492 PATHOGENIC MICROORGANISMS 



The supernatant fluid, known as TO (Tuberculin-Oberschicht), contains 

 the water-soluble constituents of the bacillus, gives no precipitate on 

 the addition of 50 per cent glycerin, and has the same physiological 

 action as the old tuberculin. The residue TR (Tuberculin-Rtickstand), 

 after pouring off TO, is again dried and ground up, and again shaken in 

 water and centrifugalized. This process is repeated several times, 

 and eventually, after three or four repetitions, all the TR goes into 

 emulsion. The total voliune of water used for these TR extractions 

 should not exceed 100 c.c. All of the TR emulsions are then mixed to- 

 gether. This gives TR a precipitate with 50 per cent of glycerin, and is 

 supposed by Koch to contain substances important in producing an 

 antibacterial immunity. For purposes of standardization, the amount 

 of solid substance in 5 c.c. of the TR is determined by evaporation in 

 vacuo and drying. To the rest are added a little glycerin and formalde- 

 hyde and enough water to allow each cubic centimeter of the solution 

 to contain 0.002 grams of solid material. Thus the culture and the 

 medium remaining the same, fairly accurate standardization is possible. 



"New Tuber culin-Bacillary Emulsion." ' — In 1901, Koch combined 

 "TO" and "TR" by putting forth a preparation referred to as 

 "Bazillenemulsion." This consists of an emulsion of pulverized bacilli 

 1 : 100 in distilled water. After several days of sedimentation to re- 

 move the coarser particles, the supernatant fluid is poured off and fifty 

 per cent volume of glycerin is added to it for purposes of preservation. 

 This preparation contains 5 milligrams of solid substance in each cubic 

 centimeter. 



Bouillon Filtre (Denys).^ — This preparation consists pf the filtrate 

 (through Chamberland filters) of 5 per cent glycerin-pepton-bouillon 

 cultures of Bacillus tuberculosis. Phenol 0.25 per cent is added to 

 insure sterility. The filtered bouillon corresponds to the unconcentrated 

 old tuberculin of Koch, but, not having been heated, is supposed by 

 Denys to contain important soluble and possibly thermolabile secretory 

 products of the bacillus. 



Tuberculoplasmin {Buchner and Hahn).^ — Buchner and Hahn, by 

 crushing tubercle baciUi by subjecting them to a pressure of 400 

 atmospheres, obtained a cell-juice in the form of an amber fluid, to 

 which they attributed qualities closely analogous to those of TR. 



^Koch, Deut. med. Woch., 1901. 



2 Denys, "Le Bouillon Filtr6," Louvain, 1905. 



' Biichner und Hahn, Munch, med. Woch., 1897; Hahn, ibid. 



