126 



Scientific Proceedings (112). 



Substances which have a smaller molecular structure than the 

 whole proteins and are more diffusible, can react with cells without 

 the intervention of antibodies. The determining criterion, there- 

 fore, upon which it depends whether a substance is antigenic or, 

 in other words, an antibody former, is, therefore, its ability or 

 inability to diffuse. 



In the case of substances which can pass through membranes 

 to some degree, antibody formation is not necessary, and hyper- 

 susceptibility may depend upon changes which cannot be measured 

 as we can measure antibodies. 



Also, because of the diffusible nature of these substances, the 

 reactions may be intracellular and this would account for the later 

 inflammatory reactions due to definite cell injury. 



60 (1642) 



A modification of Folin's uric acid method. 



By HENRY JACKSON, JR. and WALTER W. PALMER. 



[From the Chemical Division, Medical Clinic, Johns Hopkins Uni- 

 versity and Hospital, Baltimore, Maryland.] 



In an effort to improve Folin's uric acid reagent it was found 

 that by dialyzing under special conditions Folin's solution and 

 evaporating the solution so dialyzed a superior reagent was ob- 

 tained. A similar, though not identical, reagent was prepared by 

 boiling down Folin's solution and filtering off the precipitate. 

 When mixed in the proper proportions these two substances yield a 

 reagent superior to Folin's in the following respects. 



1. There is no precipitate such as is frequently encountered 

 with Folin's solution. 



2. The color developed with a given quantity of uric acid is 

 about four and a half times as intense as that developed in Folin's 

 method. 



3. The color does not fade over a period of many hours. 

 Since this work was done we have learned of Wu's isolation 



of the pure ammonium phospho-18-tungstate. 1 This substance 

 was prepared by his method and its chromogenic powers were 

 found to be the same as those of our salt. Like the latter the 



1 H. Wu, Jour. Biol. Chem. 1920, xliv, 189. 



