TOXINS AND ANTITOXINS 205 



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

 poison known as tetanolysin. 



The introduction of the test-tube experiment into the investigation 

 of these reactions permitted of much more exact observations, and by 

 this means, as well as by careful, quantitatively graded, animal experi- 

 ments, the further facts were ascertained that toxin and antitoxin com- 

 bined more speedily in concentrated than in dilute solutions, and that 

 warmth hastened, while cold retarded, the reaction — observations ^ 

 which in every way seem to bear out Ehrlich's conception of the chemi- 

 cal nature of the process. 



Ehrlich's Aaalysis of Diphtheria Toxin. — Shortly after the discovery 

 and therapeutic application of diphtheria antitoxin, it became 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 anti- 

 toxin could be estimated. Von Behring ^ 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 ascer- 

 tained 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 tOifive days. 



Appropriating the terminology of' chemical titration, v. Behring 

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

 ia a cubic centimeter, as a "norma:! toxin solution" (" DTN' M^^""), 

 and designated as " normal antitoxin " a serum capable of neutraliz- 

 ing, cubic centimeter for cubic centimeter, the normal poison.^ A cubic 

 centimeter of such an antitoxic serum was sufficient, therefore, to neu- 

 tralize one hundred toxin units, and was spoken of as an "antitoxin 

 unit." In the experiments of v. Behring, toxin and antitoxin had been 

 separately injected. Ehrlich ^ improved upon this method by mixing 

 toxin and antitoxin before injection, thereby obviating errors arising 



» Ehrlich, Berl. klin. Woch., 1898. 

 « Knorr, Fort. d. Med., 1897. 



• V. Behring, Deut. med. Woch., 1893. 



* DTN ' M^ signifies: D, Diphtheria; TN', Normal Toxin solution; M™, Meer- 

 schweinchen or guinear^pig weighing 250 grams. 



' Ehrlich, Kossel und Wassermann, Deut. med. Woch., 1894. 



