Till' I'KKCII'ITIN HI- M I II >\. 



Titer or 



Dilution 



No. of Antisera. 



4,800 9,600 12,800 19,200 25,600 76,800 102,400 204,800 

 .11 4111 



The concentration of antigen in these dilutions being known, 

 it is possible to calculate the amount of protein present in the 

 last tube in which a positive reaction occurred. The anti- 

 serum with a titer of 4,800 positively identified the presence of 

 .0088 mgms. of goat serum. The most powerful antiserum 

 produced identified sheep serum when less than .0002 mgms. of 

 protein was present. The other antisera fell in between these 

 limits. Needless to say even the weakest antiserum employed 

 was far more sensitive to a specific protein than any chemical 

 method known. Much of the value of the precipitin reaction in 

 research is based on this great sensitivity. 



TABLE II. 



THE EFFECT OF ANTIGEN CONCENTRATION ON TITER. 



