TOXINS AND ANTITOXINS 257 



Similar quantitative results were subsequently obtained by Stephens 

 and Myers 8 for cobra poison and its antitoxin, by Kossel 9 for the 

 toxic eel blood serum, and by Ehrlich 10 for the hemolytic tetanus 

 poison known as tetanolysin. 



The introduction of the test-tube experiment into the investiga- 

 tion of these reactions permitted of much more exact observations, 

 and by this means, as well as by careful, quantitatively graded, 

 animal experiments, the further facts were ascertained that toxin and 

 antitoxin combined more speedily in concentrated than in dilute 

 solutions, and that warmth hastened, while cold retarded, the reac- 

 tion observations 11 which in every way seem to bear out Ehrlich 's 

 conception of the chemical nature of the process. 



Ehrlich 's Analysis of Diphtheria Toxin. Shortly after the dis- 

 covery and therapeutic application of diphtheria antitoxin, it be- 

 came apparent that no two sera, though similarly produced, could 

 have exactly the same protective value. It was necessary, therefore, 

 to establish some measure or standard by which the approximate 

 strength of a given antitoxin could be estimated. Von Behring 12 

 attempted to do this for both tetanus and diphtheria antitoxins by 

 determining the quantity of immune sera which, in each case, was 

 needed to protect a guinea-pig of known weight against a definite 

 dose of a standard poison. He ascertained the quantity of standard 

 toxin-bouillon which would suffice to kill a guinea-pig of 250 grams, 

 and called this quantity the " toxin unit." This unit was later' 

 more exactly limited by Ehrlich, who, considering the element of 

 time, stated it as the quantity sufficient to kill a guinea-pig of the 

 given weight in from four to five days. 



Appropriating the terminology of chemical titration, v. Behring 

 spoke of a toxin-bouillon which contained one hundred such toxin 

 units in a cubic centimeter, as a " normal toxin solution" ("DTN 1 

 M 250 "), and designated as "normal antitoxin" a serum capable of 

 neutralizing, cubic centimeter for cubic centimeter, the normal 

 poison. 13 A cubic centimeter of such an antitoxic serum was suffi- 



8 Stephens and Myers, Jour, of Path, and Bact., 1898. 



9 Kossel, Berl. klin. Woch., 1898. 



10 Ehrlich, Berl. klin. Woch., 1898. 



11 Knorr, Fort. d. Med., 1897. 



12 v. Behring, Deut. med. Woch., 1893. 



13 DTN 1 M 250 signifies : D, Diphtheria ; TN 1 , Normal Toxin solution ; M 2SO , Meer- 

 schweinchen or guinea-pig weighing 250 grams. 



