244 ILLINOIS ACADEMY OF SCIENCE 



tinins, lysins and opsonins. There is no doubt that the effi- 

 ciency of bacterins depends upon their power to stimulate the 

 formation of opsonins. 



The serum or its modified and purified preparation, the 

 globulin solution, is the older and best known of these two 

 classes, i.e., bacterines and serums. The first successful serum, 

 the diphtheria anti-toxin, was discovered by Behring and Kit- 

 asato in 1890. Anti-toxins are produced within the body 

 of some animal, the horse being used in most cases. Such 

 an animal is given injection of the toxins, rarely of dead 

 bodies, of a specific disease producing micro-organisms in in- 

 creasing quantities, until the point of tolerance or maximum 

 resistance has been reached. As a result, anti-toxic sub- 

 stances are produced by these animal cells and they appear in 

 the serum. At the proper time the animal is bled and after 

 various stages of purification and concentration, the blood 

 serum is put up in suitable containers for administration to 

 the human patient. 



This serum contains anti-bodies or immune substances 

 which will directly combat the specific infection. By the in- 

 jection of a serum the physician produces passive immunity. 

 In order that a serum be of greatest therapeutic value it must 

 be of a standard specified strength so that the size of the dose 

 administered may be regulated. This process of regulating 

 serums and bacterines is termed standardization, and in the 

 case of the anti-toxin serum it is done in terms of "anti-toxin 

 units." To test the anti-toxic value guinea pigs of about 

 250 grams are used. These guinea pigs and the parents 

 of these guinea pigs should never before have been used in the 

 testing of anti-toxin. An anti-toxic unit is to be understood 

 by its effect only. 



A unit is capable of neutralizing an amount of toxin, or 

 bacterial poison ; that is, in turn, measurable by its fatal effect 

 on guinea pigs in the presence of a standard immunity unit 

 furnished by the United States Government. The immunity 

 unit is mixed with the toxin and administered to guinea pigs. 

 Sufficient toxin must be used to kill the guinea pig notwith- 

 standing the protection afforded by the immunity unit. One 

 anti-toxic unit will just save the life of the guinea pig when 

 injected together with the toxin dose above mentioned. 



