88 



A LAX ARTHUR BOYDEX. 



in the determination of antigen concentration. The precipitin 

 reaction seems worthy of better technique than this. 



4. The Effect of the Time of the Reading on Specificity. 

 Since the liters (both homologous and heterologous) of fifteen 

 antisera have been recorded at twenty, forty, and sixty minute 

 intervals, the effect of time on the specificity of the reactions can 

 be shown. The results are given in Table IV. 



TABLE IV. 



RELATIVE SPECIFICITY OF READINGS AT 20, 40, AND 60 MINUTES. 



Anti-scrum. 



A2I anti-pig 



A24 anti-beef 



P40 anti-sheep. 



The three antisera whose reactions are given in Table IV. 

 have been taken at random from the entire number and are 

 believed to be typical of them all. Of the eighteen heterologous 

 reactions recorded fourteen showed a greater specificity at twenty 

 minutes than at forty minutes or one hour. That is, the heterolo- 

 gous reactions at twenty minutes were proportionally less com- 

 pared with the homologous reactions at the same time than at 

 Those facts are of significance, for in medico- 



