476 Journal of Agricultural Research voi. xiii, no. 10 



Preparation op digestion mixtures. — ^These were prepared as indi- 

 cated in Table III and used in sets of five for obvious reasons. Mix- 

 ture A contained only the serum or antitoxin, and served as a standard 

 for comparing the antitoxin contents of the different mixtures. Guinea 

 pigs inoculated with quantities of mixture A equivalent to o.i unit of 

 antitoxin or more always survived the test dose of toxin. Mixture B 

 was to show the effect of sodium carbonate or hydrochloric acid on the 

 antitoxin. Mixture C was to show the effect of trypsin or pepsin on the 

 antitoxin. In mixture D the proteins present in the tetanus serum or 

 antitoxin were digested by pepsin-hydrochloric-acid or trypsin-sodium- 

 carbonate. In experiment 6 sodium hydroxid was used instead of 

 sodium carbonate, with practically the same results. In mixture E the 

 effect of the pepsin-hydrochloric-acid or trypsin-sodium-carbonate on 

 the toxin was shown. The antitoxin and toxin were mixed one hour 

 before inoculation ; hence, it was necessary to be certain that the reagents 

 at their final dilution under the conditions of the experiments do not 

 destroy any of the toxin. 



