72 VACCINE AND SERUM THERAPY. 



eases as this, is one that must be of the utmost importance in 

 clinical medicine. 



Because the methods for the determination of immune bodies 

 are still so inaccurate and in many cases unreliable, and because 

 the defensive agencies of the animal body against bacterial in- 

 vasion and multiplication are so manifold and complex, numer- 

 ous investigators have relied upon the clinical control of dosage 

 and inter-spacing of injections of bacterial vaccine. At all events,, 

 the value of active immunization by injection of bacterial vaccines 

 will ultimately rest upon clinical results. While it is relatively 

 easy in most cases of infection to tell when complete recovery 

 has taken place, still it is difficult to tell what clinical symptoms 

 and signs are associated with the best method of immunization. 

 The conditions ultimately desired are definitely known, but the 

 conditions in the diseased body which will produce these ulti- 

 mately desired effects, are little understood, Probably the best 

 illustration of this is seen in the use of tuberculin in the treatment of 

 tuberculosis. Tuberculin has been known and used in treatment 

 for nearly twenty years, and still today it is an open question 

 whether the dosage shall be regulated to give an anti-toxic or an 

 anti -bacterial immunity. Clinical evidence and experience is 

 deceiving as is well demonstrated in the literature on tuberculin. 



With some organisms, and in certain cases treated by the 

 vaccine method, excellent results have been obtained when the 

 dosage and interval between injections has been determined by 

 clinical signs and symptoms. The number of cases in which 

 the treatment is controlled clinically is probably larger than the 

 number of those treated according to Wright's method. Many 

 investigators, although determining the opsonic index during the 

 process of immunization, have found that it is quite as safe to 

 administer vaccine when controlled by clinical results as by op- 

 sonic index determinations. In clinical control of vaccine treat- 

 ment, it is aimed to have the dose so small and the injections so 

 far apart that immunization is accomplished without the pro- 

 duction of clinical symptoms. The doses that are usually given 

 are those recommended by Wright, though some have used larger 

 doses without the production of any reaction. 



In most clinics the doses injected are gradually increased. 

 This is also the procedure recommended by Wright. If this 



