I022 



TUBERCULIN AND THE TUBERCULIN REACTION 



she attempted the crystallization of protein present, by methods similar to those which 

 have led to the crystallization and purification of egg albumin. By half saturating 



Fig. 2. — Skin reactions in patient sensitive to tuberculin, with samples of tuberculin heated in 

 the autoclave four hours at 120° C. with HCl. Six samples of the following reactions were autoclaved: 

 No. I, neutral; No. 2, N/100; No. 3, N/20; No. 4, N/io; No. 5, N/6; No. 6 N/s. After neutralization 

 and adjustment to the same salt concentration and fluid volume, 0.05 cc. from each sample was in- 

 jected in tradermally in a tuberculous patient. The figure shows strong reactions with Nos. i, 2, 3, 

 and 4; a trace of reaction with No. 5; and no reaction with No. 6. 



Fig. 3. — Protein precipitates in tuberculin heated with acid. The same samples which were inject- 

 ed as described under Fig. 2 were treated with trichloracetic acid for the precipitation of protein. 

 Precipitation is marked in Nos. i, 2, 3, and 4. A trace of precipitation has occurred in No. 5. No. 6 

 is practically clear. 



