228 ANTITOXINS 



Antitoxins are fairly resistant bodies, and a properly prepared anti- 

 toxic serum, when kept in a cool place and protected from light and air, 

 may be preserved for a year or more with very little deterioration in 

 strength. At times, however, for unknown reasons, antitoxins gradu- 

 ally deteriorate, losing about 2 per cent, in strength a month. Manu- 

 facturers have endeavored to calculate this loss in strength, and have 

 placed a label on each package of antitoxin, bearing a date beyond which 

 the serum is not guaranteed to contain the amount of antitoxin present 

 at the time it was put up. 



The antitoxins, with few exceptions, are far more stable than the 

 toxins, resisting -heating up to 62 C., but gradually deteriorating with 

 higher temperatures. Boiling destroys them completely. They are 

 readily preserved with small amounts of chloroform, phenol, tricresol, 

 etc., although strong solutions of these produce destructive changes. 

 Putrefaction of the serum destroys the antitoxin content. Ehrlich has 

 devised the best method for their preservation, which consists in drying the 

 serum in vacuo and preserving it in the dark, at a low temperature, in the 

 presence of anhydrous phosphoric acid. So preserved, antitoxin retains 

 its strength for prolonged periods and is used in standardizing toxins. 



Natural Antitoxins. The appearance of so-called natural antitoxins 

 can be explained on the basis of Ehrlich's theory. Since the antitoxin 

 is composed of receptors that are not new bodies, but simply normal 

 receptors produced in excess, it is reasonable to assume that a few may 

 be thrown off occasionally, constituting the natural antitoxin. 



Small amounts of natural diphtheria antitoxin may be found in cer- 

 tain individuals and lower animals. Since the diphtheria bacillus is 

 so wide-spread in its distribution, it is possible that minor subinfections 

 may be responsible for antitoxin production, and this is probably always 

 the case when large amounts are found. 



Information regarding natural antitoxins for other members of the 

 toxin-producing group of microorganisms is less complete, although it 

 is highly probable that natural antitoxins for these exist. 



The Schick Test for Natural Diphtheria Antitoxin. Schick 1 has 

 worked out a simple and practical skin test which apparent^ has proved 

 satisfactory and trustworthy and of distinct value for detecting natural 

 immunity to diphtheria among persons. 



This test consists in the intradermic injection of a minute dose of 

 diphtheria toxin. If the person possesses an amount of antitoxin equal 

 to at least one-thirtieth of a unit in each cubic centimeter of blood-serum, 

 1 Munch, bed. Woch., 1913, Ix, 2608. 



