AGGLUTINATION. 537 



passed through animals. If passage is discon- 

 tinued it reverts to its former condition. 



The variations are such that the agglutination 

 reaction is of little or no value in differentiating 

 different types of streptococci. 



As to the clinical value of the test for the diag- 

 nosis of scarlet fever, the conclusions of Weaver 

 may be cited : 



1. Of streptococci cultivated from cases of scar- 

 latina, some are agglutinated by almost all scar- 

 latinal sera, but at dilutions varying from 1/60 

 to 1/4000; others are agglutinated by the same 

 sera with less constancy and at lower dilutions, and 

 many are not agglutinated at all. 



2. Streptococci cultivated from cases of scar- 

 latina are agglutinated by sera from cases of lobar 

 pneumonia and erysipelas at about the same dilu- 

 tions as by scarlatinal sera, and in the case of ery- 

 sipelas even at higher dilutions. 



3. The same appears to be true of typhoid fever 

 serum, so far as limited tests indicate, and to al- 

 most the same extent of puerperal-fever serum. 



4. The agglutination reaction between the 

 streptococci cultivated from cases of scarlatina and 

 the serum from cases of scarlet fever is in no way 

 specific, and can not be of any value as a means of 

 diagnosis. 



By growing streptococci on a medium which 

 contains serum (serum bouillon), they form fewer 

 and shorter chains and are better suited for ag- 

 glutination tests. 



III. STAPHYLOCOCCI. 



Staphylococci are spherical cells from 0.7 to 0.9 

 microns in diameter, typically, and by light stain- 



