i IIP 



-iTix 



i< \( no\. 



parable results and will come to make total nitrogen determi- 

 nations on all antigens used in titrations. Perhaps it would be 

 well to speak of the latter as secondary antigens to distinguish 

 them from proteins injected into animals for the purpose of 

 inducing antibody formation which would then be called primary 

 antigens. 



TABLE III. 



NITROGEN DETERMINATIONS ON STANDARD SOLUTIONS. 



Now when proteins other than fresh sera are used as secondary 

 antigens, the necessity of determining their concentration is 

 very much greater. For the concentration of protein in the 

 sera of animals which have died of various diseases (so often 

 used by Nuttall), or in extracts of filter paper soaked in blood 

 and then dried, or in extracts of blood stains from various 

 objects, or in extracts of tissues, varies exceedingly. This it 

 seems was the chief source of error in Nuttall 's work as it has 

 also been in the work of many others. For heretofore nothing 

 but a foam test, or a crude nitric acid boiling test have been used 



