1910.] Precipitate Obtainable in Precipitin Interactions. 403 



When the quantity of protein is not sufficient to neutralise all the 

 precipitin in a given amount of antiserum the weight of jirecipitate is 

 diminished. An experiment showing the relation of the precipitate to the 

 amounts of the interacting bodies may be now described. A rabbit was 

 immunised by the injection of 9"6 grammes dried egg-white in eight doses. 

 The quantities employed and the results obtained are recorded in Table IV. 



Table IV. 



No. of 

 tube. 



Amount of 

 antiserum. 



Weight of 

 protein. 



Amount of 

 saline solution. 



Weight of 

 precipitate. 



Weight of pre- 

 cipitate from 

 1 c.c. antiserum. 





c.c. 



milligrammes. 



c.c. 



milligrammes. 



milligrammes. 



1 



3 



1 -44 



50 -0 



1 -0 



0-33 



2 



3 



3-6 



50 -0 



1 -5 



0-5 



3 



3 



7-2 



50-0 



2-0 



0-66 



4 



3 



14-4 



50-0 



2-7 



0-9 



5 



3 



28 -8 



50 -0 



4-2 



1 -4 



6 



3 



144 -0 



50 -0 



6-5 



2-2 



It will be seen that the amount of antiserum was 3 c.c. in each tube. 

 This quantity yields such small precipitates in the tubes Nos. 1 and 2 that 

 great stress cannot be placed on these figures. The weight of the precipitates 

 has steadily increased. The amount of antiserum obtained from a rabbit 

 is not usually more than 20 c.c, so that extended series cannot be carried 

 out with antisera from rabbits. It was not considered legitimate to employ 

 mixed antisera. Other series gave similar results, but at present the data 

 are too few to discuss these results at length to determine the type of the 

 interaction. 



The effect of the degree of dilution on the weight of precipitate may be 

 now considered. Two series of experiments were carried out. In the first 

 series the quantity of egg-white was constant and the amount of saline 

 solution used to dilute the interacting masses was varied. In the second 

 series the concentration of egg-white was maintained constant in the varying 

 amounts of saline solution. The antisera employed were two fowls' egg- 

 white antisera prepared from rabbits. The results are recorded in Table V. 



The results of both series correspond, though the absolute amount of 

 precipitate from each antiserum was different. With a quantity of saline 

 solution of 25 c.c. there was a reduction in the weight of precipitate. All 

 observers have noted this reduction, which has been usually ascribed to 

 a solvent action of the concentrated serum. With a quantity of saline 

 solution of 100 c.c. the weights of the precipitates were also slightly reduced. 

 This reduction was probably due to incomplete reaction in 48 hours, since 



