THE STREPTOCOCCI 433 



Leucocyte extracts 103 have been employed in various forms of 

 streptococcus infections of man, with success in many cases. Favor- 

 able results have been obtained with these extracts in cases of ery- 

 sipelas. 



The agglutinins found in streptococcus immune sera are usually 

 most active toward the race of bacteria employed in the immunization. 

 Other streptococci are also agglutinated, but in relatively higher con- 

 centration. While a specific group reaction is useful in differentiating 

 streptococci from other species, agglutination can not be relied upon 

 to differentiate individual streptococci from one another (Hiss). It 

 has been found that a serum produced with a streptococcus from one 

 source contained a higher agglutinating value for some other, strep- 

 tococcus than for the one employed in its production. Agglutinins 

 may be produced by treating animals with dead as well as with 

 the living streptococci. The technique of streptococcus agglutina- 

 tion is difficult unless we are dealing with strains which grow with 

 even clouding in fluid media. The frequent spontaneous clumping 

 in broth cultures necessitates the use of a special technique. The 

 most simple of these methods is the one in which calcium-carbonate- 

 glucose broth is used for cultivation. 104 Growing in this medium 

 and thoroughly shaken once a day, the streptococci are found evenly 

 divided in the supernatant fluid after the settling out of the calcium- 

 carbonate powder. 



This method, however, is not often successful. In fact, a con- 

 stantly reliable method for the agglutination of hemolytic strepto- 

 cocci has not yet been devised. 



The method upon which recent antigenic study has been based, 

 has depended upon the use of a special sugar free broth containing 

 buffers, since, in acid cultures, the clumping of streptococci is par- 

 ticularly noticeable. This method has been developed particularly 

 by Krumwiede and by Dochez and Avery. 



The special broth for these purposes is made from heart muscle 

 which is carefully selected so that fat is avoided, and instead of 

 using sodium chloride, a sufficient quantity of a balanced phosphate 

 mixture is added to give the required salt concentration, and to 

 adjust the hydrogen ion to a P H of 7.4. The hemolyticus is grown 

 on this for twenty-four hours, at which time it usually produces 



103 Hiss, Jour. Med. Res., xix, 1908. 



104 7/is.s, Jour. Exp. Med., vii, 1905. 



