516 J. H. RICHARDS 



work of Swift and Thro (1911) in their study of streptococci 

 by the use of complement fixation. The difficulties of the test 

 lie in the preparation of efficient antigens. The one that has 

 given most satisfactory results in our hands is the unkilled, 

 thoroughly washed, salt ground bacterial emulsion. Tn our 

 comparative experiments this method gave a greater difference 

 between the fixing power and the anticomplementary dose than 

 the Besredka dried antigen, the heated and killed bacterial emul- 

 sion, or the extracted filtered antigen. Swift and Thro found the 

 fixing power of an extract made from dried bacteria highest com- 

 pared to the anticomplementary power. At the beginning of 

 this work, several antigens (5 to 9) prepared from different strains 

 of Streptococcus viridans were used. Hastings (1914) found the 

 necessity for the employment of many antigens to be due to the 

 fact that a group reaction could not be obtained. We also found 

 this necessary when working with an antigen of high anticom- 

 plementary action. But when an antigen was prepared as 

 just described a polyvalent antigen of pooled strains all from 

 Arthritis deformans gave satisfactory results on account of the 

 higher fixing power — anticomplementary ratio. This is illus- 

 trated by the results of case 25 on the table appended. An 

 autogenous antigen was not found more efficient than this poly- 

 valent antigen excepting in case 6. In this case we obtained no 

 inhibition excepting with an antigen prepared from an autogenous 

 tooth culture. For the past two years our bacterial vaccines 

 have been standardized by their nitrogen content. This has 

 been found much more accurate than the Wright method of 

 counting, Of late it has been found convenient to determine a 

 working dilution of our antigens by this method, and usually 

 the fixing power and the anti-complementary dose could be de- 

 termined in a dilution containing 0.000028 gram bacterial nitrogen 

 per cubic centimeter. 



Joint cultures were attempted in 54 cases and Streptococcus 

 viridans was obtained in 4 cases. These cultures were taken 

 during an acute exacerbation, and an attempt was made to 

 obtain fluid from the inflamed periarticular tissues as well as 

 from the joint cavity. 



