THE SENSITIZERS OF SERA. 255 



With 0.4 of a cubic centimeter it is nearly complete and with 0.2 

 of a cubic centimeter very slight. There is no differentiation, then, 

 between pigeon-egg white and hen-egg white by sensitization with 

 rabbit > hen-egg white serum. 



In brief, we have found no specificity either as regards precipitin 

 with or sensitizer with rabbit > egg serum. 



Rabbit > fibrinogen serum, 56 degrees. — We have found no more' 

 evidence of specificity as regards precipitation and sensitization 

 with this serum than with the two preceding sera. The serum was 

 obtained by injecting large amounts of pure fibrinogen from the 

 horse and was tested with fibrinogens from the horse, the ox and 

 the dog, all prepared in exactly the same way. An abundant and 

 immediate precipitate occurred with each fibrinogen; there was 

 apparently no difference in amount even when the active serum 

 was decreased to 0.1 of a cubic centimeter, with 0.2 of a cubic cen- 

 timeter of fibrinogen and 0.1 of a cubic centimeter of rabbit alexin. 



The same results were obtained as regards sensitization of the 

 three •fibrinogens. Whatever the dose of active serum employed 

 (3, 2, 1 or one-half volume to 1 volume of fibrinogen solution, and 

 one-half volume of rabbit alexin), a complete fixation of alexin 

 occurred with each fibrinogen with the largest dose of serum, and 

 progressively less as the serum was decreased. 



Rabbit serum active for dog serum, 56 degrees. — On account of the 

 practical value of the serum precipitation, first demonstrated by 

 Tchistovitch, we have studied the specificity of our rabbit > dog 

 serum. 



Varying amounts of serum (0.6, 0.4, 0.2 and 0.1 of a cubic cen- 

 timeter) were mixed with 0.2 of a cubic centimeter of various sera 

 heated to 56 degrees plus 0.1 of a cubic centimeter of rabbit alexin. 



We tested in this way dog, horse, ox and guinea-pig serum. 



With dog serum the precipitate formed with 0.6 and 0.4 of a 

 cubic centimeter of specific serum is very distinct; it is less with 

 0.2 of a cubic centimeter and no longer visible with 0.1 of a cubic 

 centimeter. With the other sera no precipitate occurred. Simi- 

 larly, the alexin was fixed only with dog serum and more or less 

 completely according to the amount of specific serum employed. 



The active serum, however, produced no alexin fixation with any 

 of the other sera in any dose. 



