VACCINE THERAPY IN THEORY AND PRACTICE 605 



anti-bodies are formed in the subcutaneous connective tissues, 1 

 and the correct treatment in such a case is to inject a suitable 

 dose of the appropriate vaccine under the skin. This is 

 followed by an outpouring of anti-bodies into the blood, a 

 rise in the opsonic index, and clinical improvement. The 

 result of a dose may be determined by observations on the 

 opsonic index. The inoculation is followed first by a fall in 

 resistance, called the negative phase, and if the dose is correct 

 this is succeeded by a marked rise and a gradual fall. If the 

 dose is too large the negative phase becomes pronounced and 

 the patient changes clinically for the worse. It is on these 

 principles that inoculation is employed in localised infections. 



With regard to the septicaemias the case is slightly different. 

 General infections, compared to local, are rare, because as a rule 

 any organisms which enter the blood are killed off at once by 

 the anti-bodies normally present. But when bacteria survive" 

 these and succeed in multiplying in the blood it appears that 

 fresh anti-bodies are not formed until the bacteria are deposited 

 from the blood in the proper tissues which subserve this 

 function. In some such cases a vaccine may be advantageously 

 used, but it must be borne in mind that the condition is one of 

 extreme gravity, and that the production of a negative phase of 

 any magnitude may well lead to a fatal result. Minimal doses 

 only must be used, and their effect must be scrupulously watched 

 by estimation of the opsonic index. 



The first paper on the opsonic index was published in 1903, 

 and the subject has been exhaustively investigated by numerous 

 workers ever since, and has excited not a little criticism. It is 

 not proposed to enter into any detailed defence or criticism 

 of the method in this place. All advances and variations of 

 method introduced in recent years have been made in deference 

 to its indications, and its general accuracy is assumed to be 

 established. 



At the same time it is admitted that it is not universally 

 accepted, and that some able workers have failed to obtain 

 consistent results with it. A few only of the most striking 

 evidences of its reliability will be given here, most of which 

 have transpired in Wright's laboratory. In that laboratory the 

 method is used for practical purposes only. It is employed as 

 a guide in treatment, and has been so employed for the last 

 1 Wright, Lancet, Aug. 17 and 24, 1907. 



