396 THE DIPHTHERIA BACILLUS GROUP 



taining an increased amount of toxin follows. At regular intervals 

 the injections are repeated, each time increasing the amount of toxin 

 in regular progression until after three to four months as much as 

 250 to 300 c.c. of unaltered toxin is introduced at one time. After 

 about two weeks following the last injection the animal is bled and 

 the potency of the serum tested. If it contains one hundred and fifty 

 units or more of antitoxin to the cubic centimeter, from two to five 

 liters of blood are removed from the jugular vein with sterile precau- 

 tions into sterile receptacles, and the animal is again treated with 

 toxin to induce further immunization. As a rule, about two-thirds 

 of the volume of blood taken is regained in antitoxin-containing serum. 

 It is customary in large establishments to immunize several horses 

 at the same time and mix this serum, for experience has shown that 

 the serum of certain animals contains substances which cause erythe- 

 matous rashes in man which are disagreeable and irritating although 

 not necessarily harmful. Pooling the blood reduces this possibility. 

 The serum is stored in sterile containers in a dark cold place and 

 retains its antitoxic properties well. It deteriorates less rapidly than 

 toxin. 



Concentration. Atkinson 1 noticed that the globulins of the horse 

 serum increased and the albumins diminished as the antitoxin content 

 of the blood increased, and he effected a partial purification of the anti- 

 toxin fraction by removing the albumin with protein precipitants . 

 Gibson 2 carried the process further and obtained a serum which was 

 about three times as rich in antitoxin per unit volume as the original 

 horse serum. Banzhaf 3 has reduced the proportion of non-specific 

 protein as far as is practical by purely physical agents. This reduction 

 of non-specific proteins is important for two reasons: first, because 

 it reduces the danger of anaphylaxis due to sensitization of the patient; 

 and, secondly, because the rashes and joint swellings are notably 

 reduced when the concentrated antitoxin is used instead of the whole 

 horse-serum. It is possible to obtain the same therapeutic effect by 

 the injection of about one-third the amount of solution when con- 

 centrated antitoxin is administered. 



Properties. Diphtheria antitoxin specifically neutralizes diphtheria 

 toxin both in vitro and in vivo. It has little neutralizing value for 

 the toxone, however ; consequently in severe cases when it is used late, 



1 Jour. Exp. Med., 1899, iii, 649. 



2 Jour. Biol. Chem., 1906, i, Nos. 2 and 3. 



. 3 Collected studies from the Research Laboratory, New York City Board of Health, 

 vols. v and vi. 



