606 BIOLOGY OF PNEUMOCOCCUS 



Specific serum therapy has a marked effect in preventing blood 

 invasion, and blood cultures previously positive usually become 

 negative within a few to twenty-four hours or more. The area of 

 lung involvement with few exceptions ceases to spread. If exten- 

 sion occurs, it takes place slowly. By contrast, extension is fre- 

 quent in those not treated with antiserum. Resolution appears to 

 be unrelated to immunity factors and is not obviously affected by 

 specific treatment. 



Antiserum appears to have little or no effect in reducing such 

 complications as endocarditis and meningitis. Observations in 

 Great Britain 887 suggest that the incidence of empyema may be 

 reduced. 



The crucial test of the value of antiserum is its effect on the 

 case fatality rate. The expected case fatality rate without specific 

 therapy for Type I infections may be estimated from a large series 

 of civilian cases, collected from the literature by Heffron, at about 

 25 per cent. Of 1,614 cases occurring in the United States and 

 Canada, 403 or 25.0 per cent died (Figure 2). In Great Britain 

 the fatality rate of Type I cases is somewhat lower than this. 



Figure 2 



type i : comparison of death rates of cases whose serum 



treatment was begun within ninety-six hours of 



onset and of cases not given serum 



504 cases, 56 deaths 



wSi.«A™t Illllllllllllllllillil «-°2> 



1,614 cases, 403 deaths 



* Massachusetts Pneumonia Study cases, 

 t Cases collected from the literature. 



With these figures for comparison, Heffron finds that of 2,458 



