REACTIVITY TO VARIOUS MICROORGANISMS 55 



jjliusus culture filtrates of ascertained skin-preparatory potency 

 were employed for intradermal injections. Various batches of 

 tid^erculin (). T., were injected intravenously into rabbits, 

 twenty-four horns later. Here again, severe reactions resulted 

 from five tuberculin batches (bovine tubercidins O. T., and one 

 human tubercidin) but failed with three other preparations 

 (iiuman, avian and bovine tuberculin) . It is of interest that one 

 batch of bovine tuberculin ^vhich failed to elicit reactions in the 

 experiments revealed here, proved potent ^vhen used as a skin- 

 preparatory agent. 



As is seen from the experiments thus far described, tuberctilin 

 O. T., contains in low concentration the factors necessary for the 

 elicitation of the phenomenon. This becomes obvious if the doses 

 employed in these experiments are compared with those of menin- 

 gococcus, B. typhosus, and other cultme hltrates. The reactions 

 imder discirssion cannot be obtained iniless non-tuberculotis bac- 

 terial filtrates of high potency are used either for the skin prepara- 

 tion or for intravenotis injection. In this manner the deficiency 

 in potency of tuberculin is made up for by taking advantage of 

 the strict quantitati\e reciprocity of skin-preparatory and reacting 

 (intravenous) factors recorded previotisly. 



Seibert's purified tuberculin T. P. T., and the Ne^v York 

 Board of Health tuberculin were inactive, whilst preparations 

 made in my laboratories were capable of eliciting the phenom- 

 enon. All the tuberculin jDreparations contained tuberculin sub- 

 stances jDroper. This suggests that the factors necessary for the 

 elicitation of the phenomenon inider discussion may not be re- 

 lated to the tid^erculin sidjstances proper. 



As described above, the tuberctdin of my laboratories ^vas pre- 

 pared by evaporation at 56'^ c. for t^venty-foiu' to thirty-six horns. 

 The New York Board of Health tuberculin ^vas evaporated by 

 boiling' over a free flame. As known already, prolonged exposure 

 to heat is likely to inactivate the active principles of the phenom- 

 enon. Presimiably, therefore, the lack of reacting potency in the 

 NeAV York Board of Health preparation may be due to prolonged 

 heating. Apparently, the pinification methods of Seibert also 

 remo\'e the toxic suljstances described here. 



No data are available as yet on the period of incidjation of cul- 

 tines optimimi for the production of B. tuberculosis acti\e prin- 

 ciples. 



