 that in pneumonia the serum of convalescents contains practically no 

 bactericidal properties for the pneumococcus, and that the protective 

 powers of such serum depend upon the presence of immune opsonins 

 or bacteriotropins, by means of which the pneumococci are ren- 

 dered amenable to phagocytosis. Virulent pneumococci are not as a 

 rule phagocytable in the presence of normal serum. However, in 

 the presence of immune serum powerful phagocytic action can be 

 observed. 



Neufeld has studied the conditions of pneumococcus immunity 

 most thoroughly in recent years. The most important advance from 

 a practical point of view was a discovery made by him, with Han- 

 del, 57 in 1909. They determined that there was a definite difference 

 between various pneumococci in their reactions to immune serum ; in 

 other words, pneumococci could be grouped into various serological 

 types. The serum produced with organisms of one type did not pro- 

 tect against infection with other strains. In consequence they called 

 attention to the importance of determining the type of pneumococcus 

 which causes the individual pneumonia so. that the corresponding 

 immune serum might be used. They produced a highly potent anti- 

 pneumococcus serum by the injection of horses and donkeys with 

 highly virulent pneumococci grown on fluid cultures, then deter- 

 mined the high protective power of this serum upon animals and 

 used it in the treatment of patients by intravenous injection. Their 

 results were exceedingly encouraging. In reporting their results 

 Neufeld and -Handel state that considerable doses must be given. 

 They call attention to the fact, revealed by their animal experiments, 

 that moderate amounts do not, as in the case of diphtheria serum, 

 exert a correspondingly slight amount of beneficial action, but that 

 in the case of the pneumonia serum amounts smaller than a certain 



57 Neufeld and Handel. Zeitschr. f. 1mm., Vol. 3, 1909, and Arb. am 

 (Jem kais. Gesundh. Amt. 3 Vol. 34, 1910. 



