74 APPLIED BACTEKIOLOGY FOR NURSES 



oi^soniiis. They are specific, just as are the antitoxins, 

 the bacteriolysins, and the agghitinins; that is to say, 

 when the body is injected with typhoid bacilli j only 

 the opsonic power for typhoid bacilli is affected; when 

 staphylococcus pyogenes is enii)loyed, only the opsonic 

 power for this germ is affected; when pneumococci 

 are injected, only the opsonic power for pneumococci 

 is affected. Wright devised a special technic for measur- 

 ing the amount of opsonin present in a serum, and ex- 

 pressed this in what he calls the opsonic index. This 

 is merely the opsonic i)ower of the patient's serum, as 

 compared with the opsonic power of several known nor- 

 mal sera, using the same leukocytes and the same bac- 

 teria in the one test. Although Wright believes that 

 this opsonic index is essential in the bacterial vaccine 

 treatment of infections, most other observers have 

 failed to find the index of any real help. 



Precipitins and Other Antibodies. — Wc have seen 

 above that the injection into the animal bod}^ of bac- 

 teria or other cells is followed by the production of 

 a number of different antibodies. If, instead of inject- 

 ing bacteria, we inject .solutions of albuminous material, 

 for exami)le, inject a rabbit with chicken egg-albumin 

 (white of egg), we shall find that the rabl)it's serum 

 ac(|uires the power to i)roduce a precipitate when mixed 

 with chicken egg-albumin. This action is highly sj^ecific, 

 so that if the serum is tested against albumin from any 

 other animal — e. g., from a duck — no precipitate will be 

 produced. If a rabbit is injected with human blood 

 (which, of course, is really an albuminous solution) the 

 rabbit serum will produce a precipitate when mixed with 

 human blood, but not when mixed with any other blood. 



