TOXIN AND ANTITOXIN. The diphtheria toxin has been isolated by Roux, Yersin, Brieger, Fraenkel, and others, by filtration of cultures of the living bacilli through porous porcelain. While it has not yet been successfully analyzed. it appears to be analogous to the poisons of certain venomous serpents. Fraenkel, Behring. Wer nicke, Aronson. Roux. and others have succeeded in rendering animals immune to diphtheria by the use of inoculations of virulent or somewhat attenuated vultures of diphtheria toxin. W. H. Park, of New York, says tin Century Practice) : "Tile mist important and valuable results are those which have been obtained by Behring, in conjunction with others, who showed that the blood of immune animals contains a substance which neutralizes the diphtheria toxin. The blood serum of person.; who have recovered from diphtheria has also been found to possess this protective property, which it acquires about a week after the beginning of the disease, and loses again in a few months." To obtain antitoxin for therapeutic purposes, strong toxin obtained from virulent cultures of the Klebs-Lidller bacil lus is injected into the bodies of young. healthy
horses. At the end of two months. during which time increasing doses of the toxin have been given, blood is drawn from the horses and tested for antitoxin. That having sufficiently strong antitoxin is retained and the process of inocu lating and of withdrawing serum is repeated for years, allowing three months of each year as an interval of freedom from inoculations. The serum obtained is sterilized by the addition of carbolic acid by some who prepare it. but Park considers the addition of any antiseptic as un necessary and inadvisable. The antitoxic serum is used hypodermically as early as a diagnosis of diphtheria has been made. in dosage of from 100 to 2000 units, a unit being equivalent to one cubic centimeter of 'normal serum': i.e. of blood serum of an immunized animal, NvIdeh was made so efficacious that 0.1 cubic centimeter an ta•onizes ten times the minimum of diphtheria poison fatal to a guinea-pig weighing :300 grams, or about ten ounces (Jacobi, Twentieth at u ry Pnict ice, vol. NVii., New York. 1S9S). See ANTITOXIN: BACTERIA : IMMUNITY and SERUM THERAPY.