EDWIN J. BANZHAF 755 



the first weeks of immunization, the practice is to inject about five thousand units of 

 tetanus antitoxin the day before immunisation is started. After about three months' 

 immunization a group of ten horses will average about one hundred units of antitoxin 

 to each mil of serum. Those that test one hundred units or more are posted for 

 regular full bleedings. The horses, as in the active diphtheria immunizations, will 

 usually increase in unit value with each subsequent injection and bleeding. The injec- 

 tion of horses showing less than fifty units after three months' immunization is dis- 

 continued. The standard tetanus antitoxin unit is that amount which, when mixed 

 with 1,000 M.L.D.'s of tetanus toxin and injected subcutaneously into a 350-gm. 

 guinea pig, will protect the animal four days. Theoretically, the tetanus antitoxin 

 unit is ten times larger than the unit of diphtheria antitoxin. 



Botulism antitoxin. — Immunization of horses against B. botulimis toxin (types A 

 and B) was done by the writer. Subcutaneous injections were given every second 

 day. The first injection was one guinea pig M.L.D. The injections were increased 100 

 per cent for each of twelve injections. The temperature rise after injections was 

 usually less than 2,° dropping to normal the following day; the percentage of increase 

 was then lowered to 50 per cent for twelve injections, and thereafter the increase was 

 25 per cent. After three months' immunization the antitoxin value against the type 

 "A" strain was one hundred twenty-five units and the value against the type "B" 

 was two hundred units in each mil. The standard B. botulimis antitoxin unit is that 

 amount of serum which when mixed with one hundred M.L.D.'s of toxin will protect 

 a guinea pig four days. 



"Staph, aureus''^ antitoxin. — Parker and Banzhaf^ immunized seven horses against 

 the toxin of Staphylococcus aureus. Four of the serum horses died during the 

 course of immunization, due, they believe, to the injection of the toxin at too short 

 intervals: one- to two-day intervals. A rapid temperature rise of 2° to 3° F. oc- 

 curred frequently after injections, usually disappearing after twenty-four to thirty- 

 six hours. In the successfully immunized horses the first injection was i mil of toxin 

 containing four hundred rabbit S.T.D.'s (skin-test dose). The injections were in- 

 creased 100 per cent at three- to four-day intervals for the first five injections. The 

 percentage of increase was then decreased to 50 per cent. After ten injections the 

 interval was lengthened to from seven to ten days. After two months' immunization 

 the average strength of the sera was such that i mil neutralized twenty thousand 

 rabbit S.T.D.'s of toxin. 



Scarlatinal antitoxin. — Immunization of horses against Streptococcus scarlatinae 

 and the resulting bactericidal and antitoxic value was demonstrated by Moser^ and 

 Savchenko^ and improved by the clear-cut work of Dochez^ and the Dicks. Immuni- 

 zation by the Dochez method is done by injecting small amounts of melted nutrient 

 agar subcutaneously into the horses, and then injecting living scarlatinal streptococci 

 into the agar mass. Small abscesses usually develop. When these have healed, the 

 horses are again injected with melted agar and a larger amount of living scarlatinal 



' Parker, J., and Banzhaf, E. J.: /. Immunol., 13, 25. 1927. 



^Moser: Wien. klin. Wchnschr., 15, 1053. 1902. 



3 Savchenko, G. N.: Russk. Vach., 25, 797. 1905. 



< Dochez, A. R.: Proc. Soc. Exper. Biol, b" Med., 4, 184. 1924. 



