:!•_' 1 



dried and weighed. 1 Ttie nature of the protein used to 

 immunise the rabbit and interact with the resultant anti- 

 serum is given under the heading "antigen and antiserum." 

 Incidentally these observations show that the precipit- 

 able content of different antisera varies greatly, from 0*8 

 mg. to 4'2 mg. per cc. of antiserum in those under consider- 

 ation. The conclusion that the precipitate must be com- 

 posed mainly of constituents of the antiserum has been 

 endorsed by Adami (17), and by Arrhenius (18) who states, 

 apropos of the interaction of small quantities of sheep 

 serum and its antiserum, "Der Haupttheil des Prlizii'itiits 

 stammt danach wahrscheinlich aus dem Prazipitin." 



(b) Total and partial interactions.— One reason for the 

 divergent views held by other observers lies in the failure 

 to discriminate between total and partial interactions. It 

 is a common experience that, when increasing quantities 

 of antigen interact with a fixed amount of antiserum, 

 iii(M-r;i>iug amounts of precipitate may be obtained, the 

 usual inference being that each increment of precipitate is 

 derived from each increment of antigen. We find, how- 

 ever, that this observation holds good only up to a certain 

 point which varies for each antiserum. After a certain 

 quantity (and concentration) of antigen have been reached 

 no further precipitate is obtainable from a given amount 

 of antiserum by any further addiment of antigen. We 

 interpret this to mean that it is possible to discharge 

 practically the whole of the precipitable content of an 

 antiserum by a sufficiency of antigen, and we distinguish 

 this as a total interaction. 



Different antisera, however, vary greatly in respect of 

 the amount (and concentration) of antigen required to yield 

 this maximal precipitate from fixed amounts of the antisera. 



, and also in Reference ( 



