During the past years two different preparations have been used under the name "tuberculin" for the treatment of tuberculosis. They have been distinguished by the names "old tuberculin" and "T. R." As they are not the same in their composition, a word or two in regard to the methods of their preparation may be in place.
The old tuberculin is prepared by using a culture-medium containing beef broth, salt, peptone and 5 to 7 per cent. glycerin. The sterilized medium is inoculated with the tubercle bacilli and the cultures then allowed to grow in the thermostat for several weeks, until the germs are well developed. When the development of the germ has advanced sufficiently the flasks containing the well-grown cultures are placed in the sterilizing oven and heated for about one-half hour at a temperature of 120 C. They are then removed from the oven, the contents of each flask
DE SCHWEINITZ EA. TUBERCULINS AND THEIR USE.. JAMA. 1900;XXXIV(15):898–900. doi:10.1001/jama.1900.24610150004001b