Milzer1 and associates of Michael Reese Hospital, Chicago, report evidence that ultraviolet-killed tuberculosis vaccine is superior to BCG vaccine as a prophylactic agent. Mycobacterium tuberculosis (hominis) grown for 14 days on Petragnani medium was harvested, weighed, suspended in sterile distilled water, ground for 30 minutes in a ball mill, and then diluted so as to contain 1 mg. of moist bacilli per cubic centimeter. Exposure for 0.5 seconds to ultraviolet irradiation was found sufficient to kill the bacteria, after which 1: 10,000 thimerosal was added as a preservative and the killed vaccine was stored in the refrigerator at 3 to 5 C. Freshly prepared viable BCG vaccine was used in comparison.
Comparative active immunization tests were made on groups of 24 to 40 mice. At weekly intervals, each mouse was given four subcutaneous injections of 0.5 mg. of the selected vaccine. Thirty days after the fourth dose, each mouse