ioo BACTERIOLOGY 



that used in the manufacture of diphtheria antitoxin. 

 Fresh agar cultures of the Bacillus pestis are sterilized 

 by heat and injected into horses in increasing doses. 

 From six months to a year is required for the produc- 

 tion of an active serum. It has been found difficult to 

 standardize, but the endeavor is to produce a serum 

 T V c.c. of which will protect a mouse from a dose of the 

 germs which kills a control-mouse in three days. The 

 serum is used by injection, the dose being 60 to 150 c.c. 

 Like other antitoxins, it is most efficacious when ad- 

 ministered early. 



Its use as a prophylactic is attended with most excel- 

 lent results, but the protection afforded only lasts for 

 fifteen days, so that to be effective over a longer period 

 of time it must be administered at intervals of ten 

 days to two weeks. It has been recommended that it 

 be used in connection with Haffkine's vaccine as a 

 prophylactic measure, a more lasting immunity being 

 thus established. 



VACCINE OR OPSONIC THERAPY 



Vaccine therapy is based upon the principle of phago- 

 cytosis and the opsonic theory of that process. As 

 has been shown in the discussion of immunity, the leu- 

 kocytes play an important r61e in the protection of the 

 individual against certain diseases. We have also 

 noted that their activity and ability to attack disease 

 germs depends upon the presence in the blood of cer- 



