190 IMMUNO-CATALYSIS 



ultraviolet radiation of 3600 A. At this wave length only azo-protein 

 was measured. Over the range of concentrations measured Beer's law 

 was found to be obeyed whether other proteins were present or not 

 (see further, Smith and Marrack, 1930; Marrack and Smith, 1931b; 

 Marrack, 1938b). 



Heidelberger and Landsteiner (1923) in a study on the specificity 

 of hemoglobins obtained from various species of animals, compared the 

 color of precipitates produced in the following combinations: 



(1) Hemoglobin-j-anti-hemoglobin serum^red precipitate; 



(2) Hemoglobin -[-horse serum-)-anti-horse serum=rpure white precipitate; 



(3) Hemoglobin -[-human serum -|-anti-human serum^pure white precipi- 

 tate; 



(4) Hemoglobin -[-donkey serum-[-anti-donkey serum=pure white precipi- 

 tate; 



The absence of any color (hemoglobin) in the precipitates of (2) to 

 (4) combinations demonstrated clearly that hemoglobin was not 

 dragged down non-specifically by these three different serum-anti- 

 serum precipitates. 



Haurowitz and Breinl (1933) precipitated 400 ml. of 1 : 1000 normal 

 horse serum with 40 ml. of anti-horse rabbit serum in the presence of 

 colored beef atoxyl-albumin containing 8.24 mg. of protein with a 

 61.2 microgram arsenic content. After 24 hours the precipitate was 

 centrifuged and washed once with saline. The precipitate was pure 

 white and free from dye. The dry weight of the precipitate was 55.2 

 mg. It contained less than 0.1 microgram of arsenic or at the most 0.03 

 per cent atoxyl-protein. Ten ml. of human serum (1 : 100 dilution) was 

 treated with atoxyl-horse globulin, containing 3.0 mg. of protein with 

 16.7 microgram of arsenic, and treated with 1 ml. of anti-human serum. 

 The precipitate was pure white and free from arsenic. 



d. Failure of Protein-Anti-Protein Precipitates to Adsorb Non- 

 specific Proteins. Heidelberger and Kendall (1935) in their quan- 

 titative studies on the mechanism of precipitation reaction subjected 

 the question of the effect of non-specific proteins on the amount of 

 antigen-antibody precipitates to a critical study. They found that at 0° 

 or 37° the ratio of nitrogen to Type III pneumococcus polysaccharide 

 in the precipitate was of the same order whether the precipitation was 

 carried out in the whole serum in which the antibody constituted about 

 15 per cent of the total protein, or in the antibody solution prepared 



