1907.] Precipitum obtainable in Precipitin Interactions, etc. 163 
weighing 18 milligrammes, or more than seven times the weight of the 
homologous protein concerned. 
In experiment (2) also 2°5 milligrammes dried hen egg-white interacted once 
with 20 c.c. fresh hen egg antiserum (No. 41), and yielded a precipitum of 
18 milligrammes. | 
In experiment (3) 1 milligramme dried horse blood serum, interacting 
(a) with 19 c.c. fresh horse antiserum (No. 43) produced a deposit of 2°2 milli- 
gramines, or more than twice the weight of the homologous protein. The 
‘ residual homologous protein in the clear superfluid, interacting (0) with 13 c.c. 
of a second fresh horse antiserum (No. 42), yielded a further deposit of 
5 milligrammes, making 7-2 milligrammes in all, or more than seven times the 
amount of the original homologous protein. 
In experiment (4) (a) 1 milligramme dried ostrich egg-white, interacting 
with 20 c.c. fresh ostrich egg antiserum (No. 44), led to a deposit of 5 mulli- 
grammes, and (b) the subsequent addition of 4 milligrammes dried ostrich 
ege-white to the clear superfluid led to a further deposit of 11 milligrammes. 
In experiment (5) 1 milligramme dried hen egg-white, interacting (a) with 
18 cc. fresh hen egg antiserum (No. 47), brought down a deposit of 13 mill- 
grammes. The residual protein in the clear superfluid, interacting (>) with 
16 c.c. of a second fresh hen ego antiserum (No. 46), gave a further deposit — 
of 85 milligrammes. The resulting superfluid, again interacting (¢) with 
18 cc. of a third hen egg antiserum (No. 48), gave a third deposit of 4°4 milli- 
grammes. Thus, by allowing 1 milligramme of the homologous protein to 
interact successively with three antisera (which did not mutually interact), a 
total deposit of 25°9 milligrammes was attained. 
The progressively diminishing weights of precipitum obtained from the 
successive antisera in experiment (5) (a), (0), and (c), do not necessarily indi- 
cate that the homologous protein is being appreciably used up in the inter- 
actions. A difference in weight of deposit may be an indication merely of a 
difference in precipitability of antiserum, a circumstance to which we have 
already referred. This interpretation is consistent with the control obser- 
vations made with each of these antisera and fresh homologous protein, and 
also consistent with the progressively increasing weights of deposit obtained 
in similar circumstances in experiment (3) (a) and (0) and its corresponding 
controls. Thus in the control observations in experiment,(5), when 0°1 c.c. of 
each of the three antisera concerned was tested separately with 
0:00005 gramme homologous protein, it was found that the largest 
deposit was given by (a) antiserum No. 47, and the smallest by (c) antiserum 
No. 48. 
VOL. LXXX.—B. 
