104 IMMUNE SERA 



mann-Uhlenhuth precipitin test, page 112, and the 

 recent Neisser-Sachs test, page 70. 



Practical Value of Injections of Bactericidal Sera. 



- The use of sera having specific protective 

 properties has been tried practically on a large 

 scale in man as a preventive of infection. It is 

 difficult to estimate just what value these injections 

 have had. In susceptible animals, injections of 

 some of the very virulent bacteria, as pneumococci, 

 streptococci, typhoid bacilli, and cholera spirilla, 

 can be robbed of all danger if small doses of their 

 respective serums are given before the bacteria 

 have increased to any great extent in the body. 

 If given later they are ineffective. For some 

 bacteria, such as tubercle bacilli, no serum has 

 been obtained of sufficient power to surely prevent 

 infection. Through bactericidal serums, therefore, 

 we can immunize against an infection, and even 

 stop one just commencing; but as yet we cannot 

 cure an infection which is already fully developed, 

 though even here there is reason to believe that we 

 may possibly prevent an invasion of the general 

 system from a diseased organ, as by the pneumo- 

 coccus from an infected lung in pneumonia. On 

 the whole, the bactericidal sera have not given, as 

 observed in practice, conclusive evidence of great 

 value in already developed disease. 



It is apparent from all that has been said that a 

 deeper insight into the mechanism of the bacteri- 



