254 STUDIES IN IMMUNITY. 



In addition to this series, comprising two tubes for each milk 

 tested, other tubes with decreasing doses of active and normal 

 serum, e.g., 0.4, 0.2 and 0.1 of a cubic centimeter, but all containing 

 the same amount of alexin and milk, were prepared. 



In none of the tubes containing normal rabbit serum, 56 degrees, 

 do the various milks fix alexin; in all tubes containing rabbit > milk 

 serum, on the contrary, an alexin absorption occurs. There is no 

 evidence of specificity with this serum in a dose of 0.6 of a cubic 

 centimeter of serum, 0.1 of a cubic centimeter of alexin, and 0.2 

 of a cubic centimeter of each milk in turn. Nor does decreasing 

 the active serum to 0.1 of a cubic centimeter show any difference 

 between the cow, ewe and goat milk. Human milk, however, was 

 less perfectly sensitized by the serum, even in a dose of 0.6 of a 

 cubic centimeter of serum to 0.2 of a cubic centimeter of milk; 

 fixation was not quite complete, and is almost nil with 0.2 of a 

 cubic centimeter of serum. 



Mare milk seems to lie between the first group of milks and 

 human milk ; a total fixation occurs with 0.6 of a cubic centimeter 

 of serum, 0.4 of a cubic centimeter or even with 0.2 of a cubic cen- 

 timeter, but only an imperfect fixation with 0.1 of a cubic centimeter. 



To sum up ; the sensitizer in our rabbit > milk serum is not specific. 

 It acts energetically on milks from various allied animal species (cow, 

 ewe, goat) and somewhat less distinctly on other milks (human and 

 mare). 



Rabbit > egg serum, 56 degrees. Similar experiments were per- 

 formed with the sensitizer of rabbit > egg serum. The serum was 

 obtained by injecting hen-egg white and was tested with egg white 

 from the hen, the pigeon, the turkey and the duck. On the first 

 experiments we used uniformly 0.2 of a cubic centimeter of serum; 

 an intense precipitate was found with all the albumins, and the 

 alexin was fixed in all cases so that no hemolysis of sensitized hen 

 corpuscles occurred. Hemolysis was complete in controls with 

 normal rabbit serum. 



We have not tried to establish a difference between the various 

 egg whites by using varying amounts of active serum, as in the 

 rabbit > milk experiments; such an experiment was tried, however, 

 between hen and pigeon albumin. With both species fixation is 

 complete with 0.6 or even 0.5 of a cubic centimeter of active serum. 



