Detroit, Feb. 15, 1908.
To the Editor:
—In The Journal, Jan. 25, 1908, page 260, there appears in the text, with a footnote reference, statements relative to the nature and process of manufacture of purified tuberculin for the ocular reaction. The statements attributed to me were made to one of the authors of the article over the long-distance telephone, the result being that they are not entirely correct, and at the author's suggestion I desire to offer the following correction which embodies the process as finally adopted for the manufacture of the material:A well-grown culture of human tubercle bacilli on 5 per cent. glycerin bouillon is concentrated over a water-bath at about 80 degrees C. to one-tenth its volume. The concentrated culture is filtered to remove the germ bodies. This filtrate constitutes the so-called old tuberculin of Koch. To a given volume of this old tuberculin is added from