124 



COLLECTED STUDIES IX IMMUNITY. 



the action of the normal active serum, while somewhat larger quan- 

 tities weaken the action. Still larger quantities may inhibit the 

 action completely. 



In the following experiment an immune serum was employed 

 which had been obtained by immunizing a goat with vibrio Nord- 

 hofcn. This serum w T as inactivated by heating it to 57 C. Normal 

 active goat serum served as complement. (See Table III.) 



The first column shows that normal active goat serum by itself 

 kills bacteria, even in doses of about 0.1 cc. The fourth and fifth 

 columns show that this bacteriolytic effect of the normal active goat- 

 serum is in no way affected by the addition of 1.0 cc. or 0.1 cc. in- 

 active normal goat serum. From the third column we see, however,, 

 that if we add to the normal active goat-serum 0.1 cc. inactive im- 

 mune serum, the bacteriolytic effect of the former is lowered, and 

 that it is almost neutralized when 1.0 cc. of the inactive immune 

 serum is added. (Column 2.) 



TABLE III. 



Control I. Trnr cc - bouillon culture + 2 cc. 0.85% salt solution + 3 drops 

 bouillon = oo. 



" II. Sterility of the inactive immune serum, 0. 



' HI. " ti it <i normal goat serum, 0. 



" IV. " " " active normal goat serum, 0. 

 Three drops of bouillon to each tube. 



All the tubes made up to equal volumes with 0.85 % salt solution. 

 Kept in the thermostat at 37 C. for three hours. 

 Finally, two drops of each specimen plated on agar. 



