248 STUDIES IN IMMUNITY. 



the milk (tube 2), unless the latter had undergone some combina- 

 tion with the specific serum similar to that described by Bordet and 

 by Bordet and Gengou for bacteria and corpuscles treated with their 

 appropriate immune sera. We may admit, then, that the serum of 

 rabbits that have been given injections of cow milk contains, in 

 addition to the precipitin, a sensitizer similar to those of antimi- 

 crobial and hemolytic sera, which gives cow milk the power to fix 

 the alexin of normal serum. 



The serum of rabbits injected with egg white. These animals were 

 given large doses of egg white; at intervals of 7 days they received 

 10, 10, 12 and 10 c.c. of egg white and 14 days after the last injec- 

 tion they were bled. The serum designated serum rabbit > egg 

 was heated to 56 C. for 30 minutes; clear normal rabbit serum was 

 used as alexin. 



An experiment wholly analogous to the one with rabbit > milk 

 serum, 56 degrees, was made with this rabbit >egg serum. In place 

 of milk, egg white was used. 



The results of such an experiment are identical with those 

 described for heated rabbit > milk serum. It is found that alexin 

 is fixed by hen-egg white in the presence of rabbit > egg serum 

 (56 degrees), whereas no such fixation occurs with heated normal 

 rabbit serum (tube 2) or with egg white alone (tubes 3 and 4). 



The rabbit > egg serum also gives a precipitate with egg white 

 which normal rabbit serum fails to do. 



The sera of rabbits injected with heated dog serum (56 degrees). 

 This serum, rabbit > dog serum, 56 degrees, was obtained in a 

 manner similar to the other sera described. The rabbits were 

 given at week intervals 8, 10 and 12 c.c. of dog serum that had been 

 heated to 56 degrees. The treated rabbits were bled 2 weeks after 

 the last injection and the separated serum was heated to 56 degrees 

 for one-half hour. 



Experiments similar to those described for the other active sera 

 were performed with this serum active against dog serum; similar 

 controls were also made and need not again be specified. The 

 important tubes are as follows: 



(a) Rabbit alexin, 0.1 of a cubic centimeter, serum rabbit > dog 

 serum, 56 degrees, 0.6 of a cubic centimeter, dog serum, 56 degrees, 

 0.2 of a cubic centimeter. 



