258 INFECTION AND IMMUNITY 



cient, therefore, to neutralize one hundred toxin units, and was 

 spoken of as an "antitoxin unit. 5 " In the experiments of v. Behring, 

 toxin and antitoxin had been separately injected. Ehrlich 14 im- 

 proved upon this method by mixing toxin and antitoxin before in- 

 jection, thereby obviating errors arising from differences which may 

 have existed in the depth of injection or rapidity of absorption. 



In order, however, that any such method of standardization of 

 antitoxin may be practically applicable, it is necessary to produce 

 either a stable toxin or an unchangeable antitoxin. This Ehrlich 

 achieved for antitoxin by drying antitoxic serum in vacua and pre- 

 serving it in the dark, at a low temperature and in the presence 

 of anhydrous phosphoric acid. By the use of such a stable antitoxin, 

 various toxins may be measured and other antitoxic sera estimated 

 against these. 



Toxophorex 

 / I <Jroup 



Body Cell 



FIG. 30. TOXIN AND BODY CELLS. 



Given thus a constant antitoxin, the standardization of toxins 

 would be a comparatively simple matter were the poison obtainable 

 in a perfectly pure state. Unfortunately for the ease of measure- 

 ment, however, this is not the case. The problem is rendered difficult 

 by a number of complicating factors, many of which have been 

 brought to light by Ehrlich 15 in his laborious researches into the 

 quantitative relationship between the two reacting bodies. 



As previously stated, it had been noted by Ehrlich and others 

 that toxin solutions would deteriorate with time; that is, a toxin- 

 bouillon which was found soon after production to contain, say, 

 eighty toxin units in each cubic centimeter, would, after four or 

 five months, be found to contain but forty units in the same gross 

 quantity. It had lost, therefore, in this case, just one-half of its 

 toxic power. In spite of this loss, however, Ehrlich found that such 



14 Ehrlich, Kossel und Wassermann, Dent. med. Woch., 1894. 

 Ehrlich, Klin. Jahrbuch, vi, 1897; Deut. med. Woch., 1898. 



