606 PATHOGENIC MICROORGANISMS 



itate on the addition of 50 per cent glycerin, and has the same physiolog- 

 ical action as the old tuberculin. The residue TR (Tuberculin-Ruck- 

 stand), 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 volume of water used for these TR extractions 

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

 together. 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- 

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

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

 medium remaining the same, fairly accurate standardization is possible. 



"New Tuberculin-bacillary Emulsion." 47 In 1901, Koch combined 

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

 lenemulsion." This consists of an emulsion of pulverized bacilli 

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

 remove the coarser particles, the supernatant fluid is poured off and 

 fifty per cent volume of glycerin is added to it for purposes of preserva- 

 tion. This preparation contains 5 milligrams of solid substance in each 

 cubic centimeter. 



Bouillon F litre (Denys) 48 This preparation consists of 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 unconcen- 

 trated 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. 



Tuber culoplasmin (Buchner and Hahn) 49 Buchner and Hahn, by 

 crushing tubercle bacilli by subjecting them to a pressure of 400 atmos- 

 pheres, obtained a cell-juice in the form of an amber fluid, to which they 

 attributed qualities closely analogous to those of TR. 



Other tuberculins are those of Beraneck, 50 highly recommended 



" 7 Koch, Dent. mod. Woc.h., 1901. 



48 Dei\ys, ' 'Le Bouillon Filtre, " Lonvain, 1905. 



49 Buchner mid llahn, Miinch. med. Woch., 1897; Halm, ibid. 



50 Beraneck, Compt. rend, de 1'acad. des. sci., 1903. 



