PSEUDODIPHTHERIA. 1 57 



pigs 1 and 2 survive, the antitoxin is one which in 1 c.c. has 

 protecting powers amounting to 10 multiplied by 20, or 200 

 antitoxin units. Should guinea-pig No 3 also survive this 

 injection, then the serum used is equivalent to 10 times 100, 

 or 1000 antitoxin units per c.c. 



No serum should be accepted for use in the treatment of diph- 

 theria unless its immunizing or antitoxic power is equivalent to 

 at least 200 units per c.c.; a serum used as a protective only 

 may be accepted with 100 units antitoxic power per c.c. 



In order to test the antitoxin and for the purpose of im- 

 munizing animals, it is necessary to produce toxins of a 

 standard virulence. This, as has been seen, is not always a 

 task of easy performance. The standard of toxins accepted 

 in all laboratories and establishments in which antitoxin is 

 manufactured is a toxin of which 0.10 c.c. is able to kill a 

 250- or 300-gram guinea-pig within three days, and no toxins 

 should be used excepting such as have this power. It is best 

 manufactured by growing virulent cultures of Bacillus diph- 

 therias in large Erlenmeyer flasks, with free access of air and 

 at a temperature of 37 C. The height of the toxicity of 

 the culture is reached in about eight to ten days, when the 

 culture should be removed from the incubator and filtered 

 through a Chamberlain porcelain filter, tested on guinea-pigs, 

 and if found of the required strength put away in sterile 

 bottles. Unless it shows that 0.10 c.c. when injected into 

 a guinea-pig of 250 grams causes death of the animal within 

 three days, it should not be accepted. 



The German government adopted this as a standard strength 

 for toxins, and no antitoxin is put on the market unless its 

 value has been tested by means of its power of neutralizing 

 so many units of this standard toxin. 



Value of the Antitoxin Treatment of Diphtheria. It has now 

 been used sixteen years, and has been of inestimable value. 

 As a therapeutic agent, given within the first three days of 

 the disease, it has reduced the mortality of diphtheria more 

 than one-half. When used after the third day it is of less 

 value, but still shows decidedly good effects. 



