OPSONIC INDEX AND VACCINE THERAPY 349 



2^ow, having outlined the conditions obtaining in such cases, let 

 us briefly consider whether, under the circumstances, vaccine therapy 

 may logically be regarded as a hopeful form of treatment. We may 

 assume, on the one hand, that the bacteria, being consistently present 

 and destroyed in the blood, should furnish antigen sufficient to 

 stimulate the body tissues to their utmost reactive ability. This 

 would seem a strong argument against vaccine therapy. On the 

 other hand, we must take into consideration another phase of the 

 subject, one which has some experimental justification. In discus- 

 sing the origin of antibodies in another section it will be remembered 

 that we called attention to the fact that many different tissue cells 

 probably participate in the production of these protective reaction- 

 bodies. We cited an experiment of Wassermann and his pupils in 

 which they proved that antibodies were produced most energetically 

 in the tissues about the point of injection of the antigen, namely, in 

 the place at which it came into most concentrated contact with the 

 cells. They injected bacteria into the subcutaneous tissues of the ear 

 of a rabbit, measured the progressively increasing appearance of 

 antibodies in the blood stream, and then amputated the ear. A 

 sudden drop of antibody contents followed, showing that the supply 

 of antibodies had largely emanated from the tissues surrounding 

 the injection point. Park 30 has pointed out another reason why 

 vaccine treatment may be expected to exert beneficial action in such 

 cases. He calls attention to the fact that when very large amounts 

 of antitoxin are added to toxin before injection no antibody produc- 

 tion results, and assumes that in chronic or subacute general infec- 

 tions the circulating bacteria are in contact with specific antibodies, 

 partially "sensitized/' and therefore not efficient as antigen. In 

 consequence the injection of homologous unsensitized bacteria may 

 hasten antibody formation. This assumption of Park is theoretically 

 valid, but it is not in accord with the more recent experiments of 

 Metchnikoff and Besredka, who claim to have obtained the best 

 results in prophylactic typhoid vaccination by the injection of sensi- 

 tized bacteria. 



Thus the use of vaccines in the subacute or chronic cases of in- 

 fection with bacteria in the blood stream may bo theoretically justi- 

 fied, and no one can say at the present time whether or not it has 

 therapeutic promise. At any rate, it cannot be absolutely condemned 

 on theoretical grounds. 



Like so many other phases of this question, it must be answered 

 ultimately by clinical experience, for in experimentation upon ani- 

 mals, while it is easy to produce a purely localized lesion followed 

 by rapid healing, or a generalized lesion leading to rapid death, it 

 is not easy to produce prolonged infections with anything like regu- 

 larity, and there are so many modifying accidental factors which 

 30 Park. Trans, of Amer. Phys., Vol. 8, 1910. 



