APPLICATION OF THE PHENOMENON 407 



t(j this strain may Ije acxjiiiied and nia) hiini; the attack to an 

 end, few or ])erha})s no antibodies will be produced to the less 

 abiuidant strains. These strains may then be responsible for a 

 relapse. 



For preparation of the phenomenon-neutralizing sera horses 

 were immimized for se\eral months by weekly sidjciitaneoiis and 

 intra\enoiis injections. Some of the sera recently employed were 

 obtained from horses ^vhich had received t^vo or three \veekly 

 injections. F(n" the std)ciitaneotis injections "agar washings" ctd- 

 tine filtrates and in some instances tryptic-digest broth ctdttne 

 filtrates of B. tyjjhosiis were tised. The initial dose \'aried from 

 1 to 5 c.c, and the amotnit w'as gradnally increased to 20 c.c. For 

 the intravenous injections heat-killed vaccines of several strains 

 of B. typJiosus were used. The initial dose ^vas from 3 to 5 c.c. 

 of vaccine containing approximately 1,000,000,000 microorgan- 

 isms per cubic centimeter. On subsequent injections the dose Avas 

 gradually increased to 10 c.c. Higher concentrations of the vac- 

 cine were then made, containing 5,000,000,000 microorganisms 

 per c.c, and the dose was gradually increased until 10 c.c. w-as 

 finally used. It is possil^le to continue the immunization of horses 

 w^ith B. typJiosus culture filtrates and vaccines in this manner for 

 a considerable length of time. It should be rememliered, ho^vever, 

 that the materials are toxic. Sometimes, a small amount of filtrate 

 kills a horse. Rises in temperature, cutaneous abscesses and sys- 

 temic shock are frec|uently obser\ed. In case of shock a horse can 

 often be saved by epinephrine given immediately or Avithin a few 

 hours after the injection of the immunizing material and later 

 by large bleedings. The abscesses are easily relieved by incision 

 and the evacuation of pus. 



The ability of a horse to produce antibodies is subject to con- 

 siderable indi\ idual \'ariation. Moreover, antibodies capable of 

 neutralization of the phenomenon under discussion may unex- 

 pectedly drop in titer. For this reason, it seems important that 

 the large bleeding be made as quickly as possible after the trial 

 bleeding. This is carried out as follows: The necessary groups of 

 rabbits are prepared by intradermal injections of the B. typhosus 

 "agar Avashings" filtrates on the morning of the day before the 

 trial bleeding. On the morning of the trial bleeding the rabbits 

 then receive an intra\enous injection of the mixtures to be 

 titrated. The results are read early in the afternoon of the same 

 day. If an adequate antitoxin titer is found, a large bleeding is 



