PATHOGENIC BACTERIA. 



349 



to be standardized with antitoxin specially prepared by Ehrlich for the pur- 

 pose. This antitoxin of Ehrlich is supplied to the various public and private 

 institutions where antitoxin is prepared, and is carefully standardized against 

 very fresh toxin, which therefore contains little toxoid. 



The Ehrlich standard antitoxin is really used in the first place to determine 

 the strength of a given toxin, which in turn is used to determine the value of 

 antitoxin to be standardized. The actual method is to mix varying amounts 

 of the toxin to be tested each with one unit of the standard antitoxin, and that 

 mixture which just suffices as proved by experiment to kill a 25o-gram guinea- 

 pig in three or four days is designated L + (see Immunity, page 224); the 

 mixture which is just neutral is called LO. That amount of antitoxin which 

 ju^t neutralizes L + contains one antitoxic unit according to this method of 

 standardizing. 



The injection of guinea-pigs with antitoxin serves the double, purpose of 

 determining the potency of the antitoxin and also of determining the presence 

 or absence of pathogenic substances, such as tetanus toxin. 



It has been found possible to prepare antitoxin of a high 

 degree of concentration, so that 500 to 1500 units may be con- 

 tained in a quantity of serum which it is practicable to give at a 

 single hypodermic injection. The large volume of statistics 

 that have been collected from hospitals and from physicians in 

 private practice indicates that the use of diphtheria antitoxin 

 has effected a very great reduction in the mortality from 

 diphtheria. Aside from the curative value of diphtheria anti- 

 toxin, it is of value as a preventative when administered to 

 persons who are exposed. Where a case of diphtheria occurs 

 in a family all the other members beside the patient should be 

 given an immunizing dose of antitoxin about 500 units 

 suffices. When this is done, the disease is limited to the one 

 case. 



Bacillus Fusiformis.* Under this name an organism was 

 isolated by Vincent and claimed by him to be the cause of 

 certain infectious pseudomembranous ulcerations. Vincent's 

 observations have been more or less corroborated by others, 

 but the crucial tests of cultivation and inoculation do not seem 



* Vincent. Ann. del' Institute Pasteur. 1896. p. 488. 



